问题

小程序保存图片到相册一直无响应，保存不成功

分析

小程序保存图片到相册主要用到以下三点：
wx.downloadFile下载图片
wx.openSetting授权
wx.saveImageToPhotosAlbum图片保存到本地

查看wx.downloadFile请求正常响应，不过wx.saveImageToPhotosAlbum有报错信息，下面列出真机跟调试都出现的报错信息

err.errMsg === "saveImageToPhotosAlbum:fail:auth denied" || err.errMsg === "saveImageToPhotosAlbum:fail auth deny" || err.errMsg === "saveImageToPhotosAlbum:fail authorize no response"

出现这报错信息，一般保存图片用户没有授权，可将授权方法wx.openSetting放入wx.showModal提示框中

wx.showModal({
  title: '提示',
  content: '需要您授权保存相册',
  showCancel: false,
  success: res=> {
    wx.openSetting({
      success(res) {
        console.log("success", res)
      },
      fail(err) {
        console.log("fail", err)
      },
      complete(res) {
        console.log("finish", res)
      }
    })
  }
})

保存图片完整代码示例

    wx.downloadFile({
      url: e.currentTarget.dataset.contractimg, 
      success (res) {
        if (res.statusCode === 200) {
          wx.saveImageToPhotosAlbum({
            filePath: res.tempFilePath,
            success(res) {
              util.hideToast();
              wx.showModal({
                title: '图片保存成功',
                content: '图片成功保存到相册了',
                showCancel: false,
                confirmText: '好哒',
                confirmColor: '#5096cd',
                success: function (res) {
                  if (res.confirm) {
                    console.log('用户点击确定');
                  }
                }
              })
            },
            fail (err) {
              util.hideToast()
              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,再次点击下载即可保存',
                            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: '取消了保存图片,再次点击下载即可保存',
                  showCancel: false,
                })
              } else {
                wx.showModal({
                  title: '提示',
                  content: err.errMsg,
                  showCancel: false,
                })
              }
            }
          })
        } 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,
        })
      }
    })