微信小程序实现手指触摸画板

<!--pages/shouxieban/shouxieban.wxml--><view class="container"> <view>手写板（请在下方区域手写内容）</view> <canvas style="width: {{canvasw}}px; height: {{canvash}}px" class="canvas" id="canvas" canvas-id="canvas" disable-scroll="true" bindtouchstart="canvasStart" bindtouchmove="canvasMove" bindtouchend="canvasEnd" touchcancel="canvasEnd" binderror="canvasIdErrorCallback"></canvas> <view class='btns canvaspd'> <button bindtap="cleardraw">清除画板</button> <button bindtap="setSign">确定</button> </view> <image src='{{canvasimgsrc}}'></image> </view>

var context = null;// 使用 wx.createContext 获取绘图上下文 contextvar 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.jsPage({ /** * 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();  }})

/* pages/shouxieban/shouxieban.wxss *//*手写板 */page{ background: #f6f6f6; padding: 5px auto}canvas{ border: 1px solid #d0d0d0; margin: 5rpx; background: #f2f2f2}