UIActivityIndicator not showing up

问题

I have implemented a UIActivityIndicator that shows up in one part of my program but not another. I have the activity indicator come up while i am loading a table, however, i am trying to get it to start animating again after the user has clicked a button and is waiting for the table to reload. The table reloads, but no indicator. Here is the code.

- (void)viewWillAppear:(BOOL)animated {
    CGRect frame = CGRectMake (120.0, 185.0, 80, 80);
    activity = [[UIActivityIndicatorView alloc] initWithFrame: frame];
    activity.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray;
    [activity startAnimating];

    [navigationUpdateFromDetail.window addSubview: activity];

    [super viewWillAppear:animated];
}

It comes up for that part. However, for the next part it does not want to seem to come up.

- (IBAction) btnGreaterTen_clicked :(id)sender {

    self.searchDistance = [NSNumber numberWithDouble : 10];

    CGRect frame = CGRectMake (120.0, 185.0, 80, 80);

    activity = [[UIActivityIndicatorView alloc] initWithFrame: frame];
    activity.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray;

    [navigationUpdateFromDetail.window addSubview: activity];
    [activity startAnimating];


    NSLog(@" search value after change %@", [searchDistance description]);

    [self getSetDisplay];

    [activity stopAnimating];
}

That button changes a variable and is suppose to start the animation, but it does not. I have changed the color to make sure it was not just blending in, so that is not the solution. I tried to recreate the same object, but still no luck. Thank you in advance.

回答1:

That won't work, because the animation will only show when the main application loop is "running". In your code, you're blocking the main thread by calling [self getSetDisplay].

You should load your data asynchronously to make this work (in a background thread). Then you can call startAnimating, start your thread, and when the thread finishes, stop the animation.

回答2:

This has been bugging me for ages, and I just found that when using a search display controller I had to add the activity indicator as a subview of the search results to get it to show. In my viewDidLoad, I put...

// create activity indicator
activityIndicator = [[UIActivityIndicatorView alloc]initWithFrame:CGRectMake(0.0f, 0.0f, 32.0f, 32.0f)];
[activityIndicator setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleGray];
[self.searchDisplayController.searchResultsTableView addSubview:activityIndicator];

When I want to start animating, i put...

[activityIndicator setCenter:CGPointMake(self.searchDisplayController.searchResultsTableView.frame.size.width/2.0f, self.searchDisplayController.searchResultsTableView.frame.size.height/2.0f)];
[activityIndicator startAnimating];

Hope this helps someone.

回答3:

try adding

activity.hidden = NO;

just before

[activity startAnimating];

来源：https://stackoverflow.com/questions/1984487/uiactivityindicator-not-showing-up

标签

iphone

objective-c

uiactivityindicatorview