与ALAssetsLibrary的问题

Question

我试图访问照片库上的最后一张照片，一切正常，除非，照片库没有照片我的应用程序崩溃！我怎样才能找到解决办法来停止崩溃呢？这是我的代码：

-(void)importLastImage {

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

    // Enumerate just the photos and videos group by using ALAssetsGroupSavedPhotos.
    [library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) {

        // Within the group enumeration block, filter to enumerate just photos.
        [group setAssetsFilter:[ALAssetsFilter allPhotos]];

        // Chooses the photo at the last index
        [group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:([group numberOfAssets]-1)]
                                options:0
                             usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) {

                                 // The end of the enumeration is signaled by asset == nil.
                                 if (alAsset) {


                                     ALAssetRepresentation *representation = [alAsset defaultRepresentation];
                                     latestPhoto = [UIImage imageWithCGImage:[representation fullResolutionImage]];



                                 }else {

                                 }
       }];
    }
                         failureBlock: ^(NSError *error) {
                             // Typically you should handle an error more gracefully than this.
                             NSLog(@"No groups");


}];

}

Answer 1

您是否尝试将您的方法封装到if condition中？

-(void)importLastImage {

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

    // Enumerate just the photos and videos group by using ALAssetsGroupSavedPhotos.
    [library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) {

        // Within the group enumeration block, filter to enumerate just photos.
        [group setAssetsFilter:[ALAssetsFilter allPhotos]];

        // Chooses the photo at the last index
        if ([group numberOfAssets] > 0) {
            [group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:([group numberOfAssets]-1)] options:0 usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop) {

                // The end of the enumeration is signaled by asset == nil.
                if (alAsset) {
                    ALAssetRepresentation *representation = [alAsset defaultRepresentation];
                    latestPhoto = [UIImage imageWithCGImage:[representation fullResolutionImage]];
                } else {

                }
            }];
        }
    } failureBlock: ^(NSError *error) {
        // Typically you should handle an error more gracefully than this.
        NSLog(@"No groups");
    }];

}