Make a simple fade in animation in Swift

Question

I am trying to make a simple animation in Swift  It is a fade in   I attempted   self myFirstLabel alpha   0 self myFirstButton alpha   0 self mySecondButton alpha   0   Then  I have   self view addSubview myFirstLabel  self view addSubview myFirstButton  self view addSubview mySecondButton    And then   UIView animateWithDuration 1 5  animations     self myFirstLabel alpha   1 0  self myFirstButton alpha   1 0  self mySecondButton alpha   1 0      I have all of this in my viewDidLoad function   How do I make this work

User · Answer

Swift only solution  Similar to Luca s anwer  I use a UIView extension  Compared to his solution I use DispatchQueue main async to make sure animations are done on the main thread  alpha parameter for fading to a specific value and optional duration parameters for cleaner code   extension UIView     func fadeTo   alpha  CGFloat  duration  TimeInterval   0 3        DispatchQueue main async         UIView animate withDuration  duration            self alpha   alpha                      func fadeIn   duration  TimeInterval   0 3        fadeTo 1 0  duration  duration         func fadeOut   duration  TimeInterval   0 3        fadeTo 0 0  duration  duration          How to use it      fadeIn   - always animates to alpha   1 0 yourView fadeIn          uses default duration of 0 3 yourView fadeIn 1 0      uses custom duration  1 0 in this example      fadeOut   - always animates to alpha   0 0 yourView fadeOut         uses default duration of 0 3 yourView fadeOut 1 0     uses custom duration  1 0 in this example      fadeTo   - used if you want a custom alpha value yourView fadeTo 0 5      uses default duration of 0 3 yourView fadeTo 0 5  duration  1 0

User · Answer

The problem is that you re trying start the animation too early in the view controller s lifecycle  In viewDidLoad  the view has just been created  and hasn t yet been added to the view hierarchy  so attempting to animate one of its subviews at this point produces bad results   What you really should be doing is continuing to set the alpha of the view in viewDidLoad  or where you create your views   and then waiting for the viewDidAppear  method to be called  At this point  you can start your animations without any issue   override func viewDidAppear   animated  Bool        super viewDidAppear animated       UIView animate withDuration  1 5            self myFirstLabel alpha   1 0         self myFirstButton alpha   1 0         self mySecondButton alpha   1 0

User · Answer

0x7ffffff s answer is ok and definitely exhaustive     As a plus  I suggest you to make an UIView extension  in this way    public extension UIView            Fade in a view with a duration    - parameter duration  custom animation duration        func fadeIn duration duration  NSTimeInterval   1 0        UIView animateWithDuration duration  animations            self alpha   1 0                     Fade out a view with a duration    - parameter duration  custom animation duration        func fadeOut duration duration  NSTimeInterval   1 0        UIView animateWithDuration duration  animations            self alpha   0 0                 Swift-3      Fade in a view with a duration          Parameter duration  custom animation duration func fadeIn withDuration duration  TimeInterval   1 0        UIView animate withDuration  duration  animations            self alpha   1 0               Fade out a view with a duration         - Parameter duration  custom animation duration func fadeOut withDuration duration  TimeInterval   1 0        UIView animate withDuration  duration  animations            self alpha   0 0            In this way you can do this wherever in your code   let newImage   UIImage named      newImage alpha   0    or newImage fadeOut duration  0 0  self view addSubview newImage       newImage fadeIn     Code reuse is important

User · Answer

If you want repeatable fade animation you can do that by using CABasicAnimation like below    First create handy UIView extension    extension UIView        enum AnimationKeyPath  String           case opacity    opacity             func flash animation  AnimationKeyPath  withDuration duration  TimeInterval   0 5  repeatCount  Float   5           let flash   CABasicAnimation keyPath  animation rawValue          flash duration   duration         flash fromValue   1    alpha         flash toValue   0    alpha         flash timingFunction   CAMediaTimingFunction name  kCAMediaTimingFunctionEaseInEaseOut          flash autoreverses   true         flash repeatCount   repeatCount          layer add flash  forKey  nil            How to use it          You can use it with all kind of UIViews e g  UIButton  UILabel  UIImage  UIImageView          imageView flash animation   opacity  withDuration  1  repeatCount  5      titleLabel flash animation   opacity  withDuration  1  repeatCount  5

User · Answer

import UIKit      Here is simple subclass for CAAnimation which create a fadeIn animation      class FadeInAdnimation  CABasicAnimation       override init             super init           keyPath    opacity          duration   2 0         fromValue   0         toValue   1         fillMode   CAMediaTimingFillMode forwards         isRemovedOnCompletion   false            required init  coder aDecoder  NSCoder            super init coder  aDecoder               Example of usage      class ViewController  UIViewController        weak var label  UILabel       override func loadView             let view   UIView           view backgroundColor    white          let label   UILabel           label alpha   0         label frame   CGRect x  150  y  200  width  200  height  20          label text    Hello World           label textColor    black         view addSubview label          self label   label          let button   UIButton type   custom          button frame   CGRect x  0  y  250  width  300  height  100          button setTitle  Press to Start FadeIn   for  UIControl State            button backgroundColor    red         button addTarget self  action   selector startFadeIn   for   touchUpInside          view addSubview button           self view   view                    Animation in action              objc private func startFadeIn             label layer add FadeInAdnimation    forKey   fadeIn

User · Answer

Swift 5 Other answers are correct  but in my case I need to handle other properties also  alpha  animate  completion   Because of this  I modified a bit to expose these parameters as below  extension UIView           Helper function to update view s alpha with animation         - Parameter alpha  View s alpha         - Parameter animate  Indicate alpha changing with animation or not         - Parameter duration  Indicate time for animation         - Parameter completion  Completion block after alpha changing is finished     func set alpha  CGFloat  animate  Bool  duration  TimeInterval   0 3  completion    Bool  - gt  Void     nil            let animation      view  UIView  in             view alpha   alpha                        if animate               UIView animate withDuration  duration  animations                    animation self                 completion    finished in                 completion  finished                           else               layer removeAllAnimations               animation self              completion  true

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