UI 未更新，因为 NSOperation队列等待直到完成是

Question

我遇到了一个问题。场景如下：我得到了一个NSOperationQueue，其中包含需要等待UntilDone:YES的各种NSOperationQueue。当队列或操作正在运行时，我也需要更新UI。处理这种情况的最佳方法是什么？

我已经尝试过performSelectOnMainThread，但每次需要更新UI时都有必要使用这种方法吗。这似乎不是一个好的解决方案。

- (void)loadPreviewPageWithMagazineID:(NSString *)magazineID userID:(NSString *)userID {
NSMutableArray *operationArray = [NSMutableArray array];
for (NSInteger i = 1; i <= _numTotalPages; ++i) {
    //NSLog(@"currenpage = %d, index = %d",_selectedPage,pageIndex);
    NSDictionary *arguments = [NSDictionary dictionaryWithObjectsAndKeys:magazineID, 
                               @"itemID", userID, @"userID", [NSNumber numberWithInt:i],
                               @"pageNumber", nil];
    AFOperation *imageOperation = 
        [[AFOperation alloc] initWithTarget:self 
                                   selector:@selector(savePageToDisk:) 
                                     object:arguments];
    [imageOperation addObserver:self forKeyPath:@"isFinished" options:0 context:nil];
    [imageOperation setUserInfo:arguments];
    [operationArray addObject:imageOperation];
    [imageOperation release];
}
[_imageQueue addOperations:operationArray waitUntilFinished:YES];
}

- (void)processingMagazine:(NSDictionary *)arguments {
// load pdf document from decrypted data 
NSString *userID = [arguments objectForKey:@"userID"];
NSString *magazineID = [arguments objectForKey:@"itemID"];
[self loadPreviewPageWithMagazineID:magazineID userID:userID];
}

所以每次更新UI时，我都需要调用

[_collectionCoverView performSelectorOnMainThread:@selector(setDownloadProgress:)
                                       withObject:[NSNumber numberWithFloat:progress] 
                                    waitUntilDone:YES];
Is there any appropriate way to handle the UI?

Answer 1

我对您的代码没有太多理解。但是，为了实现您想要的，您可以在AFOperation方法的末尾添加UI更新代码。我的意思是，如果你在操作方法中添加它，一旦完成一些处理，UI就会自动更新。

UI更新通常也发生在MainThread中。因此，调用performSelectionInMainThread没有错。