android虚拟按键的实现

以前看过好几次的东西又忘记了.或者写下来就会记住了吧...那就写下来~~~

SystemUI中虚拟按键的实现(Home, Back, Recently)

以Home键为例:

在layout中,定义Home键为一个KeyButtonView

从布局上看，每个虚拟按键是KeyButtonView。那么这个class是怎么构造的呢。如下。

publicKeyButtonView(Context context, AttributeSet attrs, int defStyle) {        super(context,attrs);        TypedArraya = context.obtainStyledAttributes(attrs, R.styleable.KeyButtonView,                defStyle,0);        mCode =a.getInteger(R.styleable.KeyButtonView_keyCode, 0);        mSupportsLongpress =a.getBoolean(R.styleable.KeyButtonView_keyRepeat, true);        。。。。。。        setClickable(true);        mTouchSlop= ViewConfiguration.get(context).getScaledTouchSlop();    }

构造函数里头获取了一些关键的属性。

接着继续看这个类怎么用这些属性

public boolean onTouchEvent(MotionEvent ev) {        finalint action = ev.getAction();        intx, y;         switch(action) {            caseMotionEvent.ACTION_DOWN:                //Log.d("KeyButtonView","press");                mDownTime= SystemClock.uptimeMillis();                setPressed(true);                if(mCode != 0) {                    sendEvent(KeyEvent.ACTION_DOWN,0, mDownTime);                }else {                    //Provide the same haptic feedback that the system offers for virtual keys.                    performHapticFeedback(HapticFeedbackConstants.VIRTUAL_KEY);                }                if(mSupportsLongpress) {                    removeCallbacks(mCheckLongPress);                    postDelayed(mCheckLongPress,ViewConfiguration.getLongPressTimeout());                }                break;            caseMotionEvent.ACTION_MOVE:                x= (int)ev.getX();                y= (int)ev.getY();                setPressed(x>= -mTouchSlop                        &&x < getWidth() + mTouchSlop                        &&y >= -mTouchSlop                        &&y < getHeight() + mTouchSlop);                break;            caseMotionEvent.ACTION_CANCEL:                setPressed(false);                if(mCode != 0) {                    sendEvent(KeyEvent.ACTION_UP,KeyEvent.FLAG_CANCELED);                }                if(mSupportsLongpress) {                    removeCallbacks(mCheckLongPress);                }                break;            caseMotionEvent.ACTION_UP:                finalboolean doIt = isPressed();                setPressed(false);                if(mCode != 0) {                    if(doIt) {                        sendEvent(KeyEvent.ACTION_UP,0);                        sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED);                        playSoundEffect(SoundEffectConstants.CLICK);                    }else {                        sendEvent(KeyEvent.ACTION_UP,KeyEvent.FLAG_CANCELED);                    }                }else {                    //no key code, just a regular ImageView                    if(doIt) {                        performClick();                    }                }                if(mSupportsLongpress) {                    removeCallbacks(mCheckLongPress);                }                break;        }         returntrue;    }

在这里的onTouch中，KeyButtonView处理了触摸事件，同时并派发了消息。

    void sendEvent(int action, int flags) {        sendEvent(action,flags, SystemClock.uptimeMillis());    }     void sendEvent(int action, int flags, long when) {        finalint repeatCount = (flags & KeyEvent.FLAG_LONG_PRESS) != 0 ? 1 : 0;        finalKeyEvent ev = new KeyEvent(mDownTime, when, action, mCode, repeatCount,                0,KeyCharacterMap.VIRTUAL_KEYBOARD, 0,                flags| KeyEvent.FLAG_FROM_SYSTEM | KeyEvent.FLAG_VIRTUAL_HARD_KEY,                InputDevice.SOURCE_KEYBOARD);        InputManager.getInstance().injectInputEvent(ev,                InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);    }

onTouch处理后，直接将按键上报。

剩下的R.id.home这个id用来做什么呢。单纯是为了实现触摸效果。

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