在另一个

Question

我有一个按钮，按下时会启动一个单独的线程来显示加载动画。这样做的原因是，按下按钮后立即显示加载gif，另一个过程继续，完成警报显示。我遇到的问题是在关闭警报后隐藏动画。

- (IBAction)buttonPressed:(id)sender { 
    [NSThread detachNewThreadSelector:@selector(loadAnimation) toTarget:self withObject:nil];

    ... do other things;

    UIAlertView *alert = [[UIAlertView alloc]initWithTitle: @"Complete" message:@"other things done" delegate: self cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [alert setTag:1];
    [alert show];
}

-(void) alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
    if (alertView.tag == 1) {
        loadingGif.hidden=YES;
    }
}

加载gif：

- (void) loadAnimation {
loadingGif.hidden=NO;
NSArray *imageArray = [[NSArray alloc] initWithObjects:[UIImage imageNamed:@"0.gif"], [UIImage imageNamed:@"1.gif"], [UIImage imageNamed:@"2.gif"], [UIImage imageNamed:@"3.gif"],  nil];

loadingGif = [[UIImageView alloc] initWithFrame:CGRectMake(487, 520, 50, 50)];
[self.view addSubview:loadingGif];
loadingGif.animationImages = imageArray;
loadingGif.animationDuration = 1.5;
[loadingGif startAnimating];
}

动画加载正常，但一旦点击警报确定，它就不会停止。一旦在另一个线程中启动动画，是否可以隐藏动画？

Answer 1

我不确定您是否应该在主线程以外的线程上进行UI更改。另一种方法是立即显示动画并使用NSTimer来安排其他不久之后执行的操作：

- (IBAction)buttonPressed:(id)sender { 

    // load animation on the main thread
    [self loadAnimation];

    // start a timer to do other stuff in 1 ms (will get executed on main thread)
    [NSTimer scheduledTimerWithTimeInterval:0.001
       target:self
       selector:@selector(doOtherStuff)
       userInfo:nil
       repeats:NO]; 
}

- (void)doOtherStuff { 

    ... do other things;

    UIAlertView *alert = [[UIAlertView alloc]initWithTitle: @"Complete" message:@"other things done" delegate: self cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [alert setTag:1];
    [alert show];