Android学习（十六） 通过GestureDetector进行手势识别

<LinearLayout 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:orientation="vertical"
    tools:context=".MainActivity" >

    <ImageView
        android:id="@+id/img_girl"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@drawable/girl1" />

</LinearLayout>

package com.example.gesturedetectordemo;

import android.os.Bundle;
import android.app.Activity;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
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.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnTouchListener, OnGestureListener {

    //定义一个GestureDetector对象，用来处理各种手势，实现了OnTouchListener接口
    GestureDetector myGestureDetector;
    // 图片框
    ImageView imggirl;
    // 存放女孩图片的数组
    int[] girls = { R.drawable.girl1, R.drawable.girl2, R.drawable.girl3, R.drawable.girl4, R.drawable.girl5 };
    // 存放数组下标
    private int index;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        myGestureDetector = new GestureDetector(this);

        imggirl = (ImageView) findViewById(R.id.img_girl);

        //添加OnTouchListener事件
        imggirl.setOnTouchListener(this);
        //下面两个要记得设哦，不然就没法处理轻触以外的事件了，例如抛掷动作。
        imggirl.setLongClickable(true); 
        myGestureDetector.setIsLongpressEnabled(true); 
    }

    // 向后移动
    public void goNext() {
        index++;
        index = Math.abs(index % girls.length);
        imggirl.setImageResource(girls[index]);
    }

    // 向前移动
    public void goPrevious() {
        index--;
        index = Math.abs(index % girls.length);
        imggirl.setImageResource(girls[index]);
    }

    @Override  //处理用户的触碰请求
    public boolean onTouch(View v, MotionEvent event) {
        //转交给GestureDetector来处理
        myGestureDetector.onTouchEvent(event);
        return false;
    }

    @Override  //在按下动作时被调用 
    public boolean onDown(MotionEvent e) {
        //goNext();
        return false;
    }

    @Override  //按下动作松开被调用
    public void onShowPress(MotionEvent e) {
        // TODO Auto-generated method stub

    }

    @Override  //在弹起时被调用
    public boolean onSingleTapUp(MotionEvent e) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override  //在滚动时被调用
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override   //在长按时被调用
    public void onLongPress(MotionEvent e) {
        // TODO Auto-generated method stub

    }

    @Override  //在抛掷动作时被调用 
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        if (e1.getX() - e2.getX() > 50) {
            goNext();
            Toast.makeText(MainActivity.this, "从右向左拖拽" + index, Toast.LENGTH_SHORT).show();
        } else if (e2.getX() - e1.getX() > 50) {
            goPrevious();
            Toast.makeText(MainActivity.this, "从左向右拖拽" + index, Toast.LENGTH_SHORT).show();
        }
        return false;
    }

}