Android实现拍照及图片显示效果

<uses-feature android:name="android.hardware.camera2"
    <!-- required为false时，不强制要求设备支持该功能 -->
    <!-- 如果不设置该值，一旦设备不支持camera，就不能安装该应用-->
    android:required="false"/>

public File getPhotoFile(Crime crime) {
  //获取应用对应的存储照片的外部存储路径
  File externalFilesDir = mContext
      .getExternalFilesDir(Environment.DIRECTORY_PICTURES);

  if (externalFilesDir == null) {
    return null;
  }

  //创建指向文件的File对象
  return new File(externalFilesDir, crime.getPhotoFilename());
}
.............
//每个crime对应的文件名
public String getPhotoFilename() {
  return "IMG_" + getId().toString() + ".jpg";
}

mPhotoButton = (ImageButton) v.findViewById(R.id.crime_camera);

//隐式Intent触发相机拍照
final Intent captureImageIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

//mPhotoFile保存着上文创建的指向指定地址的File
//此处判断是否有能够处理隐式Intent的组件
boolean canTakePhoto = mPhotoFile != null
    && captureImageIntent.resolveActivity(packageManager) != null;
mPhotoButton.setEnabled(canTakePhoto);

if (canTakePhoto) {
  //得到File文件对应的Uri地址
  Uri uri = Uri.fromFile(mPhotoFile);

  //将Uri地址存入到Intent中，相机拍照得到的图像将会存入到该Uri地址对应的File里
  captureImageIntent.putExtra(MediaStore.EXTRA_OUTPUT, uri);
}

mPhotoButton.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View v) {
    startActivityForResult(captureImageIntent, REQUEST_PHOTO);
  }
});

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
  .........
  } else if (requestCode == REQUEST_PHOTO) {
    updatePhotoView();
  }
  .........
}

private void updatePhotoView() {
  if (mPhotoFile == null || !mPhotoFile.exists()) {
    mPhotoView.setImageDrawable(null);
  } else {
    //加载图片对应的缩略图
    Bitmap bitmap = PictureUtils.getScaledBitmap(mPhotoFile.getPath(), getActivity());
    mPhotoView.setImageBitmap(bitmap);
  }
}

//在具体视图未加载前，无法得到视图的实际大小
//因此根据屏幕尺寸，使用估算值进行缩放
public static Bitmap getScaledBitmap(String path, Activity activity) {
  Point size = new Point();
  activity.getWindowManager().getDefaultDisplay().getSize(size);

  return getScaledBitmap(path, size.x, size.y);
}

public static Bitmap getScaledBitmap(String path, int destWidth, int destHeight) {
  BitmapFactory.Options options = new BitmapFactory.Options();
  options.inJustDecodeBounds = true;

  //按照正常尺寸解析文件
  BitmapFactory.decodeFile(path, options);

  //得到原始文件的宽和高
  float srcWidth = options.outWidth;
  float srcHeight = options.outHeight;

  //inSampleSize表示水平/竖直抽样比
  //例如，inSampleSize为2时，水平和数值均在原始基础上，每2个点抽取1个点
  //于是，新图的大小变为原来的1/4
  int inSampleSize = 1;
  if (srcHeight > destHeight || srcWidth > destWidth) {
    if (srcWidth > srcHeight) {
      inSampleSize = Math.round(srcHeight / destHeight);
    } else {
      inSampleSize = Math.round(srcWidth / destWidth);
    }
   }

  options = new BitmapFactory.Options();
  options.inSampleSize = inSampleSize;

  //按新的抽样比，重新解析文件
  return BitmapFactory.decodeFile(path, options);
}