Question

如标题所述，我无法让UIButton淡入ViewDidLoad方法。这是我到目前为止的代码：

ViewController.swift

import UIKit
import QuartzCore
class ViewController: UIViewController {

    @IBOutlet weak var nextButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        self.nextButton.fadeIn(duration: 10.0, delay: 10.0)
    }
}

UIViewExtensions.swift

import Foundation
import UIKit

extension UIView {
    func fadeIn(duration: NSTimeInterval = 1.0, delay: NSTimeInterval = 0.0, completion: ((Bool) -> Void) = {(finished: Bool) -> Void in}) {
        UIView.animateWithDuration(duration, delay: delay, options: UIViewAnimationOptions.CurveEaseIn, animations: {
            self.alpha = 1.0
            }, completion: completion)  }

    func fadeOut(duration: NSTimeInterval = 1.0, delay: NSTimeInterval = 0.0, completion: (Bool) -> Void = {(finished: Bool) -> Void in}) {
        UIView.animateWithDuration(duration, delay: delay, options: UIViewAnimationOptions.CurveEaseIn, animations: {
            self.alpha = 0.0
            }, completion: completion)
    }
}

Answer 1

您不希望在viewDidLoad上启动任何淡入效果。当类初始化（在init之后）时调用此方法。它在视图可见之前发生。您想在viewDidAppear中启动动画。一旦视图在屏幕上可见，就会调用此方法。当你在viewDidLoad中启动它时，它已经在到达viewDidAppear时完成了动画，假设当然你在大约0.5秒内完成了淡入淡出。

Answer 2

在故事板上将按钮alpha设置为0，以便您可以淡入。

因为，如果你的按钮alpha是1，那么你想要动画为1，IOS什么都不做

 override func viewDidAppear(animated: Bool) {
        self.button.fadeIn(duration: 3, delay: 0)

    }

无法让UIButton淡入ViewDidLoad

2 个答案: