如何在来自另一个 class 的有状态小部件中触发 function（当 onUnityAdsFinish 时）？

Question

我在一个有状态的小部件中有一个游戏屏幕，其中包括一个 function，它可以让玩家后退一步（撤消上一步）。 当 onUnityAdsFinish() 从另一个小部件运行时，我想触发这个 function。

这是 game.dart 上的有状态小部件，在其中玩游戏：

class GameScreen extends StatefulWidget {
  @override
  GameScreenState createState() => GameScreenState();
}

class GameScreenState extends State<GameScreen> with SingleTickerProviderStateMixin {

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        Container( 
            // game content here
        ),
        MaterialButton(
          child: Text("Tap Here to Watch Ad to Undo Move"),
          onPressed: () => unityBloc.showUnityAd(),
          // (side note: unityBloc is accessable because I have it declared as "final unityBloc = UnityBloc();" higher up the widget tree on app.dart.)
        ),
      ],
    ),                  
  }

  // This is the function I want to call after the ad is finished.
  void undoMove() {
    setState(() {
      // code to undo move
    });
  }
}

当按下按钮观看广告时，它会在我的 UnityBloc class on unity_bloc.dart 中调用 showUnityAd() function：

import 'package:unity_ads_flutter/unity_ads_flutter.dart';

class UnityBloc with UnityAdsListener {
...
  showUnityAd() {
    UnityAdsFlutter.show('rewardedVideo').whenComplete(() => null);
  } // called when undo button is pressed on game.dart

  @override
  void onUnityAdsFinish(String placementId, FinishState result) {
    print("Finished $placementId with $result");
    // here is where I want to call the undoMove() function from game.dart
  }
}

广告完美显示，并且 onUnityAdsFinish 中的打印语句在广告完成后打印到控制台，但我不知道此时如何调用 undoMove。

我整天都在看教程和阅读关于回调和全局键等的stackoverflows，但我仍然没有得到它。

有人可以帮忙吗？ 当 onUnityAdsFinish() 在 unity_bloc.ZBB14127678960FAE97D873950EA20156 上触发时，如何在 game.dart 上触发 undoMove() function？ （或者他们是另一种/更好的方法吗？）

谢谢！

Answer 1

您可以在UnityBloc class 中拥有一个包含 function 的变量，并将showUnityAd undoMove以将其分配给变量，然后您可以在 onUnityAdsFinish 方法中调用它。

所以UnityBloc变成了这样：

class UnityBloc with UnityAdsListener {
  void Function() doOnUnityAdsFinish;

  ...

  showUnityAd({@required unityAdsFinishFunction}) {
    ...
    doOnUnityAdsFinish = unityAdsFinishFunction;
  } // called when undo button is pressed on game.dart

  @override
  void onUnityAdsFinish(String placementId, FinishState result) {
   ...
   doOnUnityAdsFinish?.call(); //Only calls if the function is not null
  }
}

你可以在MaterialButton的onPressed这样：

 MaterialButton(
          child: Text("Tap Here to Watch Ad to Undo Move"),
          onPressed: () => unityBloc.showUnityAd(unityAdsFinishFunction: undoMove ),   
        ),

Answer 2

最简单的方法是全局/静态变量（回调）或 ValueNotifier/Stream。 也许，更清洁的方法是一些 package 具有依赖注入功能，如（ get ， get_it ）。

class UnityBloc with UnityAdsListener {
  /// pass a callback into the constructor.
  /// Function<String,FinishState> onAdCompleted ;
  /// UnityBloc([this.onAdCompleted]);

  /// easier approach, not very "flexible".
  static Function<String,FinishState> onAdCompleted ;

  showUnityAd() {
    UnityAdsFlutter.show('rewardedVideo').whenComplete(() => null);
  } // called when undo button is pressed on game.dart

  @override
  void onUnityAdsFinish(String placementId, FinishState result) {
    onAdCompleted?.call(placementId, result); 
    // here is where I want to call the undoMove() function from game.dart
  }
}


class GameScreenState extends State<GameScreen> with SingleTickerProviderStateMixin {

  @override
  void initState(){
     super.initState();
     UnityBloc.onAdCompleted = _onAddCompleted;
  }

  @override
  void dispose(){
     super.dispose();
     if( UnityBloc.onAdCompleted == _onAddCompleted) {
         UnityBloc.onAdCompleted = null;
     }
  }

  void _onAddCompleted(String placementId, FinishState result) 
    => print("Finished $placementId with $result"); 

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        Container( 
            // game content here
        ),
        MaterialButton(
          child: Text("Tap Here to Watch Ad to Undo Move"),
          onPressed: () => unityBloc.showUnityAd(),
          // (side note: unityBloc is accessable because I have it declared as "final unityBloc = UnityBloc();" higher up the widget tree on app.dart.)
        ),
      ],
    ),                  
  }

  // This is the function I want to call after the ad is finished.
  void undoMove() {
    setState(() {
      // code to undo move
    });
  }
}