Java 如何从服务对象关闭一个阶段

Question

我处于启动新视图的情况，但在其控制器中我向服务器发出请求以获取一些对象。这个请求需要一些时间，所以我想在这段等待时间内实现一个小的加载视图。因此，在我的控制器中，我实现了一个服务对象以在另一个线程中发出此请求：

 public void initialize(URL url, ResourceBundle resourceBundle) {
       
        try {
           

            Parent root = FXMLLoader.load(getClass().getResource("/MiniPages/LoadingPage.fxml"));

            Scene scene = new Scene(root);
            Stage primaryStage = new Stage();

            primaryStage.initStyle(StageStyle.UNDECORATED);


            Service<ProjectModel> service = new Service<ProjectModel>() {
                @Override
                protected Task<ProjectModel> createTask() {
                    return new Task<ProjectModel>() {
                        @Override
                        protected ProjectModel call() throws Exception {
                            SenderText data = new SenderText();
                            int id = Integer.parseInt(data.getData());

                            Client client = Client.getInstance();
                            JSONObject tosend = new JSONObject();

                            tosend.put("Type", "Get Project");
                            tosend.put("IDproject", id);

                            GsonBuilder gsonBuilder = new GsonBuilder();
                            gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateSerializer());
                            gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateDeserializer());
                            Gson gson = gsonBuilder.setPrettyPrinting().create();

                            client.sendText(tosend.toString());
                            String response = client.receiveText();

                            ProjectModel project = gson.fromJson(response, ProjectModel.class);
                            projectLocal = project;
                            System.out.println(gson.toJson(projectLocal));
                            primaryStage.close();
                            primaryStage.hide();
                            return project;
                        }
                    };

                }
            };
            service.start();

            primaryStage.setScene(scene);
            primaryStage.initModality(Modality.APPLICATION_MODAL);
            while (service.getValue() == null) {
                primaryStage.showAndWait();
            }
            primaryStage.close();

            System.out.println("Finish");
            primaryStage.close();

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

我测试过，对象是在 call() 方法上设置的。但是加载视图不会关闭。我也尝试调用 primaryStage.show() 而不是 showandWait() 但它没有用。知道如何解决吗？

Answer 1

JavaFX 中有两个主要线程规则（类似于大多数其他 UI 工具包）。

您不得从后台线程对 UI 执行操作。这包括创建、显示或隐藏 windows.
您不得阻塞 UI 线程（“FX 应用程序线程”）。

您在 call() 方法中调用 primaryStage.close() 违反了第一条规则。

你在繁忙的 while 循环中违反了第二条规则。（更糟；我认为该服务的 value 属性仅在 FX 应用程序线程上更新。因此，由于您阻塞了该线程，因此 value 属性不能已更新并且 while 循环永远不会退出。）

要在后台 Task 完成时执行 UI 操作，您可以使用 onSucceeded 处理程序。在后台任务成功完成后，在 FX 应用程序线程上调用此处理程序。

public void initialize(URL url, ResourceBundle resourceBundle) {
   
    try {

        Parent root = FXMLLoader.load(getClass().getResource("/MiniPages/LoadingPage.fxml"));

        Scene scene = new Scene(root);
        Stage primaryStage = new Stage();

        primaryStage.initStyle(StageStyle.UNDECORATED);


        Service<ProjectModel> service = new Service<ProjectModel>() {
            @Override
            protected Task<ProjectModel> createTask() {
                return new Task<ProjectModel>() {
                    @Override
                    protected ProjectModel call() throws Exception {
                        SenderText data = new SenderText();
                        int id = Integer.parseInt(data.getData());

                        Client client = Client.getInstance();
                        JSONObject tosend = new JSONObject();

                        tosend.put("Type", "Get Project");
                        tosend.put("IDproject", id);

                        GsonBuilder gsonBuilder = new GsonBuilder();
                        gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateSerializer());
                        gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateDeserializer());
                        Gson gson = gsonBuilder.setPrettyPrinting().create();

                        client.sendText(tosend.toString());
                        String response = client.receiveText();

                        ProjectModel project = gson.fromJson(response, ProjectModel.class);
                        return project;
                    }
                };

            }
        };

        service.setOnSucceeded(event -> {

            System.out.println("Finish");

            // I think; don't know what projectLocal is, or 
            // which threads it should be accessed from:
            projectLocal = project ;
            primaryStage.hide();
        });

        service.start();

        primaryStage.setScene(scene);
        primaryStage.showAndWait();
        
    } catch (Exception e) {
        e.printStackTrace();
    }
}

顺便说一句，您在这里可能不需要 Service。 Service 真正为重复使用而设计，您只使用一次。只需在后台线程上创建一个 Task 和运行就足够了：

public void initialize(URL url, ResourceBundle resourceBundle) {
   
    try {

        Parent root = FXMLLoader.load(getClass().getResource("/MiniPages/LoadingPage.fxml"));

        Scene scene = new Scene(root);
        Stage primaryStage = new Stage();

        primaryStage.initStyle(StageStyle.UNDECORATED);


        Task<ProjectModel> task = new Task<ProjectModel>() {

            @Override
            protected ProjectModel call() throws Exception {
                SenderText data = new SenderText();
                int id = Integer.parseInt(data.getData());

                Client client = Client.getInstance();
                JSONObject tosend = new JSONObject();

                tosend.put("Type", "Get Project");
                tosend.put("IDproject", id);

                GsonBuilder gsonBuilder = new GsonBuilder();
                gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateSerializer());
                gsonBuilder.registerTypeAdapter(LocalDate.class, new LocalDateDeserializer());
                Gson gson = gsonBuilder.setPrettyPrinting().create();

                client.sendText(tosend.toString());
                String response = client.receiveText();

                ProjectModel project = gson.fromJson(response, ProjectModel.class);
                return project;

            }
        };

        task.setOnSucceeded(event -> {

            System.out.println("Finish");

            // I think; don't know what projectLocal is, or 
            // which threads it should be accessed from:
            projectLocal = project ;
            primaryStage.hide();
        });

        new Thread(task).start();

        primaryStage.setScene(scene);
        primaryStage.showAndWait();
        
    } catch (Exception e) {
        e.printStackTrace();
    }
}

您的代码结构在这里看起来有点奇怪。看起来您需要在启动时为您的应用程序创建一个模型，并且该启动需要一些时间，因此您在加载时显示某种“启动画面”。这里奇怪的部分是您在 FXML 控制器的 initialize() 方法中执行此操作。作为生命周期方法 start() 的一部分，这确实应该在您的 Application class 中完成。结构应如下所示：

public class App extends Application {

    public static void main(String[] args) {
        Application.launch();
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        Task<ProjectModel> task = new Task<>() {
            @Override
            public ProjectModel call() throws Exception {
                return loadModel();
            }
        };

        Stage loadingStage = showLoadingStage();
        task.setOnSucceeded(e -> {
            loadingStage.hide();
            showMainStage(primaryStage, task.getValue());
        });

        new Thread(task).start();
    }

    private ProjectModel loadModel() throws Exception {
        // load model and return it....
    }

    private Stage showLoadingStage() throws Exception {
        Scene scene = new Scene(getClass().getResource("LoadingPage.fxml"));
        Stage loadingStage = new Stage();
        loadingStage.initStyle(StageStyle.UNDECORATED);
        loadingStage.setScene(scene);
        loadingStage.show();
        return loadingStage ;
    }

    private void showMainStage(Stage stage, ProjectModel model) throws Exception {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("Main.fxml"));
        Parent root = loader.load();
        MainController controller = loader.getController();
        controller.setModel(model);
        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();
    }
}

其中 MainController 是具有 setModel(...) 方法的常规 FXML 控制器：

public class MainController {

    private ProjectModel model ;

    // @FXML-annotated fields

    @FXML
    private void initialize() {
        // initialization work that does not require model
    }

    public void setModel(ProjectModel model) {
        this.model = model ;
        // initialize any UI that depends on the model, etc.
    }
}

Java 如何从服务对象关闭一个阶段

Java how to close a stage from Service Object

java

javafx