【原创】Android 4.4前后版本读取图库图片方式的变化

Android 4.4前后版本读取图库图片方式的变化

 

本文讲述Android 4.4（KitKat）前后访问图库以及访问后通过图片路径读取图片的变化

 

Android 4.4（KitKat）以前：

访问图库（方法一）：

      /**
      * Access the gallery to pick up an image.
      */
      private   void  startPickPhotoActivity() {
         Intent intent =  new  Intent(Intent. ACTION_GET_CONTENT );
         intent.setType( "image/*" ); // Or 'image/ jpeg '
         startActivityForResult(intent,  RESULT_PICK_PHOTO_NORMAL );
     }

访问图库（方法二）：

      /**
      * Access the gallery to pick up an image.
      */
      private   void  startPickPhotoActivity() {
         Intent intent =  new  Intent(Intent. ACTION_GET_CONTENT );
         intent.setType( "image/*" ); // Or 'image/ jpeg '
         Intent wrapperIntent = Intent. createChooser (intent,  null );
         startActivityForResult(wrapperIntent,  RESULT_PICK_PHOTO_NORMAL );
      }

获取文件路径&读取图片：

     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
         if (requestCode == RESULT_PICK_PHOTO_NORMAL) {
             if (resultCode == RESULT_OK && data != null) {
                 mFileName = DemoUtils.getDataColumn(getApplicationContext(),
                         data.getData(), null, null);
                 mColorBitmap = DemoUtils.getBitmap(mFileName);

                 mImage.setImageBitmap(mColorBitmap);
             }
         }
     }

     public static final Bitmap getBitmap(String fileName) {
         Bitmap bitmap = null;
         try {
             Options options = new Options();
             options.inJustDecodeBounds = true;
             BitmapFactory.decodeFile(fileName, options);
             options.inSampleSize = Math.max(1, (int) Math.ceil(Math.max(
                     (double) options.outWidth / 1024f,
                     (double) options.outHeight / 1024f)));
             options.inJustDecodeBounds = false;
             bitmap = BitmapFactory.decodeFile(fileName, options);
         } catch (OutOfMemoryError error) {
             error.printStackTrace();
         }

         return bitmap;
     }

     /**
      * 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 = MediaColumns.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;
     }

Android 4.4（KitKat）及以后：

访问图库（方法一）：同上方法一

访问图库（方法二）：同上方法二

访问图库（方法三）：

      /**
      * Access the gallery to pick up an image.
      */
      @TargetApi (Build.VERSION_CODES. KITKAT )
      private   void  startPickPhotoActivity() {
         Intent intent =  new  Intent(Intent. ACTION_OPEN_DOCUMENT );
         intent.setType( "image/*" ); // Or 'image/ jpeg '
         startActivityForResult(intent,  RESULT_PICK_PHOTO_NORMAL );
     }

获取文件路径&读取图片：

     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
         if (requestCode == RESULT_PICK_PHOTO_KITKAT) {
             if (resultCode == RESULT_OK && data != null) {
                 mFileName = DemoUtils.getPath(getApplicationContext(),
                         data.getData());
                 mColorBitmap = DemoUtils.getBitmap(mFileName);

                 mImage.setImageBitmap(mColorBitmap);
             }
         }
     }

     @TargetApi(Build.VERSION_CODES.KITKAT)
     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];
                 }
                 // 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 = MediaColumns._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;
     }

     /**
      * 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 = MediaColumns.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;
     }

     /**
      * @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());
     }

     /**
      * @param uri
      *            The Uri to check.
      * @return Whether the Uri authority is Google Photos.
      */
     public static boolean isGooglePhotosUri(Uri uri) {
         return "com.google.android.apps.photos.content".equals(uri
                 .getAuthority());
     }

为什么会不一样呢？

Android 4.4（含）开始，通过方式访问图库后，返回的Uri如下（访问“最近”）：

 Uri is：         content://com.android.providers.media.documents/document/image%3A18838
 Uri.getPath is ：/document/image:18838
 对应的图片真实路径：/storage/emulated/0/Pictures/Screenshots/Screenshot_2014-09-22-21-40-53.png

不但如此，对于不同类型图库，返回的Uri形式并不相同（访问普通相册）：

 Uri is：         content://media/external/images/media/18822
 Uri.getPath is ：/external/images/media/18822
 对应的图片真实路径：/storage/emulated/0/Download/20130224235013.jpg

而4.4之前返回的Uri只存在一种形式，如下：

 Uri is：         content://media/external/images/media/14046
 Uri.getPath is ：/external/images/media/14046
 对应的图片真实路径：/storage/emulated/0/DCIM/Camera/20130224235013.jpg

因此，在Android 4.4或更高版本设备上，通过简单的getDataColumn(Context, Uri, null, null)进行图片数据库已经不能满足所有需求，因此在获取图片真实路径的时候需要根据不同类型区分对待。