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【Dart/Flutter】Flutter Apprenticeのテクニック抜粋

2021/11/17に公開
Android
Flutter
Dart
#
flutterapprentice
tech

無料で素晴らしい教育資料Flutter Apprenticeの中で、
個人的に覚えておきたいテクニックをソースコード部分と共に抜粋したものとなります。
順を追っての説明はありませんので、詳細はFlutter Apprentice にてご確認ください。
何か思い出す際等に、お役立ちできれば幸いです。

関連記事

【Dart/Flutter】Flutter Apprenticeのテクニック抜粋

【Dart/Flutter】Flutter Apprenticeのテクニック抜粋 - 備考1

【Dart/Flutter】Flutter Apprenticeのテクニック抜粋 - 備考2

【Dart/Flutter】Flutter Apprenticeのテクニック集

はじめに

Widget小ネタ

    return CircleAvatar(
      backgroundColor: Colors.white,
      radius: imageRadius,
      // 4
      child: CircleAvatar(
        radius: imageRadius - 5,
        backgroundImage: imageProvider,
      ),
    );

                    child: RotatedBox(
                      quarterTurns: 3,
                      child: Text(
                        'Smoothies',
                        style: FooderlichTheme.lightTextTheme.headline1,
                      ),
                    ),

            Container(
              decoration: BoxDecoration(
                // 1
                color: Colors.black.withOpacity(0.6),
                // 2
                borderRadius: const BorderRadius.all(Radius.circular(10.0)),
              ),
            ),

            child: ListView.separated(
              scrollDirection: Axis.horizontal,
              itemCount: recipes.length,
              itemBuilder: (context, index) {
                final recipe = recipes[index];
                return buildCard(recipe);
              },
              separatorBuilder: (context, index) {
                return const SizedBox(width: 16);
              },
            ),

          return ListView(
            scrollDirection: Axis.vertical,
            children: [
              TodayRecipeListView(recipes: snapshot.data?.todayRecipes ?? []),
              const SizedBox(height: 16),
              FriendPostListView(
                friendPosts: snapshot.data?.friendPosts ?? [],
              )
            ],
          );

以下、上記のFriendPostListViewのListView

          ListView.separated(
            primary: false,
            physics: const NeverScrollableScrollPhysics(),
            shrinkWrap: true,
            scrollDirection: Axis.vertical,
            itemCount: friendPosts.length,
            itemBuilder: (context, index) {
              final post = friendPosts[index];
              return FriendPostTile(post: post);
            },
            separatorBuilder: (context, index) {
              return const SizedBox(height: 16);
            },
          ),

      child: GridView.builder(
        itemCount: recipes.length,
        gridDelegate: const SliverGridDelegateWithMaxCrossAxisExtent(
            maxCrossAxisExtent: 500.0),
        itemBuilder: (context, index) {
          final simpleRecipe = recipes[index];
          return RecipeThumbnail(recipe: simpleRecipe);
        },
      ),

          body: IndexedStack(
            index: tabManager.selectedTab,
            children: pages,
          ),

              child: AspectRatio(
                aspectRatio: 1 / 1,
                child: Image.asset('assets/fooderlich_assets/empty_list.png'),
              ),

                return AlertDialog(
                  content: BlockPicker(
                      pickerColor: Colors.white,
                      // 6
                      onColorChanged: (color) {
                        setState(() => _currentColor = color);
                      }),
                  actions: [
                    // 7
                    TextButton(
                      child: const Text('Save'),
                      onPressed: () {
                        Navigator.of(context).pop();
                      },
                    ),
                  ],
                );

          return Dismissible(
            // 6
            key: Key(item.id),
            // 7
            direction: DismissDirection.endToStart,
            // 8
            background: Container(
              color: Colors.red,
              alignment: Alignment.centerRight,
              child: const Icon(
                Icons.delete_forever,
                color: Colors.white,
                size: 50.0,
              ),
            ),
            // 9
            onDismissed: (direction) {
              // 10
              manager.deleteItem(index);
              // 11
              ScaffoldMessenger.of(context).showSnackBar(
                SnackBar(
                  content: Text('${item.name} dismissed'),
                ),
              );
            },
            child: InkWell(
// ・・・省略・・・
          );

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

import '../../data/memory_repository.dart';

class ShoppingList extends StatefulWidget {
  const ShoppingList({Key? key}) : super(key: key);

  @override
  State<ShoppingList> createState() => _ShoppingListState();
}

class _ShoppingListState extends State<ShoppingList> {
  /// 食材購入のチェックボックス管理
  final checkBoxValues = Map<int, bool>();

  @override
  Widget build(BuildContext context) {
    /// Consumerを利用し、監視（このウィジェットツリー下を再描画範囲とする）
    return Consumer<MemoryRepository>(builder: (context, repository, child) {
      final ingredients = repository.findAllIngredients();
      return ListView.builder(
          itemCount: ingredients.length,
          itemBuilder: (BuildContext context, int index) {
            /// ☑チェックボックスの便利ウィジェット
            return CheckboxListTile(
              /// checkBoxValuesのindexとingredientsのindexを同期させて管理
              value:
                  checkBoxValues.containsKey(index) && checkBoxValues[index]!,
              title: Text(ingredients[index].name ?? ''),
              onChanged: (newValue) {
                if (newValue != null) {
                  setState(() {
                    checkBoxValues[index] = newValue;
                  });
                }
              },
            );
          });
    });
  }
}

ロジック小ネタ

  void _scrollListener() {
    if (_controller.offset >= _controller.position.maxScrollExtent &&
        !_controller.position.outOfRange) {
      print('reached the bottom');
    }
    if (_controller.offset <= _controller.position.minScrollExtent &&
        !_controller.position.outOfRange) {
      print('reached the top!');
    }
  }

                date: DateTime(
                  _dueDate.year,
                  _dueDate.month,
                  _dueDate.day,
                  _timeOfDay.hour,
                  _timeOfDay.minute,
                ),

import 'package:equatable/equatable.dart';

import 'ingredient.dart';

// ignore: must_be_immutable
class Recipe extends Equatable {
  int? id;
  final String? label;
  final String? image;
  final String? url;
  List<Ingredient>? ingredients;
  final double? calories;
  final double? totalWeight;
  final double? totalTime;

  Recipe(
      {this.id,
      this.label,
      this.image,
      this.url,
      this.calories,
      this.totalWeight,
      this.totalTime});

  @override
  List<Object?> get props =>
      [label, image, url, calories, totalWeight, totalTime];
}

範囲大きめなテクニック

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