javascript - react native circle transform translate animation

Question

hi i want that the animated.view move like a circle. I thought to this with sinus but it does not work. Somebody knows how to do it? I dont want to rotate the view. It just should move in circle. I am new to react native. It would be nice if somebody can help me.

//import liraries
import React, { Component } from 'react';
import { View, Text, StyleSheet, Animated, Button, TouchableOpacity } from 'react-native';

// create a component
class MyClass extends Component {
  constructor() {
    super()
    this.animated = new Animated.Value(0);
  }

  animate() {    
    this.animated.setValue(0)
    Animated.timing(this.animated, {
      toValue: Math.PI *2,
      duration: 1000,
    }).start();
  }


  render() {
    const translateY = this.animated.interpolate({
      inputRange: [0, Math.PI *2],
      outputRange: [0, 200]
    });
    const translateX = translateY
    const transform = [{ translateY }, {translateX}];
    return (
      <View style={styles.container}>
        <Animated.View style={[{ transform }]}>
          <TouchableOpacity style={styles.btn}>
            <Text>hallo</Text>
          </TouchableOpacity>
        </Animated.View>
        <Button title="Test" onPress={() => { 
          this.animate() 
          }} />
      </View>
    );
  }
}

// define your styles
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#2c3e50',
  },
  btn: {
    backgroundColor: 'red',
    justifyContent: 'center',
    alignItems: 'center',
    width: 50,
  }
});

//make this component available to the app
export default MyClass;

Answer 1

You have to calculate translateX and translateY with Trigonometric Function.

translateX is corresponding to Math.sin(), and translateY is corresponding to Math.cos().

Although react-native animated.interpolate doesn't support function callback, you can simulate it by divided into several parts (I picked 50 in my code example):

Full Code:

export class App extends Component {
    constructor() {
        super()
        this.animated = new Animated.Value(0);

        var range = 1, snapshot = 50, radius = 100;
        /// translateX
        var inputRange = [], outputRange = [];
        for (var i=0; i<=snapshot; ++i) {
            var value = i/snapshot;
            var move = Math.sin(value * Math.PI * 2) * radius;
            inputRange.push(value);
            outputRange.push(move);
        }
        this.translateX = this.animated.interpolate({ inputRange, outputRange });

        /// translateY
        var inputRange = [], outputRange = [];
        for (var i=0; i<=snapshot; ++i) {
            var value = i/snapshot;
            var move = -Math.cos(value * Math.PI * 2) * radius;
            inputRange.push(value);
            outputRange.push(move);
        }
        this.translateY = this.animated.interpolate({ inputRange, outputRange });
    }

      animate() {
        this.animated.setValue(0)
        Animated.timing(this.animated, {
          toValue: 1,
          duration: 1000,
        }).start();
      }


      render() {
        const transform = [{ translateY: this.translateY }, {translateX: this.translateX}];
        return (
          <View style={styles.container}>
            <Animated.View style={[{ transform }]}>
              <TouchableOpacity style={styles.btn}>
                <Text>hallo</Text>
              </TouchableOpacity>
            </Animated.View>
            <Button title="Test" onPress={() => { 
              this.animate() 
              }} />
          </View>
        );
      }
    }

    // define your styles
    const styles = StyleSheet.create({
      container: {
        flex: 1,
        justifyContent: 'center',
        alignItems: 'center',
        backgroundColor: '#2c3e50',
      },
      btn: {
        backgroundColor: 'red',
        justifyContent: 'center',
        alignItems: 'center',
        width: 50,
      }
    });

Result: