fcs/lib/pages/test_list.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:fcs/model/test_model.dart';
import 'package:fcs/theme/theme.dart';
import 'package:fcs/vo/popup_menu.dart';

class TestList extends StatefulWidget {
  @override
  _TestListState createState() => _TestListState();
}

class _TestListState extends State<TestList> {
  bool isLoading = false;

  @override
  void initState() {
    super.initState();
    var testModel = Provider.of<TestModel>(context, listen: false);
    testModel.initData();
    print("List initState!");
  }

  @override
  void dispose() {
    print("List Dispose!");
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    var testModel = Provider.of<TestModel>(context);

    return Scaffold(
      appBar: AppBar(
        backgroundColor: primaryColor,
        title: Text("Tests"),
        actions: <Widget>[
          PopupMenuButton<PopupMenu>(
              elevation: 3.2,
              onSelected: (s) {
                if (s.index == 0) Provider.of<TestModel>(context).populate();
                if (s.index == 1) Provider.of<TestModel>(context).add();
                if (s.index == 2) Provider.of<TestModel>(context).update();
                if (s.index == 3) Provider.of<TestModel>(context).remove();
              },
              itemBuilder: (BuildContext context) {
                return [
                  PopupMenuItem<PopupMenu>(
                    value: PopupMenu(status: "Populate", index: 0),
                    child: Text("Populate"),
                  ),
                  PopupMenuItem<PopupMenu>(
                    value: PopupMenu(status: "Add", index: 1),
                    child: Text("Add"),
                  ),
                  PopupMenuItem<PopupMenu>(
                    value: PopupMenu(status: "Update", index: 2),
                    child: Text("Update"),
                  ),
                  PopupMenuItem<PopupMenu>(
                    value: PopupMenu(status: "Delete", index: 3),
                    child: Text("Delete"),
                  )
                ];
              })
        ],
      ),
      body: Column(
        children: <Widget>[
          Expanded(
            child: NotificationListener<ScrollNotification>(
              onNotification: (ScrollNotification scrollInfo) {
                if (!isLoading &&
                    scrollInfo.metrics.pixels ==
                        scrollInfo.metrics.maxScrollExtent &&
                    !testModel.ended) {
                  // start loading data
                  _loadData(testModel);
                }
                return null;
              },
              child: ListView.builder(
                  padding: EdgeInsets.only(left: 15, right: 15, top: 15),
                  shrinkWrap: true,
                  itemCount: testModel.ended
                      ? testModel.tests.length + 1
                      : testModel.tests.length,
                  itemBuilder: (BuildContext context, int index) {
                    return (testModel.ended && index == testModel.tests.length)
                        ? Center(child: Text("No more item"))
                        : buildCard(testModel.tests[index], index + 1);
                  }),
            ),
          ),
          Container(
            height: isLoading ? 50.0 : 0,
            color: Colors.transparent,
            child: Center(
              child: new CircularProgressIndicator(),
            ),
          ),
        ],
      ),
    );
  }

  Card buildCard(Test test, int index) {
    return Card(
      elevation: 10,
      color: Colors.white,
      child: new Padding(
        padding: const EdgeInsets.symmetric(vertical: 10.0),
        child: new Row(
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.all(8.0),
              child: Icon(
                Icons.account_circle,
                color: primaryColor,
                size: 55,
              ),
            ),
            Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: <Widget>[
                new Text(
                  "$index - ${test.name}",
                  style: new TextStyle(fontSize: 17.0, color: Colors.black),
                ),
                new Text(
                  test.age.toString(),
                  style: new TextStyle(fontSize: 12.0, color: Colors.black),
                ),
              ],
            ),
          ],
        ),
      ),
    );
  }

  _loadData(TestModel testModel) {
    setState(() {
      isLoading = true;
    });

    Timer(Duration(seconds: 1), () {
      testModel.load();
      setState(() {
        isLoading = false;
      });
    });
  }
}