animateWithDuration 在 iOS 下不起作用

Question

I've created a view (viewToAnimate) which I want the header to animate up or down. When I press the "down" action, it animates fine downward. When I press the "up action, it does nothing. Why is this? Why can't I get it to animate off the screen?

Git Repo: https://github.com/joshoconnor89/animation

@IBAction func down(sender: AnyObject) {
    var searchHeaderFrame = self.viewToAnimate.frame
    searchHeaderFrame.origin.y = -self.viewToAnimate.frame.size.height
    self.viewToAnimate.frame = searchHeaderFrame
    searchHeaderFrame.origin.y = 0
    
    UIView.animateWithDuration(0.5, animations: {() -> Void in
        self.viewToAnimate.frame = searchHeaderFrame
        self.view!.layoutIfNeeded()
        
    })
}

@IBAction func up(sender: AnyObject) {
    
    var searchHeaderFrame = self.viewToAnimate.frame
    searchHeaderFrame.origin.y = 0
    self.viewToAnimate.frame = searchHeaderFrame
    searchHeaderFrame.origin.y = -self.viewToAnimate.frame.size.height
    
    UIView.animateWithDuration(0.5, animations: {() -> Void in
        self.viewToAnimate.frame = searchHeaderFrame
        self.view!.layoutIfNeeded()
        
    })
    
}

View in storyboard: notice that it starts above the viewcontroller:

Answer 1

The error is you connect slide up button with the two methods try to delete the connection of up method from it and let connection of down.

Answer 2

The problem is CGRect (searchHeaderFrame) variable declare each Action (down and up action), i have run this code and update your code, then its working for me, you change the below code,

 import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var viewToAnimate: UIView!
    var searchHeaderFrame : CGRect!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func SlideDownAction(sender: AnyObject) {

        searchHeaderFrame = self.viewToAnimate.frame
        searchHeaderFrame.origin.y = -self.viewToAnimate.frame.size.height
        self.viewToAnimate.frame = searchHeaderFrame
        searchHeaderFrame.origin.y = 0

        UIView.animateWithDuration(0.5, animations: {() -> Void in
            self.viewToAnimate.frame = self.searchHeaderFrame
            self.view!.layoutIfNeeded()

        })
    }

    @IBAction func SlideUpAction(sender: AnyObject) {

        searchHeaderFrame.origin.y = 0
        self.viewToAnimate.frame = searchHeaderFrame
        searchHeaderFrame.origin.y = -self.viewToAnimate.frame.size.height

        UIView.animateWithDuration(0.5, animations: {() -> Void in
            self.viewToAnimate.frame = self.searchHeaderFrame
            self.view!.layoutIfNeeded()

        })
    }

}

see my output is below,

hope its helpful

Answer 3

I strongly suggest that you animate the constraints instead of the frame of the view when you are using AutoLayout.

Here's the code that works exactly the way you want:

@implementation TestViewController

- (IBAction)slideUp:(id)sender
{
    _topSpaceConstraint.constant = -_viewToAnimate.frame.size.height;

    [UIView animateWithDuration:0.5f animations:^
    {
        [self.view layoutIfNeeded];
    }];
}

- (IBAction)slideDown:(id)sender
{
    _topSpaceConstraint.constant = 0;

    [UIView animateWithDuration:0.5f animations:^
     {
         [self.view layoutIfNeeded];
     }];
}

@end

You see, it's much more simpler than the code you have there. You just have to change the constant value of the vertical space constraint of your viewToAnimate with superview. You can set it as the negative value of the height of your view so that it will go exactly off the screen, and then set it back to zero then it will stick to the topmost part of the screen. Simple as that.

The reason why I suggest you to animate the constraints rather than the frame is that in AutoLayout it is the constraints that dictates the position of the views. The frame is just the result of the AutoLayout process. Although animating the frame would work, but I am sure you'll encounter layout issues in the future when there comes much more complicated animations.

Hope this helps. :)