android ImagView缩放方法之一(Bitmap)

 package com.myandroid.test;

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

 public class AlterImageSize extends Activity {
     private ImageView imageView;
     private Button bt_bigger;
     private Button bt_smaller;
     private RelativeLayout layout;          //容器
     private Bitmap bmp;                     //bitmap图片对象
     private int primaryWidth;               //原图片宽
     private int primaryHeight;              //原图片高
     private double scaleWidth, scaleHeight; //高宽比例


     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);

         //初始化
         getWidget();
     }

     /**
      * 获取控件对象并初始化
      */
     private void getWidget() {

         imageView = (ImageView)findViewById(R.id.imageView);
         layout = (RelativeLayout)findViewById(R.id.relativeLayout);
         bt_bigger = (Button)findViewById(R.id.bt_bigger);
         bt_smaller = (Button)findViewById(R.id.bt_smaller);

         //创建BitMap对象，用于显示图片
         bmp = BitmapFactory.decodeResource(this.getResources(), R.drawable.butterfly);
         //原始大小
         primaryWidth = bmp.getWidth();
         primaryHeight = bmp.getHeight();
         //初始比例为1
         scaleWidth = scaleHeight = 1;

         imageView.setImageBitmap(bmp);

         bt_bigger.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 // TODO Auto-generated method stub
                 scale(1.25, 1.25);
             }
         });

         bt_smaller.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {
                 // TODO Auto-generated method stub
                 scale(0.8, 0.8);
             }
         });

     }

     /**
      * 缩放
      */
     private void scale(double  scale_width, double scale_height) {

         //这种方法，有点不好是：如果图片大小超出屏幕会报错。
         if((scale_width > 1 && scaleWidth * primaryWidth >= getWindowManager().getDefaultDisplay().getWidth())
                 || (scale_width > 1 && scale_height * primaryHeight >= getWindowManager().getDefaultDisplay().getHeight())){
             bt_bigger.setEnabled(false);
         }else {
             bt_bigger.setEnabled(true);
         }



         scaleWidth = scaleWidth * scale_width;  //缩放到原来的*倍
         scaleHeight = scaleHeight * scale_height;

         Matrix matrix = new Matrix();   //矩阵，用于图片比例缩放
         matrix.postScale((float)scaleWidth, (float)scaleHeight);    //设置高宽比例（三维矩阵）

         //缩放后的BitMap
         Bitmap newBmp = Bitmap.createBitmap(bmp, 0, 0, primaryWidth, primaryHeight, matrix, true);

         //重新设置BitMap
         imageView.setImageBitmap(newBmp);

     }
 }

xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center_horizontal" >

    <ScrollView
        android:id="@+id/scroll"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:layout_gravity="center" >

        <HorizontalScrollView
            android:id="@+id/hs"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal" >

            <ImageView
                android:id="@+id/imageView"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:gravity="center" />
        </HorizontalScrollView>
    </ScrollView>

    <LinearLayout
        android:id="@+id/linearLayout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:gravity="center" >

        <Button
            android:id="@+id/bt_smaller"
            android:layout_width="100px"
            android:layout_height="50px"
            android:text="缩小" >
        </Button>

        <Button
            android:id="@+id/bt_bigger"
            android:layout_width="100px"
            android:layout_height="50px"
            android:text="放大" >
        </Button>
    </LinearLayout>

</RelativeLayout>