<canvas type="2d" id="myCanvas"></canvas> Page({ onReady() { const query = wx.createSelectorQuery() query.select('#myCanvas') .fields({ node: true, size: true }) .exec((res) => { const canvas = res[0].node const ctx = canvas.getContext('2d') const dpr = wx.getSystemInfoSync().pixelRatio canvas.width = res[0].width * dpr canvas.height = res[0].height * dpr ctx.scale(dpr, dpr) ctx.fillRect(0, 0, 100, 100) }) } }) z针对于这种生成canvas的方式，canvas的标识为id，那么  wx.canvasToTempFilePath({   canvasId: "mycanvas",   success: function(res) {    var tempFilePath = res.tempFilePath;    that.setData({      loadImagePath: tempFilePath,   });   },    fail: function(res) {      console.log(res);    } }); wx.canvasToTempFilePath将canvas生成为图片是根据canvasId，也就导致wx.canvasToTempFilePath获取不到canvas。这怎么办。 xin.qq.com/miniprogram/dev/component/canvas.html