<LinearLayout xmlns:android=\"http://schemas.android.com/apk/res/android\"
  android:layout_width=\"match_parent\"
  android:layout_height=\"match_parent\"
  android:orientation=\"vertical\" >
  <Button
    android:id=\"@+id/take_photo\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"wrap_content\"
    android:text=\"Take Photo\" />
  <Button
    android:id=\"@+id/get_photo\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"wrap_content\"
    android:text=\"get Photo\" />
  <ImageView
    android:id=\"@+id/picture\"
    android:layout_width=\"300dp\"
    android:layout_height=\"300dp\"
    android:layout_gravity=\"center_horizontal\" />
</LinearLayout>
package com.example.choosepictest;
import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
public class MainActivity extends Activity implements OnClickListener {
  static final int REQUEST_IMAGE_CAPTURE = 1;
  private Button takePhoto;
  private Button getPhoto;
  private ImageView picture;
  private Uri imgUri;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    takePhoto = (Button) findViewById(R.id.take_photo);
    getPhoto = (Button) findViewById(R.id.get_photo);
    picture = (ImageView) findViewById(R.id.picture);
    takePhoto.setOnClickListener(this);
    getPhoto.setOnClickListener(this);
  }  
  @Override
  public void onClick(View v) {
    switch (v.getId()) {
    case R.id.take_photo:
      dispatchTakePictureIntent();
      break;
    default:
      break;
    }
  }
  // 保存全尺寸照片
  String mCurrentPhotoPath;
  private void dispatchTakePictureIntent() {
    File appDir = new File(Environment.getExternalStorageDirectory(),
        \"/etoury/picCache\");
    if (!appDir.exists()) {
      appDir.mkdir();
    }
    String timeStamp = new SimpleDateFormat(\"yyyyMMdd_HHmmss\")
        .format(new Date());
    String fileName = timeStamp + \".jpg\";
    File outputImage = new File(appDir, fileName);
    try {
      if (outputImage.exists()) {
        outputImage.delete();
      }
      outputImage.createNewFile();
    } catch (IOException e) {
      e.printStackTrace();
    }
    mCurrentPhotoPath = outputImage.getAbsolutePath();
    imgUri = Uri.fromFile(outputImage);
    // 意图 相机
    Intent intent = new Intent(\"android.media.action.IMAGE_CAPTURE\");
    intent.putExtra(MediaStore.EXTRA_OUTPUT, imgUri);
    // 如果有相机
    if (intent.resolveActivity(getPackageManager()) != null) {
      startActivityForResult(intent, REQUEST_IMAGE_CAPTURE);
    }
  }
  //解码缩放图片(Decode a Scaled Image)
  private void setPic() {
    // Get the dimensions of the View
    int targetW = picture.getWidth();
    int targetH = picture.getHeight();
    // Get the dimensions of the bitmap
    BitmapFactory.Options bmOptions = new BitmapFactory.Options();
    // 该 值设为true那么将不返回实际的bitmap，也不给其分配内存空间这样就避免内存溢出了。但是允许我们查询图片的信息这其中就包括图片大小信息
    bmOptions.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
    int photoW = bmOptions.outWidth;
    int photoH = bmOptions.outHeight;
    // Determine how much to scale down the image
    // Math.min求最小值
    int scaleFactor = Math.min(photoW/targetW, photoH/targetH);
    // Decode the image file into a Bitmap sized to fill the View
    bmOptions.inJustDecodeBounds = false;
    // 设置恰当的inSampleSize可以使BitmapFactory分配更少的空间以消除该错误
    bmOptions.inSampleSize = scaleFactor;
    // 如果inPurgeable设为True的话表示使用BitmapFactory创建的Bitmap,用于存储Pixel的内存空间在系统内存不足时可以被回收
    bmOptions.inPurgeable = true;
    Bitmap bitmap = BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
    picture.setImageBitmap(bitmap);
  }
  @Override
  protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (resultCode == RESULT_OK) {
      switch (requestCode) {
      case REQUEST_IMAGE_CAPTURE:
        setPic();
        break;
      default:
        break;
      }
    }
  }
}