uniapp中长按保存图片

long_tap() {
                console.log(111)
                 uni.previewImage({
                urls: [this.qrcode_img], //需要预览的图片http链接列表，多张的时候，url直接写在后面就行了
                current: "", // 当前显示图片的http链接，默认是第一个
                success: function (res) {},
                fail: function (res) {},
                complete: function (res) {},
            //长按保存到本地
                longPressActions: {
                itemList: ["保存图片到本地"],
                success: (data) => {
                if (data.tapIndex == 0) {
                let url = this.qrcode_img;
                uni.saveImageToPhotosAlbum({
                filePath: url,
                success: (res) => {
                uni.showToast({
                title: "已存至系统相册",
                icon: "success",
                  });
                },
                fail: (res) => {
                  uni.showToast({
                    title: "保存失败",
                    icon: "error",
                  });
                },
              });
            }
          },
          fail: function (err) {
            console.log(err.errMsg);
          },
        },
      });
},