android点击实现图片放大缩小

mainactivity类

package com.example.androidsvg;
 import android.app.Activity;
 import android.os.Bundle;
 import android.view.Menu;
 public class MainActivity extends Activity  {

 private static final double ZOOM_IN_SCALE = 1.25;//放大系数  
private static final double ZOOM_OUT_SCALE = 0.8;//缩小系数
 @SuppressWarnings("null")
 @Override
 protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(new Zoom(this));
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
   // Inflate the menu; this adds items to the action bar if it is present.
   getMenuInflater().inflate(R.menu.activity_main, menu);
   return true;
 }
 
}
 

Zoom类

package com.example.androidsvg;
 import android.view.View;
 import android.content.Context;  
 import android.graphics.Canvas;  
 import android.graphics.drawable.Drawable;  
 import android.view.KeyEvent;  
 public class Zoom extends View {
      private Drawable image;  
      private int zoomControler=20;  
      
      public Zoom(Context context){  
          super(context);  
          image=context.getResources().getDrawable(R.drawable.icon);  
          setFocusable(true);  
      }  
      
      @Override  
      protected void onDraw(Canvas canvas) {  
          // TODO Auto-generated method stub  
          super.onDraw(canvas);  
          //控制图像的宽度和高度
          image.setBounds((getWidth()/2)-zoomControler, (getHeight()/2)-zoomControler, (getWidth()/2)+zoomControler, (getHeight()/2)+zoomControler);  
          image.draw(canvas);  
      }  
      
      @Override  
      public boolean onKeyDown(int keyCode, KeyEvent event) {  
                
              if(keyCode==KeyEvent.KEYCODE_DPAD_UP)//放大 
                     zoomControler+=10;  
              
             if(keyCode==KeyEvent.KEYCODE_DPAD_DOWN) //缩小
                      zoomControler-=10;  
              
             if(zoomControler<10)  
                      zoomControler=10;  
                
              invalidate();  
              return true;  
      }  
 }