- 当前 Bug 的表现（可附上截图）打开摄像头，利用canvas绘制矩形，在开发者工具中可显示，真机调试不显示

- 预期表现  ： 真机调试也可看见矩形框

- 复现路径

- 提供一个最简复现 Demo

<camera flash="off" binderror="error" style="width: 100%; height: {{winHeight}}rpx;">

<canvas  canvas-id="rectangle" style="width: 100%; height: {{winHeight}}rpx;"></canvas>

</camera>

onReady: function () {

var that = this;

wx.getSystemInfo({

success: function (res) {

let winWidth = res.screenWidth;

console.log(res)

let scale = winWidth / 375;

let winHeight = ((res.screenHeight-120) * 2 / scale);

console.log("winHeight:" + winHeight)

that.setData({

winHeight: winHeight,

})

var rec = wx.createCanvasContext("rectangle");

rec.setStrokeStyle('red')

rec.strokeRect(res.screenWidth- 10, 10, 20, res.screenHeight - 140 )

rec.draw(true)

console.log(rec)

},

})

}，