var that = this;           // 绘制背景海报到canvas         var postersize = this.setCanvasSize(750);//动态设置画布大小         const ctx = wx.createCanvasContext('shareCanvas')         ctx.drawImage(that.data.imgUrl, 0, 0, postersize.w, postersize.h)         console.log("海报图片路径"+that.data.imgUrl);         ctx.draw();        //生成二维码         qrcode({           height:80,           width:80,           canvasId:"myQrcode",                  text:'{"ticketCode":"111"}',           colorDark: "black",           colorLight: "white",           callback: (res) => {                setTimeout(() => {                 wx.canvasToTempFilePath({                     canvasId: 'myQrcode',                     x:0,                     y:0,                                       width: 80,                     height: 80,                     success: (e) => {                         that.setData({ qrcodePath: e.tempFilePath });                            var res = wx.getSystemInfoSync();                         var scale = 750 / 180;                         var width = res.windowWidth / scale;                         var height = width                         var leftscale = 750 / 480; // 180为left                         var left = res.windowWidth / leftscale;                         var topscale = 750 / 880; // 180为top                         var top = res.windowWidth / topscale;                         ctx.drawImage(that.data.qrcodePath, left, top, width, height)                         ctx.draw(that);                             //生成二维码                         setTimeout(() => {                              //获取临时缓存code照片路径，存入data中                             console.log("二维码照片路径"+that.data.qrcodePath);                                          wx.canvasToTempFilePath({                               canvasId: 'shareCanvas',                               success: function(res) {                                                         console.log("开始展示图片");                                                    },                               fail:function(res){                                 console.log("失败");                                                   },                               complete:function(res){                                 console.log("调用接口结束")                                                  }                               })                                                     },0)                     }                               })             }, 0);           }         }); <view class="bg">   <canvas canvas-id="shareCanvas" class="canvas" />   <image wx:if="{{img}}" src="{{img}}" class="img" bindtap="previewImg"></image> </view> <view class="canvas-box">   <canvas  canvas-id="myQrcode"/> </view>