小程序原生--手写板

参考：https://www.jianshu.com/p/a1341c0d12e8

公司的小程序工程师端、客户端、销售端都需要一个签名的功能

思路：模拟儿童画板 => 画板是手机（dom） 、画笔是手

核心：canvas的touch事件

camvas通过绑定touchstart、touchmove、touchend事件，监听手画出的形状，结束后，canvas进行图片绘制

wxml

<view class="wrapper">
  <view class="handBtn">
    <button catchtap="clearClick" class="delBtn">重写</button>
    <button catchtap="saveClick" class="subBtn">完成</button> 
  </view>
  <view class="handCenter">
    <canvas class="sign" canvas-id="sign" bindtouchmove="move" bindtouchstart="start" bindtouchend="end" bindtouchcancel="cancel" bindlongtap="tap" disable-scroll="true" binderror="error">
    </canvas>
  </view>
  <view class="handRight">
    <view class="handTitle">手写签名</view>
  </view>
</view>

js

const app = getApp();
const qiniuUploader = require("../../utils/qiniuUploader");
const network = require('../../utils/network');

// 初始化签名变量，放在 Page 前
var content = null;
var touchs = [];
Page({
  data: {
    imgList:[],
    signImage: '',
        upToken: ''
  },
  // 笔迹开始
  // 画布的触摸移动开始手势响应
    start: function (event) {
        // console.log("触摸开始" + event.changedTouches[0].x);
        // console.log("触摸开始" + event.changedTouches[0].y);
        //获取触摸开始的 x,y
        let point = { x: event.changedTouches[0].x, y: event.changedTouches[0].y }
        touchs.push(point);
    },
    // 画布的触摸移动手势响应
    move: function (e) {
        let point = { x: e.touches[0].x, y: e.touches[0].y }
        touchs.push(point);
        if (touchs.length >= 2) {
            this.draw(touchs);
        }
    },
    // 画布的触摸移动结束手势响应
    end: function (e) {
        console.log("触摸结束" + e);
        //清空轨迹数组
        for (let i = 0; i < touchs.length; i++) {
            touchs.pop();
        }
    },
    // 画布的触摸取消响应
    cancel: function (e) {
        console.log("触摸取消" + e);
    },
    // 画布的长按手势响应
    tap: function (e) {
        console.log("长按手势" + e);
    },
    error: function (e) {
        console.log("画布触摸错误" + e);
    },
    /**
    * 生命周期函数--监听页面加载
    */
    onLoad: function (options) {
        //获得Canvas的上下文
        content = wx.createCanvasContext('sign');
        //设置线的颜色
        content.setStrokeStyle("#000");
        //设置线的宽度
        content.setLineWidth(3);
        //设置线两端端点样式更加圆润
        content.setLineCap('round');
        //设置两条线连接处更加圆润
        content.setLineJoin('round');
        this.getQiniuToken()
    },
    //绘制
    draw: function (touchs) {
        let point1 = touchs[0];
        let point2 = touchs[1];
        touchs.shift();
        content.moveTo(point1.x, point1.y);
        content.lineTo(point2.x, point2.y);
        content.stroke();
        content.draw(true);
    },
    //清除操作
    clearClick: function () {
        //清除画布
        content.clearRect(0, 0,750, 700);
        content.draw(true);
    },
    //保存图片
    saveClick: function () {
        var that = this;
        wx.canvasToTempFilePath({
            canvasId: 'sign',
            success: function (res) {
                that.uploadImg(res.tempFilePath)
            }
        })
    },
    /**
     * 获取qiniuToken
     */
    getQiniuToken: function() {
      const that = this;
      const url = app.config.serverUrl + '/common/qiniuToken';
      const URL = '/common/qiniuToken';
      const params = {};
      const allData = app.signature(URL, params);
      
      wx.request({
        url: url,
        method: 'POST',
        data: allData,
        header: {
          'content-type': 'application/json'
        },
        success: function(res) {
          that.setData({
            upToken: res.data.uptoken
          });
        }
      })
    },
    /**
     * 图片上传
     */
    uploadImg: function(url) {
      const that = this;
    
      const param = {
        region: 'NCN',
        domain: app.config.qiniuUrl,
        shouldUseQiniuFileName: false,
        uploadURL: app.config.qiniuUrl,
        uptoken: that.data.upToken
      };
        qiniuUploader.upload(url, function(info) {
            that.setData({
                signImage: info.key
            });
        }, function(error) {
            app.errorLog(error);
        }, param);
    },
})

wxss

page {
  background: #fbfbfb;
  height: auto;
  overflow: hidden;
}

.wrapper {
   100%;
  height: 100%;
  margin: 30rpx 0;
  overflow: hidden;
  display: flex;
  align-content: center;
  flex-direction: row;
  justify-content: center;
  font-size: 28rpx;
}

.sign {
    display: block;
  background: #fff;
   100%;
  height: 100%;
}

.handRight {
  display: inline-flex;
  align-items: center;
}

.handCenter {
  border: 4rpx dashed #e9e9e9;
  flex: 5;
  overflow: hidden;
  box-sizing: border-box;
}

.handTitle {
  transform: rotate(90deg);
  flex: 1;
    margin-bottom: 10px;
  color: #666;
}

.handBtn button {
  font-size: 28rpx;
}

.handBtn {
  height: 95vh;
  display: inline-flex;
  flex-direction: column;
  justify-content: space-between;
  align-content: space-between;
  flex: 1;
}

.delBtn,.subBtn {
  position: absolute;
  bottom: 300rpx;
  left: 0rpx;
  transform: rotate(90deg);
  color: #666;
}
.subBtn{
    bottom: 100rpx;
}

.delBtn image {
  position: absolute;
  top: 13rpx;
  left: 25rpx;
}

按照上面的写法修修改改，可以实现手写板，因为是自己的业务，当写完后点击确定时，我将图片传上七牛

效果