Android编程使用GestureDetector实现简单手势监听与处理的方法

package com.example.gesturedetector;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
   ImageView img;
  GestureDetector myGestureDetector;
  class myGestureListener extends GestureDetector.SimpleOnGestureListener {
    @Override
    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",Toast.LENGTH_LONG).show();
      }else if(e2.getX()-e1.getX()>50){
        Toast.makeText(MainActivity.this,"从左往右滑动",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);
    img = (ImageView) findViewById(R.id.img);
    myGestureDetector = new GestureDetector(new myGestureListener());
    img.setOnTouchListener(new View.OnTouchListener() {
      //motionEvent可以捕捉我们触摸屏幕的event事件
      @Override
      public boolean onTouch(View view, MotionEvent motionEvent) {
        myGestureDetector.onTouchEvent(motionEvent);
        return true;
      }
    });
  }
}

<?xml version="1.0" encoding="utf-8"?>
<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"
  android:paddingBottom="@dimen/activity_vertical_margin"
  android:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  tools:context="com.example.gesturedetector.MainActivity">
  <ImageView
    android:id="@+id/img"
    android:src="@mipmap/ic_launcher"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
</RelativeLayout>