Adding UIImageView to UIScrollView in background Thread, wont show up until all are added
I have a scrollView where I add some UIButtons and UIActivityIndicators in the main thread. Then I perform a [NSThread detachSelectorInBackground:@selector(getImages) toTarget:self withObject:nil];
getImages downloads some images and add them into UIImageViews and then adds the UIImageViews to the scrollView, but they won开发者_运维技巧t show up until the method getImages is done. Is there any way to get the scrollView to redraw or refresh or something like that?
AND If I scroll the scrollView (with my fingers..) during the getImages method, the UIImageViews that has been added shows up.
- (void) getImages {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
int x=5;
int y=0;
NSData *imgData;
UIImage *img;
UIImageView *imgView;
for (NSDictionary *tmp in thumbs) {
imgData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:[Functions urlForFile:[tmp objectForKey:@"img"]]]];
if ([imgData length] > 0) {
img = [[UIImage alloc] initWithData:imgData];
imgView = [[UIImageView alloc] initWithFrame:CGRectMake(x, y + (133-img.size.height)/2, 100, img.size.height)];
imgView.image = img;
[imgView setAlpha:0.0];
[[self.scrollView viewWithTag:1500000*[[tmp objectForKey:@"id"] intValue]] setAlpha:1.0];
[self.scrollView addSubview:imgView];
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:2.0];
[[self.scrollView viewWithTag:1500000*[[tmp objectForKey:@"id"] intValue]] setAlpha:0.0];
[imgView setAlpha:1.0];
[UIView commitAnimations];
[[self.scrollView viewWithTag:1500000*[[tmp objectForKey:@"id"] intValue]] removeFromSuperview];
[imgView release];
[img release];
[imgData release];
x+=105;
if (x > 300) {
x=5;
y+=138;
}
}
}
[pool release];
[appDelegate.loadingView setHidden:YES];
}
changing the UI in background is not thread-safe! Downloading in background but not displaying. To show an image one by one you can try to run it with performSelectorOnMainThread:@selector() withObject:nil waitUntilDone:YES
for example with self.scrollView addSubview:
.
But again, UI should always use MainThread (e.g. animations)
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