New_main.dart

import 'package:flutter/material.dart';
import './models/transaction.dart';
import './widgets/chart.dart';
import './widgets/transaction_list.dart';
import './widgets/new_transaction.dart';

void main() {
  // Import this -> import 'package:flutter/services.dart';
  // SystemChrome.setPreferredOrientations([
  //   DeviceOrientation.portraitUp,
  //   DeviceOrientation.portraitDown
  // ]);
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Personal Expenses',
      theme: ThemeData(
        primarySwatch: Colors.green,
        accentColor: Colors.green,
        errorColor: Colors.red,
        fontFamily: 'Quicksand',
        textTheme: ThemeData.light().textTheme.copyWith(
            title: TextStyle(
                fontFamily: 'OpenSans',
                fontSize: 18,
                fontWeight: FontWeight.bold),
            button: TextStyle(color: Colors.white)),
        appBarTheme: AppBarTheme(
          textTheme: ThemeData.light().textTheme.copyWith(
                  title: TextStyle(
                fontFamily: 'OpenSans',
                fontSize: 20,
              )),
        ),
      ),
      home: MyHomePage(),
    );
  }
}

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

class _MyHomePageState extends State<MyHomePage> {
  final List<Transaction> _userTransactions = [];

  List<Transaction> get _recentTransactions {
    return _userTransactions.where((tx) {
      return tx.dateTime.isAfter(DateTime.now().subtract(Duration(days: 7)));
    }).toList();
  }

  bool _showChart = false;

  _addTransaction(String title, double amount, DateTime date) {
    final newTx = Transaction(
      id: DateTime.now().toString(),
      title: title,
      amount: amount,
      dateTime: date,
    );
    setState(() {
      _userTransactions.add(newTx);
    });
  }

  _startAddNewTransaction(BuildContext ctx) {
    showModalBottomSheet(
        context: ctx,
        builder: (bCtx) {
          return NewTransaction(this._addTransaction);
        });
  }

  _deleteTransaction(id) {
    setState(() {
      _userTransactions.removeWhere((tx) => tx.id == id);
    });
  }

  @override
  Widget build(BuildContext context) {
    final isLandscape =
        MediaQuery.of(context).orientation == Orientation.landscape;
    final isPortrait =
        MediaQuery.of(context).orientation == Orientation.portrait;
    final appBar = AppBar(
      title: Text('Personal Expenses'),
      actions: <Widget>[
        IconButton(
          icon: Icon(
            Icons.add,
          ),
          onPressed: () => _startAddNewTransaction(context),
        )
      ],
    );

    final transactionList = Expanded(
      child: TransactionList(_userTransactions, this._deleteTransaction),
    );

    final transactionChart = isLandscape
        ? Expanded(
            child: Chart(this._recentTransactions),
          )
        : Container(
            child: Chart(this._recentTransactions),
            height: (MediaQuery.of(context).size.height -
                    appBar.preferredSize.height -
                    MediaQuery.of(context).padding.top) *
                0.3);

    return Scaffold(
      appBar: appBar,
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          if (isLandscape)
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text('Show chart'),
                Switch(
                    value: _showChart,
                    onChanged: (value) {
                      this.setState(() {
                        _showChart = value;
                      });
                    }),
              ],
            ),
          if (isPortrait) ...[transactionChart, transactionList],
          if (isLandscape) _showChart ? transactionChart : transactionList,
        ],
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () => _startAddNewTransaction(context),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
    );
  }
}