JavaFX 同时创建两个阶段

Question

我试图在 JavaFX 中同时显示两个阶段，其中第一个阶段应该显示一个进度条，并且应该在第二个阶段准备好显示后立即关闭。 我尝试通过 Platform.runLater 和 Tasks 运行，但问题是两个阶段都被卡住，直到两个阶段都完成加载并且进度条开始动画直到第二个阶段加载完成。

这里是代码的一些摘录:

public void start(Stage primaryStage) throws Exception {
        new Thread(progressTask()).start();
        new Thread(loginTask()).start();
    }



    public Task<Void> loginTask() {
        Task<Void> t = new Task<Void>() {

            @Override
            protected Void call() throws Exception {
                Platform.runLater(new Runnable() {

                    @Override
                    public void run() {

                        Stage s = new Stage();
                        FXMLLoader loader = new FXMLLoader(getClass().getResource("Login.fxml"));
                        Scene sc = null;
                        try {

                            sc = new Scene((Parent) loader.load());
                        } catch (IOException e) {
                            e.printStackTrace();
                        }

                        s.setScene(sc);
                        s.show();

                    }

                });
                return null;
            };
        };
        return t;
    }

    public Task<Void> progressTask() {

        Task<Void> t = new Task<Void>() {
            @Override
            protected Void call() throws Exception {
                Platform.runLater(new Runnable() {

                    @Override
                    public void run() {
                            ProgressBar bar = new ProgressBar(0);
                            bar.setPrefSize(200, 24);
                            Timeline task = new Timeline(new KeyFrame(Duration.ZERO, new KeyValue(bar.progressProperty(), 0)), new KeyFrame(
                                    Duration.seconds(5), new KeyValue(bar.progressProperty(), 1)));

                            VBox layout = new VBox(10);
                            layout.getChildren().setAll(bar);
                            Stage stage = new Stage(StageStyle.DECORATED);
                            stage.setScene(new Scene(layout));
                            stage.initModality(Modality.WINDOW_MODAL);
                            stage.show();
                            new Thread() {
                                public void run() {
                                    task.playFromStart();
                                }
                            }.start();
                            task.setOnFinished(new EventHandler<ActionEvent>() {
                                    @Override
                                    public void handle(ActionEvent event) {
                                        stage.close();


                                    }

                                });
                    }
            });
                return null;
        }


};

感谢您的帮助。

Answer 1

您应该创建 Task 来执行长时间运行的操作，并使用回调来更新 UI。很少需要自己调用 Platform.runLater(...)。

在您的代码中，Task 根本没有任何作用，因为它们只是安排所有代码在 FX 应用程序线程上使用 Platform.runLater(...)。如此有效，您创建一个新线程只是为了请求在当前线程上执行一些代码。

这是一个示例，可以执行我认为您希望执行的操作:

import javafx.application.Application;
import javafx.concurrent.Task;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.ProgressBar;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class DataLoadingStageExample extends Application {

    @Override
    public void start(Stage primaryStage) {

        Scene scene = buildInitialUI();
        primaryStage.setScene(scene);

        Stage monitorStage = new Stage();

        Task<DataClass> dataLoadingTask = createDataLoadingTask();

        // update UI when dataLoadingTask finishes
        // this will run on the FX Application Thread
        dataLoadingTask.setOnSucceeded(event -> {
            DataClass data = dataLoadingTask.getValue();
            scene.setRoot(createUIFromData(data));
            monitorStage.hide();
        });

        buildProgressUI(monitorStage, dataLoadingTask);

        // manage stage layout:
        primaryStage.yProperty().addListener((obs, oldY, newY) -> monitorStage.setY(newY.doubleValue() - 100));
        primaryStage.setTitle("Application");

        // show both stages:
        monitorStage.show();
        primaryStage.show();

        // start data loading in a background thread:
        new Thread(dataLoadingTask).start();

    }

    private void buildProgressUI(Stage monitorStage,
            Task<?> task) {
        ProgressBar progressBar = new ProgressBar();
        progressBar.progressProperty().bind(task.progressProperty());

        Scene monitorScene = new Scene(new StackPane(progressBar), 400, 75);
        monitorStage.setScene(monitorScene);
        monitorStage.setTitle("Loading progress");
    }

    private Scene buildInitialUI() {
        Label loadingLabel = new Label("Loading...");
        StackPane root = new StackPane(loadingLabel);
        Scene scene = new Scene(root, 600, 400);
        return scene;
    }

    private Task<DataClass> createDataLoadingTask() {
        return new Task<DataClass>() {
            @Override
            public DataClass call() throws Exception {
                // mimic connecting to database
                for (int i=0; i < 100; i++) {
                    updateProgress(i+1, 100);
                    Thread.sleep(50);
                }
                return new DataClass("Data");
            }
        };
    }

    private Parent createUIFromData(DataClass data) {
        // obviously much more complex in real life
        Label label = new Label(data.getData());
        return new StackPane(label);
    }

    public static class DataClass {
        // obviously much more complex in real life
        private final String data ;
        public DataClass(String data) {
            this.data = data ;
        }
        public String getData() {
            return data ;
        }
    }

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