MultiTouch————多点触控，伸缩图片，变换图片位置

 1     <?xml version="1.0" encoding="utf-8"?>  
 2     <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
 3         xmlns:tools="http://schemas.android.com/tools"  
 4         android:layout_width="match_parent"  
 5         android:layout_height="match_parent"  
 6         tools:context="com.cnwuth.mutiltouch.MainActivity">  
 7       
 8         <ImageView  
 9             android:id="@+id/iv"  
10             android:layout_width="match_parent"  
11             android:layout_height="match_parent"  
12             android:scaleType="matrix"  
13             android:src="@mipmap/ic_launcher"/>  
14       
15     </RelativeLayout>  

  1     package com.cnwuth.mutiltouch;  
  2       
  3     import android.graphics.Matrix;  
  4     import android.graphics.PointF;  
  5     import android.support.v7.app.AppCompatActivity;  
  6     import android.os.Bundle;  
  7     import android.view.MotionEvent;  
  8     import android.view.View;  
  9     import android.widget.ImageView;  
 10       
 11     public class MainActivity extends AppCompatActivity implements View.OnTouchListener{  
 12       
 13         private ImageView mImageView;  
 14       
 15         //缩放控制  
 16         private Matrix mMatrix = new Matrix();  
 17         private Matrix savedMatrix = new Matrix();  
 18       
 19         //不同状态的表示  
 20         private static final int NONE = 0;  
 21         private static final int DRAG = 1;  
 22         private static final int ZOOM = 2;  
 23         private int mode = NONE;  
 24       
 25         //定义第一个按下的点，两只接触点的重点，以及出事的两指按下的距离:  
 26         private PointF startPoint = new PointF();  
 27         private PointF midPoint = new PointF();  
 28         private float oriDis = 1f;  
 29       
 30         @Override  
 31         protected void onCreate(Bundle savedInstanceState) {  
 32             super.onCreate(savedInstanceState);  
 33             setContentView(R.layout.activity_main);  
 34             mImageView = (ImageView) findViewById(R.id.iv);  
 35             mImageView.setOnTouchListener(this);  
 36         }  
 37       
 38         @Override  
 39         public boolean onTouch(View v, MotionEvent event) {  
 40             ImageView view = (ImageView) v;  
 41             switch (event.getAction() & MotionEvent.ACTION_MASK)  
 42             {  
 43                 //单指  
 44                 case MotionEvent.ACTION_DOWN:  
 45                     mMatrix.set(view.getImageMatrix());  
 46                     savedMatrix.set(mMatrix);  
 47                     startPoint.set(event.getX(),event.getY());  
 48                     mode = DRAG;  
 49                     break;  
 50                 //双指  
 51                 case MotionEvent.ACTION_POINTER_DOWN:  
 52                     oriDis = distance(event);  
 53                     if (oriDis > 10f)  
 54                     {  
 55                         savedMatrix.set(mMatrix);  
 56                         midPoint = middle(event);  
 57                         mode = ZOOM;  
 58                     }  
 59                     break;  
 60                 //手指放开  
 61                 case MotionEvent.ACTION_UP:  
 62                 case MotionEvent.ACTION_POINTER_UP:  
 63                     mode = NONE;  
 64                     break;  
 65                 //单指滑动事件  
 66                 case MotionEvent.ACTION_MOVE:  
 67                     if (mode == DRAG)  
 68                     {  
 69                         //是一个手指拖动  
 70                         mMatrix.set(savedMatrix);  
 71                         mMatrix.postTranslate(event.getX() - startPoint.x , event.getY() - startPoint.y);  
 72                     }  
 73                     else if (mode == ZOOM)  
 74                     {  
 75                         //两个手指滑动  
 76                         float newDist = distance(event);  
 77                         if (newDist > 10f)  
 78                         {  
 79                             mMatrix.set(savedMatrix);  
 80                             float scale = newDist / oriDis;  
 81                             mMatrix.postScale(scale , scale , midPoint.x , midPoint.y);  
 82                         }  
 83                     }  
 84                     break;  
 85             }  
 86             //设置ImageView的Matrix  
 87             view.setImageMatrix(mMatrix);  
 88             return true;  
 89         }  
 90       
 91         //计算两个触摸点之间的距离  
 92         private float distance(MotionEvent event) {  
 93             float x = event.getX(0) - event.getX(1);  
 94             float y = event.getY(0) - event.getY(1);  
 95             return (float) Math.sqrt(x * x + y * y);  
 96         }  
 97       
 98         //计算两个触摸点的中点  
 99         private PointF middle(MotionEvent event){  
100             float x = event.getX(0) + event.getX(1);  
101             float y = event.getY(0) + event.getY(1);  
102             return new PointF(x / 2 , y / 2);  
103         }  
104     }