zoom in or zoom out a picture 缩小，放大图片

android demo for zoom in or zoom out picture

package net.gng.lgq;

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

public class MainActivity extends Activity {
	
	private ImageView mImageView;
	private Button zoomInBtn;
	private Button zoomOutBtn;
	private RelativeLayout layout;
	
	private Bitmap bmp;
	int id = 0;
	private int displayWidth;
	private int displayHeight;
	private float scaleWidth = 1;
	private float scaleHeight = 1;
	

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
      //取得屏幕分辨率
        DisplayMetrics dm = new DisplayMetrics();  
        getWindowManager().getDefaultDisplay().getMetrics(dm);
        displayWidth = dm.widthPixels;
        displayHeight = dm.heightPixels -100;
        
        //初始化
        bmp = BitmapFactory.decodeResource(getResources(), R.drawable.pic);
        mImageView = (ImageView)findViewById(R.id.imageView);
        zoomInBtn = (Button)findViewById(R.id.zoom_in_btn);
        zoomOutBtn = (Button)findViewById(R.id.zoom_out_btn);
        layout = (RelativeLayout)findViewById(R.id.layout);
        
        zoomInBtn.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				zoomIn();
				
			}
		});
        
        zoomOutBtn.setOnClickListener(new OnClickListener() {
			
			@Override
			public void onClick(View v) {
				zoomOut();
				
			}
		});
    }

   //放大
    private void zoomIn()
    {
    	int bmpWidth = bmp.getWidth();
    	int bmpHeight = bmp.getHeight();
    	//放大比例
    	double scale = 1.25;
    	scaleWidth = (float) (scaleWidth * scale);
    	scaleHeight = (float) (scaleHeight * scale);
    	//产生resize后的bitmap
    	Matrix matrix = new Matrix();
    	matrix.postScale(scaleWidth, scaleHeight);
    	Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth,bmpHeight,matrix,true);
    	
    	if(id == 0)
    	{
    		layout.removeView(mImageView);
    	}
    	else
    	{
    		layout.removeView((ImageView)findViewById(id));
    	}
    	id++;
    	ImageView imageView =  new ImageView(this);
    	imageView.setId(id);
    	imageView.setImageBitmap(resizeBmp);
    	layout.addView(imageView);
    	setContentView(layout);
    	
    	if(scaleWidth*scale*bmpWidth > displayWidth ||
    			scaleHeight*scale*bmpHeight > displayHeight)
    	{
    		zoomInBtn.setEnabled(false);
    	}
    }
    
    //缩小
    private void zoomOut()
    {
    	int bmpWidth = bmp.getWidth();
    	int bmpHeight = bmp.getHeight();
    	//缩小比例
    	double scale = 0.8;
    	scaleWidth = (float) (scaleWidth * scale);
    	scaleHeight = (float) (scaleHeight * scale);
    	//产生resize后的bitmap
    	Matrix matrix = new Matrix();
    	matrix.postScale(scaleWidth, scaleHeight);
    	Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth,bmpHeight,matrix,true);
    	
    	if(id == 0)
    	{
    		layout.removeView(mImageView);
    	}
    	else
    	{
    		layout.removeView((ImageView)findViewById(id));
    	}
    	id++;
    	ImageView imageView =  new ImageView(this);
    	imageView.setId(id);
    	imageView.setImageBitmap(resizeBmp);
    	layout.addView(imageView);
    	setContentView(layout);
    	
    	zoomInBtn.setEnabled(true);
    }
}

Nice but how to concave and convex an imageview image using button setonclickedlistener
Tnks in advance