在BorderPane中设置节点位置时出错

Question

每当我编译程序时，都会出现以下错误：java.lang.reflect.InvocationTargetException当我将BorderPane的内部节点（HBox）设置为底部时，就会发生该错误。 为什么会出现此错误，我该如何解决？

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.layout.*;
import javafx.scene.control.*;
import javafx.scene.shape.*;
import javafx.scene.paint.*;
import javafx.geometry.*;
import java.util.*;
import javafx.scene.text.*;
public class Test extends Application
{
   public void start(Stage stage)
   {
      BorderPane pane = new BorderPane();
      HBox hBox = new HBox(10);
      boolean player1 = true;

      Label label = new Label("Player" + ((player1) ? "1" : "2") + "'s turn");
      label.setFont(Font.font(20)); 

      TextField colField = new TextField();
      colField.setPrefColumnCount(1);

      Button submit = new Button("Submit");

      hBox.getChildren().addAll(label, colField, submit);

      pane.getChildren().add(hBox);
      pane.setBottom(hBox);

      Scene scene = new Scene(pane);
      stage.setTitle("Connect 4");
      stage.setScene(scene);
      stage.show();


   }
}

完全错误：

Exception in Application start method
Exception in thread "main" 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:497)
    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$152(LauncherImpl.java:182)
    at com.sun.javafx.application.LauncherImpl$$Lambda$49/1645995473.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: Children: duplicate children added: parent = BorderPane@6bb9ea3e
    at javafx.scene.Parent$2.onProposedChange(Parent.java:451)
    at com.sun.javafx.collections.VetoableListDecorator.add(VetoableListDecorator.java:206)
    at javafx.scene.layout.BorderPane$BorderPositionProperty.invalidated(BorderPane.java:680)
    at javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:111)
    at javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:146)
    at javafx.scene.layout.BorderPane.setBottom(BorderPane.java:296)
    at Test.start(Test.java:30)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
    at com.sun.javafx.application.LauncherImpl$$Lambda$52/5501708.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl$$Lambda$45/186276003.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
    at com.sun.javafx.application.PlatformImpl$$Lambda$48/1769582490.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
    at com.sun.javafx.application.PlatformImpl$$Lambda$47/237061348.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/2117255219.run(Unknown Source)
    ... 1 more

Answer 1

您将hbox两次添加到pane ：一次使用pane.getChildren().add(...); 然后一次与pane.setBottom(...); 。 这导致hbox在场景图中出现两次，从而出现“重复子代”错误。 您可能只需要pane.setBottom(...); 版。