怎么用react native实现圆弧拖动进度条

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先上效果图

因为需求需要实现这个效果图 非原生实现，

1. 难点1：绘制 使用svg

2. 难点2：点击事件的处理

3. 难点3：封装

由于绘制需要是使用svg

此处自行百度 按照svg以及api 教学

视图代码块

 render() { return (    //实际圆环  {this._renderCircleSvg()}  // 计算中心距离     // 暴露给外部渲染圆环中心的接口   {this.props.renderCenterView(this.state.temp)}     ); _renderCircleSvg() { //中心点 const cx = this.props.width / 2; const cy = this.props.height / 2; //计算是否有偏差角 对应图就是下面缺了一块的 const prad = this.props.angle / 2 * (Math.PI / 180); //三角计算起点 const startX = -(Math.sin(prad) * this.props.r) + cx; const startY = cy + Math.cos(prad) * this.props.r;  //终点 const endX = Math.sin(prad) * this.props.r + cx; const endY = cy + Math.cos(prad) * this.props.r; // 计算进度点 const progress = parseInt(  this._circlerate() * (360 - this.props.angle) / 100,  10 ); // 根据象限做处理 苦苦苦 高中数学全忘了，参考辅助线 const t = progress + this.props.angle / 2; const progressX = cx - Math.sin(t * (Math.PI / 180)) * this.props.r; const progressY = cy + Math.cos(t * (Math.PI / 180)) * this.props.r;// SVG的描述 这里百度下就知道什么意思 const descriptions = [  'M',  startX,  startY,  'A',  this.props.r,  this.props.r,  0,  1,  1,  endX,  endY, ].join(' '); const progressdescription = [  'M',  startX,  startY,  'A',  this.props.r,  this.props.r,  0,  //根据角度是否是0，1 看下效果就知道了  t >= 180 + this.props.angle / 2 ? 1 : 0,  1,  progressX,  progressY, ].join(' '); return (   ); }}

事件处理代码块

// 参考react native 官网对手势的讲解 iniPanResponder() { this.parseToDeg = this.parseToDeg.bind(this); this._panResponder = PanResponder.create({  // 要求成为响应者：  onStartShouldSetPanResponder: () => true,  onStartShouldSetPanResponderCapture: () => true,  onMoveShouldSetPanResponder: () => true,  onMoveShouldSetPanResponderCapture: () => true,  onPanResponderGrant: evt => {  // 开始手势操作。给用户一些视觉反馈，让他们知道发生了什么事情！  if (this.props.enTouch) {   this.lastTemper = this.state.temp;   const x = evt.nativeEvent.locationX;   const y = evt.nativeEvent.locationY;   this.parseToDeg(x, y);  }  },  onPanResponderMove: (evt, gestureState) => {  if (this.props.enTouch) {   let x = evt.nativeEvent.locationX;   let y = evt.nativeEvent.locationY;   if (Platform.OS === 'android') {   x = evt.nativeEvent.locationX + gestureState.dx;   y = evt.nativeEvent.locationY + gestureState.dy;   }   this.parseToDeg(x, y);  }  },  onPanResponderTerminationRequest: () => true,  onPanResponderRelease: () => {  if (this.props.enTouch) this.props.complete(this.state.temp);  },  // 另一个组件已经成为了新的响应者，所以当前手势将被取消。  onPanResponderTerminate: () => {},  // 返回一个布尔值，决定当前组件是否应该阻止原生组件成为JS响应者  // 默认返回true。目前暂时只支持android。  onShouldBlockNativeResponder: () => true, }); }//画象限看看就知道了 就是和中线点计算角度parseToDeg(x, y) { const cx = this.props.width / 2; const cy = this.props.height / 2; let deg; let temp; if (x >= cx && y <= cy) {  deg = Math.atan((cy - y) / (x - cx)) * 180 / Math.PI;  temp =  (270 - deg - this.props.angle / 2) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } else if (x >= cx && y >= cy) {  deg = Math.atan((cy - y) / (cx - x)) * 180 / Math.PI;  temp =  (270 + deg - this.props.angle / 2) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } else if (x <= cx && y <= cy) {  deg = Math.atan((x - cx) / (y - cy)) * 180 / Math.PI;  temp =  (180 - this.props.angle / 2 - deg) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } else if (x <= cx && y >= cy) {  deg = Math.atan((cx - x) / (y - cy)) * 180 / Math.PI;  if (deg < this.props.angle / 2) {  deg = this.props.angle / 2;  }  temp =  (deg - this.props.angle / 2) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } if (temp <= this.props.min) {  temp = this.props.min; } if (temp >= this.props.max) {  temp = this.props.max; } //因为提供步长，所欲需要做接近步长的数 temp = this.getTemps(temp); this.setState({  temp, }); this.props.valueChange(this.state.temp); } getTemps(tmps) { const k = parseInt((tmps - this.props.min) / this.props.step, 10); const k1 = this.props.min + this.props.step * k; const k2 = this.props.min + this.props.step * (k + 1); if (Math.abs(k1 - tmps) > Math.abs(k2 - tmps)) return k2; return k1; }

完整代码块

import React, { Component } from 'react';import { View, StyleSheet, PanResponder, Platform, Text } from 'react-native';import Svg, { Circle, Path } from 'react-native-svg';export default class CircleView extends Component { static propTypes = { height: React.PropTypes.number, width: React.PropTypes.number, r: React.PropTypes.number, angle: React.PropTypes.number, outArcColor: React.PropTypes.object, progressvalue: React.PropTypes.object, tabColor: React.PropTypes.object, tabStrokeColor: React.PropTypes.object, strokeWidth: React.PropTypes.number, value: React.PropTypes.number, min: React.PropTypes.number, max: React.PropTypes.number, tabR: React.PropTypes.number, step: React.PropTypes.number, tabStrokeWidth: React.PropTypes.number, valueChange: React.PropTypes.func, renderCenterView: React.PropTypes.func, complete: React.PropTypes.func, enTouch: React.PropTypes.boolean, }; static defaultProps = { width: 300, height: 300, r: 100, angle: 60, outArcColor: 'white', strokeWidth: 10, value: 20, min: 10, max: 70, progressvalue: '#ED8D1B', tabR: 15, tabColor: '#EFE526', tabStrokeWidth: 5, tabStrokeColor: '#86BA38', valueChange: () => {}, complete: () => {}, renderCenterView: () => {}, step: 1, enTouch: true, }; constructor(props) { super(props); this.state = {  temp: this.props.value, }; this.iniPanResponder(); } iniPanResponder() { this.parseToDeg = this.parseToDeg.bind(this); this._panResponder = PanResponder.create({  // 要求成为响应者：  onStartShouldSetPanResponder: () => true,  onStartShouldSetPanResponderCapture: () => true,  onMoveShouldSetPanResponder: () => true,  onMoveShouldSetPanResponderCapture: () => true,  onPanResponderGrant: evt => {  // 开始手势操作。给用户一些视觉反馈，让他们知道发生了什么事情！  if (this.props.enTouch) {   this.lastTemper = this.state.temp;   const x = evt.nativeEvent.locationX;   const y = evt.nativeEvent.locationY;   this.parseToDeg(x, y);  }  },  onPanResponderMove: (evt, gestureState) => {  if (this.props.enTouch) {   let x = evt.nativeEvent.locationX;   let y = evt.nativeEvent.locationY;   if (Platform.OS === 'android') {   x = evt.nativeEvent.locationX + gestureState.dx;   y = evt.nativeEvent.locationY + gestureState.dy;   }   this.parseToDeg(x, y);  }  },  onPanResponderTerminationRequest: () => true,  onPanResponderRelease: () => {  if (this.props.enTouch) this.props.complete(this.state.temp);  },  // 另一个组件已经成为了新的响应者，所以当前手势将被取消。  onPanResponderTerminate: () => {},  // 返回一个布尔值，决定当前组件是否应该阻止原生组件成为JS响应者  // 默认返回true。目前暂时只支持android。  onShouldBlockNativeResponder: () => true, }); } componentWillReceiveProps(nextProps) { if (nextProps.value != this.state.temp) {  this.state = {  temp: nextProps.value,  }; } } parseToDeg(x, y) { const cx = this.props.width / 2; const cy = this.props.height / 2; let deg; let temp; if (x >= cx && y <= cy) {  deg = Math.atan((cy - y) / (x - cx)) * 180 / Math.PI;  temp =  (270 - deg - this.props.angle / 2) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } else if (x >= cx && y >= cy) {  deg = Math.atan((cy - y) / (cx - x)) * 180 / Math.PI;  temp =  (270 + deg - this.props.angle / 2) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } else if (x <= cx && y <= cy) {  deg = Math.atan((x - cx) / (y - cy)) * 180 / Math.PI;  temp =  (180 - this.props.angle / 2 - deg) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } else if (x <= cx && y >= cy) {  deg = Math.atan((cx - x) / (y - cy)) * 180 / Math.PI;  if (deg < this.props.angle / 2) {  deg = this.props.angle / 2;  }  temp =  (deg - this.props.angle / 2) /   (360 - this.props.angle) *   (this.props.max - this.props.min) +  this.props.min; } if (temp <= this.props.min) {  temp = this.props.min; } if (temp >= this.props.max) {  temp = this.props.max; } temp = this.getTemps(temp); this.setState({  temp, }); this.props.valueChange(this.state.temp); } getTemps(tmps) { const k = parseInt((tmps - this.props.min) / this.props.step, 10); const k1 = this.props.min + this.props.step * k; const k2 = this.props.min + this.props.step * (k + 1); if (Math.abs(k1 - tmps) > Math.abs(k2 - tmps)) return k2; return k1; } render() { return (    {this._renderCircleSvg()}     {this.props.renderCenterView(this.state.temp)}     ); } _circlerate() { let rate = parseInt(  (this.state.temp - this.props.min) *  100 /  (this.props.max - this.props.min),  10 ); if (rate < 0) {  rate = 0; } else if (rate > 100) {  rate = 100; } return rate; } _renderCircleSvg() { const cx = this.props.width / 2; const cy = this.props.height / 2; const prad = this.props.angle / 2 * (Math.PI / 180); const startX = -(Math.sin(prad) * this.props.r) + cx; const startY = cy + Math.cos(prad) * this.props.r; // // 最外层的圆弧配置 const endX = Math.sin(prad) * this.props.r + cx; const endY = cy + Math.cos(prad) * this.props.r; // 计算进度点 const progress = parseInt(  this._circlerate() * (360 - this.props.angle) / 100,  10 ); // 根据象限做处理 苦苦苦 高中数学全忘了，参考辅助线 const t = progress + this.props.angle / 2; const progressX = cx - Math.sin(t * (Math.PI / 180)) * this.props.r; const progressY = cy + Math.cos(t * (Math.PI / 180)) * this.props.r; const descriptions = [  'M',  startX,  startY,  'A',  this.props.r,  this.props.r,  0,  1,  1,  endX,  endY, ].join(' '); const progressdescription = [  'M',  startX,  startY,  'A',  this.props.r,  this.props.r,  0,  t >= 180 + this.props.angle / 2 ? 1 : 0,  1,  progressX,  progressY, ].join(' '); return (   ); }}const styles = StyleSheet.create({ svg: {},});

外部调用

   {   }}   valueChange={temp => {}}   renderCenterView={temp => (         )}   enTouch={true} />  

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