如何在滑动时在 PageView 中加载新数据

Question

我从服务器获取数据并通过 listView - 小部件和网页浏览将其呈现给用户， 目标是加载假设 20 个问题，在列表视图中显示 3 个并向右滑动以加载下一个 3，依此类推..

 int addToIndex=0;

  List<QuestionViewV1> questions = []; //Here I load relevant data from getData method...

  @override
  void initState() {
    _getData(); 
  }
       
                   ...child: PageView.builder(
                        controller: _pageController,
                        onPageChanged: _onPageChanged,
                        itemCount: questions.length, 
                        itemBuilder: (BuildContext context, int index) {
                          return _pageView(addToIndex);
                        },
                      ),

这里我返回 Widget 巫婆代表页面和列表视图...

 Widget _pageView(addToIndex) {
    return Column(
      children: [
        Expanded(
          child: Padding(
            padding: const EdgeInsets.only(top: 15.0),
            child: Card(
              shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.all(Radius.circular(10))),
              elevation: 4,
              // margin: EdgeInsets.all(15.0),
              child: ListView.builder(
                itemBuilder: (BuildContext ctx, int index) {
                  return listItem(
                      ctx,
                      index,
                      "User " + questions[index+addToIndex].user.userName,
                      _timeAgo(index+addToIndex),
                       questions[index+addToIndex].id, 
                      questionTitle:
                      questions[index+addToIndex].title); 
                },
                itemCount: 3,
              ),
            ),
          ),
        ),
      ],
    );
  }

已编辑：这是 _getData()：

  _getData() async {
    ResourceFetchingAuthority _resourceFetchingAuthority =
        ResourceFetchingAuthority(
            configuration: ResourceFetchingConfiguration(

                maxReturnedResourcesForFirstPage: 12,
...     



    ResourceFetchingResult unansweredQuestionsResult =
        await _resourceFetchingAuthority.fetchResources();

    /*   List<QuestionViewV1>*/
    questions = unansweredQuestionsResult.resources.cast<QuestionViewV1>();

}


 _onPageChanged(int index) {
 setState(() {
     addToIndex=addToIndex+3;
});

所以在给定的示例中，我将在列表视图中每页得到 3 个问题，但每个其他页面都会有相同的问题集，我需要在滑动时加载 3 个新问题...（获取的问题数量在 getData 方法中定义.(12) )

Answer 1

_getData() 应该在 _onPageChanged 中调用 或者变成这样

 PageView.builder(
        controller: _pageController,
        onPageChanged: _onPageChanged,
        itemCount: questions.length, 
        itemBuilder: (BuildContext context, int index) {
         return FutureBuilder(
            future: _getData(),
            builder: (ctx,snap){
              if(snap.hasData){
                return _pageView(3);
              }else if(snap.connectionState == ConnectionState.waiting){
                 return Center(child:CircularProgressIndicator());
              }
            },
          );
      },
     )