Implementing Fade-In Fade-Out animation in NSView on Mac OS X

2011-07-18

It is easy to implement Fade-In animation in UIView on iOS. We just need to change alpha value in the animation.

theView.alpha = 0.0f;
[UIView beginAnimations:@"fadeIn" context:nil];
[UIView setAnimationDuration:1.0];
theView.alpha = 1.0f;
[UIView commitAnimations];

But the following code does not work in NSView on Mac Snow leopard.

[theView setAlphaValue:0.0f];
[[theView animator] setAlphaValue:0.8f];

I found addSubView and removeFromSuperview can have fade-in fade-out effects.

[[theSuperview animator] addSubview:theView];

There is a problem. We cannot change the duration time in the following code:

CABasicAnimation *animation = [CABasicAnimation animation];
animation.duration = 3.0f;
[theSuperview setAnimations:[NSDictionary dictionaryWithObjectsAndKeys:animation, @"FadeIn", nil]];
[[theSuperview animator] addSubview:theView];

Now I have the solution.

Fade-in animation:

[NSAnimationContext beginGrouping];
[[NSAnimationContext currentContext] setDuration:2.0];
[[theSuperview animator] addSubview:theView];
[NSAnimationContext endGrouping];

Fade-out animation:

[NSAnimationContext beginGrouping];
[[NSAnimationContext currentContext] setDuration:2.0];
[[theView animator] removeFromSuperview];
[NSAnimationContext endGrouping];