Android手势识别简单封装类

import android.content.Context;  
import android.util.DisplayMetrics;  
import android.view.GestureDetector;  
import android.view.GestureDetector.OnGestureListener;  
import android.view.MotionEvent;  
  
public class GestureHelper implements OnGestureListener {  
    private GestureDetector gesture_detector;  
    private int screen_width;  
    private OnFlingListener listener_onfling;  
      
    public static abstract class OnFlingListener {  
        public abstract void OnFlingLeft();  
        public abstract void OnFlingRight();  
    }  
      
    public GestureHelper(Context context) {  
        DisplayMetrics dm = context.getResources().getDisplayMetrics();  
        screen_width = dm.widthPixels;  
          
        gesture_detector = new GestureDetector(context, this);  
    }  
      
    public void setOnFlingListener(OnFlingListener listener) {  
        listener_onfling = listener;  
    }  
      
    public boolean onTouchEvent(MotionEvent event) {  
        return gesture_detector.onTouchEvent(event);  
    }  
      
    @Override  
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {  
        // 触发条件 ：  
        // X轴的坐标位移大于FLING_MIN_DISTANCE，且移动速度大于FLING_MIN_VELOCITY个像素/秒  
        final int FLING_MIN_DISTANCE = (int) (screen_width / 3.0f), FLING_MIN_VELOCITY = 200;  
        if (e1.getX() - e2.getX() > FLING_MIN_DISTANCE && Math.abs(velocityX) > FLING_MIN_VELOCITY) {  
            listener_onfling.OnFlingLeft();  
        } else if (e2.getX() - e1.getX() > FLING_MIN_DISTANCE && Math.abs(velocityX) > FLING_MIN_VELOCITY) {  
            listener_onfling.OnFlingRight();  
        }  
  
        return true;  
    }  
      
    @Override  
    public boolean onDown(MotionEvent e) {  
        return false;  
    }  
      
    @Override  
    public void onLongPress(MotionEvent e) {  
    }  
      
    @Override  
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX,  
            float distanceY) {  
        return false;  
    }  
      
    @Override  
    public void onShowPress(MotionEvent e) {  
    }  
      
    @Override  
    public boolean onSingleTapUp(MotionEvent e) {  
        return false;  
    }  
}  

public class TestActivity extends Activity {  
    private GestureHelper gh;  
      
    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_start);  
          
        gh = new GestureHelper(this);  
        gh.setOnFlingListener(new OnFlingListener() {  
            @Override  
            public void OnFlingLeft() {  
                //向左滑动  
            }  
              
            @Override  
            public void OnFlingRight() {  
                //向右滑动  
            }  
              
        });  
    }  
  
    @Override  
    public boolean onTouchEvent(MotionEvent event) {  
        return gh.onTouchEvent(event);  
    }  
      
}