如何在 Stage.show() 之后运行函数？

Question

我正在努力解决一大段代码在初始化之前运行的问题。

@FXML
public void Start(int pesel) throws IOException {
    klientPesel = pesel;
    root = FXMLLoader.load(getClass().getClassLoader().getResource("klientScene.fxml"));
    Main.mainStage.setTitle("Agencja Ubezpieczniowa - Agent");
    Scene scene = new Scene(root,800,600);
    Main.mainStage.setScene(scene);
    Main.mainStage.show();
    obtainKlient();
    setKlientLabels();
}

问题是我有一个变量@FXML private VBox KlientInfoVBOX;，并且在setKlientLabels() 运行之前它没有被初始化。如何确保setKlientLabels() 将在Main.mainStage.show(); 之后运行？

也许堆栈跟踪将有助于解决问题

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at app.KlientSearchController.setKlientLabels(KlientSearchController.java:69)
    at app.KlientSearchController.Start(KlientSearchController.java:51)
    at app.UserSceneController.StartKlientSearch(UserSceneController.java:87)
    at app.UserSceneController.lambda$wyszukajKlienta$0(UserSceneController.java:70)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8411)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:352)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:388)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)

如果我从代码中删除setKlientLabels() 运行没有异常，一切运行顺利。

Answer 1

您需要设置onShowingProperty () 的Stage。当舞台显示时，onShowingProperty () 将被触发。要设置onShowingProperty ()，只需使用setOnShowing () 方法。

Main.mainStage.setOnShowing(new EventHandler<WindowEvent>() {
    @Override
    public void handle(WindowEvent event) {
        setKlientLabels();
    }
});
Main.mainStage.show();

Answer 2

Main.mainStage.setOnShowing() 解决方案在 JavaFX 11 中对我不起作用，但将它放在主应用程序类中可以：

@Override
public void start(Stage stage) {
    stage.addEventFilter(WindowEvent.WINDOW_SHOWN,
        new EventHandler<WindowEvent>() {
            @Override
            public void handle(WindowEvent event) {
                log.info("Stage shown and {} total windows existing",
Window.getWindows().size()");
            }
        }
    );
}

或者这个更简单的 lambda 表达式等价物：

stage.setOnShown((event) -> {
    log.info("Stage shown and {} total windows existing",
Window.getWindows().size());
});

这适用于在任何 JavaFX 阶段/窗口（包括主要阶段）之后运行代码。