wxml
<!--pages/shouxieban/shouxieban.wxml--> <view> <view>手写板（请在下方区域手写内容）</view> <canvas canvas-id="canvas" disable-scroll="true" bindtouchstart="canvasStart" bindtouchmove="canvasMove" bindtouchend="canvasEnd" touchcancel="canvasEnd" binderror="canvasIdErrorCallback"></canvas> <view> <button bindtap="cleardraw">清除画板</button> <button bindtap="setSign">确定</button> </view> <image src='https://www.jb51.net/{{canvasimgsrc}}'></image> </view>
js
var context = null;// 使用 wx.createContext 获取绘图上下文 context var isButtonDown = false;//是否在绘制中 var arrx = [];//动作横坐标 var arry = [];//动作纵坐标 var arrz = [];//总做状态，标识按下到抬起的一个组合 var canvasw = 0;//画布宽度 var canvash = 0;//画布高度 // pages/shouxieban/shouxieban.js Page({ /** * 页面的初始数据 */ data: { //canvas宽高 canvasw: 0, canvash: 0, //canvas生成的图片路径 canvasimgsrc: "" }, //画布初始化执行 startCanvas: function () { var that = this; //创建canvas this.initCanvas(); //获取系统信息 wx.getSystemInfo({ success: function (res) { canvasw = res.windowWidth - 0;//设备宽度 canvash = canvasw; that.setData({ 'canvasw': canvasw }); that.setData({ 'canvash': canvash }); } }); }, //初始化函数 initCanvas: function () { // 使用 wx.createContext 获取绘图上下文 context context = wx.createCanvasContext('canvas'); context.beginPath() context.setStrokeStyle('#000000'); context.setLineWidth(4); context.setLineCap('round'); context.setLineJoin('round'); }, //事件监听 canvasIdErrorCallback: function (e) { console.error(e.detail.errMsg) }, canvasStart: function (event) { isButtonDown = true; arrz.push(0); arrx.push(event.changedTouches[0].x); arry.push(event.changedTouches[0].y); }, canvasMove: function (event) { if (isButtonDown) { arrz.push(1); arrx.push(event.changedTouches[0].x); arry.push(event.changedTouches[0].y); }; for (var i = 0; i < arrx.length; i++) { if (arrz[i] == 0) { context.moveTo(arrx[i], arry[i]) } else { context.lineTo(arrx[i], arry[i]) }; }; context.clearRect(0, 0, canvasw, canvash); context.setStrokeStyle('#000000'); context.setLineWidth(4); context.setLineCap('round'); context.setLineJoin('round'); context.stroke(); context.draw(false); }, canvasEnd: function (event) { isButtonDown = false; }, //清除画布 cleardraw: function () { //清除画布 arrx = []; arry = []; arrz = []; context.clearRect(0, 0, canvasw, canvash); context.draw(true); }, //提交签名内容 setSign: function () { var that = this; if (arrx.length == 0) { wx.showModal({ title: '提示', content: '签名内容不能为空！', showCancel: false }); return false; }; console.log("不是空的，canvas即将生成图片") //生成图片 wx.canvasToTempFilePath({ canvasId: 'canvas', success: function (res) { console.log("canvas可以生成图片") console.log(res.tempFilePath, 'canvas图片地址'); that.setData({ canvasimgsrc: res.tempFilePath }) //code 比如上传操作 }, fail: function () { console.log("canvas不可以生成图片") wx.showModal({ title: '提示', content: '微信当前版本不支持，请更新到最新版本！', showCancel: false }); }, complete: function () { } }) }, /** * 生命周期函数--监听页面加载 */ onLoad: function (options) { //画布初始化执行 this.startCanvas(); } })
css
/* pages/shouxieban/shouxieban.wxss */ /*手写板 */ page{ background: #f6f6f6; padding: 5px auto } canvas{ border: 1px solid #d0d0d0; margin: 5rpx; background: #f2f2f2 }