Question

就在appdelegates，applicationDidBecomeActive。我创建并启动一个线程，该线程等待异步下载，然后保存数据：

 - (void)applicationDidBecomeActive:(UIApplication *)application
    {
              // begins Asynchronous download data (1 second):
               [wsDataComponents updatePreparedData:NO];

               NSThread* downloadThread = [[NSThread alloc] 
                  initWithTarget:self 
                        selector: @selector (waitingFirstConnection) 
                          object:nil];
               [downloadThread start];
        }

然后

-(void)waitingFirstConnection{    

    while (waitingFirstDownload) {
      // Do nothing ...  Waiting a asynchronous download, Observers tell me when
      // finish first donwload
    }

    // begins Synchronous download, and save data (20 secons)
    [wsDataComponents updatePreparedData:YES];

    // Maybe is this the problem ?? I change a label in main view controller 
    [menuViewController.labelBadgeVideo setText:@"123 videos"];

    // Nothig else, finish and this thread is destroyed
}

在Organizer控制台中，完成后，我收到此警告：

CoreAnimation: warning, deleted thread with uncommitted CATransaction;

Answer 1

在非主线程上使用UIKit UI API时，最常出现此错误。您不必直接使用Core Animation来查看此内容。所有UIViews都由核心动画层支持，因此无论您是否直接与其进行交互，都会使用Core Animation。

在你的问题中没有足够的代码来确定确切的问题，但你使用多线程的事实是一个线索，你的问题正如我所描述的那样。您是在下载完成后和/或保存数据后更新UI吗？如果是这样，您需要将UI更新移回主线程/队列。如果您使用GCD而不是NSThread，这会更容易：

// download is finished, save data
dispatch_async(dispatch_get_main_queue(), ^{
    // Update UI here, on the main queue
});

Answer 2

如Andrew所述，确保在主线程上进行任何UI绘制的另一种方法是使用方法performSelectorOnMainThread:withObject:waitUntilDone:或performSelectorOnMainThread:withObject:waitUntilDone:modes:

- (void) someMethod
{
    […]

    // Perform all drawing/UI updates on the main thread.
    [self performSelectorOnMainThread:@selector(myCustomDrawing:)
                           withObject:myCustomData
                        waitUntilDone:YES];

    […]
}

- (void) myCustomDrawing:(id)myCustomData
{
    // Perform any drawing/UI updates here.
}

有关dispatch_async()和performSelectorOnMainThread:withObjects:waitUntilDone:之间差异的相关帖子，请参阅Whats the difference between performSelectorOnMainThread and dispatch_async on main queue?

Answer 3

我发现了问题：正在更改menuViewController中的标签

在这个帖子中，我使用了一个isntance变量而不是de menuViewController：

[menuViewController.labelBadgeVideo setText:@"123 videos"];

如果我对此行发表评论，则不会出现警告

（现在我必须在没有警告的情况下找出如何更改此标签）

如果不使用CoreAnimation，如何避免“CoreAnimation警告已删除的线程与未提交的CATransaction”

3 个答案: