微信小程序保存分享图至本地相册

//下载图标绑定方法
  saveToPhoto() {
    let that = this
    wx.showToast({
      icon: 'loading',
      title: '正在保存图片',
      duration: 1000
     })
     //判断用户是否授权"保存到相册"
     wx.getSetting({
      success (res) {
       //没有权限，发起授权
       if (!res.authSetting['scope.writePhotosAlbum']) {
        wx.authorize({
         scope: 'scope.writePhotosAlbum',
         success () {//用户允许授权，保存图片到相册
          that.savePhoto();
         },
         fail () {//用户点击拒绝授权，跳转到设置页，引导用户授权
          wx.openSetting({
           success () {
            wx.authorize({
             scope: 'scope.writePhotosAlbum',
             success() {
              that.savePhoto();
             }
            })
           }
          })
         }
        })
       } else {//用户已授权，保存到相册
        that.savePhoto()
       }
      }
    })
  },


  savePhoto() {
    let that = this
    wx.downloadFile({
     url: that.data.shareImg,
     success: function (res) {
      wx.saveImageToPhotosAlbum({
       filePath: res.tempFilePath,
       success(res) {
        wx.showToast({
         title: '保存成功',
         icon: "success",
         duration: 1000
        })
       }
      })
     }
    })
    that.setData({
      isGraph: !this.data.isGraph,
    })
  },