【Flutter】ファイルを削除する方法。〜ファイル作成から削除まで〜

environment:
  sdk: ">=2.7.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter


  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^1.0.0

  path_provider: ^0.5.0+1

//ファイル作成
final logDirectory = await getApplicationDocumentsDirectory();
filepath = '${logDirectory.path}/test.txt';
File textfilePath = File(filepath);
await textfilePath.writeAsString('test');

//ファイル削除
final dir = Directory(filepath);
dir.deleteSync(recursive: true);

import 'dart:io';

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

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(

        primarySwatch: Colors.blue,

        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  bool iconchange = false;
  String filepath;

  Future<void> _incrementCounter() async {
    if (_counter/2 == 0) {
      iconchange = true;
      //ファイル作成
      final logDirectory = await getApplicationDocumentsDirectory();
      filepath = '${logDirectory.path}/test.txt';
      File textfilePath = File(filepath);
      await textfilePath.writeAsString('test');

    } else if (_counter/2 == 1) {
      iconchange = false;
      //ファイル削除
      final dir = Directory(filepath);
      dir.deleteSync(recursive: true);

    }
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(

        title: Text(widget.title),
          actions: [
            if (iconchange==true)
              IconButton(
                icon: Icon(Icons.flag),
                color:Colors.white,
                onPressed: () {},
              ),
            if (iconchange==false)
              IconButton(
                icon: Icon(Icons.flag_outlined),
                color:Colors.red,
                onPressed: () {},
              ),
          ]
      ),
      body: Center(

        child: Column(

          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}