Scene.getWindow()始终是舞台吗?

问题描述

来自如何引用primaryStage 我了解到我可以得到 Stage使用 control.getScene.getWindow()，但是这将返回 Window 而不是 Stage .我知道 Stage 是 Window 的一种，但是我的问题是返回的对象将始终是 Stage 还是其他的东西在某些情况下?另外，我是否会知道呢?

Coming from How to reference primaryStage I learned that I can get the Stage of a particular control by using control.getScene.getWindow(), but this returns a Window instead of a Stage. I know that Stage is a type of Window, but my question is will the returned object always be a Stage, or will it be something else in some cases? Also, will I know that it will be something else?

推荐答案

JavaFX API中 Window 的子类是 Stage 和 PopupWindow .反过来， PopupWindow 是 Popup ， ContextMenu 和 Tooltip 的超类，当然可以定义您的自己的子类.因此，设计一个情况很容易，其中 control.getScene().getWindow()返回的内容不是 Stage :

The subclasses of Window in the JavaFX API are Stage and PopupWindow. PopupWindow in turn is a superclass of Popup, ContextMenu, and Tooltip, and of course it's possible to define your own subclasses. So it's reasonably easy to design a case where control.getScene().getWindow() returns something that is not a Stage:

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ContextMenu;
import javafx.scene.control.Label;
import javafx.scene.control.MenuItem;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.stage.Window;

public class ContextMenuExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        StackPane root = new StackPane();
        Label label = new Label("Right click here");
        root.getChildren().add(label);

        ContextMenu contextMenu = new ContextMenu();
        MenuItem menuItem = new MenuItem();
        contextMenu.getItems().add(menuItem);

        final Button button = new Button("Click Me");
        menuItem.setGraphic(button);
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                Window window = button.getScene().getWindow();
                System.out.println("window is a stage: "+(window instanceof Stage));
            }
        });
        label.setContextMenu(contextMenu);
        Scene scene = new Scene(root, 250, 100);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

如果您使用FXML，您可能不应该假定封闭的 Window 是 Stage ，因为您可能会想起将FXML用作 Popup 或其他非 Stage Window .

If you use FXML, you probably shouldn't assume that your enclosing Window is a Stage as you might conceivably re-use the FXML as the content of a Popup, or other non-Stage Window, in the future.

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