显示微调器并将其移除到同一个块中 [英] show spinner and remove it in the same block

问题描述

在一个可能需要几秒钟的方法中我有：

In a method that can take up to several seconds i have:

UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc]initWithFrame:CGRectMake(135,140,50,50)];
spinner.color = [UIColor blueColor];
[spinner startAnimating];
[_mapViewController.view addSubview:spinner];

// lots of code

[spinner removeFromSuperview];

微调器没有出现。可能是因为当时屏幕没有更新。
如何解决这个问题？

The spinner doesn't show up. Probably since the screen doesn't get update at that time. How can i get around this problem?

推荐答案

使用GCD：

UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc]initWithFrame:CGRectMake(135,140,50,50)];
spinner.color = [UIColor blueColor];
[spinner startAnimating];
[_mapViewController.view addSubview:spinner];

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    // lots of code run in the background

    dispatch_async(dispatch_get_main_queue(), ^{
        // stop and remove the spinner on the main thread when done
        [spinner removeFromSuperview];
    });
});

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