继承ImageView 实现了多点触碰的拖动和缩放

public class TouchView extends ImageView {


    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);
    }
    /**
     * 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);               
    }