<ec-canvas id="mychart" canvas-id="myCanvas" ec="{{ ec }}" force-use-old-canvas="true"></ec-canvas> canvasId是有的，t第二个参数this，也有，wx.canvasToTempFilePath（）调用就报错，报错信息："canvasToTempFilePath: fail canvas is empty"，求指点 setTimeout(() => {       console.log('this=====',this) wx.canvasToTempFilePath({         canvasId: 'myCanvas',         width:'200',         height:'300',         success: (res) => {           console.log("res",res)         },         fail: (err) => {           console.log("err",err)         },       }, this)     }, 2000)