Question

我使用Eclipse创建了一个简单的UI，没有像往常一样的错误迹象，我在教程中尽可能地遵循代码。虽然它没有显示任何错误，但它仍然无法运行，并自动打开调试面板，并说“应用程序启动方法中的异常。”

以下是我的代码：

package groupProject;

import javafx.application.*;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;

public class Try extends Application
{
    Stage window;
    Scene newUserScene;

public static void main(String[] args) 
{
    launch(args);
}

@Override
public void start(Stage primaryStage) throws Exception 
{
    window = primaryStage;
    window.setTitle("Automated Teller Machine");

    GridPane nUserGrid = new GridPane();
    nUserGrid.setPadding(new Insets(10,10,10,10));
    nUserGrid.setVgap(8);
    nUserGrid.setHgap(10);

    //New matric card - Label 1
    Label newMatricLabel = new Label("Matric Number: ");
    GridPane.setConstraints(newMatricLabel,0,0);//Set Position
    TextField newMatricInput = new TextField();     
    GridPane.setConstraints(newMatricInput,1,0);//Set position

    //New user name - Label 2
    Label newUsername = new Label("Your name: ");
    GridPane.setConstraints(newUsername,0,1);//Set position
    TextField newUsernameInput = new TextField();
    GridPane.setConstraints(newUsernameInput,1,1);//Set Position

    //Pin number -  Label 3
    Label newPin = new Label("Your pin: ");
    GridPane.setConstraints(newPin,0,2);//Set position
    TextField newPinInput = new TextField();
    GridPane.setConstraints(newPinInput,1,2);//Set position

    //Deposit - Label 4
    Label newDepositValue = new Label("Deposit: ");
    GridPane.setConstraints(newDepositValue,0,3);//Set position
    TextField newDepositInput = new TextField();
    GridPane.setConstraints(newDepositInput,1,1);//Set position


    //Create submit button---//
    Button submitEntree = new Button("Submit");
    GridPane.setConstraints(submitEntree,1,4);//Set Position
    nUserGrid.getChildren().addAll(newMatricLabel,newMatricInput,newMatricInput,newUsername,newUsernameInput,newPin,newPinInput,newDepositValue,newDepositInput,submitEntree);//add all to GridPane

     newUserScene = new Scene(nUserGrid,500,500);

        window.setScene(newUserScene);
        window.show();      
    }
}

调试透视图上显示的完整消息是：

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    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(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IllegalArgumentException: Children: duplicate children added: parent = Grid hgap=10.0, vgap=8.0, alignment=TOP_LEFT
    at javafx.scene.Parent$2.onProposedChange(Parent.java:454)
    at com.sun.javafx.collections.VetoableListDecorator.addAll(VetoableListDecorator.java:234)
    at com.sun.javafx.collections.VetoableListDecorator.addAll(VetoableListDecorator.java:103)
    at groupProject.Try.start(Try.java:61)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    ... 1 more
Exception running application groupProject.Try

此时此按钮和用户输入没有与之相关的任何操作，但将来也会这样做。

错误的原因是什么？如何解决此类错误，以便它可以运行并显示我所创建的用户界面？提前谢谢。

Answer 1

在此代码中：

nUserGrid.getChildren().addAll(newMatricLabel,newMatricInput,newMatricInput,newUsername,newUsernameInput,newPin,newPinInput,newDepositValue,newDepositInput,submitEntree);//add all to GridPane

您添加newMatricInput两次。删除一个。

没有错误，但代码将无法运行，Application start方法JavaFX中的异常

1 个答案: