Android手势识别容易封装类

今天在做一个项目时用到了简单的手势功能(向左，向右滑切屏)，于是简单地封装了下

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);	}	}