Android GestureDetector实现手势滑动效果

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context=".MainActivity"  
 
  <ImageView
    android:id="@+id/ivShow"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:src="@drawable/ic_launcher" / 
 
</RelativeLayout 

package com.example.gesturedetector;
 
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
import android.widget.Toast;
 
public class MainActivity extends Activity {
 
 private ImageView ivShow;
 private GestureDetector gestureDetector;
 
 class myGestureListener extends SimpleOnGestureListener{
 @Override
 /*识别滑动，第一个参数为刚开始事件，第二个参数为结束事件*/
 public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
  float velocityY) {
  if(e1.getX()-e2.getX() 50){
  Toast.makeText(MainActivity.this,"从右往左滑动"+(e1.getX()-e2.getX()),Toast.LENGTH_LONG).show();
  }else if(e2.getX()-e1.getX() 50){
  Toast.makeText(MainActivity.this,"从左往右滑动"+(e2.getX()-e1.getX()),Toast.LENGTH_LONG).show();
  }
  return super.onFling(e1, e2, velocityX, velocityY);
 }
 }
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 
 gestureDetector=new GestureDetector(MainActivity.this,new myGestureListener());
 
 ivShow=(ImageView) findViewById(R.id.ivShow);
 ivShow.setLongClickable(true); //view必须设置为true，否则手势识别无法正确工作
 ivShow.setOnTouchListener(new OnTouchListener() {
 
  
  /*可以捕获到触摸屏幕发生的Event事件*/
  @Override
  public boolean onTouch(View arg0, MotionEvent event) {
  gestureDetector.onTouchEvent(event);//转发
  return false;
  }
 });
 }
}