Question

我有一个正常运行的动画，直到我从开始到停止更改按钮文本。文本更改但动画本身消失。我做错了什么？


import UIKit

class ViewController: UIViewController {

    var counter = 1

    var timer = NSTimer()

    var isAnimating = false

    @IBOutlet weak var button: UIButton!

    @IBOutlet weak var frogsImage: UIImageView!

    @IBAction func updateImage(sender: AnyObject) {

        if isAnimating == false {
            timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: Selector("doAnimation"), userInfo: nil, repeats: true)
            isAnimating = true
            button.setTitle("Stop Jumping", forState: UIControlState.Normal)

        } else {
            timer.invalidate()
            isAnimating = false
            button.setTitle("Start Jumping", forState: UIControlState.Normal)
        }

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

    func doAnimation() {
        if counter == 4 {
            counter = 1
        } else {
            counter++
        }

        frogsImage.image = UIImage(named: "frame\(counter).png"
        )

    }


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

    override func viewDidLayoutSubviews() {

        // Hiding off the screen
        frogsImage.center = CGPointMake(frogsImage.center.x - 400, frogsImage.center.y)

    }

    override func viewDidAppear(animated: Bool) {
        UIView.animateWithDuration(1) { () -> Void in
            self.frogsImage.center = CGPointMake(self.frogsImage.center.x + 400, self.frogsImage.center.y)
        }
    }


}

Answer 1

动画已停止，因为您使计时器无效。

使计时器失效后，您应该重新启动它。所以，你将再次运行动画。

希望这有帮助。

Answer 2

以下是我会做的一些不同的事情，但我没有让它在项目中运行，因此我无法保证它会全部运作。

class ViewController: UIViewController {

    var counter = 1

    var timer = NSTimer()

    var isAnimating = false
    var didSetup = false
    var didAnimateIn = false

    @IBOutlet weak var button: UIButton!
    @IBOutlet weak var frogsImage: UIImageView!
    @IBAction func updateImage(sender: AnyObject) {

        if isAnimating == false {
            timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: Selector("doAnimation"), userInfo: nil, repeats: true)
            isAnimating = true
            button.setTitle("Stop Jumping", forState: UIControlState.Normal)

        } else {
            timer.invalidate()
            isAnimating = false
            button.setTitle("Start Jumping", forState: UIControlState.Normal)
        }

    }

    func doAnimation() {
        if counter == 4 {
            counter = 1
        } else {
            counter++
        }

        frogsImage.image = UIImage(named: "frame\(counter).png"
        )

    }

    override func viewDidLayoutSubviews() {
        // Change this to always call super first
        super.viewDidLayoutSubviews()

        // Only do this once 
        if !didSetup {
            didSetup = true
            frogsImage.center = CGPointMake(frogsImage.center.x - 400, frogsImage.center.y)
        }

    }

    override func viewDidAppear(animated: Bool) {
        // Change this to always call super
        super.viewDidAppear(animated)

        // Only do this once, after setup
        if didSetup && !didAnimateIn {
            didAnimateIn = true
            UIView.animateWithDuration(1) { () -> Void in
                self.frogsImage.center = CGPointMake(self.frogsImage.center.x + 400, self.frogsImage.center.y)
            }
        }
    }
}

Answer 3

发生的事情是你的图像再次向左移动400像素。您可以通过将向左移位更改为40px并运行应用程序来自行检查。这是因为在多个实例中调用viewDidLayoutSubviews并将图像的位置重置为您最初指定的任何位置。

换句话说，在

时调用该方法

应用程序已打开
再次在动画之前
。

我建议绕过这个是如此添加一个计数变量

import UIKit

class ViewController : UIViewController {
    var viewCount = 0 //ADD THIS

    var counter = 1

    var timer = NSTimer()

    var isAnimating = false

    @IBOutlet weak var button: UIButton!

    @IBOutlet weak var frogsImage: UIImageView!

    @IBAction func updateImage(sender: AnyObject) {

        if isAnimating == false {
            timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: Selector("doAnimation"), userInfo: nil, repeats: true)
            isAnimating = true
            button.setTitle("Stop Jumping", forState: UIControlState.Normal)

        } else {
            timer.invalidate()
            isAnimating = false
            button.setTitle("Start Jumping", forState: UIControlState.Normal)
        }

    }

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

    func doAnimation() {
        if counter == 4 {
            counter = 1
        } else {
            counter++
        }

        frogsImage.image = UIImage(named: "frame\(counter).png")
    }


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

    override func viewDidLayoutSubviews() {

        // ADD THIS IF BLOCK
        if viewCount < 2 {
            frogsImage.center = CGPointMake(frogsImage.center.x - 400, frogsImage.center.y)
            viewCount++
        }

    }

    override func viewDidAppear(animated: Bool) {
        UIView.animateWithDuration(1) { () -> Void in
            self.frogsImage.center = CGPointMake(self.frogsImage.center.x + 400, self.frogsImage.center.y)
        }
    }
}

按钮文本更改后，Swift 2 iOS 9动画消失

3 个答案: