uni-app通过canvas实现手写签名

分享一个uni-app实现手写签名的方法

具体代码如下：

<template>
<view >
<view class="title">请在下面输入签名：</view>
<canvas class="mycanvas" canvas-id="mycanvas" @touchstart="touchstart" @touchmove="touchmove" @touchend="touchend"></canvas>
<view class="footer">
<view class="left" @click="finish">完成</view>
<view class="right" @click="clear">清除</view>
</view>
</view>
</template>

<script>
var x = 20;
var y =20;
export default{
data(){
return {
ctx:'',         //绘图图像
points:[]       //路径点集合
}
},
onLoad() {
this.ctx = uni.createCanvasContext("mycanvas",this);   //创建绘图对象

//设置画笔样式
this.ctx.lineWidth = 4;
this.ctx.lineCap = "round"
this.ctx.lineJoin = "round"
},
methods:{
//触摸开始，获取到起点
touchstart:function(e){
let startX = e.changedTouches[0].x;
let startY = e.changedTouches[0].y;
let startPoint = {X:startX,Y:startY};

/* **************************************************
#由于uni对canvas的实现有所不同，这里需要把起点存起来
 * **************************************************/
this.points.push(startPoint);

//每次触摸开始，开启新的路径
this.ctx.beginPath();
},

//触摸移动，获取到路径点
touchmove:function(e){
let moveX = e.changedTouches[0].x;
let moveY = e.changedTouches[0].y;
let movePoint = {X:moveX,Y:moveY};
this.points.push(movePoint);       //存点
let len = this.points.length;
if(len>=2){
this.draw();                   //绘制路径
}

},

// 触摸结束，将未绘制的点清空防止对后续路径产生干扰
touchend:function(){
this.points=[];
},

/* ***********************************************
#   绘制笔迹
#1.为保证笔迹实时显示，必须在移动的同时绘制笔迹
#2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo)
#3.将上一次的终点作为下一次绘制的起点（即清除第一个点）
************************************************ */
draw: function() {
let point1 = this.points[0]
let point2 = this.points[1]
this.points.shift()
this.ctx.moveTo(point1.X, point1.Y)
this.ctx.lineTo(point2.X, point2.Y)
this.ctx.stroke()
this.ctx.draw(true)
},

//清空画布
clear:function(){
let that = this;
uni.getSystemInfo({
success: function(res) {
let canvasw = res.windowWidth;
let canvash = res.windowHeight;
that.ctx.clearRect(0, 0, canvasw, canvash);
that.ctx.draw(true);
},
})
},

//完成绘画并保存到本地
finish:function(){
uni.canvasToTempFilePath({
  canvasId: 'mycanvas',
  success: function(res) {
    let path = res.tempFilePath;
uni.saveImageToPhotosAlbum({
filePath:path
})
  }
})
}
},
}
</script>

<style>
.title{
height:50upx;
line-height: 50upx;
font-size: 16px;
}
.mycanvas{
width: 100%;
height: calc(100vh - 200upx);
background-color: #ECECEC;
}
.footer{
font-size: 16px;
height: 150upx;
display: flex;
justify-content: space-around;
align-items: center;
}
.left,.right{
line-height: 100upx;
height: 100upx;
width: 250upx;
text-align: center;
font-weight: bold;
color: white;
border-radius: 5upx;
}
.left{
background: #007AFF;
}
.right{
background:orange;
}
</style>