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，并且在第二个阶段准备好显示时应该立即关闭。 我尝试通过 Platform.runLater 和 Tasks 运行，但问题是两个阶段都被冻结，直到两者都完成加载，并且 progessbar 直到第二个才开始动画阶段已完成加载。

这里摘录一些代码：

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 只是为了执行长时间运行的操作，并使用回调来更新 UI。很少需要自己打电话给Platform.runLater(...)。

在您的代码中，Tasks 根本没有任何作用，因为它们只是安排所有代码在带有Platform.runLater(...) 的 FX 应用程序线程上运行。如此有效地创建一个新线程只是为了要求在当前线程上执行一些代码。

这是一个例子，我认为你想做的事情是：

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);
    }
}