<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
	<translate android:fromXDelta="100%p" android:toXDelta="0%p" android:duration="300"/>
	<alpha android:fromAlpha="0.0" android:toAlpha="1.0" android:duration="300" />
</set>

startAnimation( AnimationUtils.loadAnimation(mContext, R.anim.left_out) );

public class KeyEvent implements Parcelable {
    // key codes
    public static final int KEYCODE_UNKNOWN         = 0;
    public static final int KEYCODE_SOFT_LEFT       = 1;
    public static final int KEYCODE_SOFT_RIGHT      = 2;
    public static final int KEYCODE_HOME            = 3;
    public static final int KEYCODE_BACK            = 4;
    public static final int KEYCODE_CALL            = 5;
    public static final int KEYCODE_ENDCALL         = 6;
    public static final int KEYCODE_0               = 7;
    public static final int KEYCODE_1               = 8;
    public static final int KEYCODE_2               = 9;
    public static final int KEYCODE_3               = 10;
    public static final int KEYCODE_4               = 11;
    public static final int KEYCODE_5               = 12;
    public static final int KEYCODE_6               = 13;
    public static final int KEYCODE_7               = 14;
    public static final int KEYCODE_8               = 15;
    public static final int KEYCODE_9               = 16;
    public static final int KEYCODE_STAR            = 17;
    public static final int KEYCODE_POUND           = 18;
    public static final int KEYCODE_DPAD_UP         = 19;
    public static final int KEYCODE_DPAD_DOWN       = 20;
    public static final int KEYCODE_DPAD_LEFT       = 21;
    public static final int KEYCODE_DPAD_RIGHT      = 22;
    public static final int KEYCODE_DPAD_CENTER     = 23;
    public static final int KEYCODE_VOLUME_UP       = 24;
    public static final int KEYCODE_VOLUME_DOWN     = 25;
    public static final int KEYCODE_POWER           = 26;
    public static final int KEYCODE_CAMERA          = 27;
    public static final int KEYCODE_CLEAR           = 28;
    public static final int KEYCODE_A               = 29;
    public static final int KEYCODE_B               = 30;
    public static final int KEYCODE_C               = 31;
    public static final int KEYCODE_D               = 32;
    public static final int KEYCODE_E               = 33;
    public static final int KEYCODE_F               = 34;
    public static final int KEYCODE_G               = 35;
    public static final int KEYCODE_H               = 36;
    public static final int KEYCODE_I               = 37;
    public static final int KEYCODE_J               = 38;
    public static final int KEYCODE_K               = 39;
    public static final int KEYCODE_L               = 40;
    public static final int KEYCODE_M               = 41;
    public static final int KEYCODE_N               = 42;
    public static final int KEYCODE_O               = 43;
    public static final int KEYCODE_P               = 44;
    public static final int KEYCODE_Q               = 45;
    public static final int KEYCODE_R               = 46;
    public static final int KEYCODE_S               = 47;
    public static final int KEYCODE_T               = 48;
    public static final int KEYCODE_U               = 49;
    public static final int KEYCODE_V               = 50;
    public static final int KEYCODE_W               = 51;
    public static final int KEYCODE_X               = 52;
    public static final int KEYCODE_Y               = 53;
    public static final int KEYCODE_Z               = 54;
    public static final int KEYCODE_COMMA           = 55;
    public static final int KEYCODE_PERIOD          = 56;
    public static final int KEYCODE_ALT_LEFT        = 57;
    public static final int KEYCODE_ALT_RIGHT       = 58;
    public static final int KEYCODE_SHIFT_LEFT      = 59;
    public static final int KEYCODE_SHIFT_RIGHT     = 60;
    public static final int KEYCODE_TAB             = 61;
    public static final int KEYCODE_SPACE           = 62;
    public static final int KEYCODE_SYM             = 63;
    public static final int KEYCODE_EXPLORER        = 64;
    public static final int KEYCODE_ENVELOPE        = 65;
    public static final int KEYCODE_ENTER           = 66;
    public static final int KEYCODE_DEL             = 67;
    public static final int KEYCODE_GRAVE           = 68;
    public static final int KEYCODE_MINUS           = 69;
    public static final int KEYCODE_EQUALS          = 70;
    public static final int KEYCODE_LEFT_BRACKET    = 71;
    public static final int KEYCODE_RIGHT_BRACKET   = 72;
    public static final int KEYCODE_BACKSLASH       = 73;
    public static final int KEYCODE_SEMICOLON       = 74;
    public static final int KEYCODE_APOSTROPHE      = 75;
    public static final int KEYCODE_SLASH           = 76;
    public static final int KEYCODE_AT              = 77;
    public static final int KEYCODE_NUM             = 78;
    public static final int KEYCODE_HEADSETHOOK     = 79;
    public static final int KEYCODE_FOCUS           = 80;   // *Camera* focus
    public static final int KEYCODE_PLUS            = 81;
    public static final int KEYCODE_MENU            = 82;
    public static final int KEYCODE_NOTIFICATION    = 83;
    public static final int KEYCODE_SEARCH          = 84;
    public static final int KEYCODE_MEDIA_PLAY_PAUSE= 85;
    public static final int KEYCODE_MEDIA_STOP      = 86;
    public static final int KEYCODE_MEDIA_NEXT      = 87;
    public static final int KEYCODE_MEDIA_PREVIOUS  = 88;
    public static final int KEYCODE_MEDIA_REWIND    = 89;
    public static final int KEYCODE_MEDIA_FAST_FORWARD = 90;
    public static final int KEYCODE_MUTE            = 91;

    // NOTE: If you add a new keycode here you must also add it to:
    //  isSystem()
    //  frameworks/base/include/ui/KeycodeLabels.h
    //  tools/puppet_master/PuppetMaster/nav_keys.py
    //  frameworks/base/core/res/res/values/attrs.xml
    //  commands/monkey/Monkey.java
    //  emulator?
    //
    //  Also Android currently does not reserve code ranges for vendor-
    //  specific key codes.  If you have new key codes to have, you
    //  MUST contribute a patch to the open source project to define
    //  those new codes.  This is intended to maintain a consistent
    //  set of key code definitions across all Android devices.
  
    private static final int LAST_KEYCODE           = KEYCODE_MUTE;
   
    /**
     * @deprecated There are now more than MAX_KEYCODE keycodes.
     * Use {@link #getMaxKeyCode()} instead.
     */
    @Deprecated
    public static final int MAX_KEYCODE             = 84;

    /**
     * {@link #getAction} value: the key has been pressed down.
     */
    public static final int ACTION_DOWN             = 0;
    /**
     * {@link #getAction} value: the key has been released.
     */
    public static final int ACTION_UP               = 1;
    /**
     * {@link #getAction} value: multiple duplicate key events have
     * occurred in a row, or a complex string is being delivered.  If the
     * key code is not {#link {@link #KEYCODE_UNKNOWN} then the
     * {#link {@link #getRepeatCount()} method returns the number of times
     * the given key code should be executed.
     * Otherwise, if the key code {@link #KEYCODE_UNKNOWN}, then
     * this is a sequence of characters as returned by {@link #getCharacters}.
     */
    public static final int ACTION_MULTIPLE         = 2;

    /**
     * <p>This mask is used to check whether one of the ALT meta keys is pressed.</p>
     *
     * @see #isAltPressed()
     * @see #getMetaState()
     * @see #KEYCODE_ALT_LEFT
     * @see #KEYCODE_ALT_RIGHT
     */
    public static final int META_ALT_ON = 0x02;

    /**
     * <p>This mask is used to check whether the left ALT meta key is pressed.</p>
     *
     * @see #isAltPressed()
     * @see #getMetaState()
     * @see #KEYCODE_ALT_LEFT
     */
    public static final int META_ALT_LEFT_ON = 0x10;

    /**
     * <p>This mask is used to check whether the right the ALT meta key is pressed.</p>
     *
     * @see #isAltPressed()
     * @see #getMetaState()
     * @see #KEYCODE_ALT_RIGHT
     */
    public static final int META_ALT_RIGHT_ON = 0x20;

    /**
     * <p>This mask is used to check whether one of the SHIFT meta keys is pressed.</p>
     *
     * @see #isShiftPressed()
     * @see #getMetaState()
     * @see #KEYCODE_SHIFT_LEFT
     * @see #KEYCODE_SHIFT_RIGHT
     */
    public static final int META_SHIFT_ON = 0x1;

    /**
     * <p>This mask is used to check whether the left SHIFT meta key is pressed.</p>
     *
     * @see #isShiftPressed()
     * @see #getMetaState()
     * @see #KEYCODE_SHIFT_LEFT
     */
    public static final int META_SHIFT_LEFT_ON = 0x40;

    /**
     * <p>This mask is used to check whether the right SHIFT meta key is pressed.</p>
     *
     * @see #isShiftPressed()
     * @see #getMetaState()
     * @see #KEYCODE_SHIFT_RIGHT
     */
    public static final int META_SHIFT_RIGHT_ON = 0x80;

    /**
     * <p>This mask is used to check whether the SYM meta key is pressed.</p>
     *
     * @see #isSymPressed()
     * @see #getMetaState()
     */
    public static final int META_SYM_ON = 0x4;

    /**
     * This mask is set if the device woke because of this key event.
     */
    public static final int FLAG_WOKE_HERE = 0x1;
   
    /**
     * This mask is set if the key event was generated by a software keyboard.
     */
    public static final int FLAG_SOFT_KEYBOARD = 0x2;
   
    /**
     * This mask is set if we don't want the key event to cause us to leave
     * touch mode.
     */
    public static final int FLAG_KEEP_TOUCH_MODE = 0x4;
   
    /**
     * This mask is set if an event was known to come from a trusted part
     * of the system.  That is, the event is known to come from the user,
     * and could not have been spoofed by a third party component.
     */
    public static final int FLAG_FROM_SYSTEM = 0x8;
   
    /**
     * This mask is used for compatibility, to identify enter keys that are
     * coming from an IME whose enter key has been auto-labelled "next" or
     * "done".  This allows TextView to dispatch these as normal enter keys
     * for old applications, but still do the appropriate action when
     * receiving them.
     */
    public static final int FLAG_EDITOR_ACTION = 0x10;
   
    /**
     * When associated with up key events, this indicates that the key press
     * has been canceled.  Typically this is used with virtual touch screen
     * keys, where the user can slide from the virtual key area on to the
     * display: in that case, the application will receive a canceled up
     * event and should not perform the action normally associated with the
     * key.  Note that for this to work, the application can not perform an
     * action for a key until it receives an up or the long press timeout has
     * expired.
     */
    public static final int FLAG_CANCELED = 0x20;
   
    /**
     * This key event was generated by a virtual (on-screen) hard key area.
     * Typically this is an area of the touchscreen, outside of the regular
     * display, dedicated to "hardware" buttons.
     */
    public static final int FLAG_VIRTUAL_HARD_KEY = 0x40;
   
    /**
     * This flag is set for the first key repeat that occurs after the
     * long press timeout.
     */
    public static final int FLAG_LONG_PRESS = 0x80;
   
    /**
     * Set when a key event has {@link #FLAG_CANCELED} set because a long
     * press action was executed while it was down.
     */
    public static final int FLAG_CANCELED_LONG_PRESS = 0x100;
   
    /**
     * Set for {@link #ACTION_UP} when this event's key code is still being
     * tracked from its initial down.  That is, somebody requested that tracking
     * started on the key down and a long press has not caused
     * the tracking to be canceled.
     */
    public static final int FLAG_TRACKING = 0x200;
   
    /**
     * Private control to determine when an app is tracking a key sequence.
     * @hide
     */
    public static final int FLAG_START_TRACKING = 0x40000000;
   
    /**
     * Returns the maximum keycode.
     */
    public static int getMaxKeyCode() {
        return LAST_KEYCODE;
    }

    /**
     * Get the character that is produced by putting accent on the character
     * c.
     * For example, getDeadChar('`', 'e') returns &egrave;.
     */
    public static int getDeadChar(int accent, int c) {
        return KeyCharacterMap.getDeadChar(accent, c);
    }
   
    static final boolean DEBUG = false;
    static final String TAG = "KeyEvent";
   
    private int mMetaState;
    private int mAction;
    private int mKeyCode;
    private int mScancode;
    private int mRepeatCount;
    private int mDeviceId;
    private int mFlags;
    private long mDownTime;
    private long mEventTime;
    private String mCharacters;

    public interface Callback {
        /**
         * Called when a key down event has occurred.  If you return true,
         * you can first call {@link KeyEvent#startTracking()
         * KeyEvent.startTracking()} to have the framework track the event
         * through its {@link #onKeyUp(int, KeyEvent)} and also call your
         * {@link #onKeyLongPress(int, KeyEvent)} if it occurs.
         *
         * @param keyCode The value in event.getKeyCode().
         * @param event Description of the key event.
         *
         * @return If you handled the event, return true.  If you want to allow
         *         the event to be handled by the next receiver, return false.
         */
        boolean onKeyDown(int keyCode, KeyEvent event);

        /**
         * Called when a long press has occurred.  If you return true,
         * the final key up will have {@link KeyEvent#FLAG_CANCELED} and
         * {@link KeyEvent#FLAG_CANCELED_LONG_PRESS} set.  Note that in
         * order to receive this callback, someone in the event change
         * <em>must</em> return true from {@link #onKeyDown} <em>and</em>
         * call {@link KeyEvent#startTracking()} on the event.
         *
         * @param keyCode The value in event.getKeyCode().
         * @param event Description of the key event.
         *
         * @return If you handled the event, return true.  If you want to allow
         *         the event to be handled by the next receiver, return false.
         */
        boolean onKeyLongPress(int keyCode, KeyEvent event);

        /**
         * Called when a key up event has occurred.
         *
         * @param keyCode The value in event.getKeyCode().
         * @param event Description of the key event.
         *
         * @return If you handled the event, return true.  If you want to allow
         *         the event to be handled by the next receiver, return false.
         */
        boolean onKeyUp(int keyCode, KeyEvent event);

        /**
         * Called when multiple down/up pairs of the same key have occurred
         * in a row.
         *
         * @param keyCode The value in event.getKeyCode().
         * @param count Number of pairs as returned by event.getRepeatCount().
         * @param event Description of the key event.
         *
         * @return If you handled the event, return true.  If you want to allow
         *         the event to be handled by the next receiver, return false.
         */
        boolean onKeyMultiple(int keyCode, int count, KeyEvent event);
    }

    /**
     * Create a new key event.
     *
     * @param action Action code: either {@link #ACTION_DOWN},
     * {@link #ACTION_UP}, or {@link #ACTION_MULTIPLE}.
     * @param code The key code.
     */
    public KeyEvent(int action, int code) {
        mAction = action;
        mKeyCode = code;
        mRepeatCount = 0;
    }

    /**
     * Create a new key event.
     *
     * @param downTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this key code originally went down.
     * @param eventTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this event happened.
     * @param action Action code: either {@link #ACTION_DOWN},
     * {@link #ACTION_UP}, or {@link #ACTION_MULTIPLE}.
     * @param code The key code.
     * @param repeat A repeat count for down events (> 0 if this is after the
     * initial down) or event count for multiple events.
     */
    public KeyEvent(long downTime, long eventTime, int action,
                    int code, int repeat) {
        mDownTime = downTime;
        mEventTime = eventTime;
        mAction = action;
        mKeyCode = code;
        mRepeatCount = repeat;
    }

    /**
     * Create a new key event.
     *
     * @param downTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this key code originally went down.
     * @param eventTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this event happened.
     * @param action Action code: either {@link #ACTION_DOWN},
     * {@link #ACTION_UP}, or {@link #ACTION_MULTIPLE}.
     * @param code The key code.
     * @param repeat A repeat count for down events (> 0 if this is after the
     * initial down) or event count for multiple events.
     * @param metaState Flags indicating which meta keys are currently pressed.
     */
    public KeyEvent(long downTime, long eventTime, int action,
                    int code, int repeat, int metaState) {
        mDownTime = downTime;
        mEventTime = eventTime;
        mAction = action;
        mKeyCode = code;
        mRepeatCount = repeat;
        mMetaState = metaState;
    }

    /**
     * Create a new key event.
     *
     * @param downTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this key code originally went down.
     * @param eventTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this event happened.
     * @param action Action code: either {@link #ACTION_DOWN},
     * {@link #ACTION_UP}, or {@link #ACTION_MULTIPLE}.
     * @param code The key code.
     * @param repeat A repeat count for down events (> 0 if this is after the
     * initial down) or event count for multiple events.
     * @param metaState Flags indicating which meta keys are currently pressed.
     * @param device The device ID that generated the key event.
     * @param scancode Raw device scan code of the event.
     */
    public KeyEvent(long downTime, long eventTime, int action,
                    int code, int repeat, int metaState,
                    int device, int scancode) {
        mDownTime = downTime;
        mEventTime = eventTime;
        mAction = action;
        mKeyCode = code;
        mRepeatCount = repeat;
        mMetaState = metaState;
        mDeviceId = device;
        mScancode = scancode;
    }

    /**
     * Create a new key event.
     *
     * @param downTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this key code originally went down.
     * @param eventTime The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this event happened.
     * @param action Action code: either {@link #ACTION_DOWN},
     * {@link #ACTION_UP}, or {@link #ACTION_MULTIPLE}.
     * @param code The key code.
     * @param repeat A repeat count for down events (> 0 if this is after the
     * initial down) or event count for multiple events.
     * @param metaState Flags indicating which meta keys are currently pressed.
     * @param device The device ID that generated the key event.
     * @param scancode Raw device scan code of the event.
     * @param flags The flags for this key event
     */
    public KeyEvent(long downTime, long eventTime, int action,
                    int code, int repeat, int metaState,
                    int device, int scancode, int flags) {
        mDownTime = downTime;
        mEventTime = eventTime;
        mAction = action;
        mKeyCode = code;
        mRepeatCount = repeat;
        mMetaState = metaState;
        mDeviceId = device;
        mScancode = scancode;
        mFlags = flags;
    }

    /**
     * Create a new key event for a string of characters.  The key code,
     * action, and repeat could will automatically be set to
     * {@link #KEYCODE_UNKNOWN}, {@link #ACTION_MULTIPLE}, and 0 for you.
     *
     * @param time The time (in {@link android.os.SystemClock#uptimeMillis})
     * at which this event occured.
     * @param characters The string of characters.
     * @param device The device ID that generated the key event.
     * @param flags The flags for this key event
     */
    public KeyEvent(long time, String characters, int device, int flags) {
        mDownTime = time;
        mEventTime = time;
        mCharacters = characters;
        mAction = ACTION_MULTIPLE;
        mKeyCode = KEYCODE_UNKNOWN;
        mRepeatCount = 0;
        mDeviceId = device;
        mFlags = flags;
    }

    /**
     * Make an exact copy of an existing key event.
     */
    public KeyEvent(KeyEvent origEvent) {
        mDownTime = origEvent.mDownTime;
        mEventTime = origEvent.mEventTime;
        mAction = origEvent.mAction;
        mKeyCode = origEvent.mKeyCode;
        mRepeatCount = origEvent.mRepeatCount;
        mMetaState = origEvent.mMetaState;
        mDeviceId = origEvent.mDeviceId;
        mScancode = origEvent.mScancode;
        mFlags = origEvent.mFlags;
        mCharacters = origEvent.mCharacters;
    }

    /**
     * Copy an existing key event, modifying its time and repeat count.
     *
     * @deprecated Use {@link #changeTimeRepeat(KeyEvent, long, int)}
     * instead.
     *
     * @param origEvent The existing event to be copied.
     * @param eventTime The new event time
     * (in {@link android.os.SystemClock#uptimeMillis}) of the event.
     * @param newRepeat The new repeat count of the event.
     */
    @Deprecated
    public KeyEvent(KeyEvent origEvent, long eventTime, int newRepeat) {
        mDownTime = origEvent.mDownTime;
        mEventTime = eventTime;
        mAction = origEvent.mAction;
        mKeyCode = origEvent.mKeyCode;
        mRepeatCount = newRepeat;
        mMetaState = origEvent.mMetaState;
        mDeviceId = origEvent.mDeviceId;
        mScancode = origEvent.mScancode;
        mFlags = origEvent.mFlags;
        mCharacters = origEvent.mCharacters;
    }

    /**
     * Create a new key event that is the same as the given one, but whose
     * event time and repeat count are replaced with the given value.
     *
     * @param event The existing event to be copied.  This is not modified.
     * @param eventTime The new event time
     * (in {@link android.os.SystemClock#uptimeMillis}) of the event.
     * @param newRepeat The new repeat count of the event.
     */
    public static KeyEvent changeTimeRepeat(KeyEvent event, long eventTime,
            int newRepeat) {
        return new KeyEvent(event, eventTime, newRepeat);
    }
   
    /**
     * Create a new key event that is the same as the given one, but whose
     * event time and repeat count are replaced with the given value.
     *
     * @param event The existing event to be copied.  This is not modified.
     * @param eventTime The new event time
     * (in {@link android.os.SystemClock#uptimeMillis}) of the event.
     * @param newRepeat The new repeat count of the event.
     * @param newFlags New flags for the event, replacing the entire value
     * in the original event.
     */
    public static KeyEvent changeTimeRepeat(KeyEvent event, long eventTime,
            int newRepeat, int newFlags) {
        KeyEvent ret = new KeyEvent(event);
        ret.mEventTime = eventTime;
        ret.mRepeatCount = newRepeat;
        ret.mFlags = newFlags;
        return ret;
    }
   
    /**
     * Copy an existing key event, modifying its action.
     *
     * @param origEvent The existing event to be copied.
     * @param action The new action code of the event.
     */
    private KeyEvent(KeyEvent origEvent, int action) {
        mDownTime = origEvent.mDownTime;
        mEventTime = origEvent.mEventTime;
        mAction = action;
        mKeyCode = origEvent.mKeyCode;
        mRepeatCount = origEvent.mRepeatCount;
        mMetaState = origEvent.mMetaState;
        mDeviceId = origEvent.mDeviceId;
        mScancode = origEvent.mScancode;
        mFlags = origEvent.mFlags;
        // Don't copy mCharacters, since one way or the other we'll lose it
        // when changing the action.
    }

    /**
     * Create a new key event that is the same as the given one, but whose
     * action is replaced with the given value.
     *
     * @param event The existing event to be copied.  This is not modified.
     * @param action The new action code of the event.
     */
    public static KeyEvent changeAction(KeyEvent event, int action) {
        return new KeyEvent(event, action);
    }
   
    /**
     * Create a new key event that is the same as the given one, but whose
     * flags are replaced with the given value.
     *
     * @param event The existing event to be copied.  This is not modified.
     * @param flags The new flags constant.
     */
    public static KeyEvent changeFlags(KeyEvent event, int flags) {
        event = new KeyEvent(event);
        event.mFlags = flags;
        return event;
    }
   
    /**
     * Don't use in new code, instead explicitly check
     * {@link #getAction()}.
     *
     * @return If the action is ACTION_DOWN, returns true; else false.
     *
     * @deprecated
     * @hide
     */
    @Deprecated public final boolean isDown() {
        return mAction == ACTION_DOWN;
    }

    /**
     * Is this a system key?  System keys can not be used for menu shortcuts.
     *
     * TODO: this information should come from a table somewhere.
     * TODO: should the dpad keys be here?  arguably, because they also shouldn't be menu shortcuts
     */
    public final boolean isSystem() {
        switch (mKeyCode) {
        case KEYCODE_MENU:
        case KEYCODE_SOFT_RIGHT:
        case KEYCODE_HOME:
        case KEYCODE_BACK:
        case KEYCODE_CALL:
        case KEYCODE_ENDCALL:
        case KEYCODE_VOLUME_UP:
        case KEYCODE_VOLUME_DOWN:
        case KEYCODE_MUTE:
        case KEYCODE_POWER:
        case KEYCODE_HEADSETHOOK:
        case KEYCODE_MEDIA_PLAY_PAUSE:
        case KEYCODE_MEDIA_STOP:
        case KEYCODE_MEDIA_NEXT:
        case KEYCODE_MEDIA_PREVIOUS:
        case KEYCODE_MEDIA_REWIND:
        case KEYCODE_MEDIA_FAST_FORWARD:
        case KEYCODE_CAMERA:
        case KEYCODE_FOCUS:
        case KEYCODE_SEARCH:
            return true;
        default:
            return false;
        }
    }

    /**
     * <p>Returns the state of the meta keys.</p>
     *
     * @return an integer in which each bit set to 1 represents a pressed
     *         meta key
     *
     * @see #isAltPressed()
     * @see #isShiftPressed()
     * @see #isSymPressed()
     * @see #META_ALT_ON
     * @see #META_SHIFT_ON
     * @see #META_SYM_ON
     */
    public final int getMetaState() {
        return mMetaState;
    }

    /**
     * Returns the flags for this key event.
     *
     * @see #FLAG_WOKE_HERE
     */
    public final int getFlags() {
        return mFlags;
    }

    /**
     * Returns true if this key code is a modifier key.
     *
     * @return whether the provided keyCode is one of
     * {@link #KEYCODE_SHIFT_LEFT} {@link #KEYCODE_SHIFT_RIGHT},
     * {@link #KEYCODE_ALT_LEFT}, {@link #KEYCODE_ALT_RIGHT}
     * or {@link #KEYCODE_SYM}.
     */
    public static boolean isModifierKey(int keyCode) {
        return keyCode == KEYCODE_SHIFT_LEFT || keyCode == KEYCODE_SHIFT_RIGHT
                || keyCode == KEYCODE_ALT_LEFT || keyCode == KEYCODE_ALT_RIGHT
                || keyCode == KEYCODE_SYM;
    }

    /**
     * <p>Returns the pressed state of the ALT meta key.</p>
     *
     * @return true if the ALT key is pressed, false otherwise
     *
     * @see #KEYCODE_ALT_LEFT
     * @see #KEYCODE_ALT_RIGHT
     * @see #META_ALT_ON
     */
    public final boolean isAltPressed() {
        return (mMetaState & META_ALT_ON) != 0;
    }

    /**
     * <p>Returns the pressed state of the SHIFT meta key.</p>
     *
     * @return true if the SHIFT key is pressed, false otherwise
     *
     * @see #KEYCODE_SHIFT_LEFT
     * @see #KEYCODE_SHIFT_RIGHT
     * @see #META_SHIFT_ON
     */
    public final boolean isShiftPressed() {
        return (mMetaState & META_SHIFT_ON) != 0;
    }

    /**
     * <p>Returns the pressed state of the SYM meta key.</p>
     *
     * @return true if the SYM key is pressed, false otherwise
     *
     * @see #KEYCODE_SYM
     * @see #META_SYM_ON
     */
    public final boolean isSymPressed() {
        return (mMetaState & META_SYM_ON) != 0;
    }

    /**
     * Retrieve the action of this key event.  May be either
     * {@link #ACTION_DOWN}, {@link #ACTION_UP}, or {@link #ACTION_MULTIPLE}.
     *
     * @return The event action: ACTION_DOWN, ACTION_UP, or ACTION_MULTIPLE.
     */
    public final int getAction() {
        return mAction;
    }

    /**
     * For {@link #ACTION_UP} events, indicates that the event has been
     * canceled as per {@link #FLAG_CANCELED}.
     */
    public final boolean isCanceled() {
        return (mFlags&FLAG_CANCELED) != 0;
    }
   
    /**
     * Call this during {@link Callback#onKeyDown} to have the system track
     * the key through its final up (possibly including a long press).  Note
     * that only one key can be tracked at a time -- if another key down
     * event is received while a previous one is being tracked, tracking is
     * stopped on the previous event.
     */
    public final void startTracking() {
        mFlags |= FLAG_START_TRACKING;
    }
   
    /**
     * For {@link #ACTION_UP} events, indicates that the event is still being
     * tracked from its initial down event as per
     * {@link #FLAG_TRACKING}.
     */
    public final boolean isTracking() {
        return (mFlags&FLAG_TRACKING) != 0;
    }
   
    /**
     * For {@link #ACTION_DOWN} events, indicates that the event has been
     * canceled as per {@link #FLAG_LONG_PRESS}.
     */
    public final boolean isLongPress() {
        return (mFlags&FLAG_LONG_PRESS) != 0;
    }
   
    /**
     * Retrieve the key code of the key event.  This is the physical key that
     * was pressed, <em>not</em> the Unicode character.
     *
     * @return The key code of the event.
     */
    public final int getKeyCode() {
        return mKeyCode;
    }

    /**
     * For the special case of a {@link #ACTION_MULTIPLE} event with key
     * code of {@link #KEYCODE_UNKNOWN}, this is a raw string of characters
     * associated with the event.  In all other cases it is null.
     *
     * @return Returns a String of 1 or more characters associated with
     * the event.
     */
    public final String getCharacters() {
        return mCharacters;
    }
   
    /**
     * Retrieve the hardware key id of this key event.  These values are not
     * reliable and vary from device to device.
     *
     * {@more}
     * Mostly this is here for debugging purposes.
     */
    public final int getScanCode() {
        return mScancode;
    }

    /**
     * Retrieve the repeat count of the event.  For both key up and key down
     * events, this is the number of times the key has repeated with the first
     * down starting at 0 and counting up from there.  For multiple key
     * events, this is the number of down/up pairs that have occurred.
     *
     * @return The number of times the key has repeated.
     */
    public final int getRepeatCount() {
        return mRepeatCount;
    }

    /**
     * Retrieve the time of the most recent key down event,
     * in the {@link android.os.SystemClock#uptimeMillis} time base.  If this
     * is a down event, this will be the same as {@link #getEventTime()}.
     * Note that when chording keys, this value is the down time of the
     * most recently pressed key, which may <em>not</em> be the same physical
     * key of this event.
     *
     * @return Returns the most recent key down time, in the
     * {@link android.os.SystemClock#uptimeMillis} time base
     */
    public final long getDownTime() {
        return mDownTime;
    }

    /**
     * Retrieve the time this event occurred,
     * in the {@link android.os.SystemClock#uptimeMillis} time base.
     *
     * @return Returns the time this event occurred,
     * in the {@link android.os.SystemClock#uptimeMillis} time base.
     */
    public final long getEventTime() {
        return mEventTime;
    }

    /**
     * Return the id for the keyboard that this event came from.  A device
     * id of 0 indicates the event didn't come from a physical device and
     * maps to the default keymap.  The other numbers are arbitrary and
     * you shouldn't depend on the values.
     *
     * @see KeyCharacterMap#load
     */
    public final int getDeviceId() {
        return mDeviceId;
    }

    /**
     * Renamed to {@link #getDeviceId}.
     *
     * @hide
     * @deprecated
     */
    public final int getKeyboardDevice() {
        return mDeviceId;
    }

    /**
     * Get the primary character for this key.  In other words, the label
     * that is physically printed on it.
     */
    public char getDisplayLabel() {
        return KeyCharacterMap.load(mDeviceId).getDisplayLabel(mKeyCode);
    }
   
    /**
     * <p>
     * Returns the Unicode character that the key would produce.
     * </p><p>
     * Returns 0 if the key is not one that is used to type Unicode
     * characters.
     * </p><p>
     * If the return value has bit
     * {@link KeyCharacterMap#COMBINING_ACCENT}
     * set, the key is a "dead key" that should be combined with another to
     * actually produce a character -- see {@link #getDeadChar} --
     * after masking with
     * {@link KeyCharacterMap#COMBINING_ACCENT_MASK}.
     * </p>
     */
    public int getUnicodeChar() {
        return getUnicodeChar(mMetaState);
    }
   
    /**
     * <p>
     * Returns the Unicode character that the key would produce.
     * </p><p>
     * Returns 0 if the key is not one that is used to type Unicode
     * characters.
     * </p><p>
     * If the return value has bit
     * {@link KeyCharacterMap#COMBINING_ACCENT}
     * set, the key is a "dead key" that should be combined with another to
     * actually produce a character -- see {@link #getDeadChar} -- after masking
     * with {@link KeyCharacterMap#COMBINING_ACCENT_MASK}.
     * </p>
     */
    public int getUnicodeChar(int meta) {
        return KeyCharacterMap.load(mDeviceId).get(mKeyCode, meta);
    }
   
    /**
     * Get the characters conversion data for the key event..
     *
     * @param results a {@link KeyData} that will be filled with the results.
     *
     * @return whether the key was mapped or not.  If the key was not mapped,
     *         results is not modified.
     */
    public boolean getKeyData(KeyData results) {
        return KeyCharacterMap.load(mDeviceId).getKeyData(mKeyCode, results);
    }
   
    /**
     * The same as {@link #getMatch(char[],int) getMatch(chars, 0)}.
     */
    public char getMatch(char[] chars) {
        return getMatch(chars, 0);
    }
   
    /**
     * If one of the chars in the array can be generated by the keyCode of this
     * key event, return the char; otherwise return '\0'.
     * @param chars the characters to try to find
     * @param modifiers the modifier bits to prefer.  If any of these bits
     *                  are set, if there are multiple choices, that could
     *                  work, the one for this modifier will be set.
     */
    public char getMatch(char[] chars, int modifiers) {
        return KeyCharacterMap.load(mDeviceId).getMatch(mKeyCode, chars, modifiers);
    }
   
    /**
     * Gets the number or symbol associated with the key.  The character value
     * is returned, not the numeric value.  If the key is not a number, but is
     * a symbol, the symbol is retuned.
     */
    public char getNumber() {
        return KeyCharacterMap.load(mDeviceId).getNumber(mKeyCode);
    }
   
    /**
     * Does the key code of this key produce a glyph?
     */
    public boolean isPrintingKey() {
        return KeyCharacterMap.load(mDeviceId).isPrintingKey(mKeyCode);
    }
   
    /**
     * @deprecated Use {@link #dispatch(Callback, DispatcherState, Object)} instead.
     */
    @Deprecated
    public final boolean dispatch(Callback receiver) {
        return dispatch(receiver, null, null);
    }
   
    /**
     * Deliver this key event to a {@link Callback} interface.  If this is
     * an ACTION_MULTIPLE event and it is not handled, then an attempt will
     * be made to deliver a single normal event.
     *
     * @param receiver The Callback that will be given the event.
     * @param state State information retained across events.
     * @param target The target of the dispatch, for use in tracking.
     *
     * @return The return value from the Callback method that was called.
     */
    public final boolean dispatch(Callback receiver, DispatcherState state,
            Object target) {
        switch (mAction) {
            case ACTION_DOWN: {
                mFlags &= ~FLAG_START_TRACKING;
                if (DEBUG) Log.v(TAG, "Key down to " + target + " in " + state
                        + ": " + this);
                boolean res = receiver.onKeyDown(mKeyCode, this);
                if (state != null) {
                    if (res && mRepeatCount == 0 && (mFlags&FLAG_START_TRACKING) != 0) {
                        if (DEBUG) Log.v(TAG, "  Start tracking!");
                        state.startTracking(this, target);
                    } else if (isLongPress() && state.isTracking(this)) {
                        try {
                            if (receiver.onKeyLongPress(mKeyCode, this)) {
                                if (DEBUG) Log.v(TAG, "  Clear from long press!");
                                state.performedLongPress(this);
                                res = true;
                            }
                        } catch (AbstractMethodError e) {
                        }
                    }
                }
                return res;
            }
            case ACTION_UP:
                if (DEBUG) Log.v(TAG, "Key up to " + target + " in " + state
                        + ": " + this);
                if (state != null) {
                    state.handleUpEvent(this);
                }
                return receiver.onKeyUp(mKeyCode, this);
            case ACTION_MULTIPLE:
                final int count = mRepeatCount;
                final int code = mKeyCode;
                if (receiver.onKeyMultiple(code, count, this)) {
                    return true;
                }
                if (code != KeyEvent.KEYCODE_UNKNOWN) {
                    mAction = ACTION_DOWN;
                    mRepeatCount = 0;
                    boolean handled = receiver.onKeyDown(code, this);
                    if (handled) {
                        mAction = ACTION_UP;
                        receiver.onKeyUp(code, this);
                    }
                    mAction = ACTION_MULTIPLE;
                    mRepeatCount = count;
                    return handled;
                }
                return false;
        }
        return false;
    }

    /**
     * Use with {@link KeyEvent#dispatch(Callback, DispatcherState, Object)}
     * for more advanced key dispatching, such as long presses.
     */
    public static class DispatcherState {
        int mDownKeyCode;
        Object mDownTarget;
        SparseIntArray mActiveLongPresses = new SparseIntArray();
       
        /**
         * Reset back to initial state.
         */
        public void reset() {
            if (DEBUG) Log.v(TAG, "Reset: " + this);
            mDownKeyCode = 0;
            mDownTarget = null;
            mActiveLongPresses.clear();
        }
       
        /**
         * Stop any tracking associated with this target.
         */
        public void reset(Object target) {
            if (mDownTarget == target) {
                if (DEBUG) Log.v(TAG, "Reset in " + target + ": " + this);
                mDownKeyCode = 0;
                mDownTarget = null;
            }
        }
       
        /**
         * Start tracking the key code associated with the given event.  This
         * can only be called on a key down.  It will allow you to see any
         * long press associated with the key, and will result in
         * {@link KeyEvent#isTracking} return true on the long press and up
         * events.
         *
         * <p>This is only needed if you are directly dispatching events, rather
         * than handling them in {@link Callback#onKeyDown}.
         */
        public void startTracking(KeyEvent event, Object target) {
            if (event.getAction() != ACTION_DOWN) {
                throw new IllegalArgumentException(
                        "Can only start tracking on a down event");
            }
            if (DEBUG) Log.v(TAG, "Start trackingt in " + target + ": " + this);
            mDownKeyCode = event.getKeyCode();
            mDownTarget = target;
        }
       
        /**
         * Return true if the key event is for a key code that is currently
         * being tracked by the dispatcher.
         */
        public boolean isTracking(KeyEvent event) {
            return mDownKeyCode == event.getKeyCode();
        }
       
        /**
         * Keep track of the given event's key code as having performed an
         * action with a long press, so no action should occur on the up.
         * <p>This is only needed if you are directly dispatching events, rather
         * than handling them in {@link Callback#onKeyLongPress}.
         */
        public void performedLongPress(KeyEvent event) {
            mActiveLongPresses.put(event.getKeyCode(), 1);
        }
       
        /**
         * Handle key up event to stop tracking.  This resets the dispatcher state,
         * and updates the key event state based on it.
         * <p>This is only needed if you are directly dispatching events, rather
         * than handling them in {@link Callback#onKeyUp}.
         */
        public void handleUpEvent(KeyEvent event) {
            final int keyCode = event.getKeyCode();
            if (DEBUG) Log.v(TAG, "Handle key up " + event + ": " + this);
            int index = mActiveLongPresses.indexOfKey(keyCode);
            if (index >= 0) {
                if (DEBUG) Log.v(TAG, "  Index: " + index);
                event.mFlags |= FLAG_CANCELED | FLAG_CANCELED_LONG_PRESS;
                mActiveLongPresses.removeAt(index);
            }
            if (mDownKeyCode == keyCode) {
                if (DEBUG) Log.v(TAG, "  Tracking!");
                event.mFlags |= FLAG_TRACKING;
                mDownKeyCode = 0;
                mDownTarget = null;
            }
        }
    }
   
    public String toString() {
        return "KeyEvent{action=" + mAction + " code=" + mKeyCode
            + " repeat=" + mRepeatCount
            + " meta=" + mMetaState + " scancode=" + mScancode
            + " mFlags=" + mFlags + "}";
    }

    public static final Parcelable.Creator<KeyEvent> CREATOR
            = new Parcelable.Creator<KeyEvent>() {
        public KeyEvent createFromParcel(Parcel in) {
            return new KeyEvent(in);
        }

        public KeyEvent[] newArray(int size) {
            return new KeyEvent[size];
        }
    };

    public int describeContents() {
        return 0;
    }

    public void writeToParcel(Parcel out, int flags) {
        out.writeInt(mAction);
        out.writeInt(mKeyCode);
        out.writeInt(mRepeatCount);
        out.writeInt(mMetaState);
        out.writeInt(mDeviceId);
        out.writeInt(mScancode);
        out.writeInt(mFlags);
        out.writeLong(mDownTime);
        out.writeLong(mEventTime);
    }

    private KeyEvent(Parcel in) {
        mAction = in.readInt();
        mKeyCode = in.readInt();
        mRepeatCount = in.readInt();
        mMetaState = in.readInt();
        mDeviceId = in.readInt();
        mScancode = in.readInt();
        mFlags = in.readInt();
        mDownTime = in.readLong();
        mEventTime = in.readLong();
    }
}

1. Activating components: intents : 컴포넌트 활성화(실행) : 인텐트
2. Shutting down components : 컴포넌트 죽이기
3. The manifest file  : 명세서 파일
4. Intent filters : 활성화 필터

Application Components

A central feature of Android is that one application can make use of elements of other applications (provided those applications permit it).

For example, if your application needs to display a scrolling list of images and another application has developed a suitable scroller and made it available to others, you can call upon that scroller to do the work, rather than develop your own. Your application doesn't incorporate the code of the other application or link to it. Rather, it simply starts up that piece of the other application when the need arises.

For this to work, the system must be able to start an application process when any part of it is needed, and instantiate the Java objects for that part. Therefore, unlike applications on most other systems, Android applications don't have a single entry point for everything in the application (no main() function, for example). Rather, they have essential components that the system can instantiate and run as needed.

There are four types of components:

Content providers

Content providers

A content provider makes a specific set of the application's data available to other applications. The data can be stored in the file system, in an SQLite database, or in any other manner that makes sense. The content provider extends the ContentProvider base class to implement a standard set of methods that enable other applications to retrieve and store data of the type it controls. However, applications do not call these methods directly. Rather they use a ContentResolver object and call its methods instead. A ContentResolver can talk to any content provider; it cooperates with the provider to manage any interprocess communication that's involved.

See the separate Content Providers document for more information on using content providers.

Whenever there's a request that should be handled by a particular component, Android makes sure that the application process of the component is running, starting it if necessary, and that an appropriate instance of the component is available, creating the instance if necessary.

Activating components: intents (시작)

Content providers are activated when they're targeted by a request from a ContentResolver. The other three components — activities, services, and broadcast receivers — are activated by asynchronous messages called intents. An intent is an Intent object that holds the content of the message. For activities and services, it names the action being requested and specifies the URI of the data to act on, among other things. For example, it might convey a request for an activity to present an image to the user or let the user edit some text. For broadcast receivers, the Intent object names the action being announced. For example, it might announce to interested parties that the camera button has been pressed.

There are separate methods for activating each type of component:

• An activity is launched (or given something new to do) by passing an Intent object to Context.startActivity() or Activity.startActivityForResult(). The responding activity can look at the initial intent that caused it to be launched by calling its getIntent() method. Android calls the activity's onNewIntent() method to pass it any subsequent intents.

  One activity often starts the next one. If it expects a result back from the activity it's starting, it calls startActivityForResult() instead of startActivity(). For example, if it starts an activity that lets the user pick a photo, it might expect to be returned the chosen photo. The result is returned in an Intent object that's passed to the calling activity's onActivityResult() method.

• A service is started (or new instructions are given to an ongoing service) by passing an Intent object to Context.startService(). Android calls the service's onStart() method and passes it the Intent object.

  Similarly, an intent can be passed to Context.bindService() to establish an ongoing connection between the calling component and a target service. The service receives the Intent object in an onBind() call. (If the service is not already running, bindService() can optionally start it.) For example, an activity might establish a connection with the music playback service mentioned earlier so that it can provide the user with the means (a user interface) for controlling the playback. The activity would call bindService() to set up that connection, and then call methods defined by the service to affect the playback.

  A later section, Remote procedure calls, has more details about binding to a service.

• An application can initiate a broadcast by passing an Intent object to methods like Context.sendBroadcast(), Context.sendOrderedBroadcast(), and Context.sendStickyBroadcast() in any of their variations. Android delivers the intent to all interested broadcast receivers by calling their onReceive() methods.

For more on intent messages, see the separate article, Intents and Intent Filters.

Shutting down components 종료

A content provider is active only while it's responding to a request from a ContentResolver. And a broadcast receiver is active only while it's responding to a broadcast message. So there's no need to explicitly shut down these components.

Activities, on the other hand, provide the user interface.
They're in a long-running conversation with the user and may remain active, even when idle, as long as the conversation continues.
Similarly, services may also remain running for a long time.
So Android has methods to shut down activities and services in an orderly way:

• An activity can be shut down by calling its finish() method.
  One activity can shut down another activity (one it started with startActivityForResult()) by calling finishActivity().
• A service can be stopped by calling its stopSelf() method, or by calling Context.stopService().

Components might also be shut down by the system when they are no longer being used or when Android must reclaim memory for more active components. A later section, Component Lifecycles, discusses this possibility and its ramifications in more detail.

The manifest file

Before Android can start an application component, it must learn that the component exists.
Therefore, applications declare their components in a manifest file that's bundled into the Android package,
the .apk file that also holds the application's code, files, and resources.

The manifest is a structured XML file and is always named AndroidManifest.xml for all applications. It does a number of things in addition to declaring the application's components, such as naming any libraries the application needs to be linked against (besides the default Android library) and identifying any permissions the application expects to be granted.

But the principal task of the manifest is to inform Android about the application's components. For example, an activity might be declared as follows:

<?xml version="1.0" encoding="utf-8"?>

<manifest . . . >


    <application . . . >

        <activity android:name="com.example.project.FreneticActivity"

                  android:icon="@drawable/small_pic.png"

                  android:label="@string/freneticLabel" 

                  . . .  >

        </activity>

        . . .

    </application>

</manifest>

The name attribute of the <activity> element names the Activity subclass that implements the activity. The icon and label attributes point to resource files containing an icon and label that can be displayed to users to represent the activity.

The other components are declared in a similar way — <service> elements for services, <receiver> elements for broadcast receivers, and <provider> elements for content providers. Activities, services, and content providers that are not declared in the manifest are not visible to the system and are consequently never run. However, broadcast receivers can either be declared in the manifest, or they can be created dynamically in code (as BroadcastReceiver objects) and registered with the system by calling Context.registerReceiver().

For more on how to structure a manifest file for your application, see The AndroidManifest.xml File.

Intent filters

An Intent object can explicitly name a target component. If it does, Android finds that component (based on the declarations in the manifest file) and activates it. But if a target is not explicitly named, Android must locate the best component to respond to the intent. It does so by comparing the Intent object to the intent filters of potential targets. A component's intent filters inform Android of the kinds of intents the component is able to handle. Like other essential information about the component, they're declared in the manifest file. Here's an extension of the previous example that adds two intent filters to the activity:

<?xml version="1.0" encoding="utf-8"?>

<manifest . . . >

    <application . . . >

        <activity android:name="com.example.project.FreneticActivity"

                  android:icon="@drawable/small_pic.png"

                  android:label="@string/freneticLabel" 

                  . . .  >

            <intent-filter . . . >

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

            <intent-filter . . . >

                <action android:name="com.example.project.BOUNCE" />

                <data android:mimeType="image/jpeg" />

                <category android:name="android.intent.category.DEFAULT" />

            </intent-filter>

        </activity>

        . . .

    </application>

</manifest>

The first filter in the example — the combination of the action "android.intent.action.MAIN" and the category "android.intent.category.LAUNCHER" — is a common one. It marks the activity as one that should be represented in the application launcher, the screen listing applications users can launch on the device. In other words, the activity is the entry point for the application, the initial one users would see when they choose the application in the launcher.

The second filter declares an action that the activity can perform on a particular type of data.

A component can have any number of intent filters, each one declaring a different set of capabilities. If it doesn't have any filters, it can be activated only by intents that explicitly name the component as the target.

For a broadcast receiver that's created and registered in code, the intent filter is instantiated directly as an IntentFilter object. All other filters are set up in the manifest.

For more on intent filters, see a separate document, Intents and Intent Filters.

Android applications are written in the Java programming language. The compiled Java code — along with any data and resource files required by the application — is bundled by the aapt tool into an Android package, an archive file marked by an .apk suffix.

This file is the vehicle for distributing the application and installing it on mobile devices; it's the file users download to their devices.

All the code in a single .apk file is considered to be one application.

In many ways, each Android application lives in its own world:

By default, each application is assigned a unique Linux user ID. Permissions are set so that the application's files are visible only to that user and only to the application itself — although there are ways to export them to other applications as well.

It's possible to arrange for two applications to share the same user ID, in which case they will be able to see each other's files. To conserve system resources, applications with the same ID can also arrange to run in the same Linux process, sharing the same VM.


출처 : http://www.kandroid.org/guide/topics/fundamentals.html

Android Runtime

Android includes a set of core libraries that provides most of the functionality available in the core libraries of the Java programming language.

Every Android application runs in its own process, with its own instance of the Dalvik virtual machine. Dalvik has been written so that a device can run multiple VMs efficiently. The Dalvik VM executes files in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool.

The Dalvik VM relies on the Linux kernel for underlying functionality such as threading and low-level memory management.

Linux Kernel

Android relies on Linux version 2.6 for core system services such as security, memory management, process management, network stack, and driver model. The kernel also acts as an abstraction layer between the hardware and the rest of the software stack.

번역 : jameroid.tistory.com
분류 : Android Basics
출처 : http://developer.android.com/guide/basics/what-is-android.html

Libraries

Android includes a set of C/C++ libraries used by various components of the Android system. These capabilities are exposed to developers through the Android application framework. Some of the core libraries are listed below:

• System C library - a BSD-derived implementation of the standard C system library (libc), tuned for embedded Linux-based devices
• Media Libraries - based on PacketVideo's OpenCORE; the libraries support playback and recording of many popular audio and video formats, as well as static image files, including MPEG4, H.264, MP3, AAC, AMR, JPG, and PNG
• Surface Manager - manages access to the display subsystem and seamlessly composites 2D and 3D graphic layers from multiple applications
• LibWebCore - a modern web browser engine which powers both the Android browser and an embeddable web view
• SGL - the underlying 2D graphics engine
• 3D libraries - an implementation based on OpenGL ES 1.0 APIs; the libraries use either hardware 3D acceleration (where available) or the included, highly optimized 3D software rasterizer
• FreeType - bitmap and vector font rendering
• SQLite - a powerful and lightweight relational database engine available to all applications

What is Android?

Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language.

특징들
- 어플리케이션 프레임웍 :  컴포턴트의 교체와 재새용을 가능하게 한다.
- 달빅 가상 머신 : 모바일 디바이스을 위해 최적화 되었다.
- 내장된 브라우저 : 공개소스 WebKit 엔진을 기초로 한다.
- 최적화된 그래픽 : 맞춤 2D 그래픽 라이브, OpenGL ES1.0 규격을 기초한 3D그래픽으로 로 강해졌다.
- SQLite : 구조적 데이타 저장을 위해
- 미디어 지원 : 오디오, 비디오 그리고 정지 이미지 포맷  (MPEG4, H.264, MP3, AAC, JPG, PNG, GIF)
- (하드웨어 의존) GSM 기술
- (하드웨어 의존) 블루투스, EDGE, 3G 와 WiFI
- (하드웨어 의존) 카메라, GPS, 나침반(compass) 그리고 가속도계(accelerometer)
- 풍부한 개발 환경 : 디바이스 에뮬레이터(장비모방),디버그 툴, 메모리와 성능 분석(performance profiling)
                          그리고 이클립스 IDE를 위한 플러그인 을 포함한다.

Features

• Application framework enabling reuse and replacement of components
• Dalvik virtual machine optimized for mobile devices
• Integrated browser based on the open source WebKit engine
• Optimized graphics powered by a custom 2D graphics library; 3D graphics based on the OpenGL ES 1.0 specification (hardware acceleration optional)
• SQLite for structured data storage
• Media support for common audio, video, and still image formats (MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, GIF)
• GSM Telephony (hardware dependent)
• Bluetooth, EDGE, 3G, and WiFi (hardware dependent)
• Camera, GPS, compass, and accelerometer (hardware dependent)
• Rich development environment including a device emulator, tools for debugging, memory and performance profiling, and a plugin for the Eclipse IDE

안드로이드 아키텍쳐
  : 아래 그림도료는 안드로이드 운영시스텝ㅁ의 주요 구성품(컴포턴트)을 보여준다

Applications

Android will ship with a set of core applications including an email client, SMS program, calendar, maps, browser, contacts, and others. All applications are written using the Java programming language.

Application Framework

By providing an open development platform, Android offers developers the ability to build extremely rich and innovative applications. Developers are free to take advantage of the device hardware, access location information, run background services, set alarms, add notifications to the status bar, and much, much more.

Developers have full access to the same framework APIs used by the core applications. The application architecture is designed to simplify the reuse of components; any application can publish its capabilities and any other application may then make use of those capabilities (subject to security constraints enforced by the framework). This same mechanism allows components to be replaced by the user.

Underlying all applications is a set of services and systems, including:

• A rich and extensible set of Views that can be used to build an application, including lists, grids, text boxes, buttons, and even an embeddable web browser
• Content Providers that enable applications to access data from other applications (such as Contacts), or to share their own data
• A Resource Manager, providing access to non-code resources such as localized strings, graphics, and layout files
• A Notification Manager that enables all applications to display custom alerts in the status bar
• An Activity Manager that manages the lifecycle of applications and provides a common navigation backstack

For more details and a walkthrough of an application, see the Notepad Tutorial.

public class TestImages extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ImageView image = (ImageView) findViewById(R.id.test_image);
        Bitmap bMap = BitmapFactory.decodeFile("/sdcard/test2.png");
        image.setImageBitmap(bMap);
    }
}

public class TestImages extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ImageView image = (ImageView) findViewById(R.id.test_image);
        FileInputStream in;
        BufferedInputStream buf;
        try {
            in = new FileInputStream("/sdcard/test2.png");
            buf = new BufferedInputStream(in);
            Bitmap bMap = BitmapFactory.decodeStream(buf);
            image.setImageBitmap(bMap);
            if (in != null) {
         in.close();
            }
            if (buf != null) {
         buf.close();
            }
        } catch (Exception e) {
            Log.e("Error reading file", e.toString());
        }
    }
}

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ImageView image = (ImageView) findViewById(R.id.test_image);
        Bitmap bMap = 
               BitmapFactory.decodeResource(getResources(), R.drawable.icon);
        image.setImageBitmap(bMap);
    }

public class TestImages extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ImageView image = (ImageView) findViewById(R.id.test_image);
        FileInputStream in;
        BufferedInputStream buf;
        try {
            in = new FileInputStream("/sdcard/test2.png");
            buf = new BufferedInputStream(in);
            byte[] bMapArray= new byte[buf.available()];
            buf.read(bMapArray);
            Bitmap bMap = 
                BitmapFactory.decodeByteArray(bMapArray, 0, bMapArray.length);
            image.setImageBitmap(bMap);
            if (in != null) {
         in.close();
            }
            if (buf != null) {
         buf.close();
            }
        } catch (Exception e) {
            Log.e("Error reading file", e.toString());
        }
    }
}