canvas

属性名 类型 默认值 说明
hidden Boolean false 设置画布的显示/隐藏,hidden值为true表示隐藏,值为false表示显示
canvas-id String canvas组件的唯一标识符
binderror EventHandle 当发生错误时触发error事件,detail = { errMsg: 'something wrong' }

注:

  1. canvas标签默认宽度300px、高度225px

  2. 同一页面中的canvas-id不可重复,如果使用一个已经出现过的canvas-id,该canvas标签对应的画布将被隐藏并不再正常工作

示例代码:下载

<!-- 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
    });
  }
});

相关api:wx.createContextwx.drawCanvas

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