手指劃動切換Activity

 以下代碼用于Activity之間的劃動切換，大概實現原理就是判斷手指的劃動速度和劃動方向以確定向哪個Activity跳轉，switchTo***Activity（）為Activity的跳轉方法

private VelocityTracker velocityTracker;//用于得到手勢在屏幕上的滑動速度
private static final int VELOCITY = 600;

       @Override
public boolean onTouchEvent(MotionEvent event) {
    String localClassName = getLocalClassName();//當前所在類名
    LogUtil.log(TAG, "class Name:"+localClassName);
    int action = event.getAction();
    //float x = event.getX();
    //float y = event.getY();


switch (action) {
case MotionEvent.ACTION_DOWN:
    if(velocityTracker == null){
        velocityTracker = VelocityTracker.obtain();//取得手勢在屏幕上的滑動速度
        velocityTracker.addMovement(event);
    }           
    //lastMotionX = x;

    break;

case MotionEvent.ACTION_MOVE:
    //int deltaX = (int) (lastMotionX - x);
    if(velocityTracker != null){
        velocityTracker.addMovement(event);
    }
    //lastMotionX = x;
    break;

case MotionEvent.ACTION_UP:

    int velocityX = 0;
    if(velocityTracker != null){
        velocityTracker.addMovement(event);
        velocityTracker.computeCurrentVelocity(1000);//計算每秒滑動多少個像素
        velocityX = (int) velocityTracker.getXVelocity();//最后計算檢索X速度
    }

    if(velocityX > VELOCITY ){
        if("ui.MainActivity".equals(localClassName)){
            switchToTvLiveActivity();
        }else if("ui.LocalMediaActivity".equals(localClassName)){
            switchToMainActivity();
        }else if("ui.NetMediaActivity".equals(localClassName)){
            switchToLocalMediaActivity();
        }else if("ui.TvLiveActivity".equals(localClassName)){
            switchToNetMediaActivity();
        }
    } else if(velocityX < -VELOCITY ){
        if("ui.MainActivity".equals(localClassName)){
            switchToLocalMediaActivity();
        }else if("ui.LocalMediaActivity".equals(localClassName)){
            switchToNetMediaActivity();
        }else if("ui.NetMediaActivity".equals(localClassName)){
            switchToTvLiveActivity();
        }else if("ui.TvLiveActivity".equals(localClassName)){
            switchToMainActivity();
        }
    }

    if(velocityTracker != null){
        velocityTracker.recycle();//回收
        velocityTracker = null;
    }

    break;
}

return true;

}</pre>