simple_command 1.0.1

A simple Flutter package for wrapping method executions in a Command object

example/lib/main.dart

import 'package:flutter/material.dart';
import 'package:simple_command/commands.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;
  final MyHomeViewModel viewModel = MyHomeViewModel();

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also a layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            ValueListenableBuilder<int>(
              valueListenable: viewModel.counter,
              builder: (context, counter, child) {
                return Text(
                  '$counter',
                  style: Theme.of(context).textTheme.headline4,
                );
              },
            ),
          ],
        ),
      ),
      floatingActionButton: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          FloatingActionButton(
            onPressed: viewModel.incrementCounterCommand,
            tooltip: 'Increment',
            child: const Icon(Icons.add),
          ),
          FloatingActionButton(
            onPressed: viewModel.decrementCounterCommand,
            tooltip: 'Decrement',
            child: const Icon(Icons.remove),
          ),
        ],
      ), // This trailing comma makes auto-formatting nicer for build methods.s
    );
  }
}

class MyHomeViewModel {
  final ValueNotifier<int> counter = ValueNotifier(0);

  late final RelayCommand incrementCounterCommand = RelayCommand.withoutParam(_incrementCounter);

  late final RelayCommand decrementCounterCommand = RelayCommand.withoutParam(_decrementCounter);

  void _incrementCounter() {
    counter.value++;

    if (counter.value > 4) {
      incrementCounterCommand.canExecute.value = false;
    } else {
      decrementCounterCommand.canExecute.value = true;
    }
  }

  void _decrementCounter() {
    counter.value--;

    if (counter.value <= 5 && counter.value > 0) {
      incrementCounterCommand.canExecute.value = true;
    } else {
      decrementCounterCommand.canExecute.value = false;
    }
  }
}