disable-scroll

当在 canvas 中移动时且有绑定手势事件时，禁止屏幕滚动以及下拉刷新

bindtouchstart

手指触摸动作开始

bindtouchmove

手指触摸后移动

bindtouchend

手指触摸动作结束

bindtouchcancel

手指触摸动作被打断

binderror

当发生错误时触发 error 事件，detail =  {errMsg}

<view>

   <view>画板</view>

   <canvas style="width: {{canvasw}}px; height: {{canvash}}px" 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>

Page({

   data: {

     canvasw: 0,

     canvash: 0,

   //初始化函数

   initCanvas: function () {

     context = wx.createCanvasContext('canvas');

     context.beginPath()

     context.setStrokeStyle('#000000');

     context.setLineWidth(4);

     context.setLineCap('round');

     context.setLineJoin('round');

   },

 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);

     };

     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 () {

     arrx = [];

     arry = [];

     arrz = [];

     context.clearRect(0, 0, canvasw, canvash);

     context.draw(true);

   },

   onLoad: function (options) {

     //画布初始化执行

     this.startCanvas();

  }

})