Android Uri和文件路径互相转换的实例代码

public class GetPathFromUri { 
  /** 
   * 专为Android4.4设计的从Uri获取文件绝对路径 
   */ 
  public static String getPath(final Context context, final Uri uri) { 
    final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT; 
    // DocumentProvider 
    if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) { 
      // ExternalStorageProvider 
      if (isExternalStorageDocument(uri)) { 
        final String docId = DocumentsContract.getDocumentId(uri); 
        final String[] split = docId.split(":"); 
        final String type = split[0]; 
        if ("primary".equalsIgnoreCase(type)) { 
          return Environment.getExternalStorageDirectory() + "/" + split[1]; 
        } 
      } 
      // DownloadsProvider 
      else if (isDownloadsDocument(uri)) { 
        final String id = DocumentsContract.getDocumentId(uri); 
        final Uri contentUri = ContentUris.withAppendedId( 
            Uri.parse("content://downloads/public_downloads"), Long.valueOf(id)); 
        return getDataColumn(context, contentUri, null, null); 
      } 
      // MediaProvider 
      else if (isMediaDocument(uri)) { 
        final String docId = DocumentsContract.getDocumentId(uri); 
        final String[] split = docId.split(":"); 
        final String type = split[0]; 
        Uri contentUri = null; 
        if ("image".equals(type)) { 
          contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI; 
        } else if ("video".equals(type)) { 
          contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI; 
        } else if ("audio".equals(type)) { 
          contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI; 
        } 
        final String selection = "_id=?"; 
        final String[] selectionArgs = new String[]{split[1]}; 
        return getDataColumn(context, contentUri, selection, selectionArgs); 
      } 
    } 
    // MediaStore (and general) 
    else if ("content".equalsIgnoreCase(uri.getScheme())) { 
      return getDataColumn(context, uri, null, null); 
    } 
    // File 
    else if ("file".equalsIgnoreCase(uri.getScheme())) { 
      return uri.getPath(); 
    } 
    return null; 
  } 
  /** 
   * Get the value of the data column for this Uri. This is useful for 
   * MediaStore Uris, and other file-based ContentProviders. 
   * 
   * @param context    The context. 
   * @param uri      The Uri to query. 
   * @param selection   (Optional) Filter used in the query. 
   * @param selectionArgs (Optional) Selection arguments used in the query. 
   * @return The value of the _data column, which is typically a file path. 
   */ 
  public static String getDataColumn(Context context, Uri uri, String selection, 
                String[] selectionArgs) { 
    Cursor cursor = null; 
    final String column = "_data"; 
    final String[] projection = {column}; 
    try { 
      cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, 
          null); 
      if (cursor != null && cursor.moveToFirst()) { 
        final int column_index = cursor.getColumnIndexOrThrow(column); 
        return cursor.getString(column_index); 
      } 
    } finally { 
      if (cursor != null) 
        cursor.close(); 
    } 
    return null; 
  } 
  /** 
   * @param uri The Uri to check. 
   * @return Whether the Uri authority is ExternalStorageProvider. 
   */ 
  public static boolean isExternalStorageDocument(Uri uri) { 
    return "com.android.externalstorage.documents".equals(uri.getAuthority()); 
  } 
  /** 
   * @param uri The Uri to check. 
   * @return Whether the Uri authority is DownloadsProvider. 
   */ 
  public static boolean isDownloadsDocument(Uri uri) { 
    return "com.android.providers.downloads.documents".equals(uri.getAuthority()); 
  } 
  /** 
   * @param uri The Uri to check. 
   * @return Whether the Uri authority is MediaProvider. 
   */ 
  public static boolean isMediaDocument(Uri uri) { 
    return "com.android.providers.media.documents".equals(uri.getAuthority()); 
  } 
}