Android放大缩小显示图片

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;
import android.widget.Toast;

public class MainActivity extends Activity
{
private ImageView photoView;
private Button smallButton,bigButton,turnButton;
private LinearLayout photoLayout;
private int displayWidth, displayHeight;
private float scaleWidth = 1, scaleHeight = 1;
private int degree = 30;
private Bitmap bmp;
private int id=0;

private void showPhoto()
{
photoView.setImageBitmap(bmp);
//BufferedInputStream bis;
//bis = new BufferedInputStream(getAssets().open(studentId + ".jpg"));
//bmp = BitmapFactory.decodeStream(bis);
bmp = BitmapFactory.decodeResource(this.getResources(),R.drawable.ic_launcher);//设置默认照片
photoView.setImageBitmap(bmp);
}
private void findViews()
{
photoView = (ImageView) findViewById(R.id.photoView);
photoLayout = (LinearLayout) findViewById(R.id.photoLayout);
smallButton = (Button) findViewById(R.id.smallButton);
bigButton = (Button) findViewById(R.id.bigButton);
turnButton = (Button) findViewById(R.id.turnButton);
}
private OnClickListener buttonClickListener=new OnClickListener()
{
public void onClick(View v)
{
switch(v.getId())
{
case R.id.smallButton:small();
break;
case R.id.bigButton: big();
break;
case R.id.turnButton: turn();
break;
}
}
};
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViews();

showPhoto();//显示照片

DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
displayWidth = dm.widthPixels;
displayHeight = dm.heightPixels - 80;

System.out.println(displayWidth + "," + displayHeight);

smallButton.setOnClickListener(buttonClickListener);
bigButton.setOnClickListener(buttonClickListener);
turnButton.setOnClickListener(buttonClickListener);
}
private void small()
{
int bmpWidth = bmp.getWidth();// 获得Bitmap的高和宽
int bmpHeight = bmp.getHeight();

double scale = 0.8;//设置缩小比例
if(scaleWidth * scale < 0.35)
{
Toast.makeText(this, "再缩小还看得清吗？",Toast.LENGTH_SHORT).show();
return;
}
scaleWidth = (float) (scaleWidth * scale);// 计算出这次要缩小的比例
scaleHeight = (float) (scaleHeight * scale);

Matrix matrix = new Matrix();// 产生resize后的Bitmap对象
matrix.postScale(scaleWidth, scaleHeight);
Bitmap resizeBmp = Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight,matrix, true);
if (id == 0)
photoLayout.removeView(photoView);
else
photoLayout.removeView((ImageView) findViewById(id));
id++;
ImageView imageView = new ImageView(this);
imageView.setId(id);
imageView.setImageBitmap(resizeBmp);
photoLayout.addView(imageView);
setContentView(photoLayout);
bigButton.setEnabled(true);
}
private void big()
{
int bmpWidth = bmp.getWidth();// 获得Bitmap的高和宽
int bmpHeight = bmp.getHeight();
double scale = 1.25;// 设置放大比例
scaleWidth = (float) (scaleWidth * scale);// 计算出这次要放大的比例
scaleHeight = (float) (scaleHeight * scale);
Matrix matrix = new Matrix();// 产生resize后的Bitmap对象
matrix.postScale(scaleWidth, scaleHeight);
Bitmap resizeBmp = Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight,matrix, true);
if (id == 0)
photoLayout.removeView(photoView);
else
photoLayout.removeView((ImageView) findViewById(id));
id++;
ImageView imageView = new ImageView(this);
imageView.setId(id);
imageView.setImageBitmap(resizeBmp);
photoLayout.addView(imageView);
setContentView(photoLayout);
if (scaleWidth * scale * bmpWidth > displayWidth|| scaleHeight * scale * scaleHeight > displayHeight)//大到一定程度不能再放大
{
Toast.makeText(this, "已经不能再放大！",Toast.LENGTH_SHORT).show();
bigButton.setEnabled(false);
}
}
private void turn()// 位图的旋转
{
int bmpWidth = bmp.getWidth();// 获得Bitmap的高和宽
int bmpHeight = bmp.getHeight();
Matrix matrix = new Matrix();// 产生resize后的Bitmap对象
matrix.postRotate(degree);
degree += 30;
Bitmap resizeBmp = Bitmap.createBitmap(bmp, 0, 0, bmpWidth, bmpHeight,matrix, true);
if (id == 0)
photoLayout.removeView(photoView);
else
photoLayout.removeView((ImageView) findViewById(id));
id++;
ImageView imageView = new ImageView(this);
imageView.setId(id);
imageView.setImageBitmap(resizeBmp);
photoLayout.addView(imageView);
setContentView(photoLayout);
}
}

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

<LinearLayout
android:paddingLeft="40sp"
android:paddingRight="40sp"
android:paddingTop="30sp"
android:paddingBottom="20sp"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >

<Button
android:id="@+id/smallButton"
android:layout_width="80dp"
android:layout_height="40dp"
android:text="缩小"
android:textSize="18sp"/>
<Button
android:id="@+id/bigButton"
android:layout_width="80dp"
android:layout_height="40dp"
android:text="放大"
android:textSize="18sp"/>
<Button
android:id="@+id/turnButton"
android:layout_width="80dp"
android:layout_height="40dp"
android:text="旋转"
android:textSize="18sp"/>
</LinearLayout>

<TextView android:id="@+id/photoInfo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingBottom="20sp"
android:layout_gravity="center_horizontal" />

<ImageView
android:id="@+id/photoView"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
</ImageView>
</LinearLayout>