微信小程序 wxapp画布 canvas详细介绍

<!-- canvas.wxml --><canvas style="width: 300px; height: 200px;" canvas-id="firstCanvas"></canvas><!-- 当使用绝对定位时，文档流后边的canvas的显示层级高于前边的canvas--><canvas style="width: 400px; height: 500px;" canvas-id="secondCanvas"></canvas><!-- 因为canvas-id与前一个canvas重复，该canvas不会显示，并会发送一个错误事件到AppService --><canvas style="width: 400px; height: 500px;" canvas-id="secondCanvas" binderror="canvasIdErrorCallback"></canvas>// canvas.js

Page({ canvasIdErrorCallback: function (e) {  console.error(e.detail.errMsg); }, onReady: function (e) {  //使用wx.createContext获取绘图上下文context  var context = wx.createContext();  context.setStrokeStyle("#00ff00");  context.setLineWidth(5);  context.rect(0,0,200,200);  context.stroke()  context.setStrokeStyle ("#ff0000") ;  context.setLineWidth (2)  context.moveTo(160,100)  context.arc(100,100,60,0,2*Math.PI,true);  context.moveTo(140,100);  context.arc(100,100,40,0,Math.PI,false);  context.moveTo(85,80);  context.arc(80,80,5,0,2*Math.PI,true);  context.moveTo(125,80);  context.arc(120,80,5,0,2*Math.PI,true);  context.stroke();  //调用wx.drawCanvas，通过canvasId指定在哪张画布上绘制，通过actions指定绘制行为  wx.drawCanvas({   canvasId: 'firstCanvas',   actions: context.getActions() //获取绘图动作数组  }); }});