我尝试从showRecords调用MainApp.java中的LoginController.java方法，但在尝试完成此操作时遇到了一些困难。当我使用构造函数以便我可以使用showRecords时，抛出InvocationTargetException并且我不知道如何修复。我试图在其他类似的问题中遵循答案，但我无法自己修复代码。
我将来如何在其他课程中调用showRecords和方法？
MainApp.java
package com.fivefourdee.aglaea;
import java.io.IOException;
import com.fivefourdee.aglaea.record.model.Person;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
public class MainApp extends Application{
static final String title = "title";
private Stage primaryStage;
private BorderPane rootLayout;
private ObservableList<Person> personData = FXCollections.observableArrayList();
@Override
public void start(Stage primaryStage){
this.primaryStage = primaryStage;
this.primaryStage.setTitle(getAppTitle());
initRootLayout();
showLogin();
}
public MainApp(){
}
public void initRootLayout(){
try{
FXMLLoader loader = new FXMLLoader();
loader.setLocation(MainApp.class.getResource("record/view/RootLayout.fxml"));
rootLayout = (BorderPane)loader.load();
Scene scene = new Scene(rootLayout);
primaryStage.setScene(scene);
primaryStage.show();
}catch(IOException e){
e.printStackTrace();
}
}
public void showLogin(){
try{
FXMLLoader loader = new FXMLLoader();
loader.setLocation(MainApp.class.getResource("login/view/LoginPanel.fxml"));
BorderPane records = (BorderPane)loader.load();
rootLayout.setCenter(records);
}catch (IOException e){
e.printStackTrace();
}
}
public void showRecords(){
try{
FXMLLoader loader = new FXMLLoader();
loader.setLocation(MainApp.class.getResource("record/view/RecordViewer.fxml"));
AnchorPane records = (AnchorPane)loader.load();
rootLayout.setCenter(records);
}catch (IOException e){
e.printStackTrace();
}
}
public static void main(String[] args){
launch(args);
}
public static String getAppTitle(){
return title;
}
public ObservableList<Person> getPersonData(){
return personData;
}
public Stage getPrimaryStage(){
return primaryStage;
}
}
LoginController.java：
package com.fivefourdee.aglaea;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.paint.Color;
public class LoginController{
int trials=5;
@FXML
private TextField userfield;
@FXML
private PasswordField passwordfield;
@FXML
private void onLogin(ActionEvent event){
if(userfield.getText().equals("admin")&&passwordfield.getText().equals("admin")){
/* do other things */
MainApp mainapp = new MainApp();
mainapp.showRecords();
}
else{
/* do other things */
}
}
}
例外：
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1770)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1653)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Node.fireEvent(Node.java:8390)
at javafx.scene.control.Button.fire(Button.java:185)
at com.sun.javafx.scene.control.skin.ButtonSkin.lambda$new$279(ButtonSkin.java:102)
at com.sun.javafx.scene.control.skin.ButtonSkin$$Lambda$154/400371281.run(Unknown Source)
at com.sun.javafx.scene.KeyboardShortcutsHandler.processAccelerators(KeyboardShortcutsHandler.java:347)
at com.sun.javafx.scene.KeyboardShortcutsHandler.dispatchBubblingEvent(KeyboardShortcutsHandler.java:163)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Node.fireEvent(Node.java:8390)
at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.forwardToParent(TextInputControlBehavior.java:432)
at com.sun.javafx.scene.control.behavior.TextFieldBehavior.fire(TextFieldBehavior.java:183)
at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callAction(TextInputControlBehavior.java:178)
at com.sun.javafx.scene.control.behavior.BehaviorBase.callActionForEvent(BehaviorBase.java:218)
at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callActionForEvent(TextInputControlBehavior.java:127)
at com.sun.javafx.scene.control.behavior.BehaviorBase.lambda$new$75(BehaviorBase.java:135)
at com.sun.javafx.scene.control.behavior.BehaviorBase$$Lambda$88/263344979.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$KeyHandler.process(Scene.java:3965)
at javafx.scene.Scene$KeyHandler.access$1800(Scene.java:3911)
at javafx.scene.Scene.impl_processKeyEvent(Scene.java:2040)
at javafx.scene.Scene$ScenePeerListener.keyEvent(Scene.java:2502)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:197)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:147)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleKeyEvent$349(GlassViewEventHandler.java:228)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$$Lambda$179/475935975.get(Unknown Source)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:404)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:227)
at com.sun.glass.ui.View.handleKeyEvent(View.java:546)
at com.sun.glass.ui.View.notifyKey(View.java:956)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
at com.sun.glass.ui.win.WinApplication$$Lambda$36/2117255219.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1765)
... 67 more
Caused by: java.lang.NullPointerException
at com.fivefourdee.aglaea.MainApp.showRecords(MainApp.java:59)
at com.fivefourdee.aglaea.LoginController.onLogin(LoginController.java:24)
... 77 more