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。