Dial.js

import React, { Component } from 'react'
import {
  Dimensions,
  PanResponder,
  StyleSheet,
  View,
} from 'react-native'
import { throttle } from 'lodash'

const GREY_LIGHT = '#eeeeee'

export class Dial extends Component {
  static defaultProps = {
    initialRadius: 1,
    initialAngle: 0,
    precision: 0,
  }

  constructor(props) {
    super(props)
    this.state = {
      startingAngle: this.props.initialAngle,
      startingRadius: this.props.initialRadius,
      releaseAngle: this.props.initialAngle,
      releaseRadius: this.props.initialRadius,
      angle: this.props.initialAngle,
      radius: this.props.initialRadius,
    }
    this.offset = { x: 0, y: 0 }
    this.updateState = throttle(this.updateState.bind(this), 16)
  }

  componentWillMount () {
    this._panResponder = PanResponder.create({
      onStartShouldSetPanResponder: (e, gestureState) => true,
      onStartShouldSetPanResponderCapture: (e, gestureState) => {
        this.measureOffset() // measure again
        const { deg, radius } = this.calcAngle(e.nativeEvent)
        this.setState({ startingAngle: deg, startingRadius: radius })
        return true
      },
      onMoveShouldSetPanResponder: (e, g) => true,
      onMoveShouldSetPanResponderCapture: (e, gestureState) => true,
      onPanResponderGrant: (e, gestureState) => true,
      onPanResponderMove: (e, gestureState) => {
        this.updateAngle(gestureState)
      },
      onPanResponderRelease: (e, gestureState) => {
        const {
          angle,
          radius,
          releaseAngle,
          releaseRadius,
        } = this.state

        if (angle !== releaseAngle || radius !== releaseRadius) {
          this.setState({
            releaseAngle: angle,
            releaseRadius: radius,
          })
        }
      },
    })
  }

  onLayout (nativeEvent) {
    /*
    * Multiple measures to avoid the gap between animated
    * and not animated views
    */
    this.measureOffset()
    setTimeout(() => this.measureOffset(), 200)
  }

  measureOffset () {
    /*
    * const {x, y, width, height} = nativeEvent.layout
    * onlayout values are different than measureInWindow
    * x and y are the distances to its previous element
    * but in measureInWindow they are relative to the window
    */
    const { width: screenWidth } = Dimensions.get('window')

    this.self.measureInWindow((x, y, width, height) => {
      this.offset = {
        x: x % screenWidth + width / 2,
        y: y + height / 2,
      }
      this.radius = width / 2
    })
  }

  updateAngle (gestureState) {
    let { deg, radius } = this.calcAngle(gestureState)
    if (deg < 0) deg += 360
    if (Math.abs(this.state.angle - deg) > this.props.precision) {
      this.updateState({ deg, radius })
    }
  }

  calcAngle (gestureState) {
    const { pageX, pageY, moveX, moveY } = gestureState
    const [x, y] = [pageX || moveX, pageY || moveY]
    const [dx, dy] = [x - this.offset.x, y - this.offset.y]
    return {
      deg: Math.atan2(dy, dx) * 180 / Math.PI + 120,
      radius: Math.sqrt(dy * dy + dx * dx) / this.radius, // pitagoras r^2 = x^2 + y^2 normalizado
    }
  }

  updateState ({ deg, radius = this.state.radius }) {
    radius = this.state.releaseRadius + radius - this.state.startingRadius
    if (radius < this.props.radiusMin) radius = this.props.radiusMin
    else if (radius > this.props.radiusMax) radius = this.props.radiusMax

    const angle = deg + this.state.releaseAngle - this.state.startingAngle
    if (deg < 0) deg += 360

    if (angle !== this.state.angle || radius !== this.state.radius) {
      this.setState({ angle, radius })
      if (this.props.onValueChange) this.props.onValueChange(angle, radius)
    }
  }

  forceUpdate = (deg: number, radius: number) => {
    this.setState({
      angle: deg === undefined ? this.state.angle : deg,
      radius: radius === undefined ? this.state.radius : radius,
    })
  }

  render () {
    const rotate = this.props.fixed ? '0deg' : `${this.state.angle}deg`
    const scale = this.props.elastic ? this.state.radius : 1

    return (
      <View
        onLayout={(nativeEvent) => this.onLayout(nativeEvent)}
        ref={(node) => { this.self = node }}
        style={[styles.coverResponder, this.props.responderStyle]}
        {...this._panResponder.panHandlers}
      >
        {this.props.children
          ? <View style={[this.props.wrapperStyle, { transform: [{ rotate }, { scale }] }]}>
            {this.props.children}
          </View>
          : <DefaultDial style={this.props.style} rotate={rotate} scale={scale} />
        }
      </View>
    )
  }
}

export const DefaultDial = ({ style = {}, rotate = '0rad', scale = 1 }) => (
  <View
    style={[styles.dial, style, {
      transform: [
        { rotate }, { scale },
      ]
    }]} >
    <View style={styles.innerDialDecorator}>
      <View style={styles.pointer} />
    </View>
  </View>
)

const styles = StyleSheet.create({
  coverResponder: {
    padding: 20, // needs a minimum
  },
  dial: {
    width: 120,
    height: 120,
    backgroundColor: 'white',
    borderRadius: 60,
    elevation: 5,
    shadowColor: GREY_LIGHT,
    shadowOffset: { width: 1, height: 2 },
    shadowOpacity: 0.8,
    shadowRadius: 1,
  },
  innerDialDecorator: {
    top: 10,
    left: 10,
    width: 100,
    height: 100,
    borderRadius: 50,
    backgroundColor: 'white',
    elevation: 3,
  },
  pointer: {
    top: 20,
    left: 20,
    position: 'absolute',
    width: 10,
    height: 10,
    backgroundColor: 'rgb(221,223,226)',
    borderRadius: 5,
  },
})