【非常全】微信小程序下载图片到相册，微信小程序自动获取分享图片到相册

    wx.downloadFile({
      url: '文件路径', 
      success (res) {
        if (res.statusCode === 200) {
          wx.saveImageToPhotosAlbum({
            filePath: res.tempFilePath,
            success(res) {
              
            wx.showToast({
              title: '保存成功'
            });
            },
            fail (err) {
              if (
                err.errMsg === "saveImageToPhotosAlbum:fail:auth denied" || 
                err.errMsg === "saveImageToPhotosAlbum:fail auth deny" || 
                err.errMsg === "saveImageToPhotosAlbum:fail authorize no response"
              ) {
                wx.showModal({
                  title: '提示',
                  content: '需要您授权保存相册',
                  showCancel: false,
                  success: res=> {
                    wx.openSetting({
                      success(res) {
                        if (settingdata.authSetting['scope.writePhotosAlbum']) {
                          wx.showModal({
                            title: '提示',
                            content: '获取权限成功,再次点击分享即可保存',
                            showCancel: false,
                          })
                        } else {
                          wx.showModal({
                            title: '提示',
                            content: '获取权限失败，将无法保存到相册哦~',
                            showCancel: false,
                          })
                        }
                      },
                      fail(err) {
                        console.log("fail", err)
                      },
                      complete(res) {
                        console.log("finish", res)
                      }
                    })
                  }
                })
              } else if (err.errMsg === "saveImageToPhotosAlbum:fail cancel") {
                wx.showModal({
                  title: '提示',
                  content: '取消了保存分享图片,再次点击分享即可保存',
                  showCancel: false,
                })
              } else {
              }
            }
          })
        } else {
          util.hideToast()
          wx.showModal({
            title: '提示',
            content: "图片下载失败",
            showCancel: false,
          })
        }
      },
      fail () {
        util.hideToast()
        wx.showModal({
          title: '提示',
          content: "图片下载失败",
          showCancel: false,
        })
      }
    })