Fade between text in a UILabel with delay - ios

Question

I want to animate the text of a UILabel so that it shows one text for a couple of seconds and after that fades into a default text.
I'm currently using the following code:
-(void)tapOnBalance:(id)sender{
[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
cell.amountLabel.text = #"Hola!";
} completion:nil];
// Pause the function - act as a 'delay'
[[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:3]];
[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
cell.amountLabel.text = #"Hallo!";
} completion:nil];
}
This works, but the [NSRunLoop currentRunLoop] is pausing the entire app, blocking everything for 3 seconds.
How do I get rid of the block on the main thread and still get the same result?

Answer 1

A simple fade (not a cross-fade) can go like this:
// change a label's text after some delay by fading
// out, changing the text, then fading back in
- (void)fadeLabel:(UILabel *)label toText:(NSString *)toText completion:(void (^)(BOOL))completion {
[UIView animateWithDuration:0.2 delay:0.0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
label.alpha = 0.0;
} completion:^(BOOL finished) {
label.text = toText;
[UIView animateWithDuration:0.2 delay:0.0 options:UIViewAnimationOptionCurveEaseIn animations:^{
label.alpha = 1.0;
} completion:completion];
}];
}
// simpler signature that can be done on a perform
- (void)changeLabelText:(NSString *)toText {
[self fadeLabel:self.myLabel toText:toText completion:nil];
}
// set the label to something, then change it with a fade, then change it back
self.myLabel.text = #"text";
[self performSelector:#selector(changeLabelText:) withObject:#"hola!" afterDelay:4];
[self performSelector:#selector(changeLabelText:) withObject:#"text" afterDelay:8];
You could also nest the calls' completion blocks (and add a delay param) to do something similar without the performs. To do a cross-fade, apply a similar technique with two labels (that have the same frame) where one's alpha is zero and the other's alpha is one.