[Android] URI那些事

1. 从URI中获取真实文件路径

	private String uriToRealPath(Uri uri) {
		Cursor cursor = managedQuery(uri,
				new String[] {MediaStore.Images.Media.DATA},
				null,
				null,
				null);
		cursor.moveToFirst();
		String path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA));
		return path;
	}

2. 从真实路径转换为文件URI

	Uri uri = Uri.fromFile(new File(filePath));

3. 从真实路径转换为媒体库URI

	private Uri pathToMediaUri(String path) {
		Uri mediaUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
		
		Cursor cursor = getContentResolver().query(mediaUri,
				null,
				MediaStore.Images.Media.DISPLAY_NAME + "=" + path.substring(path.lastIndexOf("/") + 1),
				null,
				null);
		cursor.moveToFirst();
		
		Uri uri = ContentUris.withAppendedId(mediaUri, cursor.getLong(0));
		return uri;
	}

  PS: 如果想调用"com.android.camera.action.CROP"裁剪图片，文件URI是用不了的，必须要获取媒体库的URI。