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passerby
Asked: 2025-04-25 16:53:02 +0800 CST

使用 lightTheme.copyWith(brightness: Brightness.dark) 创建 darkTheme 不起作用

  • 772

我正在尝试使用 基于现有亮色主题创建暗色主题lightTheme.copyWith(brightness: Brightness.dark)。但是，该应用似乎忽略了暗色主题的亮度。

我的 main.dart 使用以下代码：

@override
Widget build(BuildContext context) {
  return MaterialApp(
      theme: Themes.lightTheme,
      darkTheme: Themes.darkTheme,
      themeMode: ThemeMode.dark,
      ...
  );
}

其中Themes.lightTheme和Themes.darkTheme定义如下：

class Themes {
  static ThemeData get lightTheme => ThemeData(
        colorSchemeSeed: Colors.green,
      );

  static ThemeData get darkTheme => lightTheme.copyWith(
        brightness: Brightness.dark,
      );
}

调试器显示深色主题包含brightness: Brightness.dark。

但是，当我按如下方式定义黑暗主题时，一切正常copyWith：

class Themes {
  static ThemeData get lightTheme => ThemeData(
        colorSchemeSeed: Colors.green,
      );

  static ThemeData get darkTheme => ThemeData(
        colorSchemeSeed: Colors.green,
        brightness: Brightness.dark,
      );
}

有人能指出我对 Dart/Flutter 知识的盲点并解释一下发生了什么吗？

环境：

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.29.3, on Microsoft Windows [Version 10.0.22631.5262], locale xx-XX)
[✓] Windows Version (11 Home 64-bit, 23H2, 2009)
[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.1)
[✓] Chrome - develop for the web
[✓] Visual Studio - develop Windows apps (Visual Studio Community 2022 17.13.6)
[✓] Android Studio (version 2024.3)
[✓] VS Code (version 1.99.3)
[✓] Connected device (3 available)
[✓] Network resources
flutter

2 个回答

  1. 它ThemeData.copyWith只会改变brightness属性本身（或者更确切地说，是ColorScheme属性内部）。亮度本身只会影响 iOS 系统状态栏文本颜色等内容。

    ThemeData另一方面，构造函数的功能要多得多。给定colorSchemeSeed并brightness为你创建一整套配色方案：

    // https://github.com/flutter/flutter/blob/0cff5a3a45eeb42c24c3cd913e2716aedb656211/packages/flutter/lib/src/material/theme_data.dart#L423-L432
final Brightness effectiveBrightness =
    brightness ?? colorScheme?.brightness ?? Brightness.light;
final bool isDark = effectiveBrightness == Brightness.dark;
if (colorSchemeSeed != null || useMaterial3) {
  if (colorSchemeSeed != null) {
    colorScheme = ColorScheme.fromSeed(
      seedColor: colorSchemeSeed,
      brightness: effectiveBrightness,
    );
  }
    • 0
  2. Best Answer

    这里的问题是，简单地使用lightTheme.copyWith(brightness: Brightness.dark)并不能将主题完全转换为适当的暗主题。

    虽然brightness:Brightness.dark它确实会更新亮度字段，但它无法正确更新其他主题属性，例如背景颜色、文本颜色和默认样式，这些属性是纯深色主题自带的。这些属性是在你使用以下代码显式创建主题时由 Flutter 内部生成的：brightness: Brightness.dark.

    解决方案：

    ThemeData使用with单独定义您的黑暗主题brightness: Brightness.dark，就像您在此处所做的那样：

    static ThemeData get darkTheme => ThemeData(colorSchemeSeed: Colors.green, brightness: Brightness.dark,);

    这可确保所有与主题相关的属性与深色主题正确对齐。

    • 0

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