当我点击登录页面主页上的提交按钮时，应显示但是我收到此错误：
异常
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1768)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1651)
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:204)
at javafx.scene.Node.fireEvent(Node.java:8175)
at javafx.scene.control.Button.fire(Button.java:185)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
at com.sun.javafx.event.CompositeEventHandler$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:204)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3746)
at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3471)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1695)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2486)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:314)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:243)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:345)
at com.sun.glass.ui.View.handleMouseEvent(View.java:526)
at com.sun.glass.ui.View.notifyMouse(View.java:898)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
at com.sun.glass.ui.win.WinApplication$4$1.run(WinApplication.java:112)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1765)
... 47 more
Caused by: java.lang.NullPointerException
at com.emo.Navigator.showLoginPage(Navigator.java:61)
at com.emo.view.LoginController.authenticate(LoginController.java:37)
... 57 more
MAIN APP
package com.emo;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
import com.emo.view.HomePageController;
import com.emo.view.LoginController;
public class MainApp extends Application {
/**
* Constructor
*/
@Override
public void start(Stage primaryStage) {
Navigator nav = new Navigator();
nav.primaryStage = primaryStage;
primaryStage.setTitle("EMO APP");
nav.initRootLayout();
nav.showLoginPage();
}
public static void main(String[] args) {
launch(args);
}
}
登录控制器
package com.emo.view;
import javafx.fxml.FXML;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import com.emo.MainApp;
import com.emo.Navigator;
public class LoginController {
@FXML
private TextField usernameText;
@FXML
private PasswordField passwordText;
@FXML
private Label statusLabel;
int attempt = 0;
private MainApp mainApp;
public void setMainApp(MainApp mainApp) {
this.mainApp = mainApp;
}
/*
* @FXML void nextPane() { VistaNavigator.loadVista(VistaNavigator.VISTA_2);
* }
*/
@FXML
public void authenticate() {
if (attempt < 3) {
if (usernameText.getText().equals("abc")
&& passwordText.getText().equals("abc")) {
statusLabel.setText("");
Navigator nav = new Navigator();
nav.showLoginPage();
} else {
attempt++;
statusLabel.setText("Invalid Credentials");
}
} else {
statusLabel.setText("Your account has been locked");
}
}
}
主页控制器
package com.emo.view;
import javafx.fxml.FXML;
import com.emo.MainApp;
public class HomePageController {
// Reference to the main application.
private MainApp mainApp;
public void setMainApp(MainApp mainApp) {
this.mainApp = mainApp;
}
@FXML
public void emo() {
}
@FXML
public void cashManagement() {
}
@FXML
public void reports() {
}
@FXML
public void userProfile() {
}
@FXML
public void email() {
}
}
导航
package com.emo;
import java.io.IOException;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
import com.emo.view.HomePageController;
import com.emo.view.LoginController;
public class Navigator {
Stage primaryStage;
BorderPane rootLayout=null;
FXMLLoader loader = new FXMLLoader();
AnchorPane pane = null;
/**
* Returns the main stage.
*
* @return
*/
public Stage getPrimaryStage() {
return primaryStage;
}
/**
* Initializes the root layout.
*/
public void initRootLayout() {
try {
// Load root layout from fxml file.
FXMLLoader loader = new FXMLLoader();
loader.setLocation(MainApp.class
.getResource("view/RootLayout.fxml"));
rootLayout = (BorderPane) loader.load();
// Show the scene containing the root layout.
Scene scene = new Scene(rootLayout);
primaryStage.setScene(scene);
primaryStage.show();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* Shows the Login Page inside the root layout.
*/
public void showLoginPage() {
try {
// Load person overview.
loader.setLocation(MainApp.class
.getResource("view/eMO_SignIn.fxml"));
pane = (AnchorPane) loader.load();
// Set person overview into the center of root layout.
rootLayout.setCenter(pane);
// Give the controller access to the main app.
LoginController controller = loader.getController();
controller.setMainApp(new MainApp());
} catch (IOException e) {
e.printStackTrace();
}
}
public void showHomePage() {
try {
pane = null;
// Load person overview.
loader.setLocation(MainApp.class
.getResource("view/eMO_HomePage.fxml"));
pane = (AnchorPane) loader.load();
// Set person overview into the center of root layout.
rootLayout.setCenter(pane);
// Give the controller access to the main app.
HomePageController controller = loader.getController();
controller.setMainApp(new MainApp());
} catch (IOException e) {
e.printStackTrace();
}
}
}
eMO_Homepage.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.shape.*?>
<?import javafx.scene.effect.*?>
<?import javafx.scene.text.*?>
<?import javafx.scene.image.*?>
<?import java.lang.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="250.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.emo.view.HomePageController">
<children>
<ImageView fitHeight="49.0" fitWidth="250.0" layoutY="-2.0" pickOnBounds="true">
<image>
<Image url="@../../../../../../Desktop/thCA60O0D6.jpg" />
</image>
</ImageView>
<Label layoutX="27.0" layoutY="14.0" text="Home Page" textFill="#a12121">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Label>
<ImageView fitHeight="354.0" fitWidth="250.0" layoutY="46.0" pickOnBounds="true">
<image>
<Image url="@../../../../../../Desktop/thCA7ZWC4O.jpg" />
</image>
</ImageView>
<Button layoutX="117.0" layoutY="10.0" mnemonicParsing="false" text="Sync" />
<VBox layoutX="2.0" layoutY="50.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="50.0">
<children>
<Button id="emo" layoutY="-1.0" mnemonicParsing="false" onAction="#emo" prefHeight="57.0" prefWidth="256.0" text="EMO">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Button>
<Button id="cashManagement" layoutY="56.0" mnemonicParsing="false" onAction="#cashManagement" prefHeight="57.0" prefWidth="256.0" text="Cash Management">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Button>
<Button id="reports" layoutY="113.0" mnemonicParsing="false" onAction="#reports" prefHeight="57.0" prefWidth="256.0" text="Reports">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Button>
<Button id="userProfile" layoutY="170.0" mnemonicParsing="false" onAction="#userProfile" prefHeight="57.0" prefWidth="256.0" text="User Profile">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Button>
<Button id="email" layoutY="227.0" mnemonicParsing="false" onAction="#email" prefHeight="57.0" prefWidth="256.0" text="Email">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Button>
</children>
</VBox>
</children>
</AnchorPane>
eMO_SignIn.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.text.*?>
<?import javafx.scene.image.*?>
<?import java.lang.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="250.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.emo.view.LoginController">
<children>
<ImageView fitHeight="49.0" fitWidth="250.0" layoutY="-2.0" pickOnBounds="true">
<image>
<Image url="@../../../../Images/Grey.jpg" />
</image>
</ImageView>
<Label layoutX="27.0" layoutY="14.0" text="Sign In" textFill="#a12121">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Label>
<ImageView fitHeight="354.0" fitWidth="250.0" layoutY="46.0" pickOnBounds="true">
<image>
<Image url="@../../../../Images/Red.jpg" />
</image>
</ImageView>
<VBox layoutX="27.0" layoutY="79.0" spacing="5.0" AnchorPane.leftAnchor="15.0">
<children>
<Label layoutX="27.0" layoutY="79.0" text="Username:-*" textFill="#f8e4e4">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Label>
<TextField fx:id="usernameText" layoutX="27.0" layoutY="105.0" prefHeight="42.0" prefWidth="150.0" />
<Label layoutX="28.0" layoutY="148.0" text="Password:-*" textFill="#f8e4e4">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Label>
<PasswordField fx:id="passwordText" layoutX="28.0" layoutY="174.0" prefHeight="42.0" prefWidth="150.0" />
</children>
</VBox>
<Button layoutX="125.0" layoutY="236.0" mnemonicParsing="false" onAction="#authenticate" prefHeight="25.0" prefWidth="68.0" text="Sign In" AnchorPane.leftAnchor="100.0" AnchorPane.rightAnchor="82.0">
<font>
<Font name="System Bold" size="12.0" />
</font>
</Button>
<Label fx:id="statusLabel" alignment="CENTER" layoutX="46.0" layoutY="294.0" prefHeight="17.0" prefWidth="164.0" AnchorPane.bottomAnchor="100.0" AnchorPane.leftAnchor="10.0" AnchorPane.rightAnchor="10.0" AnchorPane.topAnchor="280.0" />
</children>
</AnchorPane>
RootLayout.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.BorderPane?>
<BorderPane prefHeight="400.0" prefWidth="600.0"
xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8">
<top>
<MenuBar BorderPane.alignment="CENTER">
<menus>
<Menu mnemonicParsing="false" text="File">
<items>
<MenuItem mnemonicParsing="false" text="Close" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Edit">
<items>
<MenuItem mnemonicParsing="false" text="Delete" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Help">
<items>
<MenuItem mnemonicParsing="false" text="About" />
</items>
</Menu>
</menus>
</MenuBar>
</top>
</BorderPane>
答案 0 :(得分：0)
在LoginController.authenticate()中，您可以：
Navigator nav = new Navigator();
nav.showLoginPage();
并且Navigator.showLoginPage()你有：
pane = loader.load();
rootLayout.setCenter(pane);
但是，此rootLayout实例的Navigator没有被初始化，因此您可以获得堆栈跟踪中显示的NullPointerException。
一种可能的解决方法是为LoginController提供您已创建的Navigator（并正确初始化），这样就不必创建新的：{/ p >
public class LoginController {
private Navigator navigator ;
public void setNavigator(navigator) {
this.navigator = navigator ;
}
// everything else as before...
@FXML
public void authenticate() {
if (attempt < 3) {
if (usernameText.getText().equals("abc")
&& passwordText.getText().equals("abc")) {
statusLabel.setText("");
navigator.showLoginPage();
} else {
attempt++;
statusLabel.setText("Invalid Credentials");
}
} else {
statusLabel.setText("Your account has been locked");
}
}
}
然后
public class Navigator {
// everything else as before....
public void showLoginPage() {
try {
// Load person overview.
loader.setLocation(MainApp.class
.getResource("view/eMO_SignIn.fxml"));
pane = (AnchorPane) loader.load();
// Set person overview into the center of root layout.
rootLayout.setCenter(pane);
// Give the controller access to the main app.
LoginController controller = loader.getController();
controller.setMainApp(new MainApp());
// Give the controller access to this navigator:
controller.setNavigator(this);
} catch (IOException e) {
e.printStackTrace();
}
}
}