自定义圆形图片实现多点触控放大缩小和拖动

package com.bwie.view;

import android.content.Context;   
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.Bitmap.Config;
import android.graphics.PorterDuff.Mode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.FloatMath;   
import android.view.MotionEvent;   
import android.view.animation.TranslateAnimation;   
import android.widget.ImageView;   
/**  
 * 继承ImageView 实现了多点触碰的拖动和缩放  
 * @author lihua    
 */   
public class TouchView extends ImageView {
    
    private Paint p;
    static final int NONE = 0;   
    static final int DRAG = 1;     //拖动中    
    static final int ZOOM = 2;     //缩放中    
    static final int BIGGER = 3;   //放大ing    
    static final int SMALLER = 4;  //缩小ing    
    private int mode = NONE;       //当前的事件     
   
    private float beforeLenght;   //两触点距离    
    private float afterLenght;    //两触点距离    
    private float scale = 0.04f;  //缩放的比例 X Y方向都是这个值 越大缩放的越快    
      
    private int screenW;   
    private int screenH;   
       
    /*处理拖动 变量 */   
    private int start_x;   
    private int start_y;   
    private int stop_x ;   
    private int stop_y ;   
       
    private TranslateAnimation trans; //处理超出边界的动画    
    
    /**
     * 默认构造函数
     * @param context
     */
    public TouchView(Context context){
        super(context);
    }
    /**
     * 该构造方法在静态引入XML文件中是必须的
     * @param context
     * @param paramAttributeSet
     */
    public TouchView(Context context,AttributeSet paramAttributeSet){
        super(context,paramAttributeSet);
         // TODO Auto-generated constructor stub
        p = new Paint();
    }
    
    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        Drawable drawable = getDrawable();
        if(null!=drawable){
            Bitmap bitmap = ((BitmapDrawable)drawable).getBitmap();
            Bitmap b = getCircleBitmap(bitmap, 14);
            final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
            final Rect rectDest = new Rect(0, 0, getWidth(), getHeight());
            p.reset();
            canvas.drawBitmap(b, rectSrc,rectDest, p);
            
        }else{
            super.onDraw(canvas);
        }
        
    } 

    private Bitmap getCircleBitmap(Bitmap bitmap,int pixels){
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
        Canvas canvas = new Canvas(output);
        final int color = 0xff424242;
        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        p.setAntiAlias(true);
        int x = bitmap.getWidth();
        canvas.drawCircle(x/2, x/2, x/2, p);
        p.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, p);
        return output;
    }
    /**
     * 该构造函数在动态创建时，指定图片的初始高宽
     * @param context
     * @param w
     * @param h
     */
    public TouchView(Context context,int w,int h) {   
        super(context);   
        this.setPadding(0, 0, 0, 0);   
        screenW = w;   
        screenH = h;   
    }   
       
    /**  
     * 就算两点间的距离  
     */   
    private float spacing(MotionEvent event) {   
        float x = event.getX(0) - event.getX(1);   
        float y = event.getY(0) - event.getY(1);   
        return FloatMath.sqrt(x * x + y * y);   
    }   
       
    /**  
     * 处理触碰..  
     */   
    @Override   
    public boolean onTouchEvent(MotionEvent event)   
    {      
        switch (event.getAction() & MotionEvent.ACTION_MASK) {   
        case MotionEvent.ACTION_DOWN:   
                mode = DRAG;   
                stop_x = (int) event.getRawX();   
                stop_y = (int) event.getRawY();   
                start_x = (int) event.getX();   
                start_y = stop_y - this.getTop();   
                if(event.getPointerCount()==2)   
                    beforeLenght = spacing(event);   
                break;   
        case MotionEvent.ACTION_POINTER_DOWN:   
                if (spacing(event) > 10f) {   
                        mode = ZOOM;   
                        beforeLenght = spacing(event);   
                }   
                break;   
        case MotionEvent.ACTION_UP:   
            /*判断是否超出范围     并处理*/   
                int disX = 0;   
                int disY = 0;   
                if(getHeight()<=screenH || this.getTop()<0)   
                {   
                    if(this.getTop()<0 )   
                    {   
                        int dis = getTop();   
                        this.layout(this.getLeft(), 0, this.getRight(), 0 + this.getHeight());   
                        disY = dis - getTop();   
                    }   
                    else if(this.getBottom()>screenH)   
                    {   
                        disY = getHeight()- screenH+getTop();   
                        this.layout(this.getLeft(), screenH-getHeight(), this.getRight(), screenH);   
                    }   
                }   
                if(getWidth()<=screenW)   
                {   
                    if(this.getLeft()<0)   
                    {   
                        disX = getLeft();   
                        this.layout(0, this.getTop(), 0+getWidth(), this.getBottom());   
                    }   
                    else if(this.getRight()>screenW)   
                    {   
                        disX = getWidth()-screenW+getLeft();   
                        this.layout(screenW-getWidth(), this.getTop(), screenW, this.getBottom());   
                    }   
                }   
                if(disX!=0 || disY!=0)   
                {   
                    trans = new TranslateAnimation(disX, 0, disY, 0);   
                    trans.setDuration(500);   
                    this.startAnimation(trans);   
                }   
                mode = NONE;   
                break;   
        case MotionEvent.ACTION_POINTER_UP:   
                mode = NONE;   
                break;   
        case MotionEvent.ACTION_MOVE:   
                /*处理拖动*/   
                if (mode == DRAG) {   
                    if(Math.abs(stop_x-start_x-getLeft())<88 && Math.abs(stop_y - start_y-getTop())<85)   
                    {   
                        this.setPosition(stop_x - start_x, stop_y - start_y, stop_x + this.getWidth() - start_x, stop_y - start_y + this.getHeight());                 
                        stop_x = (int) event.getRawX();   
                        stop_y = (int) event.getRawY();   
                    }   
                }    
                /*处理缩放*/   
                else if (mode == ZOOM) {   
                    if(spacing(event)>10f)   
                    {   
                        afterLenght = spacing(event);   
                        float gapLenght = afterLenght - beforeLenght;                        
                        if(gapLenght == 0) {     
                           break;   
                        }   
                        else if(Math.abs(gapLenght)>5f)   
                        {   
                            if(gapLenght>0) {  
                                
                                this.setScale(scale,BIGGER);      
                            }else {     
                                this.setScale(scale,SMALLER);      
                            }                                
                            beforeLenght = afterLenght;    
                        }   
                    }   
                }   
                break;   
        }   
        return true;       
    } 
    
    
    /**  
     * 实现处理缩放  
     */   
    private void setScale(float temp,int flag) {      
           
        if(flag==BIGGER) {      
            this.setFrame(this.getLeft()-(int)(temp*this.getWidth()),       
                          this.getTop()-(int)(temp*this.getHeight()),       
                          this.getRight()+(int)(temp*this.getWidth()),       
                          this.getBottom()+(int)(temp*this.getHeight()));         
        }else if(flag==SMALLER){      
            this.setFrame(this.getLeft()+(int)(temp*this.getWidth()),       
                          this.getTop()+(int)(temp*this.getHeight()),       
                          this.getRight()-(int)(temp*this.getWidth()),       
                          this.getBottom()-(int)(temp*this.getHeight()));      
        }      
    }   
       
    /**  
     * 实现处理拖动  
     */   
    private void setPosition(int left,int top,int right,int bottom) {     
        this.layout(left,top,right,bottom);                
    }   
}

<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"
    android:background="@android:color/black"
    >

    <com.bwie.view.TouchView
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:src="@drawable/aefwfaw"
        android:scaleType="matrix"
       android:id="@+id/img" />

</LinearLayout>