Question

Below is a block of code that runs in a separate thread from my app’s main thread. How do I get the UI to update after each button gets its thumbnail? Right now it doesn’t update until the whole method finishes. The buttons are already added to a UIScrollView.

(LotsGridButton is just a UIButton with some extra properties.)

- (void)fetchThumbnails {
    CCServer* server = [[CCServer alloc] init];
    for (int i=0; i<[buttons count]; i++) {
        LotsGridButton* button = [buttons objectAtIndex:i];     
        if (button.lot.thumbnail) continue;
        // load the thumbnail image from the server
        button.lot.thumbnail = [server imageWithPath:button.lot.thumbnailURL];
        [button setImage:button.lot.thumbnail forState:UIControlStateNormal];
    }
    [server release];
}

Answer 1

In place of setImage:forState:, take a look at the performSelectorOnMainThread: method, e.g.:

[myButton performSelectorOnMainThread:@selector(setThumbnail:) withObject:[server imageWithPath:myButton.lot.thumbnailURL] waitUntilDone:NO];