android VelocityTracker和 GestureDetector滑动监听工具类

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这次将两个滑动监听工具类，是方便我们判断当前滑动状态的。
VelocityTracker：速度监听，能够监听x轴和y轴上的分量速度。
GestureDetector：能够检测用户的单击，滑动，双击等行为。
使用例子如下：

public class MainActivity extends AppCompatActivity {    private MyView view;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        view = new MyView(this);        setContentView(view);    }}public class MyView extends View implements GestureDetector.OnGestureListener {    private int x,y,left,right,top,bottom,rawX,rawY,touchslop;    private int startx=0,starty=0,endx=0,endy=0;    private String state="";    private GestureDetector mGestureDetector ;    public MyView(Context context) {        super(context);        setFocusable(true);        touchslop= ViewConfiguration.get(context).getScaledTouchSlop();        mGestureDetector = new GestureDetector(this);        //解决长按后屏幕无法拖动，但是却无法判断长按的情况        mGestureDetector.setIsLongpressEnabled(false);    }    @Override protected void onDraw(Canvas canvas) {        Paint paint = new Paint();        paint.setColor(Color.BLACK);        paint.setTextSize(40);        canvas.drawText(" x:" + x + " y:" + y, 50, 100, paint);        super.onDraw(canvas);    }    @Override public boolean onKeyDown(int keyCode,KeyEvent event) {        return super.onKeyDown(keyCode, event);    }    @Override public boolean onKeyUp(int keyCode,KeyEvent event) {        return super.onKeyUp(keyCode, event);    }    @Override public boolean onTouchEvent(MotionEvent event) {        VelocityTracker velocityTracker = VelocityTracker.obtain();        velocityTracker.addMovement(event);        velocityTracker.computeCurrentVelocity(1000);        x=(int)velocityTracker.getXVelocity();        y=(int)velocityTracker.getYVelocity();        invalidate();        velocityTracker.clear();        velocityTracker.recycle();        mGestureDetector.onTouchEvent(event);        return true;    }    @Override    public boolean onDown(MotionEvent e) {        Log.v("zzw","onDown");        return false;    }    @Override    public void onShowPress(MotionEvent e) {        Log.v("zzw","onShowPress");    }    @Override    public boolean onSingleTapUp(MotionEvent e) {        Log.v("zzw","onSingleTapUp");        return false;    }    @Override    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {        Log.v("zzw","onScroll");        return false;    }    @Override    public void onLongPress(MotionEvent e) {        Log.v("zzw","onLongPress");    }    @Override    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {        Log.v("zzw","onFling");        return false;    }}

使用方法都很简单，mGestureDetector.setIsLongpressEnabled(false)这个命令慎用，因为它会导致GestureDetector无法判断长按状态。
还有就是 velocityTracker.clear();
velocityTracker.recycle();，记得用完VelocityTracker，要进行回收资源。
再见

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