更改UILabel文本有延迟，但为什么？ [英] Changing UILabel text has delay, but why?

问题描述

在我的应用中，我想设置 UILabel 的文本。该文本来自JSON对象。我将 UILabel 添加到我的故事板，设置 IBOutlet 并调用我的async-method来获取我的JSON对象。
在响应方法中，我设置了 UILabel 的文本。但文本更改需要几秒钟。
当响应响起时，我将其打印到控制台。我可以看到，延迟不是来自异步方法。
响应来了，我可以在控制台中看到它。等待 UIlabel 更改的几秒钟。
我不明白这种行为，有没有一个技巧可以立即刷新 UIlabel ？

in my app I want to set the text of an UILabel. The text comes from a JSON-object. I add my UILabel to my storyboard, set the IBOutlet and call my async-method to get my JSON-object. In the response-method I set the text of the UILabel. But the text change needs some seconds. When the response comes I print it to the console. There I can see, that the delay doesnt comes from the async-method. The response comes, I can see it in the console. Wait some seconds than the UIlabel changes. I dont understand this behaviour, is there a trick to refresh the UIlabel instantly?

一些代码：

@IBOutlet weak var label_news: UILabel!;

override func viewDidLoad() {
    super.viewDidLoad()
    self.label_news.text = "CHANGE";
    rcall.GetNews_GET_NewsResponse_0(self.NewsResponseHandler);
}

func NewsResponseHandler(resp:NewsResponse!){
    self.label_news.text = resp.NewsText;
    println(resp.NewsText);
}

很抱歉，如果这是一个初学者问题，swift和故事板对我来说都是全新的。

Sorry if this is a beginner question, swift and storyboards are totally new for me.

最好的问候

推荐答案

就像Rob在评论中所说的那样，所有UI更改都需要在主线程上完成。我还没有在Swift中实现它，但Objective-C和我假设的Swift在下面......

Like what Rob stated in the comment, all UI changes need to be done on the main thread. I haven't implemented it in Swift yet, but the Objective-C and what I'm assuming would be the Swift is below...

Objective-C

Objective-C

dispatch_async(dispatch_get_main_queue(), ^{
    self.label_news.text = resp.NewsText;
});

Swift：

dispatch_async(dispatch_get_main_queue()) {
    self.label_news.text = resp.NewsText;
}

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