字体缩放与暗色主题实现

class AppState extends ChangeNotifier {
  double _fontScale = 1.0;
  
  double get fontScale => _fontScale;
  
  Future<void> setFontScale(double scale) async {
    _fontScale = scale;
    final prefs = await SharedPreferences.getInstance();
    await prefs.setDouble('font_scale', scale);
    notifyListeners();
  }
  
  Future<void> _loadPreferences() async {
    final prefs = await SharedPreferences.getInstance();
    _fontScale = prefs.getDouble('font_scale') ?? 1.0;
    // ...
  }
}

MaterialApp(
  // ...
  builder: (context, child) {
    final media = MediaQuery.of(context);
    final scale = appState.fontScale;
    return MediaQuery(
      data: media.copyWith(
        textScaler: TextScaler.linear(scale),
      ),
      child: child ?? const SizedBox.shrink(),
    );
  },
)

ListTile(
  leading: Icon(Icons.format_size),
  title: Text('字体大小'),
  subtitle: Text(_getFontSizeLabel(state.fontScale)),
  trailing: Icon(Icons.chevron_right),
  onTap: _showFontSizeDialog,
)
 
void _showFontSizeDialog() {
  showDialog(
    context: context,
    builder: (ctx) => AlertDialog(
      title: Text('调整字体大小'),
      content: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          _buildFontOption('小', 0.8),
          _buildFontOption('正常', 1.0),
          _buildFontOption('大', 1.2),
          _buildFontOption('超大', 1.5),
        ],
      ),
    ),
  );
}
 
Widget _buildFontOption(String label, double scale) {
  return RadioListTile<double>(
    title: Text(label),
    value: scale,
    groupValue: state.fontScale,
    onChanged: (value) {
      if (value != null) {
        state.setFontScale(value);
        Navigator.pop(context);
      }
    },
  );
}
 
String _getFontSizeLabel(double scale) {
  if (scale <= 0.8) return '小';
  if (scale <= 1.0) return '正常';
  if (scale <= 1.2) return '大';
  return '超大';
}

class AppState extends ChangeNotifier {
  ThemeMode _themeMode = ThemeMode.system;
  
  ThemeMode get themeMode => _themeMode;
  
  Future<void> setThemeMode(ThemeMode mode) async {
    _themeMode = mode;
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString('theme_mode', mode.toString());
    notifyListeners();
  }
  
  Future<void> _loadPreferences() async {
    final prefs = await SharedPreferences.getInstance();
    final themeModeStr = prefs.getString('theme_mode');
    if (themeModeStr != null) {
      _themeMode = ThemeMode.values.firstWhere(
        (e) => e.toString() == themeModeStr,
        orElse: () => ThemeMode.system,
      );
    }
    // ...
  }
}

MaterialApp(
  theme: /* 浅色主题 */,
  darkTheme: /* 暗色主题 */,
  themeMode: appState.themeMode,  // ← 关键：从 AppState 读取
  // ...
)

ListTile(
  leading: Icon(Icons.palette),
  title: Text('外观主题'),
  subtitle: Text(_getThemeModeLabel(state.themeMode)),
  trailing: Icon(Icons.chevron_right),
  onTap: _showThemeModeDialog,
)
 
void _showThemeModeDialog() {
  showDialog(
    context: context,
    builder: (ctx) => AlertDialog(
      title: Text('选择主题'),
      content: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          _buildThemeOption('浅色', ThemeMode.light),
          _buildThemeOption('暗色', ThemeMode.dark),
          _buildThemeOption('跟随系统', ThemeMode.system),
        ],
      ),
    ),
  );
}
 
Widget _buildThemeOption(String label, ThemeMode mode) {
  return RadioListTile<ThemeMode>(
    title: Text(label),
    value: mode,
    groupValue: state.themeMode,
    onChanged: (value) {
      if (value != null) {
        state.setThemeMode(value);
        Navigator.pop(context);
      }
    },
  );
}
 
String _getThemeModeLabel(ThemeMode mode) {
  switch (mode) {
    case ThemeMode.light:
      return '浅色';
    case ThemeMode.dark:
      return '暗色';
    case ThemeMode.system:
      return '跟随系统';
  }
}

// transfers_page.dart
if (item.status == TransferStatus.failed) {
  IconButton(
    icon: Icon(Icons.refresh),
    onPressed: () => _retryTransfer(item),
    tooltip: '重试',
  ),
}
 
Future<void> _retryTransfer(TransferItem item) async {
  if (item.type == TransferType.upload) {
    // 从数据库加载任务详情并重新加入队列
    await state.retryUpload(item.id);
  } else {
    await state.retryDownload(item.id);
  }
}

Widget _buildStatusIcon(TransferStatus status) {
  switch (status) {
    case TransferStatus.queued:
      return Icon(Icons.schedule, size: 16, color: Colors.grey);
    case TransferStatus.running:
      return SizedBox(
        width: 16,
        height: 16,
        child: CircularProgressIndicator(strokeWidth: 2),
      );
    case TransferStatus.finishing:
      return SizedBox(
        width: 16,
        height: 16,
        child: CircularProgressIndicator(strokeWidth: 2),
      );
    case TransferStatus.success:
      return Icon(Icons.check_circle, size: 16, color: Colors.green);
    case TransferStatus.failed:
      return Icon(Icons.error, size: 16, color: Colors.red);
    case TransferStatus.cancelled:
      return Icon(Icons.cancel, size: 16, color: Colors.orange);
  }
}