小程序保存图片到本地

  saveTap: function(){
    var self =this
    wx.getSetting({
      success(res) {
        console.log(res)
        //判断是否已授权
        if (!res.authSetting['scope.writePhotosAlbum']) {
          wx.authorize({
            scope: 'scope.writePhotosAlbum',
            success() {
              //授权成功
              self.savePhoto()
            },
            fail : function(){
              //未授权
              self.imageErrorAuth()
            }
          })
        }else{
          //已授权直接保存图片
          self.savePhoto()
        }
      },
      
      
    })
  },

　　

imageErrorAuth() {
    //打开设置必须在按钮点击事件中所以搞一个modal
    wx.showModal({
      title: '提示',
      content: '需要您授权保存至相册',
      showCancel: false,
      success: modalSuccess => {
        wx.openSetting({
          success(settingData) {
            if (settingData.authSetting['scope.writePhotosAlbum']) {
              wx.showModal({
                title: '提示',
                content: '获取权限成功,再次保存图片即可',
                showCancel: false
              })
            } else {
              wx.showModal({
                title: '提示',
                content: '获取权限失败，将无法保存到相册',
                showCancel: false
              })
            }
          },
          fail(failData) {
            console.log("failData", failData)
          },
          complete(finishData) {
            console.log("finishData", finishData)
          }
        })
      }
    })
  },

　　

savePhoto: function(){
    var imgSrc = app.globalData.httpHeader+'qr_code.png'
    wx.downloadFile({
      url: imgSrc,
      success: function (res) {
        //图片保存到本地
        wx.saveImageToPhotosAlbum({
          filePath: res.tempFilePath,
          success: function (data) {
            console.log('保存成功')
            wx.showToast({
              title: '保存成功',
              icon: 'success',
              duration: 2000
            })
          },
          fail: function (err) {
            console.log('保存失败');
            console.log(err)
            if (err.errMsg == "saveImageToPhotosAlbum:fail auth deny") {
              //在这种逻辑下这种错误不会出现
              console.log("未授权")
  
            } else if (err.errMsg == 'saveImageToPhotosAlbum:fail cancel'){
              //用户点击了取消
              console.log('用户点击了取消')
            }
          },
          complete(res) {
            //结束回调
          }
        })
      }
    })
  },

　　代码注释很清晰了