フラッターテーマの色を黒に変更中にエラーが発生しました
Flutterでの最初のステップAndroid Studio。私のステップ：
- Android Studioをダウンロードしてインストールします
- FlutterとDartをダウンロードしてインストールする
- Flutterで最初のデフォルトアプリを作成する
これはデモアプリです：
このアプリのコードの解説では、次のようになっています。
// 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"
Colors.blueをColors.greenに変更しました。アプリが緑色に変わっても、ホットリロードは正常に機能します。しかし、Colors.blackに変更しようとすると、エラーが発生します。
タイプ 'Color'はタイプ 'MaterialColor'のサブタイプではありません。
デモアプリの完全なコード：
import 'package:flutter/material.Dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new 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 press Run > Flutter Hot Reload in IntelliJ). Notice that the
// counter didn't reset back to zero; the application is not restarted.
primarySwatch: Colors.black,
),
home: new MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, 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;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
@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 new Scaffold(
appBar: new 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: new Text(widget.title),
),
body: new Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: new Column(
// Column is also 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 Paint" (press "p" in the console where you ran
// "flutter run", or select "Toggle Debug Paint" from the Flutter tool
// window in IntelliJ) 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>[
new Text(
'You have pushed the button this many times:',
),
new Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: new FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: new Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
Colors.blackはMaterialColorではなく、primarySwatchはマテリアルカラーパレットを想定しているため、使用できません。
ThemeDataの定義に移動すると、次のように表示されます。
/// * The primary color palette (the [primarySwatch]), chosen from
/// one of the swatches defined by the material design spec. This
/// should be one of the maps from the [Colors] class that do not
/// have "accent" in their name.
たとえば、Colors.blueの定義は次のとおりです。
static const MaterialColor blue = MaterialColor(
_bluePrimaryValue,
<int, Color>{
50: Color(0xFFE3F2FD),
100: Color(0xFFBBDEFB),
200: Color(0xFF90CAF9),
300: Color(0xFF64B5F6),
400: Color(0xFF42A5F5),
500: Color(_bluePrimaryValue),
600: Color(0xFF1E88E5),
700: Color(0xFF1976D2),
800: Color(0xFF1565C0),
900: Color(0xFF0D47A1),
},
);
static const int _bluePrimaryValue = 0xFF2196F3;
Colors.blackの定義は次のとおりです。
static const Color black = Color(0xFF000000);
そこで黒を使用することはできません。同じ理由で、Colors.whiteは使用できません。これらの2つは、アクセントのない色を使用する上記の説明の例外です。
黒が必要な場合は、独自のパレットを作成できます。
const MaterialColor primaryBlack = MaterialColor(
_blackPrimaryValue,
<int, Color>{
50: Color(0xFF000000),
100: Color(0xFF000000),
200: Color(0xFF000000),
300: Color(0xFF000000),
400: Color(0xFF000000),
500: Color(_blackPrimaryValue),
600: Color(0xFF000000),
700: Color(0xFF000000),
800: Color(0xFF000000),
900: Color(0xFF000000),
},
);
const int _blackPrimaryValue = 0xFF000000;
そして、Colors.blackの代わりにprimaryBlackを使用します。
パレットでさまざまな色を調整できます。
primaryColor: Colors.black
このprimarySwatch cr＃^全体を取得していません...
また、単にテーマを使用するだけです：ThemeData.dark（）を使用して、アプリケーションのテーマをダークに変更します
以下のコードを使用してBlack Colorテーマを取得しました。
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primaryColor: Colors.black,
//primarySwatch: Colors.black,
),
home: MyHomePage(title: 'Flutter First Home Page' ),
);
}
}
カラーコード：
内部テーマデータ：（theme_data.Dart）
........
......
brightness ??= Brightness.light;
final bool isDark = brightness == Brightness.dark;
primarySwatch ??= Colors.blue;
primaryColor ??= isDark ? Colors.grey[900] : primarySwatch;
primaryColorBrightness ??= estimateBrightnessForColor(primaryColor);
primaryColorLight ??= isDark ? Colors.grey[500] : primarySwatch[100];
primaryColorDark ??= isDark ? Colors.black : primarySwatch[700];
final bool primaryIsDark = primaryColorBrightness == Brightness.dark;
toggleableActiveColor ??= isDark ? Colors.tealAccent[200] : (accentColor ?? primarySwatch[600]);
accentColor ??= isDark ? Colors.tealAccent[200] : primarySwatch[500];
accentColorBrightness ??= estimateBrightnessForColor(accentColor);
final bool accentIsDark = accentColorBrightness == Brightness.dark;
canvasColor ??= isDark ? Colors.grey[850] : Colors.grey[50];
scaffoldBackgroundColor ??= canvasColor;
bottomAppBarColor ??= isDark ? Colors.grey[800] : Colors.white;
cardColor ??= isDark ? Colors.grey[800] : Colors.white;
dividerColor ??= isDark ? const Color(0x1FFFFFFF) : const Color(0x1F000000);
.....
.......
出力
