java JavaFX - getScene() 返回 null
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JavaFX - getScene() returns null
提问by The_Dude
I just started using JavaFX Scene Builder to build a small application.
我刚刚开始使用 JavaFX Scene Builder 来构建一个小型应用程序。
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)':
它由属于“login.fxml”的控制器类“Login.java”组成，其中通过名为“registrationClicked(ActionEvent event)”的方法加载FXML文件“registrierung.fxml”：
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();
}
}
Now I want to get a reference to the stage of 'registrierung.fxml' in the controller class 'Registrierung.java' via the root node vboxRoot:
现在我想通过根节点 vboxRoot 获得对控制器类“Registrierung.java”中“registrierung.fxml”阶段的引用：
@FXML
private VBox vboxRoot;
Stage stage = (Stage) vboxRoot.getScene().getWindow();
However 'getScene()' always leads to a NullPointerException. The controller classes for both FXML files are adjusted in Scene Builder.
然而，'getScene()' 总是会导致 NullPointerException。两个 FXML 文件的控制器类都在 Scene Builder 中进行了调整。
This is how I set up the rood node in 'registrierung.fxml':
这就是我在“registrierung.fxml”中设置 rood 节点的方式：
<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">
What am I doing wrong?
我究竟做错了什么？
采纳答案by The_Dude
you are trying to get the scene for an object that has not been initialized yet. if you were doing the same operation in
您正在尝试获取尚未初始化的对象的场景。如果你在做同样的操作
@Override
public void initialize(URL fxmlFileLocation, ResourceBundle resources) {
Stage stage = (Stage) vboxRoot.getScene().getWindow();
}
or if you have an event that triggers once you click something (which executes after the scene has loaded)
或者如果您有一个在您单击某物时触发的事件（在场景加载后执行）
@FXML
private void action(ActionEvent event) throws IOException {
Stage stage = (Stage) vboxRoot.getScene().getWindow();
}
This would work!
这会奏效！
回答by purring pigeon
I have run into this issue and have found by placing a call to a method like this (When the scene becomes visible and is attached to the node, this will fire):
我遇到了这个问题，并通过调用这样的方法发现（当场景变得可见并附加到节点时，这将触发）：
private void determinePrimaryStage() {
rootPane.sceneProperty().addListener((observableScene, oldScene, newScene) -> {
if (oldScene == null && newScene != null) {
// scene is set for the first time. Now its the time to listen stage changes.
newScene.windowProperty().addListener((observableWindow, oldWindow, newWindow) -> {
if (oldWindow == null && newWindow != null) {
primaryStage = (Stage)newWindow;
}
});
}
});
}`
Then I can do something like this later:
然后我可以稍后做这样的事情：
if(primaryStage == null) {
Platform.runLater(()-.{......
}else {
//do whatever
}
Hope this helps.
希望这可以帮助。
回答by Holgi P
Implementing the Initializable interface did not work for me(Java 8). The method getScene() always returned null for me. So i had to do the following:
实现 Initializable 接口对我不起作用（Java 8）。方法 getScene() 总是为我返回 null。所以我不得不做以下事情：
FXMLLoader loader = new FXMLLoader(getClass().getResource("MyGui.fxml"));
Parent root = (Parent)loader.load();
//do stage and scene stuff - i skip it here
MyController controller = (MyController)loader.getController();
stage.setOnShown(controller::adjustUI);
And in the controller i have:
在控制器中，我有：
public void adjustUI(WindowEvent event) {
Scene scene = myComponent.getScene();
//do stuff and do ui adjustments here
}
