JavaFX - getScene（）返回null [英] JavaFX - getScene() returns null

问题描述

我刚开始使用JavaFX Scene Builder来构建一个小应用程序。

I just started using JavaFX Scene Builder to build a small application.

它由一个属于'login的控制器类'Login.java'组成。 fxml'，其中FXML文件'registrierung.fxml'通过名为'registrationClicked（ActionEvent event）'的方法加载：

It is made up of a controller class 'Login.java' which belongs to 'login.fxml', in which the FXML file 'registrierung.fxml' is loaded via a method called 'registrationClicked(ActionEvent event)':

public class Login {

@FXML
private void registrationClicked(ActionEvent event){
    try{
        ((Node) (event.getSource())).getScene().getWindow().hide();
        FXMLLoader loader = new FXMLLoader(getClass().getResource("/view/fxml/registrierung.fxml"));
        Parent root = (Parent) loader.load();
        Stage stage = new Stage();
        Scene scene = new Scene(root);      
        stage.setTitle("Registration");
        stage.setScene(scene);
        stage.setResizable(false);
        stage.show();
    } catch(IOException e){
        e.printStackTrace();
    }
}

现在我想获得对阶段的引用控制器类'Registrierung.java'中的'registrierung.fxml'通过根节点vboxRoot：

Now I want to get a reference to the stage of 'registrierung.fxml' in the controller class 'Registrierung.java' via the root node vboxRoot:

@FXML
private VBox vboxRoot;

Stage stage = (Stage) vboxRoot.getScene().getWindow();

但是'getScene（）'总是会导致NullPointerException。 FXML文件的控制器类在Scene Builder中调整。

However 'getScene()' always leads to a NullPointerException. The controller classes for both FXML files are adjusted in Scene Builder.

这是我在'registrierung.fxml'中设置rood节点的方式：

This is how I set up the rood node in 'registrierung.fxml':

<VBox fx:id="vboxRoot" maxHeight="-Infinity" maxWidth="-Infinity" prefHeight="267.0" prefWidth="355.0" stylesheets="@../css/styles.css" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="businesslogik.Registrierung">

我做错了什么？

推荐答案

您正在尝试获取尚未初始化的对象的场景。

you are trying to get the scene for an object that has not been initialized yet. if you were doing the same operation in

@Override 
    public void initialize(URL fxmlFileLocation, ResourceBundle resources) {
    Stage stage = (Stage) vboxRoot.getScene().getWindow();
}

或者如果你有点击某事后触发的事件（后执行）场景已加载）

or if you have an event that triggers once you click something (which executes after the scene has loaded)

@FXML
private void action(ActionEvent event) throws IOException {
    Stage stage = (Stage) vboxRoot.getScene().getWindow();
}

这样可行！

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