javascript - Display Animated Value in React Native Render Text Component - Stack Overflow

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I can not display the Value of Animated on the Render and returns this error.

Invariant Violation: Objects are not valid as a React child (found: object with keys {value}). If you meant to render a collection of children, use an array instead.

Of course, I see the Value in the console

constructor(props) {
    super(props);

    this.state={
       progress:0
    }

    this.animatedValue = new Animated.Value(0);

    this.animatedValue.addListener((progress) => {
        this.setState({progress})
    });
}

ponentDidMount() {
    this.animate()
}

animate() {
    this.animatedValue.setValue(0);
    Animated.timing(
        this.animatedValue,
        {
            toValue: 1,
            duration: 15000,
            easing: Easing.linear
        }
    ).start()
}

render() {
    return(
        <View>
            <Text> {this.state.progress} </Text>
        </View>
    );

}

I can not display the Value of Animated on the Render and returns this error.

Invariant Violation: Objects are not valid as a React child (found: object with keys {value}). If you meant to render a collection of children, use an array instead.

Of course, I see the Value in the console

constructor(props) {
    super(props);

    this.state={
       progress:0
    }

    this.animatedValue = new Animated.Value(0);

    this.animatedValue.addListener((progress) => {
        this.setState({progress})
    });
}

ponentDidMount() {
    this.animate()
}

animate() {
    this.animatedValue.setValue(0);
    Animated.timing(
        this.animatedValue,
        {
            toValue: 1,
            duration: 15000,
            easing: Easing.linear
        }
    ).start()
}

render() {
    return(
        <View>
            <Text> {this.state.progress} </Text>
        </View>
    );

}

• javascript
• reactjs
• react-native

Share Improve this question Follow edited Jul 3, 2018 at 18:30 Tholle 113k2222 gold badges208208 silver badges197197 bronze badges asked Jul 3, 2018 at 18:25 Mahdi BashirpourMahdi Bashirpour 18.9k1717 gold badges131131 silver badges151151 bronze badges 0

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 9

The function given to addListener will be called with an object with a value key as argument, so instead of setting progress with the entire object, use the value instead:

this.animatedValue.addListener((progress) => {
  this.setState({ progress: progress.value });
});

Tholle solution works fine if the animated value doesn't change that much, because it will cause a ponent re-render(as mentioned by @saeedZhiany in his ment) each time the value changes and that can lead to performance issues.

The better solution for these cases is to use ._value property of animatedValue, something like this:

 <Text>
    {Math.round(this.animatedValue._value)}
 </Text>

This way you get the real value at anytime without updating the ponent state. Thus avoiding performance issues.

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