本篇文章主要介绍了react-native之ART绘图方法详解，小编觉得挺不错的，现在分享给大家，也给大家做个参考。一起跟随小编过来看看吧
背景
在移动应用的开发过程中，绘制基本的二维图形或动画是必不可少的。然而，考虑到Android和iOS均有一套各自的API方案，因此采用一种更普遍接受的技术方案，更有利于代码的双平台兼容。
art是一个旨在多浏览器兼容的Node style CommonJS模块。在它的基础上，Facebook又开发了React-art ，封装art，使之可以被react.js所使用，即实现了前端的svg库。然而，考虑到react.js的JSX语法，已经支持将 等等svg标签直接插入到dom中（当然此时使用的就不是react-art库了）此外还有HTML canvas的存在，因此，在前端上，react-art并非不可替代。
然而，在移动端，考虑到跨平台的需求，加之web端的技术积累，react-art成为了现成的绘制图形的解决方案。react-native分别在0.10.0和0.18.0上添加了ios和android平台上对react-art的支持。
示例代码
React.js和React-Native的区别，只在于下文所述的ART获取上，然后该例子就可以同时应用在Web端和移动端上了。react-art自带的官方例子：Vector-Widget
Vector-Widget额外实现了旋转，以及鼠标点击事件的旋转加速响应。Web端可以看到点击加速，但是在移动端无效，原因是React Native并未对Group中onMouseDown和onMouseUp属性作处理。本文着重于静态svg的实现，暂时无视动画部分效果即可。
ART
在react native中ART是个非常重要的库，它让非常酷炫的绘图及动画变成了可能。需要注意的是，在React Native引入ART过程中，Android默认就包含ART库，IOS需要单独添加依赖库。
ios添加依赖库
1、使用xcode中打开React-native中的iOS项目，选中‘Libraries'目录 ――> 右键选择‘Add Files to 项目名称' ――> ‘node_modules/react-native/Libraries/ART/ART.xcodeproj' 添加；
2、选中项目根目录 ――> 点击'Build Phases‘ ――> 点击‘Link Binary With Libraries' ――> 点击左下方‘+' ――> 选中‘libART.a'添加。
基础组件
ART暴露的组件共有7个，本文介绍常用的四个组件：Surface、Group、Shape、Text。
- Surface - 一个矩形可渲染的区域，是其他元素的容器
- Group - 可容纳多个形状、文本和其他的分组
- Shape - 形状定义，可填充
- Text - 文本形状定义
属性
Surface
- width : 渲染区域的宽
- height : 定义渲染区域的高
Shape
- d : 定义绘制路径
- stroke : 描边颜色
- strokeWidth : 描边宽度
- strokeDash : 定义虚线
- fill : 填充颜色
Text
- funt : 字体样式，定义字体、大小、是否加粗 如: bold 35px Heiti SC
Path
- moveTo(x,y) : 移动到坐标（x,y）
- lineTo(x,y) : 连线到（x,y）
- arc() : 绘制弧线
- close() : 封闭空间
代码示例
绘制直线
import React from 'react' import { View, ART } from 'react-native' export default class Line extends React.Component{ render(){ const path = ART.Path(); path.moveTo(1,1); //将起始点移动到(1,1) 默认(0,0) path.lineTo(300,1); //连线到目标点(300,1) return( ) } }
绘制虚线
了解strokeDash的参数，
[10,5] : 表示绘10像素实线在绘5像素空白，如此循环
[10,5,20,5] : 表示绘10像素实线在绘制5像素空白在绘20像素实线及5像素空白
import React from 'react' import { View, ART } from 'react-native' const {Surface, Shape, Path} = ART; export default class DashLine extends React.Component{ render(){ const path = Path() .moveTo(1,1) .lineTo(300,1); return( ) } }
绘制矩形
首先通过lineTo绘制三条边，在使用close链接第四条边。fill做颜色填充.
import React from 'react' import { View, ART } from 'react-native' const {Surface, Shape, Path} = ART; export default class Rect extends React.Component{ render(){ const path = new Path() .moveTo(1,1) .lineTo(1,99) .lineTo(99,99) .lineTo(99,1) .close(); return( ) } }
绘圆
了解arc(x,y,radius)的使用, 终点坐标距离起点坐标的相对距离。
import React from 'react' import { View, ART } from 'react-native' const {Surface, Shape, Path} = ART; export default class Circle extends React.Component{ render(){ const path = new Path() .moveTo(50,1) .arc(0,99,25) .arc(0,-99,25) .close(); return( ) } }
绘制文字
了解funt属性的使用，规则是“粗细 字号 字体”
注意： 字体应该是支持path属性的，应该是实现bug并没有不生效。 Android通过修改源码是可以解决的，IOS没看源码。
import React, {Component} from 'react'; import { AppRegistry, StyleSheet, ART, View } from 'react-native'; const {Surface, Text, Path} = ART; export default class ArtTextView extends Component { render() { return ( React ); } } const styles = StyleSheet.create({ container: { flex: 1, justifyContent: 'center', alignItems: 'center', backgroundColor: '#F5FCFF', }, });
绘制扇形
在这里需要使用arc做路径绘制。
Wedge.js
import React, { Component, PropTypes } from 'react'; import { ART } from 'react-native'; const { Shape, Path } = ART; /** * Wedge is a React component for drawing circles, wedges and arcs. Like other * ReactART components, it must be used in a . */ export default class Wedge extends Component { static propTypes = { outerRadius: PropTypes.number.isRequired, startAngle: PropTypes.number.isRequired, endAngle: PropTypes.number.isRequired, originX: PropTypes.number.isRequired, originY: PropTypes.number.isRequired, innerRadius: PropTypes.number, }; constructor(props : any) { super(props); (this:any).circleRadians = Math.PI * 2; (this:any).radiansPerDegree = Math.PI / 180; (this:any)._degreesToRadians = this._degreesToRadians.bind(this); } /** * _degreesToRadians(degrees) * * Helper function to convert degrees to radians * * @param {number} degrees * @return {number} */ _degreesToRadians(degrees : number) : number { if (degrees !== 0 && degrees % 360 === 0) { // 360, 720, etc. return (this:any).circleRadians; } return degrees * (this:any).radiansPerDegree % (this:any).circleRadians; } /** * _createCirclePath(or, ir) * * Creates the ReactART Path for a complete circle. * * @param {number} or The outer radius of the circle * @param {number} ir The inner radius, greater than zero for a ring * @return {object} */ _createCirclePath(or : number, ir : number) : Path { const path = new Path(); path.move(0, or) .arc(or * 2, 0, or) .arc(-or * 2, 0, or); if (ir) { path.move(or - ir, 0) .counterArc(ir * 2, 0, ir) .counterArc(-ir * 2, 0, ir); } path.close(); return path; } /** * _createArcPath(sa, ea, ca, or, ir) * * Creates the ReactART Path for an arc or wedge. * * @param {number} startAngle The starting degrees relative to 12 o'clock * @param {number} endAngle The ending degrees relative to 12 o'clock * @param {number} or The outer radius in pixels * @param {number} ir The inner radius in pixels, greater than zero for an arc * @return {object} */ _createArcPath(originX : number, originY : number, startAngle : number, endAngle : number, or : number, ir : number) : Path { const path = new Path(); // angles in radians const sa = this._degreesToRadians(startAngle); const ea = this._degreesToRadians(endAngle); // central arc angle in radians const ca = sa > ea ? (this:any).circleRadians - sa + ea : ea - sa; // cached sine and cosine values const ss = Math.sin(sa); const es = Math.sin(ea); const sc = Math.cos(sa); const ec = Math.cos(ea); // cached differences const ds = es - ss; const dc = ec - sc; const dr = ir - or; // if the angle is over pi radians (180 degrees) // we will need to let the drawing method know. const large = ca > Math.PI; // TODO (sema) Please improve theses comments to make the math // more understandable. // // Formula for a point on a circle at a specific angle with a center // at (0, 0): // x = radius * Math.sin(radians) // y = radius * Math.cos(radians) // // For our starting point, we offset the formula using the outer // radius because our origin is at (top, left). // In typical web layout fashion, we are drawing in quadrant IV // (a.k.a. Southeast) where x is positive and y is negative. // // The arguments for path.arc and path.counterArc used below are: // (endX, endY, radiusX, radiusY, largeAngle) path.move(or + or * ss, or - or * sc) // move to starting point .arc(or * ds, or * -dc, or, or, large) // outer arc .line(dr * es, dr * -ec); // width of arc or wedge if (ir) { path.counterArc(ir * -ds, ir * dc, ir, ir, large); // inner arc } return path; } render() : any { // angles are provided in degrees const startAngle = this.props.startAngle; const endAngle = this.props.endAngle; // if (startAngle - endAngle === 0) { // return null; // } // radii are provided in pixels const innerRadius = this.props.innerRadius || 0; const outerRadius = this.props.outerRadius; const { originX, originY } = this.props; // sorted radii const ir = Math.min(innerRadius, outerRadius); const or = Math.max(innerRadius, outerRadius); let path; if (endAngle >= startAngle + 360) { path = this._createCirclePath(or, ir); } else { path = this._createArcPath(originX, originY, startAngle, endAngle, or, ir); } return ; } }
示例代码：
import React from 'react' import { View, ART } from 'react-native' const {Surface} = ART; import Wedge from './Wedge' export default class Fan extends React.Component{ render(){ return( ) } }
综合示例
相关代码：
/** * Sample React Native App * https://github.com/facebook/react-native * @flow */ import React, { Component }from 'react'; import { ART as Art, StyleSheet, View, Dimensions, TouchableWithoutFeedback, Animated } from 'react-native'; var HEART_SVG = "M130.4-0.8c25.4 0 46 20.6 46 46.1 0 13.1-5.5 24.9-14.2 33.3L88 153.6 12.5 77.3c-7.9-8.3-12.8-19.6-12.8-31.9 0-25.5 20.6-46.1 46-46.2 19.1 0 35.5 11.7 42.4 28.4C94.9 11 111.3-0.8 130.4-0.8" var HEART_COLOR = 'rgb(226,38,77,1)'; var GRAY_HEART_COLOR = "rgb(204,204,204,1)"; var FILL_COLORS = [ 'rgba(221,70,136,1)', 'rgba(212,106,191,1)', 'rgba(204,142,245,1)', 'rgba(204,142,245,1)', 'rgba(204,142,245,1)', 'rgba(0,0,0,0)' ]; var PARTICLE_COLORS = [ 'rgb(158, 202, 250)', 'rgb(161, 235, 206)', 'rgb(208, 148, 246)', 'rgb(244, 141, 166)', 'rgb(234, 171, 104)', 'rgb(170, 163, 186)' ] getXYParticle = (total, i, radius) => { var angle = ( (2 * Math.PI) / total ) * i; var x = Math.round((radius * 2) * Math.cos(angle - (Math.PI / 2))); var y = Math.round((radius * 2) * Math.sin(angle - (Math.PI / 2))); return { x: x, y: y, } } getRandomInt = (min, max) => { return Math.floor(Math.random() * (max - min)) + min; } shuffleArray = (array) => { for (var i = array.length - 1; i > 0; i--) { var j = Math.floor(Math.random() * (i + 1)); var temp = array[i]; array[i] = array[j]; array[j] = temp; } return array; } var { Surface, Group, Shape, Path } = Art; //使用Animated.createAnimatedComponent对其他组件创建对话 //创建一个灰色的新型图片 var AnimatedShape = Animated.createAnimatedComponent(Shape); var { width: deviceWidth, height: deviceHeight } = Dimensions.get('window'); export default class ArtAnimView extends Component { constructor(props) { super(props); this.state = { animation: new Animated.Value(0) }; } explode = () => { Animated.timing(this.state.animation, { duration: 1500, toValue: 28 }).start(() => { this.state.animation.setValue(0); this.forceUpdate(); }); } getSmallExplosions = (radius, offset) => { return [0, 1, 2, 3, 4, 5, 6].map((v, i, t) => { var scaleOut = this.state.animation.interpolate({ inputRange: [0, 5.99, 6, 13.99, 14, 21], outputRange: [0, 0, 1, 1, 1, 0], extrapolate: 'clamp' }); var moveUp = this.state.animation.interpolate({ inputRange: [0, 5.99, 14], outputRange: [0, 0, -15], extrapolate: 'clamp' }); var moveDown = this.state.animation.interpolate({ inputRange: [0, 5.99, 14], outputRange: [0, 0, 15], extrapolate: 'clamp' }); var color_top_particle = this.state.animation.interpolate({ inputRange: [6, 8, 10, 12, 17, 21], outputRange: shuffleArray(PARTICLE_COLORS) }) var color_bottom_particle = this.state.animation.interpolate({ inputRange: [6, 8, 10, 12, 17, 21], outputRange: shuffleArray(PARTICLE_COLORS) }) var position = getXYParticle(7, i, radius) return ( ) }, this) } render() { var heart_scale = this.state.animation.interpolate({ inputRange: [0, .01, 6, 10, 12, 18, 28], outputRange: [1, 0, .1, 1, 1.2, 1, 1], extrapolate: 'clamp' }); var heart_fill = this.state.animation.interpolate({ inputRange: [0, 2], outputRange: [GRAY_HEART_COLOR, HEART_COLOR], extrapolate: 'clamp' }) var heart_x = heart_scale.interpolate({ inputRange: [0, 1], outputRange: [90, 0], }) var heart_y = heart_scale.interpolate({ inputRange: [0, 1], outputRange: [75, 0], }) var circle_scale = this.state.animation.interpolate({ inputRange: [0, 1, 4], outputRange: [0, .3, 1], extrapolate: 'clamp' }); var circle_stroke_width = this.state.animation.interpolate({ inputRange: [0, 5.99, 6, 7, 10], outputRange: [0, 0, 15, 8, 0], extrapolate: 'clamp' }); var circle_fill_colors = this.state.animation.interpolate({ inputRange: [1, 2, 3, 4, 4.99, 5], outputRange: FILL_COLORS, extrapolate: 'clamp' }) var circle_opacity = this.state.animation.interpolate({ inputRange: [1, 9.99, 10], outputRange: [1, 1, 0], extrapolate: 'clamp' }) return ( {this.getSmallExplosions(75, {x: 89, y: 75})} ); } }; class AnimatedCircle extends Component { render() { var radius = this.props.radius; var path = Path().moveTo(0, -radius) .arc(0, radius * 2, radius) .arc(0, radius * -2, radius) .close(); return React.createElement(AnimatedShape); } } var styles = StyleSheet.create({ container: { flex: 1, } });
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