iphone - 用相同的方法满足特定条件后如何使计时器无效？

Question

嗨，我正在尝试在我的iPhone应用程序中显示自定义进度条，因为我正在编写一种增加进度条值的方法，一旦其值变为100％，则我需要使计时器无效，并且需要停止此递归并显示下一个viewController。
我的代码段如下所示，

-(void)progressNextValue
{
    progressValue += 1.0f;
    if(progressValue >= progress.maxValue){
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"end" message:@"TimeOut!!!" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alert show];
        NSLog(@"Time Out!!!!");
        [mytimer invalidate];
        Second *sec = [[Second alloc] initWithNibName:@"Second" bundle:nil];
        [self.view addSubview:sec.view];    
    }

    progress.currentValue = progressValue;
    mytimer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(progressNextValue) userInfo:nil repeats:YES];

}

- (void)viewDidLoad
{
    [super viewDidLoad];
    progress.maxValue = 100.0f;    
    [self progressNextValue];
}

即使我的 progressValue = progress.maxValue， mytimer没有在这里失效。

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Answer 1

每次运行该方法时，您都在设置计时器。添加一个return语句，或将计时器实例化放置在else语句中。

例如:

-(void)progressNextValue
{
    progressValue += 1.0f;
    if(progressValue >= progress.maxValue){
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"end" message:@"TimeOut!!!" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
        [alert show];
        NSLog(@"Time Out!!!!");
        [mytimer invalidate];
        Second *sec = [[Second alloc] initWithNibName:@"Second" bundle:nil];
        [self.view addSubview:sec.view];    
    } else {
        // Move this line inside the else statements so that it only gets run if 
        // the progress bar is not full.
        mytimer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(progressNextValue) userInfo:nil repeats:YES];
    }

    progress.currentValue = progressValue;
}