PullToRefreshHeader

PullToRefreshHeader.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:pull_to_refresh_notification/pull_to_refresh_notification.dart';

class PullToRefreshHeader extends StatefulWidget {
  @override
  _PullToRefreshHeaderState createState() => _PullToRefreshHeaderState();
}

class _PullToRefreshHeaderState extends State<PullToRefreshHeader> {
  int listlength = 5;
  @override
  Widget build(BuildContext context) {
    return PullToRefreshNotification(
      color: Colors.blue,
      onRefresh: onRefresh,
      maxDragOffset: 80.0,
      child: CustomScrollView(
        slivers: <Widget>[
          SliverAppBar(
            pinned: true,
            title: Text("PullToRefreshHeader"),
          ),
          PullToRefreshContainer(buildPulltoRefreshHeader),
          SliverList(
              delegate:
                  SliverChildBuilderDelegate((BuildContext context, int index) {
            return Container(
                padding: EdgeInsets.only(bottom: 4.0),
                child: Column(
                  children: <Widget>[
                    Text(
                      "List item : ${listlength - index}",
                      style: TextStyle(fontSize: 15.0, inherit: false),
                    ),
                    Divider(
                      color: Colors.grey,
                      height: 2.0,
                    )
                  ],
                ));
          }, childCount: listlength)),
          SliverList(
              delegate:
                  SliverChildBuilderDelegate((BuildContext context, int index) {
            return Container(
                padding: EdgeInsets.only(bottom: 4.0),
                child: Column(
                  children: <Widget>[
                    Text(
                      "List item : ${listlength - index}",
                      style: TextStyle(fontSize: 15.0, inherit: false),
                    ),
                    Divider(
                      color: Colors.grey,
                      height: 2.0,
                    )
                  ],
                ));
          }, childCount: listlength)),
          SliverGrid(
              gridDelegate:
                  SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
              delegate:
                  SliverChildBuilderDelegate((BuildContext context, int index) {
                return Container(
                    padding: EdgeInsets.only(bottom: 4.0),
                    child: Column(
                      children: <Widget>[
                        Text(
                          "List item : ${listlength - index}",
                          style: TextStyle(fontSize: 15.0, inherit: false),
                        ),
                        Divider(
                          color: Colors.grey,
                          height: 2.0,
                        )
                      ],
                    ));
              }, childCount: listlength)),
        ],
      ),
    );
  }

  Widget buildPulltoRefreshHeader(PullToRefreshScrollNotificationInfo info) {
    //print(info?.mode);
    //print(info?.dragOffset);
//    print("------------");
    var offset = info?.dragOffset ?? 0.0;
    var mode = info?.mode;
    Widget refreshWiget = Container();
    //it should more than 18, so that RefreshProgressIndicator can be shown fully
    if (info?.refreshWiget != null &&
        offset > 18.0 &&
        mode != RefreshIndicatorMode.error) {
      refreshWiget = info.refreshWiget;
    }

    Widget child = null;
    if (mode == RefreshIndicatorMode.error) {
      child = GestureDetector(
          onTap: () {
            // refreshNotification;
            info?.pullToRefreshNotificationState?.show();
          },
          child: Container(
            color: Colors.grey,
            alignment: Alignment.bottomCenter,
            height: offset,
            width: double.infinity,
            //padding: EdgeInsets.only(top: offset),
            child: Container(
              padding: EdgeInsets.only(left: 5.0),
              alignment: Alignment.center,
              child: Text(
                mode?.toString() + "  click to retry" ?? "",
                style: TextStyle(fontSize: 12.0, inherit: false),
              ),
            ),
          ));
    } else {
      child = Container(
        color: Colors.grey,
        alignment: Alignment.bottomCenter,
        height: offset,
        width: double.infinity,
        //padding: EdgeInsets.only(top: offset),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            refreshWiget,
            Container(
              padding: EdgeInsets.only(left: 5.0),
              alignment: Alignment.center,
              child: Text(
                mode?.toString() ?? "",
                style: TextStyle(fontSize: 12.0, inherit: false),
              ),
            )
          ],
        ),
      );
    }

    return SliverToBoxAdapter(
      child: child,
    );
  }

  bool success = false;
  Future<bool> onRefresh() {
    final Completer<bool> completer = new Completer<bool>();
    new Timer(const Duration(seconds: 2), () {
      completer.complete(success);
      success = true;
    });
    return completer.future.then((bool success) {
      if (success) {
        setState(() {
          listlength += 10;
        });
      }
      return success;
    });
  }
}