此功能参照GitHub上的有插件源码，现在找不到那个网址了，就是借鉴别人的。

onLoad: function () {    var that = this    wx.getStorage({      key: 'accessToken',      success: function (res) {        //console.log(res)        wx.request({          url: +/user/userInfo.htm",          method: 'POST',          header: {            'content-type': 'application/x-www-form-urlencoded'          },          data: { accessToken: res.data },          success: function (res) {            //console.log(res.data.data.id)            var str = res.data.data.id + ''            if (res.data.data.avatarUrl) {              that.setData({                avatarUrl: res.data.data.avatarUrl,                nickName: res.data.data.nickName,                placeholder: str              })            } else {              that.setData({                avatarUrl: '../../resources/login-1.jpg',                placeholder: str              })            }            //console.log(that.data.placeholder)            that.draw();          }        })      }    })  },  draw(){    var size = this.setCanvasSize();//动态设置画布大小    var initUrl = this.data.placeholder;    this.createQrCode(initUrl, "mycanvas", 192, 192);  },    setCanvasSize: function () {    var size = {};    try {      var res = wx.getSystemInfoSync();      var scale = 750 / 686;//不同屏幕下canvas的适配比例；设计稿是750宽      var width = res.windowWidth / scale;      var height = width;//canvas画布为正方形      size.w = width;      size.h = height;    } catch (e) {      // Do something when catch error      console.log("获取设备信息失败" + e);    }    return size;  },  createQrCode: function (url, canvasId, cavW, cavH) {    //调用插件中的draw方法，绘制二维码图片    QR.api.draw(url, canvasId, cavW, cavH);    setTimeout(() = { this.canvasToTempImage(); }, 1000);  },  //获取临时缓存照片路径，存入data中  canvasToTempImage: function () {    var that = this;    wx.canvasToTempFilePath({      canvasId: 'mycanvas',      success: function (res) {        var tempFilePath = res.tempFilePath;        that.setData({          imagePath: tempFilePath,          // canvasHidden:true        });      },      fail: function (res) {        console.log(res);      }    });  },  //点击图片进行预览，长按保存分享图片  previewImg: function (e) {    var img = this.data.imagePath;    console.log(img);    wx.previewImage({      current: img, // 当前显示图片的http链接      urls: [img] // 需要预览的图片http链接列表    })  },  saveCodeImg: function () {    console.log(111)    wx.saveImageToPhotosAlbum({      filePath: this.data.imagePath,      success(res) {        wx.showToast({          title: '图片保存成功',          icon: 'success',          duration: 2000        })      }    })  },  onPullDownRefresh: function () {    wx.stopPullDownRefresh()  }  })

还有一个canvas用于生成二维码的文件，没有办法发出来，要了联系我1136395932