Swapnil Dhanwal Swapnil Dhanwal - 2 months ago 6
Swift Question

Frames changing suddenly instead of animation [iOS]

I have a view with a scroll view in my app (a percentage calculator). I am trying to animate the view to fly out and then fly in again from the left albeit with different contents, on the press of a button.
Here's my code:

func next()
{
UIView.animateWithDuration(0.5, animations: {
self.mainView.frame = CGRectMake(-500, self.view.bounds.height/2-self.mainHeight/2, self.mainWidth, self.mainHeight)
self.mainView.center.x -= 600
}) { (success) in
self.mainView.center.x += 1200
}

UIView.animateWithDuration(0.5, animations: {
self.mainView.frame = CGRectMake(self.view.bounds.width/2-self.mainWidth/2, self.view.bounds.height/2-self.mainHeight/2, self.mainWidth, self.mainHeight)
}) { (success) in
print("Animation Successful!")
self.drawView()
}
}


I don't understand why, but the animation doesn't occur, the view disappears completely and I see
"Animation Successful"
in the logs.
To be clear, I have created the view programmatically.

Here's the code in viewDidLoad(); the view displays correctly when it's called:

mainHeight = self.view.bounds.height * 0.85
mainWidth = self.view.bounds.width * 0.85
let viewHeight = self.view.bounds.height
let viewWidth = self.view.bounds.width

mainView.frame = CGRectMake(viewWidth/2-mainWidth/2, viewHeight/2-mainHeight/2, mainWidth, mainHeight)
mainView.layer.cornerRadius = 8
mainView.layer.masksToBounds = true
mainView.backgroundColor = getColor(0, green: 179, blue: 164)
self.view.addSubview(mainView)

scrollView.frame = CGRectMake(0, 0, mainWidth, mainHeight)
scrollView.contentSize = CGSizeMake(mainWidth, 800)
self.mainView.addSubview(scrollView)

contentView.frame = CGRectMake(0, 0, mainWidth, 800);
contentView.backgroundColor = getColor(0, green: 179, blue: 164)
contentView.layer.masksToBounds = true
contentView.clipsToBounds = true
self.scrollView.addSubview(contentView)

Answer

Place self.layoutViewIfNeeded() before frame/center changes. Additionally you may need to put your next animation within a completion handler of the next animation.

func next() {
    UIView.animateWithDuration(0.5, animations: {
        self.view.layoutIfNeeded() // add this
        self.mainView.frame = CGRectMake(-500, self.view.bounds.height/2-self.mainHeight/2, self.mainWidth, self.mainHeight)
        self.mainView.center.x -= 600

    }) { (success) in
        self.view.layoutIfNeeded() // add this
        self.mainView.center.x += 1200

        // your next animation within a completion handler of previous animation
        UIView.animateWithDuration(0.5, animations: {

            self.mainView.frame = CGRectMake(self.view.bounds.width/2-self.mainWidth/2, self.view.bounds.height/2-self.mainHeight/2, self.mainWidth, self.mainHeight)

        }) { (success) in

            print("Animation Successful!")
            self.drawView()
        }
    }
}   

I haven't tested it yet, perhaps some changes or lines ordering is needed.