//获取一个VelocityTracker对象, 用完后记得回收  //回收后代表你不需要使用了，系统将此对象在此分配到其他请求者  static public VelocityTracker obtain();  public void recycle();   //计算当前速度, 其中units是单位表示， 1代表px/毫秒, 1000代表px/秒, ..  //maxVelocity此次计算速度你想要的最大值  public void computeCurrentVelocity(int units, float maxVelocity);  //经过一次computeCurrentVelocity后你就可以用一下几个方法获取此次计算的值  //id是touch event触摸点的ID, 来为多点触控标识，有这个标识在计算时可以忽略  //其他触点干扰，当然干扰肯定是有的  public float getXVelocity();  public float getYVelocity();  public float getXVelocity(int id);  public float getYVelocity(int id);

public class VelocityTrackerTest extends Activity {      private TextView mInfo;      private VelocityTracker mVelocityTracker;      private int mMaxVelocity;      private int mPointerId;        @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);            mInfo = new TextView(this);          mInfo.setLines(4);          mInfo.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));          mInfo.setTextColor(Color.WHITE);            setContentView(mInfo);            mMaxVelocity = ViewConfiguration.get(this).getMaximumFlingVelocity();      }        @Override      public boolean onTouchEvent(MotionEvent event) {           if(null == mVelocityTracker) {              mVelocityTracker = VelocityTracker.obtain();          }          mVelocityTracker.addMovement(event);          final VelocityTracker verTracker = mVelocityTracker;          switch (event.getAction()) {              case MotionEvent.ACTION_DOWN:                  //求第一个触点的id， 此时可能有多个触点，但至少一个                  mPointerId = event.getPointerId(0);                  break;                case MotionEvent.ACTION_MOVE:                  //求伪瞬时速度                  verTracker.computeCurrentVelocity(1000, mMaxVelocity);                  float velocityX = verTracker.getXVelocity(mPointerId);                  float velocityY = verTracker.getYVelocity(mPointerId);                  recodeInfo(velocityX, velocityY);                  break;                case MotionEvent.ACTION_UP:              case MotionEvent.ACTION_CANCEL:                    if(null != mVelocityTracker) {                mVelocityTracker.clear();                mVelocityTracker.recycle();                mVelocityTracker = null;                    }                   break;                default:                  break;          }          return super.onTouchEvent(event);      }          private static final String sFormatStr = "velocityX=%f\nvelocityY=%f";        /**       * 记录当前速度       *       * @param velocityX x轴速度       * @param velocityY y轴速度       */      private void recodeInfo(final float velocityX, final float velocityY) {          final String info = String.format(sFormatStr, velocityX, velocityY);          mInfo.setText(info);      }  }