import java.io.File;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
public class A10Activity extends Activity {
 private Button b;
 private ImageView iv;
 private TextView tv;
 private String fileName="sdcard/picture/红叶.jpg";
 //private String fileName="sdcard/picture/红叶.jpg";这种写法是错误的，路径不是以
//设备开头
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    b=(Button)findViewById(R.id.button);
    b.setOnClickListener(new OnClickListener(){
  @Override
  public void onClick(View v) {
  // TODO Auto-generated method stub
  iv=(ImageView)findViewById(R.id.imageview);
  tv=(TextView)findViewById(R.id.textview);
  File f=new File(fileName);
//先判断图片文件是否存在
  if(f.exists()){
//如果存在，通过Bitmap将图片放入ImageView中显示出来
/*BitmapFactory(Android.graphics.BitmapFactory)是Android API提供的对象，该对象
*的decodeFile()方法将手机中的图片文件转换成Bitmap对象。*/
   Bitmap bm=BitmapFactory.decodeFile(fileName);
   iv.setImageBitmap(bm);
   tv.setText(fileName);
  }
  else{
   tv.setText("文件不存在");
  }
  }
  });
  }
}

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
public class A11Activity extends Activity {
 private ImageView iv;
 private TextView tv;
 private Button left,right; 
 private int times;
 private int angle;
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    times=1;
    angle=1;
    iv=(ImageView)findViewById(R.id.iv);
    tv=(TextView)findViewById(R.id.tv);
    left=(Button)findViewById(R.id.left);
    left.setText("向左转");    
    right=(Button)findViewById(R.id.right);
    right.setText("向右转");
    final Bitmap bmp=BitmapFactory.decodeResource(getResources(), R.drawable.a); //自己引入一张图片a.png
    final int width=bmp.getWidth();
    final int height=bmp.getHeight();
    iv.setImageBitmap(bmp);
    left.setOnClickListener(new OnClickListener(){
  @Override
  public void onClick(View v) {
  // TODO Auto-generated method stub
  angle--;
  if(angle<-20){ //设置最多旋转20度
   angle=-20;
  }
  int width01=width*times;
  int height01=height*times;
  float width02=(float)(width01/width);
  float height02=(float)(width02/height);
  Matrix m=new Matrix();
  m.postScale(width02, height02);
  m.setRotate(5*angle);
  Bitmap bmp01=Bitmap.createBitmap(bmp, 0, 0, width, height, m, true);
  BitmapDrawable bd=new BitmapDrawable(bmp01);
  iv.setImageDrawable(bd);
  tv.setText(Integer.toString(5*angle));
  }
  });
  right.setOnClickListener(new OnClickListener(){
  @Override
  public void onClick(View v) {
  // TODO Auto-generated method stub
  angle++;
  if(angle>20){
   angle=20;
  }
  int width01=width*times;
  int height01=height*times;
  float width02=(float)(width01/width);
  float height02=(float)(width02/height);
  Matrix m=new Matrix();
  m.postScale(width02, height02);
  m.setRotate(5*angle);
  Bitmap bmp01=Bitmap.createBitmap(bmp, 0, 0, width, height, m, true);
  BitmapDrawable bd=new BitmapDrawable(bmp01);
  iv.setImageDrawable(bd);
  tv.setText(Integer.toString(5*angle));
  }
  });
  }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical" >
  <TextView
    android:id="@+id/tv"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello" />
  <Button 
    android:id="@+id/left"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />
  <Button 
    android:id="@+id/right"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />
  <ImageView 
    android:id="@+id/iv"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />
</LinearLayout>