Image的放大,缩小(zoom in,zoom out)

Java代码 
package com.example;  
 
import android.content.Context;  
import android.graphics.Canvas;  
import android.graphics.drawable.Drawable;  
import android.view.KeyEvent;  
import android.view.View;  
 
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);  
 
    }  
 
    protected void onDraw(Canvas canvas) {  
        // TODO Auto-generated method stub  
        super.onDraw(canvas);  
        // here u can control the width and height of the images........ this  
        // line is very important  
        image.setBounds((getWidth() / 2) - zoomControler, (getHeight() / 2)  
                - zoomControler, (getWidth() / 2) + zoomControler,  
                (getHeight() / 2) + zoomControler);  
        image.draw(canvas);  
    }  
 
    public boolean onKeyDown(int keyCode, KeyEvent event) {  
 
        if (keyCode == KeyEvent.KEYCODE_DPAD_UP)// zoom in  
            zoomControler += 10;  
        if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN) // zoom out  
            zoomControler -= 10;  
        if (zoomControler < 10)  
            zoomControler = 10;  
 
        invalidate();  
        return true;  
    }  
}