Flutter Mobile Development · レッスン

基本的なページナビゲーション

Navigatorを使ってルートをpushおよびpopし、Flutterアプリ内の画面間を簡単に遷移する方法を学びます。

「基本的なページナビゲーション」はCoddyKit上の無料Flutter Mobile Developmentレッスンです。これはレッスン1/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはFlutter Mobile Development学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Flutter Mobile Developmentコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Navigating Your App

Think of a mobile app as a collection of pages or "screens." Navigation is how users move between these screens, like going from a product list to a product detail page.

Apps need a clear way to move forward.
Apps also need a way to go back.
Flutter provides powerful tools for this.

Meet the Navigator

In Flutter, the Navigator widget manages a stack of Route objects. When you want to show a new screen, you "push" a route onto this stack. When you want to go back, you "pop" a route off the stack.

It's like a stack of playing cards.
New cards go on top (push).
You remove cards from the top (pop).

Understanding Routes

A Route is an abstraction for a "screen" or "page" in your app. Flutter provides a common type of route called MaterialPageRoute, which creates a platform-specific transition animation (like sliding in from the right on Android).

It's the blueprint for how a new screen will look and behave when shown.

Moving Forward with push()

To navigate to a new screen, you use Navigator.push(). This method takes a BuildContext and a MaterialPageRoute as arguments.

The builder function inside MaterialPageRoute tells Flutter which widget to build for the new screen.

Try Pushing a Route

This example shows how to push a new screen when a button is pressed. Run it and tap the button!

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomeScreen(),
    );
  }
}

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Home Screen')),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => SecondScreen()),
            );
          },
          child: const Text('Go to Second Screen'),
        ),
      ),
    );
  }
}

class SecondScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Second Screen')),
      body: const Center(
        child: Text('You are on the second screen!'),
      ),
    );
  }
}

What is BuildContext?

You might have noticed context being passed around. BuildContext is a handle to the location of a widget in the widget tree. It helps widgets locate other widgets or data higher up in the tree.

The Navigator uses this context to know which navigation stack to operate on.

Going Back with pop()

When you want to return to the previous screen, you "pop" the current route off the navigation stack using Navigator.pop(). This will reveal the screen that was underneath.

Flutter's AppBar often provides a back button automatically when a new route is pushed, which internally calls Navigator.pop().

Try Popping a Route

Let's modify our previous example to include a button on the second screen that allows us to explicitly go back to the home screen.

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomeScreen(),
    );
  }
}

class HomeScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Home Screen')),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => SecondScreen()),
            );
          },
          child: const Text('Go to Second Screen'),
        ),
      ),
    );
  }
}

class SecondScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Second Screen')),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            Navigator.pop(context); // This will go back!
          },
          child: const Text('Go Back'),
        ),
      ),
    );
  }
}

Visualizing the Stack

Imagine the Navigator maintains a stack of screens. When you push, a new screen is placed on top. When you pop, the top screen is removed.

The user always sees the topmost screen. This stack behavior is fundamental to how navigation works in Flutter.

Push: Adds to top.
Pop: Removes from top.
First screen is at the bottom.

Navigation Check

Consider a Flutter app with two screens, ScreenA and ScreenB. If you are currently on ScreenA and want to move to ScreenB, then later return to ScreenA, which sequence of Navigator methods would you use?

Recap: Basic Navigation

Great job! You've learned the core concepts of basic navigation in Flutter:

The Navigator manages a stack of routes.
MaterialPageRoute defines a new screen.
Navigator.push() adds a new screen to the stack.
Navigator.pop() removes the current screen from the stack.
BuildContext is essential for navigation operations.

Next, we'll explore more advanced navigation techniques like named routes!

よくある質問

「基本的なページナビゲーション」レッスンは無料ですか？

はい。「基本的なページナビゲーション」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Flutter Mobile Developmentコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Flutter Mobile Developmentコースには全4レッスンが含まれています。

「基本的なページナビゲーション」で何を学びますか？

Navigatorを使ってルートをpushおよびpopし、Flutterアプリ内の画面間を簡単に遷移する方法を学びます。ブラウザで直接実行するハンズオンコードでFlutter Mobile Developmentを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Flutter Mobile Developmentを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのFlutter Mobile Developmentは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン1/4です。

「基本的なページナビゲーション」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このFlutter Mobile Developmentレッスンでコードを書いて実行できますか？

はい。すべてのFlutter Mobile Developmentレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

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