Running Multiple Animations

If you need to run one type of animation after another in macOS, Swift provides a simple way to do this where the code looks like this:

        NSAnimationContext.runAnimationGroup({ (context) -> Void in
               // First animation code here
        }, completionHandler: { () -> Void in
              // Second animation code here          
        })

By itself, this runAnimationGroup code does nothing. What you need to do is put your animation code within the first set of curly brackets and when that first animation completes, then you can run a second set of animation if you wish.

Suppose you want to rotate an item such as a label and when it’s done rotating, flip it back to its original position. First, create a label and an IBOutlet such as:

@IBOutlet weak var lblMessage: NSTextField!

Once you have an IBOutlet to represent a label on the user interface, you can rotate it using this code:

    @IBAction func animateMe(_ sender: NSButton) {
        NSAnimationContext.runAnimationGroup({ (context) -> Void in
            context.duration = 5
            lblMessage.animator().frameRotation = 45
        }, completionHandler: { () -> Void in
            self.lblMessage.animator().frameRotation = 0
        })
    }

Thea love code takes five seconds to rotate a label (lblMessage) 45 degrees. When it’s completed, it changes the label’s rotation back to 0 again.

While this simple example shows how to rotate an item, the more important lesson is to see how the runAnimationGroup lets you combine two different types of animations where the second animation runs after the first animation completes. Any time you need to run two different types of animation back to back, use the runAnimationGroup structure.

March 13th, 2017 by
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