ALAssetsLibrary從ALAssetsGroupAll加載單張照片

Question

我試圖構建一個類似於iOS 7的照片應用的自定義圖像選擇器。我能夠從相機膠捲中挑選一張照片（ALAssetsGroupSavedPhotos），但我很難從另一張相冊中加載單張圖像 - 我爲測試目的而創建的一張相冊。

下面是我使用的加載從相機膠捲照片的代碼：

ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init]; 

[library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) { 

    [group setAssetsFilter:[ALAssetsFilter allPhotos]]; 
    numberOfPhotos = [group numberOfAssets]; 

    [group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:index] options:0 usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) { 


          if (alAsset) { 

           ALAssetRepresentation *representation = [alAsset defaultRepresentation]; 
           UIImage *lastImage = [UIImage imageWithCGImage:[representation fullScreenImage]]; 


          } 

         }]; 

} 
        failureBlock: ^(NSError *error2) { 


        }]; 

我試圖取代ALAssetsGroupSavedPhotos與ALAssetsGroupAll但它返回以下錯誤：

Terminating app due to uncaught exception 'NSRangeException', reason: 'indexSet count or lastIndex must not exceed -numberOfAssets'

Answer 1

你正在枚舉庫中的所有文件夾並試圖從每個文件夾中獲取照片。這是錯誤的。首先你必須得到你的文件夾。

__block ALAssetsGroup* folder; 
NSString *yourFolderName = ...; 

[library enumerateGroupsWithTypes:ALAssetsGroupAlbum 
          usingBlock:^(ALAssetsGroup *group, BOOL *stop) 
{ 
     if ([[group valueForProperty:ALAssetsGroupPropertyName] isEqualToString:yourFolderName]) 
     { 
      folder = group; 
     } 
} 
          failureBlock:^(NSError* error) 
{ 
    // Error handling.  
}]; 

然後，從文件夾中獲得的圖像：

[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:index] 
         options:0 
        usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) 
{ 
    if (alAsset) 
    { 
     ALAssetRepresentation *representation = [alAsset defaultRepresentation]; 
     UIImage *lastImage = [UIImage imageWithCGImage:[representation fullScreenImage]]; 
    } 
}]; 

但要確保index是正確的。