objective-c - 为什么我的 UIActivityIndi​​cator 不停止旋转？

Question

在调用 GCD 进程之前，我有以下代码显示 ActivityIndi​​cator。后台进程在完成或遇到错误时会抛出一个通知。我正在错误处理程序中调用 stopAnimating 方法，但微调器一直在旋转。为什么？

UIActivityIndicatorView *mIndicator;

@interface VC_Main ()
@end

- (void)viewDidLoad
{
   [super viewDidLoad];
   [NSLog(@"viewDidLoad");

   // create indicator for download activity
   mIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
   [mIndicator setCenter:CGPointMake([self getScreen].x /2.0, [self getScreen].y / 2.0)]; // landscape mode
   [self.view addSubview:mIndicator]; 

   // fire off a single interval
   [NSTimer scheduledTimerWithTimeInterval:0.0
                                    target:self
                                  selector:@selector(timerTask:)
                                  userInfo:nil
                                   repeats:NO];

...
}


- (void) timerTask:(NSTimer *) timer
{
   NSLog(@"DEBUG: timertask timeout");

   [mIndicator startAnimating];
   ... 
}




// if there is an error parsing xml downloaded from server, it notifies here
- (void) xmlError:(NSNotification *)note
{
   NSLog(@"error parsing xml");
   [mIndicator stopAnimating];  // this doesn't work

   // fire off a refresh using retry timeout
   [NSTimer scheduledTimerWithTimeInterval:TIMEOUT_RETRY_MINS
                                                target:self
                                              selector:@selector(timerTask:)
                                              userInfo:nil
                                               repeats:NO];

   NSLog(@"will retry in %d", TIMEOUT_RETRY_MINS);   
}

Answer 1

与每个 UIKit 调用一样，您需要在主线程上执行此操作。

只需这样做:

dispatch_async(dispatch_get_main_queue(), ^{
    [mIndicator stopAnimating];
});

它应该工作