Here is some code I struggle with for a while.
If you start the fade in animation, the label text fades in. If I start the fade out animation the the label text fades out.
When I start the startFade
method, only fade out is shown. How can I wait for the fadeIn
method to finish visually before starting the fadeOut
method.
-(IBAction)startFade:(id)sender{
[self fadeIn];
[self fadeOut];
}
-(IBAction)fadeIn:(id)sender{
[self fadeIn];
}
-(IBAction)fadeOut:(id)sender{
[self fadeOut];
}
-(void) fadeIn{
[_label setAlpha:0];
[UILabel beginAnimations:NULL context:nil];
[UILabel setAnimationDuration:2.0];
[_label setAlpha:1];
[UILabel commitAnimations];
}
-(void) fadeOut{
[UILabel beginAnimations:NULL context:nil];
[UILabel setAnimationDuration:2.0];
[_label setAlpha:0];
[UILabel commitAnimations];
}
When you call the fadeIn
and fadeOut
methods back to back like you're doing, the code is run instantaneously, so you'll only see animation from the last method called. UIView block based animation provides a completion handler, which seems to be exactly what you're looking for. So your code might looks something like this:
-(IBAction)startFade:(id)sender {
[_label setAlpha:0.0f];
//fade in
[UIView animateWithDuration:2.0f animations:^{
[_label setAlpha:1.0f];
} completion:^(BOOL finished) {
//fade out
[UIView animateWithDuration:2.0f animations:^{
[_label setAlpha:0.0f];
} completion:nil];
}];
}
Swift:
@IBAction func startFade(_ sender: AnyObject) {
label.alpha = 0.0
// fade in
UIView.animate(withDuration: 2.0, animations: {
label.alpha = 1.0
}) { (finished) in
// fade out
UIView.animate(withDuration: 2.0, animations: {
label.alpha = 0.0
})
}
}