我试图显示一个初始屏幕，直到加载所有必要的资源并随后打开主界面为止，但是我一直遇到InvocationTargetException。
换句话说，我的主要阶段加载了一个FXML，其中包含一个如下所示的Controller：
public class SplashController {
@FXML
VBox splashScreenVBox = new VBox();
@FXML
protected void initialize() throws InterruptedException, IOException {
Stage primaryStage = (Stage) splashScreenVBox.getScene().getWindow();
primaryStage.close();
new MainStage();
}
}
MainStage类只是加载FXML并显示场景：
public MainStage() throws IOException {
Parent root = FXMLLoader.load(getClass().getResource("/core/views/Main.fxml"));
this.setScene(new Scene(root, 800, 600));
this.show();
}
我遇到的错误指向我第一次FXMLLoader.load() FXML所在的行（我有两个FXML文件，每个阶段一个）。
请问有人可以说明为什么会发生这种情况，最好是如何正确使用FXMLLoader，以防万一我正在做的事情有问题？
编辑：堆栈跟踪
Exception in Application start method
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException:
/C:/Users/REDACTED/out/production/REDACTED/core/views/Splash.fxml
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2571)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at core.Scenes.start(Scenes.java:19)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
... 1 more
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2566)
... 17 more
Caused by: java.lang.NullPointerException
at core.controllers.SplashController.initialize(SplashController.java:18)
... 28 more
Exception running application core.Scenes
答案 0 :(得分：1)
从堆栈跟踪中可以看到，您在NullPointerException行的initialize的{{1}}方法中得到了SplashController。我假设18行是这一行：
18问题很可能是此电话：Stage primaryStage = (Stage) splashScreenVBox.getScene().getWindow();
。方法getScene().getWindow()将在此处返回getScene()，因为null还不是splashScreenVBox的一部分。怎么会这样？ Scene方法在执行initialize的过程中称为。这意味着您还没有机会将FXMLLoader.load()的结果添加到FXMLLoader.load()中。
要解决此问题，请在您的Scene中添加一种方法来加载SplashController。
MainStage我将FXMLLoader loader = new FXMLLoader(getClass().getResource("your/resource"));
Parent root = loader.load();
Stage splashStage = new Stage();
splashStage.setScene(new Scene(root));
splashStage.show();
SplashController controller = loader.getController();
controller.loadMainApp(splashStage);
传递给该方法，以便在准备显示主splashStage时可以将其隐藏/关闭。根据代码的设计，除了传递参数外，还有其他方法可以实现。
如何创建一个抽象控制器的示例，当根添加到Stage且Scene已经添加到Scene时，该抽象控制器将自动调用方法。
Window这要求您的FXML文件中有一个import java.util.function.Consumer;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.fxml.FXML;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.stage.Window;
public abstract class AbstractController<T extends Node> {
// protected so subclasses can access the root
// directly. You could also hide this behind a
// getter.
@FXML protected T root;
// Subclasses that override this method must call the
// super implementation
@FXML
protected void initialize() {
Consumer<Window> onNewWindow = this::onAddedToWindow;
Consumer<Scene> onNewScene = scene ->
scene.windowProperty().addListener(new SelfRemovingChangeListener<>(onNewWindow));
root.sceneProperty().addListener(new SelfRemovingChangeListener<>(onNewScene));
}
protected abstract void onAddedToWindow(Window window);
private static class SelfRemovingChangeListener<T> implements ChangeListener<T> {
private final Consumer<? super T> onNewValue;
private SelfRemovingChangeListener(Consumer<? super T> onNewValue) {
this.onNewValue = onNewValue;
}
@Override
public void changed(ObservableValue<? extends T> observable, T oldValue, T newValue) {
onNewValue.accept(newValue);
observable.removeListener(this);
}
}
}
，并且根对象是fx:id="root"。将Node添加到onAddedToWindow时，仅将root称为 first 。您仍然必须将Window添加到其他地方的root中（无论您叫Window是什么）。