在主域中按照如下可以操作 sharedCanvas

   let openDataContext = wx.getOpenDataContext()

    let sharedCanvas = openDataContext.canvas

    sharedCanvas.width = 300

    sharedCanvas.height = 500

    let sharedCanvasContext = sharedCanvas.getContext('2d')

    sharedCanvasContext.fillStyle="#FF0000";

    sharedCanvasContext.fillRect(0,0,300,500);

    canvasCtx.drawImage(sharedCanvas, 40, 60, 300, 500)

反而在开放数据域确无法操作sharedCanvas

let sharedCanvas = wx.getSharedCanvas()

let sharedCanvasContext = sharedCanvas.getContext('2d')

sharedCanvasContext.fillStyle = 'blue'

  sharedCanvasContext.fillRect(0, 0, 100, 100)

  var grd=sharedCanvasContext.createLinearGradient(0,0,200,0);

  grd.addColorStop(0,"red");

  grd.addColorStop(1,"green");

  // 填充渐变 

  sharedCanvasContext.fillStyle=grd;

  sharedCanvasContext.fillRect(10,10,150,80)

请问一下我是写的有问题吗