Ios UIActivityIndicatorView不显示/启动动画

我有一个带有UIActivityIndicatorView的视图控制器和一个触发同步的按钮。同步在单独的类中执行，通常在后台执行。同步可以从我的应用程序的不同部分触发，并且我的view controller会收到同步事件的通知

现在，当我单击按钮时，UIActivityIndicatorView既不可见也不设置动画

以下是我在viewDiDLoad中的代码：

self.syncNowActivityIndicatorView.hidesWhenStopped = YES;
self.syncNowActivityIndicatorView.color = [MRStyleController getFirstLightColor];



[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(leechStarted)
                                             name:MRLeechStartedNotification
                                           object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(mergeStarted)
                                             name:MRMergeStartedNotification
                                           object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(fileSyncStarted)
                                             name:MRFileSyncStartedNotification
                                           object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(leechFailed)
                                             name:MRLeechFailedNotification
                                           object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(mergeFailed)
                                             name:MRMergeFailedNotification
                                           object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(fileSyncFailed)
                                             name:MRFileSyncFailedNotification
                                           object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(leechCompleted)
                                             name:MRLeechCompletedNotification
                                           object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(mergeCompleted)
                                             name:MRMergeCompletedNotification
                                           object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(fileSyncCompleted)
                                             name:MRFileSyncCompletedNotification
                                           object:nil];

我在其他一些帖子中读到，如果我在同一个方法中启动和停止指示器视图，它将不起作用，因为在方法执行时ui不会更新。因此，动画必须在一个单独的线程中启动和停止，但在我的例子中，启动和停止调用都采用不同的方法

请注意，我正在接收日志显示的通知

以下是其他方法：

-(void)leechStarted{
    NSLog(@"Leech started");
    if (!_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView startAnimating];
    }
}
-(void)mergeStarted{
    NSLog(@"Merge started");
    if (!_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView startAnimating];
    }
}
-(void)fileSyncStarted{
    NSLog(@"FileSync started");
    if (!_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView startAnimating];
    }
}

-(void)leechFailed{
    NSLog(@"Leech failed");
    if (_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView stopAnimating];
    }
}
-(void)mergeFailed{
    NSLog(@"Merge failed");
    if (_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView stopAnimating];
    }
}
-(void)fileSyncFailed{
    NSLog(@"FileSync failed");
    if (_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView stopAnimating];
    }
}

-(void)leechCompleted{
    NSLog(@"Leech completed");
    if (_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView stopAnimating];
    }
}
-(void)mergeCompleted{
    NSLog(@"Merge completed");
    if (_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView stopAnimating];
    }
 }
 -(void)fileSyncCompleted{
    NSLog(@"FileSync completed");
    if (_syncNowActivityIndicatorView.isAnimating) {
        [_syncNowActivityIndicatorView stopAnimating];
    }
 }

这里是按钮的IBAction：

- (IBAction)syncNow:(id)sender {
    // perform synchronisation
    CoreDataHelper *cdh = [(MRMedSafeAppDelegate *) [[UIApplication sharedApplication] delegate] cdh];
    if ([cdh canSynchronize]) {
        [cdh mergeEnsemble];
        [cdh synchroniseFiles];
    }
}

---

mergeemble

发布leech和merge通知，以及

synchronizefile

文件同步通知，我根据日志接收它们。

您必须在主线程上执行开始/停止动画：

-(void)stopAnimation:(id)sender {
   if( _syncNowActivityIndicatorView.isAnimating ) {
      [_syncNowActivityIndicatorView stopAnimating];
   }
}

-(void)startAnimation:(id)sender {
   if( !_syncNowActivityIndicatorView.isAnimating ) {
      [_syncNowActivityIndicatorView startAnimating];
   }
}

-(void)leechStarted{
    NSLog(@"Leech started");
    [self performSelectorOnMainThread:@selector(startAnimation:) withObject:self waitUntilDone:YES];
}

-(void)leechFailed{
    NSLog(@"Leech failed");
    [self performSelectorOnMainThread:@selector(stopAnimation:) withObject:self waitUntilDone:YES];
}

---

我不确定，如果它工作，但这可能是因为同步发生得太快，我甚至没有看到指标渲染。当下次发生较大的同步时，必须查看它是否可见并具有动画效果。但我认为你是对的，所以我接受你的回答。