通过Uri获得文件扩展名位于android

Question

我想检查手机中选择文件的扩展名。 当我选择，我得到：content://com.android.providers.media.documents/document/image%3A20247 我的方法来获取延期返回null：

public static String getMimeType(String url) { 
     String type = null; 
     String extension = MimeTypeMap.getFileExtensionFromUrl(url); 
     if (extension != null) { 
      type = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension); 
     } 
     return type; 
    } 

任何想法，为什么？

Answer 1

尝试使用此，它为我工作

public static String getAbsolutePath(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]; 
     } 

     // TODO handle non-primary volumes 
    } 
    // 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 the remote address 
    if (isGooglePhotosUri(uri)) 
     return uri.getLastPathSegment(); 

    return getDataColumn(context, uri, null, null); 
} 
// File 
else if ("file".equalsIgnoreCase(uri.getScheme())) { 
    return uri.getPath(); 
} 

return null; 
} 


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 index = cursor.getColumnIndexOrThrow(column); 
     return cursor.getString(index); 
    } 
} finally { 
    if (cursor != null) 
     cursor.close(); 
} 
return null; 
} 

public static boolean isExternalStorageDocument(Uri uri) { 
return "com.android.externalstorage.documents".equals(uri.getAuthority()); 
} 

public static boolean isDownloadsDocument(Uri uri) { 
return "com.android.providers.downloads.documents".equals(uri.getAuthority()); 
} 


public static boolean isMediaDocument(Uri uri) { 
return "com.android.providers.media.documents".equals(uri.getAuthority()); 
} 

public static boolean isGooglePhotosUri(Uri uri) { 
return "com.google.android.apps.photos.content".equals(uri.getAuthority()); 
} 

Answer 2

我觉得您的网址需要后缀。

这是MimeTypeMap的源代码：

/** 
* Returns the file extension or an empty string iff there is no 
* extension. This method is a convenience method for obtaining the 
* extension of a url and has undefined results for other Strings. 
* @param url 
* @return The file extension of the given url. 
*/ 
public static String getFileExtensionFromUrl(String url) { 
    if (!TextUtils.isEmpty(url)) { 
     int fragment = url.lastIndexOf('#'); 
     if (fragment > 0) { 
      url = url.substring(0, fragment); 
     } 

     int query = url.lastIndexOf('?'); 
     if (query > 0) { 
      url = url.substring(0, query); 
     } 

     int filenamePos = url.lastIndexOf('/'); 
     String filename = 
      0 <= filenamePos ? url.substring(filenamePos + 1) : url; 

     // if the filename contains special characters, we don't 
     // consider it valid for our matching purposes: 
     if (!filename.isEmpty() && 
      Pattern.matches("[a-zA-Z_0-9\\.\\-\\(\\)\\%]+", filename)) { 
      int dotPos = filename.lastIndexOf('.'); 
      if (0 <= dotPos) { 
       return filename.substring(dotPos + 1); 
      } 
     } 
    } 

    return ""; 
} 



    /** 
* Return the registered extension for the given MIME type. Note that some 
* MIME types map to multiple extensions. This call will return the most 
* common extension for the given MIME type. 
* @param mimeType A MIME type (i.e. text/plain) 
* @return The extension for the given MIME type or null iff there is none. 
*/ 
public String getExtensionFromMimeType(String mimeType) { 
    return MimeUtils.guessExtensionFromMimeType(mimeType); 
} 

及注意事项： MimeTypeMap是 “包android.webkit” ...