JavaFX - 向窗格添加监听器以检查它是否正在显示

Question

我在过去几个月里一直在研究JavaFX.我试图找到一种方法来实现在根窗格/场景中显示特定窗格时触发的侦听器.在Java中,我可以使用JPanel上的ancestorListener实现它,如下所示,但我找不到JavaFX上的等效方法.

JPanel panel = new JPanel ();
panel.addAncestorListener ( new AncestorListener ()
{
    public void ancestorAdded ( AncestorEvent event ) {
        System.out.println("This panel is shown on screen now");
    }

    public void ancestorRemoved ( AncestorEvent event ){}

    public void ancestorMoved ( AncestorEvent event ){}
} );

Answer 1

你可以观察一下sceneProperty().这将告诉您窗格(或任何其他节点)是否是场景图的一部分:

pane.sceneProperty().addListener((obs, oldScene, newScene) -> {
    if (newScene == null) {
        // not showing...
    } else {
        // showing ...
    }
});

如果您想要更进一步,并查看窗格是否是显示的窗口中的场景图的一部分,您可以使用EasyBind:

EasyBind.select(pane.sceneProperty())
    .select(Scene::windowProperty)
    .select(Window::showingProperty)
    .orElse(false)
    .addListener((obs, wasShowing, isNowShowing) -> {
         if (isNowShowing) {
             // pane is showing in a window...
         } else {
             // pane is not showing in a window...
    });