ImageView 控制图片大小

package com.practice.imageviewpic;
import android.app.Activity;
import android.content.Context;
import android.graphics.*;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.view.MotionEvent;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
public class ImageViewPic extends Activity {
 
 /*
  * 利用多点触控来控制ImageView中图像的放大与缩小
  * 手指控制图片移动
  */
 
 private MyImageView imageView;
 private Bitmap bitmap;
 
 //两点触屏后之间的长度
 private float beforeLenght;
 private float afterLenght;
 
 //单点移动的先后坐标值
 private float afterX,afterY;
 private float beforeX,beforeY;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        findView();
        setContentView(imageView);
        config();
    }
   
    private void findView() {
     imageView = new MyImageView(this);
     //得到图片
     bitmap = ((BitmapDrawable)getResources().getDrawable(R.drawable.xing)).getBitmap();
    }
   
    private void config() {
     //设置imageView的显示图片
     imageView.setImageBitmap(bitmap);
     //设置图片填充ImageView
     imageView.setScaleType(ScaleType.FIT_XY);
    }
   
    //建立一个本身的ImageView类
 class MyImageView extends ImageView {
  private float scale = 0.1f;
  
  public MyImageView(Context context) {
   super(context);
  }
  //用来设置ImageView的位置
  private void setLocation(int x,int y) {
   this.setFrame(this.getLeft()+x, this.getTop()+y, this.getRight()+x, this.getBottom()+y);
  }
  
  
  /*
   * 用来放大缩小ImageView
   * 由于图片是填充ImageView的，因此也就有放大缩小图片的效果
   * flag为0是放大图片，为1是小于图片
   */
  private void setScale(float temp,int flag) {
   
   if(flag==0) {
    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 {
    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()));
   }
  }
  
  //绘制边框  
   @Override
       protected void onDraw(Canvas canvas) {
           super.onDraw(canvas);   
           Rect rec=canvas.getClipBounds();
           rec.bottom--;
           rec.right--;
           Paint paint=new Paint();
           paint.setColor(Color.RED);
           paint.setStyle(Paint.Style.STROKE);
           canvas.drawRect(rec, paint);
       }
  
  
  /* 让图片跟随手指触屏的位置移动
   * beforeX、Y是用来保存前一位置的坐标
   * afterX、Y是用来保存当前位置的坐标
   * 它们的差值就是ImageView各坐标的增长或减小值
   */
  public void moveWithFinger(MotionEvent event) {
   
   switch(event.getAction()) {
   
   case MotionEvent.ACTION_DOWN:
    beforeX = event.getX();
    beforeY = event.getY();
    break;
   case MotionEvent.ACTION_MOVE:
    afterX = event.getX();
    afterY = event.getY();
    
    this.setLocation((int)(afterX-beforeX),(int)(afterY-beforeY));
    
    beforeX = afterX;
    beforeY = afterY;
    break;
    
   case MotionEvent.ACTION_UP:
    break;
   }
  }
  
  /*
   * 经过多点触屏放大或缩小图像
   * beforeLenght用来保存前一时间两点之间的距离
   * afterLenght用来保存当前时间两点之间的距离
   */
  public void scaleWithFinger(MotionEvent event) {
   float moveX = event.getX(1) - event.getX(0);
   float moveY = event.getY(1) - event.getY(0);
   
   switch(event.getAction()) {
   case MotionEvent.ACTION_DOWN:
    beforeLenght = (float) Math.sqrt( (moveX*moveX) + (moveY*moveY) );
    break;
   case MotionEvent.ACTION_MOVE:
    //获得两个点之间的长度
    afterLenght = (float) Math.sqrt( (moveX*moveX) + (moveY*moveY) );
    
    float gapLenght = afterLenght - beforeLenght;
    
    if(gapLenght == 0) {
     break;
    }
    
    //若是当前时间两点距离大于前一时间两点距离，则传0，不然传1
    if(gapLenght>0) {
     this.setScale(scale,0);
    }else {
     this.setScale(scale,1);
    }
    
    beforeLenght = afterLenght;
    break;
   }
  }
 
    }
 
   //这里来监听屏幕触控时间
   @Override
 public boolean onTouchEvent(MotionEvent event) {
   
    /*
     * 断定用户是否触摸到了图片
     * 若是是单点触摸则调用控制图片移动的方法
     * 若是是2点触控则调用控制图片大小的方法
     */
     if(event.getY() > imageView.getTop() && event.getY() < imageView.getBottom()
       && event.getX() > imageView.getLeft() && event.getX() < imageView.getRight()) {
      if(event.getPointerCount() == 2) {
       imageView.scaleWithFinger(event);
      }else if(event.getPointerCount() == 1) {
       imageView.moveWithFinger(event);
      }      
     }
  return true;
 }  
   
}