flutter Infinite Scrolling for ListView.builder

Question

I've to use graphql query and I've got data page by page. so I need to Infinite Scrolling in my list view builder but I don't know how to add num in page. can anyone help me, please?

this is my query:

query homeview(\$moreId: ID!, \$page: Int! ){
    homeview(HM_ID: \$moreId, page: \$page){
    HM_ID
    HM_Type_ID
    HM_Type_Name 
  }
}
""";

and this is my variable to pass int number in page: dynamic pageNum = 0;

here is the controller :

 ScrollController _scrollController = new ScrollController(  initialScrollOffset: 10, 

and this is my list view builder:

   class MoreEpd extends StatefulWidget {
  final String moreId;
  const MoreEpd({Key? key, required this.moreId}) : super(key: key);

  @override
  _MoreEpdState createState() => _MoreEpdState();
}

class _MoreEpdState extends State<MoreEpd> {
  double pageWidth = 0;
  double pageHeigh = 0;
  dynamic pageNum = 0;

  final String leftArrow = 'assets/icons/left-arrow.svg';
  String getSearchResult = """
 query homeview(\$moreId: ID!, \$page: Int! ){
    homeview(HM_ID: \$moreId, page: \$page){
    HM_ID
    Priority
    Details{
      Ep_ID
      Image
      title
      Pod_title
      
    }
  }
}
""";

  @override
  Widget build(BuildContext context) {
    pageWidth = MediaQuery.of(context).size.width;
    pageHeigh = MediaQuery.of(context).size.height;
    return Container(
      child: Query(
        options: QueryOptions(
          document: gql(getSearchResult),
          variables: {'moreId': widget.moreId, 'page': pageNum},
        ),
        builder: (
          QueryResult result, {
          Refetch? refetch,
          FetchMore? fetchMore,
        }) {
          return handleResult(result);
        },
      ),
    );
  }

 
  Widget handleResult(QueryResult result) {
    var data = result.data!['homeview']['Details'] ?? [];
    return Container(
        child: ListView.builder(
            padding: EdgeInsets.only(top: 15),
            shrinkWrap: true,
            itemCount: data.length ,
            itemBuilder: (context, index) {
              return InkWell(
                onTap: () {},
                child: Padding(
                  padding: EdgeInsets.only(
                      top: pageWidth * 0.0,
                      right: pageWidth * 0.08,
                      left: pageWidth * 0.08,
                      bottom: pageWidth * 0.0),
                  child: Container(
                    child: Stack(
                      children: [
                        Column(
                          children: [
                            Padding(
                              padding:
                                  EdgeInsets.only(bottom: pageWidth * 0.060),
                              child: Row(
                                children: [
                                  Padding(
                                    padding:
                                        EdgeInsets.only(left: pageWidth * 0.01),
                                    child: Container(
                                      // alignment: Alignment.centerRight,
                                      width: pageWidth * 0.128,
                                      height: pageWidth * 0.128,
                                      decoration: BoxDecoration(
                                          image: DecorationImage(
                                              fit: BoxFit.cover,
                                              image: CachedNetworkImageProvider(
                                                data[index]['Image'],
                                              )),
                                          borderRadius: BorderRadius.all(
                                              Radius.circular(15)),
                                          // color: Colors.redAccent,
                                          border: Border.all(
                                            color: MyColors.lightGrey,
                                            width: 1,
                                          )),
                                    ),
                                  ),
                                  Expanded(
                                    child: Row(
                                      children: [
                                        Column(
                                          crossAxisAlignment:
                                              CrossAxisAlignment.start,
                                          children: [
                                            Container(
                                              width: pageWidth * 0.5,
                                              alignment: Alignment.centerRight,
                                              child: Text(
                                                data[index]['title'],
                                                textAlign: TextAlign.right,
                                                overflow: TextOverflow.ellipsis,
                                                maxLines: 1,
                                                // softWrap: true,
                                                style: TextStyle(
                                                  // fontWeight: FontWeight.bold,
                                                  fontSize: 14,
                                                ),
                                              ),
                                            ),
                                          ],
                                        ),
                                      ],
                                    ),
                                  )
                                ],
                              ),
                            ),
                          ],
                        ),
                      ],
                    ),
                  ),
                ),
              );
            }));
  }}

can anyone help me please how can I use infinite scrolling to load other pages in my query?

Solution

The easiest way is to use a ListView.builder without specifying the itemCount parameter.

Here is the simplest example:

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text("Infinite List"),
      ),
      body: ListView.builder(
        itemBuilder: (context, index) {
          return Text("$index");
        },
      ),
    );
  }
}

Later, you can enhance this by fetching real data. You could show a 'CircularProgressIndicator' in the last item of the list while waiting for the new data.

body: ListView.builder(
    itemBuilder: (context, index) {
      if (index < data.length) {
        // Show your info
        return Text("$index");
      } else {
        getMoreData();
        return Center(child: CircularProgressIndicator());
      }
    },
    itemCount: data.length + 1,
  ),

You can see that we trick the list by adding an index, and calling for more data when displaying that final index.

getMoreData() would include a call to setState() to force a rebuild and to take into account the new data.

Comments

[quim]

why do you need infinite scroll? listview.builder will be as big as it needs to fit all data

[Admin]

because I should pass int num to page query and get data from it.

[Admin]

what is getMoreData()? class or method?

[Admin]

I don't know what I should put in getMoreData . i just want to pageNum +=1; this happen and load more data

[Infostans]

@stysh it is function _getMoreData() async { final moreItems = await widget.onRequest(items.length); if (!mounted) return; if (moreItems.isEmpty) { setState(() => end = true); return; } setState(() => items = [...items, ...moreItems]); }

[Infostans]

@stysh also you can check this tutorial dartpad.dev/… . If it helps then please upvote it

[Admin]

@lnfostans it's cool but I can't match it with my project. I upload my class in question. Would you please see it and tell me how can I do it?