You already have the correct code answer from @Mark but, just to share my findings: The issue is that you are requesting a change in the view and assuming that it will happen instantly. In reality, the loading of a view depends on the available resources. If everything loads quickly enough and there are no delays then you don't notice anything. In scenarios, where there is any delay due to the process thread being busy etc, the application runs into a situation where it is supposed to display something even though its not ready yet. Hence, it is advisable to dispatch these requests in a asynchronous queues so, they get executed based on the load.

我在UITableView中重新加载数据时遇到了这个问题。简单调度重新加载如下固定的问题为我。

    dispatch_async(dispatch_get_main_queue(), { () -> Void in
        self.tableView.reloadData()
    })

显然你正在后台线程上做一些UI更新。在没有看到代码的情况下，无法准确预测位置。

以下是一些可能发生的情况:-

你可能正在后台线程上做一些事情，但没有使用。在同一个函数中，这段代码更容易被发现。

DispatchQueue.main.async { // do UI update here }

在后台线程调用func进行web请求调用，它的完成处理程序调用其他func进行UI更新。 要解决这个问题，请尝试检查您在webrequest调用后更新UI的代码。

// Do something on background thread
DispatchQueue.global(qos: .userInitiated).async {
   // update UI on main thread
   DispatchQueue.main.async {
                // Updating whole table view
                self.myTableview.reloadData()
            }
}

它需要放在一个不同的线程中，允许UI在线程函数执行完成后立即更新:

现代迅速:

DispatchQueue.main.async {
    // Update UI
}

旧版本的Swift，在Swift 3之前。

dispatch_async(dispatch_get_main_queue(){
    // code here
})

objective - c:

dispatch_async(dispatch_get_main_queue(), ^{
    // code here
});

当我在一个NSURLConnection异步请求完成处理程序中调用一个做UI更新的块时，我有这个问题，因为更新到iOS 9 SDK。使用dispatch_main_queue将块调用放在dispatch_async中解决了这个问题。

它在iOS 8中运行良好。

I also encountered this problem, seeing a ton of these messages and stack traces being printed in the output, when I resized the window to a smaller size than its initial value. Spending a long time figuring out the problem, I thought I'd share the rather simple solution. I had once enabled Can Draw Concurrently on an NSTextView through IB. That tells AppKit that it can call the view's draw(_:) method from another thread. After disabling it, I no longer got any error messages. I didn't experience any problems before updating to macOS 10.14 Beta, but at the same time, I also started modifying the code to perform work with the text view.