The following article is part of The Ultimate Guide to React Native Optimization and discusses the use of native solutions to achieve smooth animations and gesture-driven interface at 60FPS.
Why is it important?
Nice and smooth animations are a crucial part of the success of your app. But, when done incorrectly, they can seriously damage your product by slowing it down. In this article, we describe some useful practices to achieve smooth 60FPS animations in React Native with no harm to the speed of your app.
In other blog posts based on The Ultimate Guide to React Native Optimization, we touch on the following topics related to improving performance through understanding the React Native implementation details:
- Picking the right external libraries for your app
- Optimizing battery drain with mobile-dedicated libraries
- Improving React Native performance with high-order components
Be sure to check them out. Now let’s move to the main topic.
The importance of smooth 60FPS animations on mobile devices
Mobile users are used to smooth and well-designed interfaces that quickly respond to their interactions and provide prompt visual feedback. ’ve explained in this article As a result, applications have to register a lot of animations in many places that will have to run while other work is happening.
As we’ve explained in this article, the amount of information that can be passed over through the bridge is limited. There’s no built-in priority queue as of now. In other words, it is on you to structure and design your application so that both the business logic and animations can function without disruptions. This is different from the way we are used to performing animations. For example, on iOS, the built-in APIs offer unprecedented performance and are always scheduled with the appropriate priority. Long story short – we don’t have to worry much about ensuring they’re running at 60 FPS.
With React Native, this story is a bit different. If you do not think about your animations top-down beforehand and choose the right tools to tackle this challenge, you’re on the best way to run into dropped frames sooner or later.
Janky animations make your app look slow and unfinished to users
In today’s world of a sea of applications, providing smooth and interactive UI might be one of your only ways to win over customers that are looking to choose the app to go.
If your application fails to provide a responsive interface that works well with the user interactions (such as gestures), it may affect the new customers and decrease the ROI and user sentiment.
Mobile users like the interfaces that follow them along and look top-notch, so ensuring the animations are always running smoothly is a fundamental part of buildingsuch experience.
Solution: If it’s possible, use native and correct animations
One-off animations in React Native with native driver
Enabling the usage of native driver is the easiest way to improveyour animations performance quickly. However, the subset of style props that can be used together with native driver is limited. You can use it with non-layout properties like transforms and opacity. It will not work with colors, height, and others. Those are enough to implement most of the animations in your app because you usually want to show/hide something or change its position.
Enabling native driver for opacity animation
For more complex use cases, you can use <rte-code>React Native Reanimated<rte-code> library. Its API is compatible with basic <rte-code>Animated<rte-code> library and also introduce a set of more low-level functions to control your animations. Even more importantly, it introduces the possibility to animate all possible style props with native driver. So animating height or color will no longer be an issue. However, transform and opacity animations still will be slightly faster since they are GPU accelerated. But regular users should not see any difference.
Ways to achieve gesture-driven 60FPS animations
The most desired effect that can be achieved with animations is being able to control animation with a gesture. For your customers, this is the most enjoyable part of the interface. It builds a strong sentiment and makes the app feel very smooth and responsive. Plain React Native is very limited when it comes to combining gestures with native driven animations. You can utilize <rte-code>ScrollView<rte-code> scroll events to build things like smooth collapsible header.
For more sophisticated use cases there is an awesome library – React Native Gesture Handler – which allows you to handle different gestures natively and interpolate those into animations. You can build a simple swipeable element by combining it with Animated. However, it will still require JS callbacks, but there is a remedy for that!
The most powerful pair of tools for gesture-driven animations is the usage of Gesture Handler combined with Reanimated. Those were designed to work together and give the possibility to build complex gesture-driven animations that are fully calculated on the native side. The only limitation here is your imagination (and coding skills, since Reanimated low-level API is not so straightforward).
Low-level handling of gestures might not be a piece of cake, but fortunately, there are already 3rd party libraries that utilize mentioned tools and expose the prop <rte-code>callbackNode<rte-code>. It’s nothing more than an <rte-code>Animated.Value<rte-code> derived from specific gesture behavior. Its value range is usually from 0 to 1, which follows the progress of the gesture. You can interpolate the values to animated elements on the screen. A great example of libraries that expose <rte-code>CallbackNode<rte-code> are <rte-code>reanimated-bottom-sheet<rte-code> and <rte-code>react-native-tab-view<rte-code>.
Giving your JS operations lower priority for smoother animations
Read more: https://snack.expo.io/Wv8u!mKwJ
Let users enjoy smooth animations and gesture-driven interface at 60 FPS
There’s no one single right way of doing animations in React Native. The ecosystem is full of different libraries and approaches to handling interactions. The ideas suggested in this section are just recommendations to encourage you not to take the smooth interface for granted.
With such an approach, the application you create will be smoother and snappy. It will not only be pleasant for your users to use but also for you to debug and have fun with it while developing.
If you’ve enjoyed this article, check out the 20th React Native Show episode, in which Łukasz Chludziński and Burger discuss Remotion and animations in React Native.