android图片放大 缩小 旋转

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;

public class ChangePicture extends Activity {

     private ImageView mImageView;
     private Button btn1,btn2,btn3;
     private LinearLayout layout1;
     private Bitmap bmp;
     private int id=0;
     private int displayWidth,displayHeight;
     private float scaleWidth=1,scaleHeight=1;
     private int degree = 30;
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.picture);
            //取得屏幕分辨率
            DisplayMetrics dm=new DisplayMetrics();
            getWindowManager().getDefaultDisplay().getMetrics(dm);
            displayWidth=dm.widthPixels;
            displayHeight=dm.heightPixels-80;
           
            System.out.println(displayWidth +","+displayHeight);
          
            bmp=BitmapFactory.decodeResource(this.getResources(),R.drawable.pic);
            layout1=(LinearLayout)findViewById(R.id.layout1);
            mImageView=(ImageView)findViewById(R.id.myImageView);
            btn1=(Button)findViewById(R.id.myButton1);
            btn1.setOnClickListener(new OnClickListener(){
             public void onClick(View v){
              small();
             }
            });
            btn2=(Button)findViewById(R.id.myButton2);
            btn2.setOnClickListener(new OnClickListener(){
             public void onClick(View v){
              big();
             }
            });
            btn3 = (Button)findViewById(R.id.myButton3);
            btn3.setOnClickListener(new OnClickListener() {
               
                @Override
                public void onClick(View v) {
                    circle();
                   
                }
            });
        }
        private void small(){
         //获得Bitmap的高和宽
         int bmpWidth=bmp.getWidth();
         int bmpHeight=bmp.getHeight();
         //设置缩小比例
         double scale=0.8;
         //计算出这次要缩小的比例
         scaleWidth=(float)(scaleWidth*scale);
         scaleHeight=(float)(scaleHeight*scale);
         //产生resize后的Bitmap对象
         Matrix matrix=new Matrix();
         matrix.postScale(scaleWidth, scaleHeight);
         Bitmap resizeBmp=Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight, matrix, true);
         if(id==0){
          layout1.removeView(mImageView);
         }
         else{
          layout1.removeView((ImageView)findViewById(id));
         
         }
         id++;
         ImageView imageView=new ImageView(this);
         imageView.setId(id);
         imageView.setImageBitmap(resizeBmp);
         layout1.addView(imageView);
         setContentView(layout1);
         btn2.setEnabled(true);
        }
        private void big(){
         //获得Bitmap的高和宽
         int bmpWidth=bmp.getWidth();
         int bmpHeight=bmp.getHeight();
         //设置缩小比例
         double scale=1.25;
         //计算出这次要缩小的比例
         scaleWidth=(float)(scaleWidth*scale);
         scaleHeight=(float)(scaleHeight*scale);
         //产生resize后的Bitmap对象
         Matrix matrix=new Matrix();
         matrix.postScale(scaleWidth, scaleHeight);
         Bitmap resizeBmp=Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight, matrix, true);
         if(id==0){
          layout1.removeView(mImageView);
         }
         else{
          layout1.removeView((ImageView)findViewById(id));
         
         }
         id++;
         ImageView imageView=new ImageView(this);
         imageView.setId(id);
         imageView.setImageBitmap(resizeBmp);
         layout1.addView(imageView);
         setContentView(layout1);
         if(scaleWidth*scale*bmpWidth>displayWidth||scaleHeight*scale*scaleHeight>displayHeight){
          btn2.setEnabled(false);
         }
        }
        //旋转
        private void circle() {
            //位图的旋转
             //获得Bitmap的高和宽
             int bmpWidth=bmp.getWidth();
             int bmpHeight=bmp.getHeight();
          
             //产生resize后的Bitmap对象
             Matrix matrix=new Matrix();
             matrix.postRotate(degree);
             degree += 30;
             Bitmap resizeBmp=Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight, matrix, true);
//            int id = 0;
             if(id==0){
              layout1.removeView(mImageView);
             }
             else{
              layout1.removeView((ImageView)findViewById(id));
             
             }
           
             id++;
             ImageView imageView=new ImageView(this);
             imageView.setId(id);
             imageView.setImageBitmap(resizeBmp);
             layout1.addView(imageView);
             setContentView(layout1);
           
        }

    }




//xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:id="@+id/layout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android"
  >

   <LinearLayout
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
   
    >
     <Button
      android:id="@+id/myButton1"
      android:layout_width="90px"
      android:layout_height="60px"
      android:text="缩小"
      android:textSize="18sp"
    >
    </Button>
    <Button
      android:id="@+id/myButton2"
      android:layout_width="90px"
      android:layout_height="60px"
      android:text="放大"
      android:textSize="18sp"
    >
    </Button>
    <Button
     android:id="@+id/myButton3"
      android:layout_width="90px"
      android:layout_height="60px"
      android:text="旋转"
      android:textSize="18sp"
   
   
   
    />
   
   
   
    </LinearLayout>
    <ImageView
      android:id="@+id/myImageView"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:src="@drawable/pic"
      android:layout_x="0px"
      android:layout_y="0px"
    >
    </ImageView>
  
  
  </LinearLayout>