Flutter：如何将变量从 StatelessWidget 传递到 StatefulWidget答案

【问题标题】：Flutter: How to pass variables from StatelessWidget to StatefulWidgetFlutter：如何将变量从 StatelessWidget 传递到 StatefulWidget
【发布时间】：2019-08-25 00:39:45
【问题描述】：

问题是我无法将我自己的类 ForceSelection 值从另一个屏幕传递到另一个屏幕的 StatefulWidget。它在 StatelessWidget 中运行良好。我已经尝试从这个 Flutter 教程中学习：https://flutter.dev/docs/cookbook/navigation/passing-data#4-navigate-and-pass-data-to-the-detail-screen

我在 levelSelection.dart 中有这种类

class ForceSelection {
  final String forceSelection;
  final String langSelection;

  ForceSelection(this.forceSelection, this.langSelection);
}

我正在尝试将值传递给下一个文件 PlayQuiz.dart

Game(forceSelection: ForceSelection('maa', 'fin'))

game.dart 如下所示：

class Game extends StatelessWidget {
  final ForceSelection forceSelection;

  Game({Key key, @required this.forceSelection}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: forceSelection.langSelection, // TODO should work and change later
      theme: new ThemeData(
        primaryColor: Colors.white,
      ),
      home: PlayQuiz(),
    );
  }
}

我想将 ForceSelection 值传递给 PlayQuiz()

class PlayQuizState extends State<PlayQuiz> {
  Game.forceSelection // <--- How can I get the value out of here?
}

class PlayQuiz extends StatefulWidget {
  @override
  PlayQuizState createState() => new PlayQuizState(); 
}

完整的代码可以在这里找到：https://pastebin.com/nKssz42R 还有levelSelection.dart：https://pastebin.com/8QbBD0A2

【问题讨论】：

您希望从父级 -> 子级或子级 -> 父级传递吗？
我的解决方案对你有用吗？

标签： android dart flutter

【解决方案1】：

试试这个代码

在 PlayQuiz() 中添加 forceSelecton 参数

class Game extends StatelessWidget {
final ForceSelection forceSelection;

Game({Key key, @required this.forceSelection}) : super(key: key);

@override
Widget build(BuildContext context) {
  return MaterialApp(
    title: forceSelection.langSelection, // TODO should work and change later
    theme: new ThemeData(
      primaryColor: Colors.white,
    ),
    home: PlayQuiz(forceSelection),
  );
 }
}

游戏中测验

class PlayQuiz extends StatefulWidget {
  final ForceSelection forceSelection;

  PlayQuiz(this.forceSelection);

  @override
  PlayQuizState createState() => new PlayQuizState(forceSelection); 
}

在 PlayQuizState

class PlayQuizState extends State<PlayQuiz> {
  ForceSelection forceSelection;

  PlayQuizState(ForceSelection forceSelection) {
    this.forceSelection = forceSelection;
  }
}

【讨论】：