React Native ref is undefined until page reload

Question

I am using refs to animate a View, but the refs are throwing an undefined error. However, if I comment-out my attempt to access the ref, load the page, un-comment the code, & reload the page, the animation works fine.

My code:

    export const AccountScreen = ({ navigation }) => {
        
          return (
            <SafeAreaView style={{ backgroundColor:'#FFFFFF', flex: 1 }}>
              <Animatable.View style={styles.container} ref={ref => {this.containerRef = ref}}>
              </Animatable.View>
            </SafeAreaView>
          )
      };

   launchOpenAnimation()
   function launchOpenAnimation () {
     this.containerRef.animate(appearContainerAnimation); //If I comment this out, reload, and un-comment, it works
   }

What can I do to fix this? It appears that the ref isn't defined at the time that my launchOpenAnimation() is executed, but that it is defined after, thus resulting in the code working if I comment it out, reload, un-comment, and reload again.

`AccountScreen ` is functional component there is no `this` keyword — Tony Nguyen, Jul 04 '20 at 09:44

Tony Nguyen · Accepted Answer · 2020-07-04T09:49:14.593

First thing first, your question is messed up between calls component and functional component, cuz there is no this in functional component. I'll convert them to function component using useRef and useEffect

In the first run this.containerRef have not be assign to ref of Animatable yet.

Try this

export const AccountScreen = ({ navigation }) => { 
  const animateRef = useRef()
  useEffect(() =>{
     launchOpenAnimation()
     function launchOpenAnimation () {
       // add ? to make sure animate is called only when this.containerRef exists
     containerRef?.current.animate(appearContainerAnimation);
}    
  },[])
      
  return (
    <SafeAreaView style={{ backgroundColor:'#FFFFFF', flex: 1 }}>
      <Animatable.View style={styles.container} ref={ref => {
            ref.animate(appearContainerAnimation); // add this if you need to run when initial render run
            animateRef.current = ref
            }}>
      </Animatable.View>
    </SafeAreaView>
  )
};

React Native ref is undefined until page reload

1 Answers1