参考链接：https://www.jianshu.com/p/504c639063b3
前提：集成好react-native-svg
以上链接博主大佬用的是ART绘画系统，受此启发我就使用SVG画图了，因为项目里面还有其他操作，例如箭头、圆圈、矩形等类似电脑截图后编辑操作，而ART用法个人不是很熟悉，所以采用SVG，SVG不是很熟悉的可以看一下我之前写的这篇https://www.jianshu.com/p/ef91237a89a4，也可以自己上菜鸟教程简单的练一下再上手，做了个小demo，效果图如下：
441637732888_.pic.jpg
把以下代码复制粘贴到一个新页面即可尝试，至于Util.size.width、Util.size.height是屏幕宽高，换一下就好了。这只是画线功能，其他功能效果（例如圆圈、矩形、箭头等功能）请看另外一篇文章: https://www.jianshu.com/p/06d3bdfae98a
import React, {Component} from 'react';
import {View, Text, StyleSheet, Image, TouchableOpacity, PanResponder, ART, ImageBackground} from 'react-native'
import Util from './common/util'
import Svg, {Path} from "react-native-svg";
class SvgDrawTest extends Component {
constructor(props) {
super(props);
this.allPoint = ''
this.state = {
// drawPath: 'M25 10 L98 65 L70 25 L16 77 L11 30 L0 4 L90 50 L50 10 L11 22 L77 95 L20 25'
drawPath: ''
}
}
componentWillMount() {
this._panResponderDrawLine = PanResponder.create({
onStartShouldSetPanResponder: (evt, gestureState) => true,
onStartShouldSetPanResponderCapture: (evt, gestureState) => true,
onMoveShouldSetPanResponder: (evt, gestureState) => true,
onMoveShouldSetPanResponderCapture: (evt, gestureState) => true,
onPanResponderGrant: (evt, gestureState) => {
let tempfirstX = evt.nativeEvent.pageX
let tempFirstY = evt.nativeEvent.pageY
this.firstPoint = ' M' + tempfirstX + ' ' + tempFirstY
this.allPoint = this.allPoint + this.firstPoint //上一次的画的全部的点(this.allPoint)，拼接上当前这次画的M点，在svg中M为线的起始点,拼接上后在 onPanResponderMove 中将当前移动的所有点再次拼接,当前和之前的拼接完之后，更新页面线条
},
onPanResponderMove: (evt, gestureState) => {
let pointX = evt.nativeEvent.pageX
let pointY = evt.nativeEvent.pageY
// console.log(`X:${pointX}`, `Y:${pointY}`)
let point = ' L' + pointX + ' ' + pointY
this.allPoint += point
console.log('point====', this.allPoint)
let drawPath = this.allPoint
this.setState({
drawPath
})
},
onPanResponderTerminationRequest: (evt, gestureState) => true,
onPanResponderRelease: (evt, gestureState) => { },
onPanResponderTerminate: (evt, gestureState) => { },
onShouldBlockNativeResponder: (evt, gestureState) => {
return true;
},
})
}
clearOut(){
this.allPoint = ''
this.setState({
drawPath:''
})
}
render() {
return (
this.clearOut()} style={styles.btn}>
清空
);
}
}
export default SvgDrawTest;
const styles = StyleSheet.create({
btn:{elevation:5,backgroundColor:'#fff',paddingHorizontal:30,paddingVertical:10,borderRadius:999,justifyContent:'center',alignItems:'center'},
})
在项目里使用实例，效果图如下
192451637727165_.pic.jpg
本来在手势那里，因为画图是在图片范围内，我是尝试用locationX,locationY 而不是pageX、pageY,后来发现
locationX超过范围后那个点会返回对立的那一面，想着解决太麻烦了，所以采用pageX和pageY,如图所见，手势起始点的位置和移动的位置点减去他的边距即可。目前是画笔，后续操作实现了再更新实现代码。
import React, {Component} from 'react';
import {View, Text, Image, StyleSheet, PanResponder,TouchableOpacity} from 'react-native'
import Svg, {Path} from "react-native-svg";
let marginY = 50 + 15 + 5 //头部导航height 50 下方内容padding 15 图片与父盒子距离 5
let marginX = 15 + 5 // 下方内容padding 15 图片与父盒子距离 5
class Comp3 extends Component {
constructor(props) {
super(props);
this.allPoint = ''
this.state = {
drawPath: ''
}
}
componentWillMount() {
this._panResponderDrawLine = PanResponder.create({
onStartShouldSetPanResponder: (evt, gestureState) => true,
onStartShouldSetPanResponderCapture: (evt, gestureState) => true,
onMoveShouldSetPanResponder: (evt, gestureState) => true,
onMoveShouldSetPanResponderCapture: (evt, gestureState) => true,
onPanResponderGrant: (evt, gestureState) => {
let tempfirstX = evt.nativeEvent.pageX.toFixed(0)-marginX
let tempFirstY = evt.nativeEvent.pageY.toFixed(0)-marginY
this.firstPoint = ' M' + tempfirstX + ' ' + tempFirstY
this.allPoint += this.firstPoint //上一次的画的全部的点(this.allPoint)，拼接上当前这次画的M点，在svg中M为线的起始点,拼接上后在 onPanResponderMove 中将当前移动的所有点再次拼接,当前和之前的拼接完之后，更新页面线条
},
onPanResponderMove: (evt, gestureState) => {
let pointX = evt.nativeEvent.pageX.toFixed(0)-marginX
let pointY = evt.nativeEvent.pageY.toFixed(0)-marginY
// console.log(`X:${pointX}`, `Y:${pointY}`)
let point = ` L${pointX} ${pointY}`
this.allPoint += point
let drawPath = this.allPoint
this.setState({
drawPath
})
},
onPanResponderTerminationRequest: (evt, gestureState) => true,
onPanResponderRelease: (evt, gestureState) => { },
onPanResponderTerminate: (evt, gestureState) => {},
onShouldBlockNativeResponder: (evt, gestureState) => {
return true;
},
})
}
render() {
return (
选择
线条选择
粗细
色彩
操作
撤销
{this.setState({drawPath:''});this.allPoint = ''}} style={styles.bottom_btn}>
清空
保存
);
}
}
export default Comp3;
const styles = StyleSheet.create({
/**内容*/
content_left: {
backgroundColor: '#fff',
flex: 3,
marginRight: 15,
padding: 5,
},
content_left_camera: {
flex: 1,
},
camera_bottom: {
backgroundColor: '#fff',
height: '25%',
flexDirection: 'row',
alignItems: 'center',
justifyContent: 'center'
},
bottom_item: {
paddingHorizontal: 10,
borderRightWidth: 1,
borderColor: '#eee',
height: '70%',
justifyContent: 'space-between'
},
bottom_icon: {
flexDirection: 'row',
alignItems: 'center',
justifyContent: 'space-between',
},
bottom_title: {fontSize: 12, marginBottom: 10},
bottom_btn: {
borderWidth: 1,
borderRadius: 999,
width: '30%',
borderColor: '#A5AAC1',
justifyContent: 'center',
alignItems: 'center',
paddingVertical: 3
},
colorSelect: {
flexDirection: 'row',
alignItems: 'center',
borderWidth: 1,
borderRadius: 5,
paddingHorizontal: 2,
paddingVertical: 2,
borderColor: '#eee'
},
});