添加子视图后，如何使它立即出现在UI中? [英] How do I make subview appear in UI immediately after adding it?

问题描述

基本上，我希望标签在添加时显示为子视图，而不是等到当前线程完成其操作后再显示.在下面的示例中，标签在打印唤醒"的同时出现在应用程序的用户界面中.您知道如何让子视图在线程休眠之前显示在UI中吗?

Essentially I want a label to appear as a subview when I add it and not wait until the current thread has finished what it is doing. In the below example, the label appears in the UI of the app at the same time 'Awake' is printed. Do you know how I can get the subview to appear in the UI before the thread sleeps?

@IBAction func ButtonTapped(_ sender: Any) {

    let label = UILabel(frame: self.view.bounds)
    label.text = "Label Text"
    self.view.addSubview(label) // I want this to appear on the UI before...
    sleep(3)
    print("Awake") // ... this is printed

}

将addSubView()放在DispatchQueue.main.async {}中并不能解决问题.

And enclosing the addSubView() line within DispatchQueue.main.async {} doesn't fix the issue.

谢谢.

推荐答案

感谢Paulw11，我发现我需要在后台线程上进行处理.快速的简单解决方案:

Thanks to Paulw11, I figured out that I need to do the processing on a background thread. Simple solution in swift:

@IBAction func ButtonTapped(_ sender: Any) {

    let label = UILabel(frame: self.view.bounds)
    label.text = "Label Text"
    self.view.addSubview(label) // I want this to appear on the UI before...

    DispatchQueue.global(qos: .background).async {
        sleep(3)
        print("Awake") // ... this is printed
    }

}

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