This is useful when making gesture transitions. spring.stopAnimation(callback) will stop the animation and invoke callback with the final value.If you need to run JavaScript in response to the current value, there are two approaches: This is because the value may only be known in the native runtime due to optimizations. You may notice that there is no clear way to read the current value while animating. Responding to the current animation value Custom duration or even a delay before the animation starts is also supported.įor example, if we want to create a 2-second long animation of an object that slightly backs up before moving to its final position: You can specify a different easing function by passing an easing parameter. Easing functions are typically used in animation to convey gradual acceleration and deceleration of objects.īy default, timing will use an easeInOut curve that conveys gradual acceleration to full speed and concludes by gradually decelerating to a stop. It supports animating a value over time using one of various predefined easing functions, or you can use your own. Custom and predefined easing functions, delays, durations, decay factors, spring constants, and more can all be tweaked depending on the type of animation.Īnimated provides several animation types, the most commonly used one being Animated.timing(). Configuring animations Īnimations are heavily configurable. Because the entire configuration is declarative, we will be able to implement further optimizations that serialize the configuration and runs the animation on a high-priority thread. This is done in an optimized way that is faster than calling setState and re-rendering. Then, an easing animation is started on the fadeAnim animated value, which will update all of its dependent mappings (in this case, only the opacity) on each frame as the value animates to the final value of 1. When the component mounts, the opacity is set to 0. Behind the scenes, the numeric value is extracted and used to set opacity. The opacity property on the View is mapped to this animated value. In the FadeInView constructor, a new Animated.Value called fadeAnim is initialized as part of state. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and start/ stop methods to control time-based animation execution.Īnimated exports six animatable component types: View, Text, Image, ScrollView, FlatList and SectionList, but you can also create your own using Animated.createAnimatedComponent().įor example, a container view that fades in when it is mounted may look like this: The Animated API is designed to concisely express a wide variety of interesting animation and interaction patterns in a very performant way. React Native provides two complementary animation systems: Animated for granular and interactive control of specific values, and LayoutAnimation for animated global layout transactions. Animations allow you to convey physically believable motion in your interface. Objects in motion have momentum and rarely come to a stop immediately. Stationary objects must overcome inertia as they start moving. Animations are very important to create a great user experience.
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