无法获取活动指示器以显示在iPhone应用程序上

Question

我有一个在IB中创建的视图.在里面我有一个以编程方式创建的滚动视图.在滚动视图中,我连接到Web服务并获取内容和图像.我想在执行此操作时显示活动指示器.所以我有:

- (void)viewDidLoad
{
    [super viewDidLoad];
    activityIndicator = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
    activityIndicator.frame = CGRectMake(0.0, 0.0, 40.0, 40.0);
    activityIndicator.center = self.view.center;
    [self.view.window addSubview:activityIndicator];

在添加scrollview之后,我有:

[self.view addSubview:scrollView];
// ADD Scroll View Ends


    //Add the Lisitng Image
    NSOperationQueue *queue = [NSOperationQueue new];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc] 
                                        initWithTarget:self
                                        selector:@selector(loadImage) 
                                        object:nil];
    [queue addOperation:operation]; 

在loadimage我有:

- (void)loadImage {

    [activityIndicator startAnimating];

我试过[self.view.window addSubview:activityIndi​​cator] ;, [self-> ScrollView addSubview:activityIndi​​cator] ;, [self.view addSubview:activityIndi​​cator];

但我无法得到指标显示.任何人都知道可能出错了什么？

Answer 1

您应该在viewDidload中执行此操作

- (void)viewDidLoad
{
    //Start Activity Indicator View
    indicatorView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    indicatorView.frame = CGRectMake(40.0, 20.0, 60.0, 60.0);
    indicatorView.center = self.view.center;
    [self.view addSubview:indicatorView];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    [indicatorView startAnimating];

    [self performSelectorInBackground:@selector(loadscroll) withObject:self];
}

注意:"performSelectorInBackground"将在视图上显示活动指示器,您的loadScroll方法将从Internet获取所有数据并执行其他工作.

-(void)loadscroll
{
    //Your Scroll View 
        //Your other Data Manipulation even from internet
        //When data is fetched display it 
       [self removeActivityIndicator]; //To stop activity Indicator       
}

- (void)removeActivityIndicator
{
       [indicatorView stopAnimating];
}