1、    //首先获得VelocityTracker的实例/*** obtain()的方法介绍* Retrieve a new VelocityTracker object to watch the velocity of a motion. * Be sure to call recycle() when done. You should generally only maintain * an active object while tracking a movement, so that the VelocityTracker * can be re-used elsewhere.* 翻译：* 得到一个速率追踪者对象去检测一个事件的速率。确认在完成的时候调用recycle()方法。* 一般情况下，你只要维持一个活动的速率追踪者对象去追踪一个事件，那么，这个速率追踪者* 可以在别的地方重复使用。*/VelocityTracker mVelocityTracker = null;if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}2、    //假设有一个事件event,将事件加入到VelocityTracker类实例中 /*** addMovement (MotionEvent event)方法介绍* Add a user's movement to the tracker. You should call this for the initial * ACTION_DOWN, the following ACTION_MOVE events that you receive,*  and the final ACTION_UP. You can, however, call this for whichever events *  you desire.*  翻译：向速率追踪者中加入一个用户的移动事件，你应该最先在ACTION_DOWN调用这个方法，*  然后在你接受的ACTION_MOVE，最后是ACTION_UP。你可以为任何一个你愿意的事件调用该方法*/mVelocityTracker.addMovement(event);3、//判断当事件MotionEvent.ACTION_UP的时候，调用下面的方法/*** public void computeCurrentVelocity (int units, float maxVelocity)方法介绍：* Compute the current velocity based on the points that have been* collected. Only call this when you actually want to retrieve velocity* information, as it is relatively expensive. You can then retrieve the* velocity with {@link #getXVelocity()} and {@link #getYVelocity()}.* * @param units*            The units you would like the velocity in. A value of 1*            provides pixels per millisecond, 1000 provides pixels per*            second, etc.* @param maxVelocity*            The maximum velocity that can be computed by this method. This*            value must be declared in the same unit as the units*            parameter. This value must be positive.* 翻译：基于你所收集到的点计算当前的速率。       当你确定要获得速率信息的时候，在调用该方法，* 因为使用它需要消耗很大的性能。然后，你可以通过getXVelocity()和getYVelocity()获得横向和竖向的速率。* * 参数：units  你想要指定的得到的速度单位，如果值为1，代表1毫秒运动了多少像素。如果值为1000，代表* 1秒内运动了多少像素。* * 参数：maxVelocity  该方法所能得到的最大速度，这个速度必须和你指定的units使用同样的单位，而且* 必须是整数。（也就是，你指定一个速度的最大值，如果计算超过这个最大值，就使用这个最大值，否则，使用计算的的结果）* * public void computeCurrentVelocity (int units)方法介绍* 这个方法与上面的方法没什么差别，就是在maxVelocity上，他会自动使用Float.MAX_VALUE常量*/mVelocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);    4、//然后调用getXVelocity ()、getXVelocity (int id)、getYVelocity ()、getYVelocity (int id)得到速率/*** 调用这几个方法之前，必须确定你之前调用了computeCurrentVelocity方法。* 参数 id   代表返回指定触点的速率*/Log.i("test", mVelocityTracker.getXVelocity() + "");Log.i("test", mVelocityTracker.getYVelocity() + "");

public class GestureTestActivity extends Activity {private GestureDetector gestureDetector;private VelocityTracker mVelocityTracker = null;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);gestureDetector = new GestureDetector(this, new GestureListener());gestureDetector.setIsLongpressEnabled(false);}@Overridepublic boolean onTouchEvent(MotionEvent event) {int action = event.getAction();if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}mVelocityTracker.addMovement(event);switch (action) {case MotionEvent.ACTION_DOWN:Log.i("test", "ACTION_DOWN");break;case MotionEvent.ACTION_MOVE:// 移动的时候Log.i("test", "ACTION_MOVE");break;case MotionEvent.ACTION_UP:mVelocityTracker.computeCurrentVelocity(1000);Log.i("test", "ACTION_UP");Log.i("11111", mVelocityTracker.getXVelocity(0) + "");Log.i("11111", mVelocityTracker.getYVelocity(0) + "");break;}return gestureDetector.onTouchEvent(event);}// 继承于SimpleOnGestureListener，实现所有事件监听方法private class GestureListener extends SimpleOnGestureListener {@Overridepublic boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {Log.i("test", "onFling  -----------------------");Log.i("2222", velocityX + "");Log.i("2222", velocityY + "");return super.onFling(e1, e2, velocityX, velocityY);}}@Overrideprotected void onDestroy() {super.onDestroy();//释放
        mVelocityTracker.recycle();mVelocityTracker=null;}
}