javafx - 在 JavaFX 中出现闪屏后尝试切换阶段

Question

我正在尝试显示启动画面，直到我加载所有必要的资源并随后打开主舞台，但我一直遇到InvocationTargetException.

换句话说，我的初级阶段加载了一个 FXML，它有一个如下所示的控制器：

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();            
    }
}

该类MainStage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();
}

我得到的错误指向我FXMLLoader.load()第一次使用 FXML 的行（我有两个 FXML 文件，每个阶段一个）。

有人可以解释一下为什么会发生这种情况，最好是如何正确使用FXMLLoader，以防我正在做的事情是一个问题，好吗？

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

标签： javafxfxmlloader

Answer 1

正如您从堆栈跟踪中看到的那样，您在 on lineNullPointerException的initialize方法中得到了一个。我将假设该行是这一行：SplashController1818

Stage primaryStage = (Stage) splashScreenVBox.getScene().getWindow();

问题很可能是这个电话：getScene().getWindow(). 该方法getScene()将返回null此处，因为splashScreenVBox它还不是 a 的一部分Scene。怎么会这样？该initialize方法在执行期间FXMLLoader.load()被调用。这意味着您还没有机会将结果添加FXMLLoader.load()到 a中Scene。

要解决这个问题，一个选项是向您添加一个方法来SplashController加载MainStage.

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);

我将 传递splashStage给该方法，因此您可以在准备显示 main 时隐藏/关闭它Stage。根据您的代码设计，除了传递参数之外，可能还有其他方法可以做到这一点。

---

一个如何创建一个抽象控制器的示例，该控制器将在根添加到 aScene并且Scene已添加到 a时自动调用方法Window。

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);
    }

  }

}

这要求fx:id="root"您的 FXML 文件中有一个 并且根对象是一个Node. 仅在第一次添加到aonAddedToWindow时才调用。您仍然必须将 添加到其他地方（无论您打电话到哪里）。rootWindowrootWindowFXMLLoader.load