顯示旋塗器在同一個塊

Question

刪除它在這最多需要幾秒鐘我有一個方法：

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]; 

旋轉器不顯示。可能因爲屏幕當時沒有更新。 我該如何解決這個問題？

Answer 1

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]; 
    }); 
});