uniapp电子签名canvas实现代码记录

<template>
  <view class="all_content">
    <view class="title">立即签名</view>
    <view class="subtitle">请在下面方框中手写您的名字，然后点击确认</view>

    <canvas
      class="mycanvas"
      canvas-id="mycanvas"
      @touchstart="touchstart"
      disable-scroll="true"
      @touchmove="touchmove"
      @touchend="touchend"></canvas>
    <view class="footer">
      <button class="right" @click="clear">清除</button>
      <button class="left" @click="finish">完成</button>
    </view>
  </view>
</template>

<script>
import {
    
     message } from "../../utils/message";
var x = 20;

var y = 20;

export default {
    
    
  data() {
    
    
    return {
    
    
      ctx: "", //绘图图像
      points: [], //路径点集合
      alreadySign: false,
      flag: false,
    };
  },
  created() {
    
    
    //页面挂载，创建canvans绘图对象
    this.$nextTick(() => {
    
    
      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();
      this.ctx.moveTo(startX, startY);
    },
    //触摸移动，获取到路径点
    touchmove: function (e) {
    
    
      this.flag = true;
      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) {
    
    //路径点达到一定长度，绘制路径
        this.draw(); 
      }
    },
    // 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 () {
    
    
      this.flag = false;
      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 () {
    
    
      if (!this.flag) {
    
    
        message.toast("请先完成签名");
        return;
      }
      let that = this;
      uni.canvasToTempFilePath(
        {
    
    
          canvasId: "mycanvas",
          success: function (res) {
    
    
            let path = res.tempFilePath;
            that.alreadySign = true;
            uni.showLoading({
    
    
			  title: "上传签名中",
			});
			uni.uploadFile({
    
    
			  url: `${
      
      utils.config.baseUrl}/uploadSignImg`, //后端提供的上传图片接口地址
			  filePath: path,//文件路径
			  name: "img",
			  success: (ress) => {
    
    
			    uni.hideLoading();
			    if (ress.statusCode == 200) {
    
    
			      uni.showToast({
    
    title:"上传签名成功"});
			    }
			  },
			  fail: (errorr) => {
    
    
			    uni.hideLoading();
			  },
			});
          },
          fail: function (error) {
    
    
            console.log(error);
          },
        },
        this
      );
    },
  },
};
</script>

<style>
.mycanvas {
    
    
  width: 100%;
  overflow: hidden;
  height: 35vh;
  background-color: #ececec;
}
.all_content {
    
    
  position: relative;
}
.footer {
    
    
  font-size: 16px;
  width: 100vw;
  background-color: #fff;
  height: 5vh;
  display: flex;
  bottom: 0;
  justify-content: space-around;
  align-items: center;
  padding: 10px 0;
}
.left,
.right {
    
    
  line-height: 5vh;
  height: 5vh;
  width: 30vw;
  text-align: center;
  font-weight: bold;
  color: white;
  border-radius: 1.875rem;
}
.left {
    
    
  background: #5e8deb;
  color: #fff;
}
.right {
    
    
  background: #fff;
  color: #5e8deb;
  border: 0.0625rem solid #5e8deb;
}
</style>