/lottie-ios

An iOS library to natively render After Effects vector animations

Primary LanguageObjective-CApache License 2.0Apache-2.0

Lottie for iOS, MacOS (and Android and React Native)

Table of Contents

Introduction

Lottie is a mobile library for Android and iOS that parses Adobe After Effects animations exported as json with bodymovin and renders the vector animations natively on mobile and through React Native!

For the first time, designers can create and ship beautiful animations without an engineer painstakingly recreating it by hand. Since the animation is backed by JSON they are extremely small in size but can be large in complexity! Animations can be played, resized, looped, sped up, slowed down, reversed, and even interactively scrubbed. Lottie can play or loop just a portion of the animation as well, the possibilities are endless! Animations can even be changed at runtime in various ways! Change the color, position or any keyframable value! Lottie also supports native UIViewController Transitions out of the box!

Here is just a small sampling of the power of Lottie

Example1 Example2

Example3

Abcs

Installing Lottie

Github Repo

You can pull the Lottie Github Repo and include the Lottie.xcodeproj to build a dynamic or static library.

Cocoapods

Get Cocoapods Add the pod to your podfile

pod 'lottie-ios'

run

pod install

After installing the cocoapod into your project import Lottie with Objective C #import <Lottie/Lottie.h> Swift import Lottie

Carthage

Get Carthage

Add Lottie to your Cartfile

github "airbnb/lottie-ios" "master"

run

carthage update

In your application targets “General” tab under the “Linked Frameworks and Libraries” section, drag and drop lottie-ios.framework from the Carthage/Build/iOS directory that carthage update produced.

iOS Sample App

Clone this repo and try out the Sample App The repo can build a MacOS Example and an iOS Example

The iOS Example App demos several of the features of Lottie

Example 1Example 2 Example 3

The animation Explorer allows you to scrub, play, loop, and resize animations. Animations can be loaded from the app bundle or from Lottie Files using the built in QR Code reader.

MacOS Sample App

Clone this repo and try out the Sample App The repo can build a MacOS Example and an iOS Example

Lottie Viewer

The Lottie Viewer for MacOS allows you to drag and drop JSON files to open, play, scrub and loop animations. This app is backed by the same animation code as the iOS app, so you will get an accurate representation of Mac and iOS animations.

Objective C Examples

Lottie animations can be loaded from bundled JSON or from a URL To bundle JSON just add it and any images that the animation requires to your target in xcode.

LOTAnimationView *animation = [LOTAnimationView animationNamed:@"Lottie"];
[self.view addSubview:animation];
[animation playWithCompletion:^(BOOL animationFinished) {
// Do Something
}];

If you are working with multiple bundles you can use.

LOTAnimationView *animation = [LOTAnimationView animationNamed:@"Lottie" inBundle:[NSBundle YOUR_BUNDLE]];
[self.view addSubview:animation];
[animation playWithCompletion:^(BOOL animationFinished) {
// Do Something
}];

Or you can load it programmatically from a NSURL

LOTAnimationView *animation = [[LOTAnimationView alloc] initWithContentsOfURL:[NSURL URLWithString:URL]];
[self.view addSubview:animation];

Lottie supports the iOS UIViewContentModes aspectFit, aspectFill and scaleFill

You can also set the animation progress interactively.

CGPoint translation = [gesture getTranslationInView:self.view];
CGFloat progress = translation.y / self.view.bounds.size.height;
animationView.animationProgress = progress;

Or you can play just a portion of the animation:

[lottieAnimation playFromProgress:0.25 toProgress:0.5 withCompletion:^(BOOL animationFinished) {
// Do Something
}];

Swift Examples

Lottie animations can be loaded from bundled JSON or from a URL To bundle JSON just add it and any images that the animation requires to your target in xcode.

let animationView = LOTAnimationView(name: "LottieLogo")
self.view.addSubview(animationView)
animationView.play{ (finished) in
      // Do Something
}

If your animation is in another bundle you can use

let animationView = LOTAnimationView(name: "LottieLogo" bundle:yourBundle)
self.view.addSubview(animationView)
animationView.play()

Or you can load it asynchronously from a URL

let animationView = LOTAnimationView(contentsOf: WebURL)
self.view.addSubview(animationView)
animationView.play()

You can also set the animation progress interactively.

let translation = gesture.getTranslationInView(self.view)
let progress = translation.y / self.view.bounds.size.height;
animationView.animationProgress = progress

Or you can play just a portion of the animation:

animationView.play(fromProgress: 0.25, toProgress: 0.5, withCompletion: nil)

iOS View Controller Transitioning

Lottie comes with a UIViewController animation-controller for making custom viewController transitions!

Transition1 Transition2

Just become the delegate for a transition

- (void)_showTransitionA {
  ToAnimationViewController *vc = [[ToAnimationViewController alloc] init];
  vc.transitioningDelegate = self;
  [self presentViewController:vc animated:YES completion:NULL];
}

And implement the delegate methods with a LOTAnimationTransitionController

#pragma mark -- View Controller Transitioning

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented
presentingController:(UIViewController *)presenting
sourceController:(UIViewController *)source {
LOTAnimationTransitionController *animationController = [[LOTAnimationTransitionController alloc] initWithAnimationNamed:@"vcTransition1"
fromLayerNamed:@"outLayer"
toLayerNamed:@"inLayer"
applyAnimationTransform:NO];
return animationController;
}

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed {
LOTAnimationTransitionController *animationController = [[LOTAnimationTransitionController alloc] initWithAnimationNamed:@"vcTransition2"
fromLayerNamed:@"outLayer"
toLayerNamed:@"inLayer"
applyAnimationTransform:NO];
return animationController;
}

By setting applyAnimationTransform to YES you can make the Lottie animation move the from and to view controllers. They will be positioned at the origin of the layer. When set to NO Lottie just masks the view controller with the specified layer while resepecting z order.

Debugging

Lottie has a couple of debugging features to know about. When an animation is loaded unsupported features are logged out in the console with their function names.

If you checkout LOTHelpers.h you will see two debug flags. ENABLE_DEBUG_LOGGING and ENABLE_DEBUG_SHAPES. ENABLE_DEBUG_LOGGING increases the verbosity of Lottie Logging. It logs anytime an animation node is set during animation. If your animation if not working, turn this on and play your animation. The console log might give you some clues as to whats going on.

ENABLE_DEBUG_SHAPES Draws a colored square for the anchor-point of every layer and shape. This is helpful to see if anything is on screen.

Keypaths

LOTAnimationView provides - (void)logHierarchyKeypaths which will recursively log all settable keypaths for the animation. This is helpful for changing animationations at runtime.

Changing Animations At Runtime

Lottie can do more than just play beautiful animations. Lottie allows you to change animations at runtime.

Say we want to create 4 toggle switches.

Toggle Its easy to create the four switches and play them:

let animationView = LOTAnimationView(name: "toggle");
self.view.addSubview(animationView)
animationView.frame.origin.x = 40
animationView.frame.origin.y = 20
animationView.autoReverseAnimation = true
animationView.loopAnimation = true
animationView.play()

let animationView2 = LOTAnimationView(name: "toggle");
self.view.addSubview(animationView2)
animationView2.frame.origin.x = 40
animationView2.frame.origin.y = animationView.frame.maxY + 4
animationView2.autoReverseAnimation = true
animationView2.loopAnimation = true
animationView2.play()

let animationView3 = LOTAnimationView(name: "toggle");
self.view.addSubview(animationView3)
animationView3.frame.origin.x = 40
animationView3.frame.origin.y = animationView2.frame.maxY + 4
animationView3.autoReverseAnimation = true
animationView3.loopAnimation = true
animationView3.play()

let animationView4 = LOTAnimationView(name: "toggle");
self.view.addSubview(animationView4)
animationView4.frame.origin.x = 40
animationView4.frame.origin.y = animationView3.frame.maxY + 4
animationView4.autoReverseAnimation = true
animationView4.loopAnimation = true
animationView4.play()

Now lets change their colors

Recolored Toggle

animationView2.setValue(UIColor.green, forKeypath: "BG-On.Group 1.Fill 1.Color", atFrame: 0)
animationView3.setValue(UIColor.red, forKeypath: "BG-On.Group 1.Fill 1.Color", atFrame: 0)
animationView4.setValue(UIColor.orange, forKeypath: "BG-On.Group 1.Fill 1.Color", atFrame: 0)
[animationView2 setValue:[UIColor greenColor]
              forKeypath:@"BG-On.Group 1.Fill 1.Color"
                 atFrame:@0];

The keyPath is a dot separated path of layer and property names from After Effects. LOTAnimationView provides - (void)logHierarchyKeypaths which will recursively log all settable keypaths for the animation. Key Path "BG-On.Group 1.Fill 1.Color"

Now lets change a couple of properties

Multiple Colors

animationView2.setValue(UIColor.green, forKeypath: "BG-On.Group 1.Fill 1.Color", atFrame: 0)
animationView2.setValue(UIColor.red, forKeypath: "BG-Off.Group 1.Fill 1.Color", atFrame: 0)

Lottie allows you to change any property that is animatable in After Effects. If a keyframe does not exist, a linear keyframe is created for you. If a keyframe does exist then just its data is replaced.

Supported After Effects Features

Keyframe Interpolation

  • Linear Interpolation
  • Bezier Interpolation
  • Hold Interpolation
  • Rove Across Time
  • Spatial Bezier

Solids

  • Transform Anchor Point
  • Transform Position
  • Transform Scale
  • Transform Rotation
  • Transform Opacity

Masks

  • Path
  • Opacity
  • Multiple Masks (additive, subtractive and intersection)

Track Mattes

  • Alpha Matte

Parenting

  • Multiple Parenting
  • Nulls

Shape Layers

  • Anchor Point
  • Position
  • Scale
  • Rotation
  • Opacity
  • Path
  • Group Transforms (Anchor point, position, scale etc)
  • Rectangle (All properties)
  • Eclipse (All properties)
  • Multiple paths in one group
  • Even-Odd winding paths
  • Reverse Fill Rule

Stroke (shape layer)

  • Stroke Color
  • Stroke Opacity
  • Stroke Width
  • Line Cap
  • Dashes (Now Animated!)

Fill (shape layer)

  • Fill Color
  • Fill Opacity

Trim Paths (shape layer)

  • Trim Paths Start
  • Trim Paths End
  • Trim Paths Offset

Repeaters

  • Supports repeater transforms
  • Offset currently not supported.

Gradients

  • Support for Linear Gradients
  • Support for Radial Gradients

Polystar and Polygon

  • Supported! Theres a known bug if the roundness is greater than 100 percent.

Layer Features

  • Precomps
  • Image Layers
  • Shape Layers
  • Null Layers
  • Solid Layers
  • Parenting Layers
  • Alpha Matte Layers

Currently Unsupported After Effects Features

  • Merge Shapes
  • Trim Shapes Individually feature of Trim Paths
  • Expressions
  • 3d Layer support
  • Time remapping / Layer Reverse
  • Layer Blend Modes
  • Layer Effects

Community Contributions

Alternatives

  1. Build animations by hand. Building animations by hand is a huge time commitment for design and engineering across Android and iOS. It's often hard or even impossible to justify spending so much time to get an animation right.
  2. Facebook Keyframes. Keyframes is a wonderful new library from Facebook that they built for reactions. However, Keyframes doesn't support some of Lottie's features such as masks, mattes, trim paths, dash patterns, and more.
  3. Gifs. Gifs are more than double the size of a bodymovin JSON and are rendered at a fixed size that can't be scaled up to match large and high density screens.
  4. Png sequences. Png sequences are even worse than gifs in that their file sizes are often 30-50x the size of the bodymovin json and also can't be scaled up.

Why is it called Lottie?

Lottie is named after a German film director and the foremost pioneer of silhouette animation. Her best known films are The Adventures of Prince Achmed (1926) – the oldest surviving feature-length animated film, preceding Walt Disney's feature-length Snow White and the Seven Dwarfs (1937) by over ten years The art of Lotte Reineger

Contributing

Contributors are more than welcome. Just upload a PR with a description of your changes.

If you would like to add more JSON files feel free to do so!

Issues or feature requests?

File github issues for anything that is unexpectedly broken. If an After Effects file is not working, please attach it to your issue. Debugging without the original file is much more difficult. Lottie is developed and maintained by Brandon Withrow. Feel free to reach out via email or Twitter

Roadmap (In no particular order)

  • Add support for interactive animated transitions
  • Animation Breakpoints/Seekpoints