在接收 ALAssetsLibraryChangedNotification 时从 ALAssetsGroupSavedPhotos 组中检索 ALAsset 时应用程序崩溃

Posted 2023-03-07

【中文标题】在接收 ALAssetsLibraryChangedNotification 时从 ALAssetsGroupSavedPhotos 组中检索 ALAsset 时应用程序崩溃

【英文标题】：app crashes when retrieving the ALAssets from ALAssetsGroupSavedPhotos group up on receiving ALAssetsLibraryChangedNotification

【发布时间】：2014-01-08 11:07:01

【问题描述】：

我的应用程序的一部分有一个类似于 Apple 的照片应用程序的照片浏览器（类似网格的视图）。为了在原始照片应用程序发生任何变化时刷新我的照片，我注册了 ALAssetsLibraryChangedNotification

self.assetsLibrary = [[ALAssetsLibrary alloc] init];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveLibraryChangedNotification:) name:ALAssetsLibraryChangedNotification object:self.assetsLibrary];

在“receiveLibraryChangedNotification”方法中 - 我检查 userInfo 是否有 ALAssetLibraryUpdatedAssetsKey 然后调用刷新照片方法。

 - (void) receiveLibraryChangedNotification:(NSNotification *) notif
        NSDictionary *userInfo = [notif userInfo];
        if(userInfo)
            id updatedAssets = [userInfo objectForKey:ALAssetLibraryUpdatedAssetsKey];

            if(updatedAssets)

                   [self refreshPhotos];
                
    




- (void) refreshPhotos 

    self.assetArray = nil;

        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^(void)
                [self.assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) 

                    if(group)
                        [group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, [group numberOfAssets])] options:0 usingBlock:^(ALAsset *result, NSUInteger index, BOOL *shouldStop) 
                            if(result)

                                if([[result valueForProperty:@"ALAssetPropertyType"] isEqualToString:@"ALAssetTypePhoto"])
                                    [self.assetArray addObject:result];
                                
                            
                        ];
                    
                 failureBlock:^(NSError *error) 

                    DebugLog(@"error >>> %@",[error description]);

                ];
            );

我面临的问题是，有时通知被多次触发，应用程序崩溃

[self.assetArray addObject:result];

有错误-

malloc: *** error for object 0x4aa9000: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug

或

malloc: *** error for object 0x16fd3e74: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug

有时我没有在通知的 userInfo 中收到 ALAssetLibraryUpdatedAssetsKey，因此照片永远不会刷新。

谁能指引我正确的方向。

提前致谢。

【参考方案1】：

分配 self.assetArray 在nil 分配之后或写[self.assetArray removeAllObjects] 而不是分配给nil。

- (void) refreshPhotos 

    self.assetArray = nil;
    self.assetArray = [[NSMutableArray alloc] init];

    //or remove the top 2 lines and try `[self.assetArray removeAllObjects]`

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^(void)
            [self.assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) 

                if(group)
                    [group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, [group numberOfAssets])] options:0 usingBlock:^(ALAsset *result, NSUInteger index, BOOL *shouldStop) 
                        if(result)

                            if([[result valueForProperty:@"ALAssetPropertyType"] isEqualToString:@"ALAssetTypePhoto"])
                                [self.assetArray addObject:result];
                            
                        
                    ];
                
             failureBlock:^(NSError *error) 

                DebugLog(@"error >>> %@",[error description]);

            ];
        );

有时我也没有收到 ALAssetLibraryUpdatedAssetsKey 在通知的userInfo中，

有四个键用于从ALAssetsLibraryChangedNotification 通知的用户信息字典中获取值。

NSString * const ALAssetLibraryUpdatedAssetsKey;
NSString * const ALAssetLibraryInsertedAssetGroupsKey;
NSString * const ALAssetLibraryUpdatedAssetGroupsKey;
NSString * const ALAssetLibraryDeletedAssetGroupsKey;