Flutter Future 异步 FutureBuilder 获取数据后 加载Widget

// 不使用FutureBuilder，直接在then或whenComplete中加载渲染Widget会报错

future几个函数：
then：异步操作逻辑在这里写。
whenComplete：异步完成时的回调。
catchError：捕获异常或者异步出错时的回调。

///图片
FutureBuilder(
  future: getImages(
      "${Global.baseUrl}${API.readCommentImageURL}?commentPkid=${parentItem.comment_pkid}&isThumbnail=true",
      context),
  builder:
      (BuildContext context, AsyncSnapshot<List> s) {
    LogUtils.log("ssss", s.data);
    return reportCommentImageWidget(s.data);
  },
),

//获取一条评论的相关图片及widget
Future<List> getImages(String url, BuildContext context) async {
  List<Widget> imageWidgetList = [];
  //commentPkid 图片文件夹标识
  var httpClient = new HttpClient();
  String result;
  try {
    var request = await httpClient.getUrl(Uri.parse(url));
    request.headers.add("Semf-Token", Global.token);

    var response = await request.close();

    if (response.statusCode == 200) {
      var json = await response.transform(utf8.decoder).join();
      List imageBase64List = jsonDecode(json);

      if (imageBase64List != null) {
        for (var imageBase64Str in imageBase64List) {
          Uint8List bytes = Base64Decoder().convert(imageBase64Str);
          LogUtils.log("bytes", bytes);

          Widget imageWidget;
          if (bytes != null) {
            imageWidget = Container(
                child: InkWell(
              child: Container(
                child:
                    Image.memory(bytes != null ? bytes : "", fit: BoxFit.fill),
              ),
              onTap: () {
                Navigator.of(context).push(
                    CustomRoute(ReportCommentImagePage(imageByte: bytes)));
              },
            ));
          } else {
            imageWidget = Container(
              child: Image.asset('images/report_imagePlaceholder.png'),
            );
          }
          imageWidgetList.add(imageWidget);
        }
        LogUtils.log("imageWidgetList-0-", imageWidgetList);
        return await imageWidgetList;
      } else {
        return imageWidgetList;
      }
    } else {
      result = 'Error getting IP address:\nHttp status ${response.statusCode}';
    }
  } catch (exception) {
    result = 'Failed getting IP address';
  }
}

///评论图片
Widget reportCommentImageWidget(List<Widget> imageWidgetList) {
  var size = 0.0;

  if (imageWidgetList != null && imageWidgetList.length > 0) {
    LogUtils.log("图片控件数组", imageWidgetList);
    if (imageWidgetList.length == 1) {
      size = ScreenUtil.getInstance().width / 3.0;
    } else if (imageWidgetList.length == 2) {
      size = ScreenUtil.getInstance().width / 5.0;
    } else if (imageWidgetList.length >= 3) {
      size = ScreenUtil.getInstance().width / 6.5;
    }
    var crossAxisCount = 0;
    var height = 0.0;
    var width = 0.0;
    if (imageWidgetList.length >= 3) {
      crossAxisCount = 3;

      ///向上取整ceil   20 边距
      height = size * ((imageWidgetList.length / 3.0).ceil()) +
          10 * (imageWidgetList.length / 3.0).ceil() +
          20;
      width = (size + 10) * 3.0 + 20;
    } else if (imageWidgetList.length > 0 && imageWidgetList.length < 3) {
      crossAxisCount = imageWidgetList.length;
      height = size + 20;
      width = (size + 10) * imageWidgetList.length + 20;
    }
    return Center(
      child: Container(
          padding: EdgeInsets.all(10),
          height: height,
          width: width,
          child: GridView.count(
            primary: false,
            physics: const NeverScrollableScrollPhysics(),
            //禁止滚动
            mainAxisSpacing: 10,
            crossAxisSpacing: 10,
            crossAxisCount: crossAxisCount == 0 ? 1 : crossAxisCount,

            ///一行数量
            children: imageWidgetList,
          )),
    );
  } else {
    return Container();
  }
}