当我运行我的应用程序时，它会打开，当我按下按钮以产生随机数时，我会得到一个NullPointerException。我是JavaFX的新手，所以我不知道如何解决这个问题。 主要课程：
package application;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class BobMarley extends Application {
FXMLLoader loader = new FXMLLoader();
public BobMarley() throws IOException {
}
public void start(Stage stage) throws IOException {
Parent root = FXMLLoader.load(getClass().getClassLoader().getResource("application/BobMarleyLayout.fxml"));
Scene scene = new Scene(root, 700, 300);
stage.setTitle("Bob Marley");
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
Application.launch(args);
}
}
控制器：
import java.net.URL;
import java.util.Random;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
public class Controller implements Initializable {
@FXML
Label l;
Label l1;
Label l2;
Label l3;
Label l4;
Label l5;
Label l6;
Random r = new Random();
Random r1 = new Random();
Random r2 = new Random();
Random r3 = new Random();
Random r4 = new Random();
Random r5 = new Random();
boolean b1;
boolean b2;
int z1;
int z2;
int z3;
int z4;
int z5;
int z6;
public Controller() {
b1 = r.nextBoolean();
Random r0 = new Random();
b2 = r0.nextBoolean();
z1 = r1.nextInt(15) + 5;
z2 = r2.nextInt(15) + 5;
z3 = r3.nextInt(15) + 5;
z4 = r4.nextInt(15) + 5;
z5 = r5.nextInt(15) + 5;
z6 = z1 + z2 + z3;
}
@FXML
private void handleButtonAction(ActionEvent event) {
l.setText(Integer.toString(z1));
l1.setText(String.valueOf(z2 + " " + "|"));
l2.setText(String.valueOf(z3 + " " + "|"));
l3.setText(String.valueOf(z4 + " " + "|"));
l3.setVisible(b1);
l4.setText(String.valueOf(z5 + " " + "|"));
l4.setVisible(b2);
l5.setText("=");
if (b1 == true && b2 == true && z6 + z4 + z5 >= 65) {
l6.setText("NOPE");
} else if (b1 == true && b2 == true) {
l6.setText(String.valueOf(z6 + z4 + z5));
} else if (b1 == true && b2 == false && z6 + z4 + z5 >= 65) {
l6.setText("NOPE");
} else if (b1 == true && b2 == false) {
l6.setText(String.valueOf(z6 + z4));
} else if (b1 == false && b2 == true && z6 + z4 + z5 >= 65) {
l6.setText("NOPE");
} else if (b1 == false && b2 == true) {
l6.setText(String.valueOf(z6 + z5));
} else {
l6.setText(String.valueOf(z6));
}
}
@Override
public void initialize(URL location, ResourceBundle resources) {
}
}
我的FXML文件：
<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.paint.*?>
<?import javafx.scene.text.*?>
<VBox prefHeight="400.0" prefWidth="640.0" xmlns="http://javafx.com/javafx/8" fx:controller="application.Controller"
xmlns:fx="http://javafx.com/fxml/1">
<children>
<MenuBar VBox.vgrow="NEVER">
<menus>
<Menu mnemonicParsing="false" text="File">
<items>
<MenuItem mnemonicParsing="false" text="New" />
<MenuItem mnemonicParsing="false" text="Open…" />
<Menu mnemonicParsing="false" text="Open Recent" />
<SeparatorMenuItem mnemonicParsing="false" />
<MenuItem mnemonicParsing="false" text="Close" />
<MenuItem mnemonicParsing="false" text="Save" />
<MenuItem mnemonicParsing="false" text="Save As…" />
<MenuItem mnemonicParsing="false" text="Revert" />
<SeparatorMenuItem mnemonicParsing="false" />
<MenuItem mnemonicParsing="false" text="Preferences…" />
<SeparatorMenuItem mnemonicParsing="false" />
<MenuItem mnemonicParsing="false" text="Quit" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Edit">
<items>
<MenuItem mnemonicParsing="false" text="Undo" />
<MenuItem mnemonicParsing="false" text="Redo" />
<SeparatorMenuItem mnemonicParsing="false" />
<MenuItem mnemonicParsing="false" text="Cut" />
<MenuItem mnemonicParsing="false" text="Copy" />
<MenuItem mnemonicParsing="false" text="Paste" />
<MenuItem mnemonicParsing="false" text="Delete" />
<SeparatorMenuItem mnemonicParsing="false" />
<MenuItem mnemonicParsing="false" text="Select All" />
<MenuItem mnemonicParsing="false" text="Unselect All" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Help">
<items>
<MenuItem mnemonicParsing="false" text="About MyHelloApp" />
</items>
</Menu>
</menus>
</MenuBar>
<AnchorPane maxHeight="-1.0" maxWidth="-1.0" prefHeight="-1.0"
prefWidth="-1.0" VBox.vgrow="ALWAYS" id="root">
<children>
<Button layoutX="294.0" layoutY="219.0" mnemonicParsing="false"
onAction="#handleButtonAction" text="Let it Rip" />
<Label id="l6" layoutX="499.0" layoutY="182.0" text="1" />
<Label id="l" layoutX="184.0" layoutY="182.0" text="1"/>
<Label id="l1" layoutX="245.0" layoutY="182.0" text="1"/>
<Label id="l2" layoutX="256.0" layoutY="182.0" text="1"/>
<Label id="l3" layoutX="318.0" layoutY="182.0" text="1"/>
<Label id="l4" layoutX="385.0" layoutY="182.0" text="1"/>
<Label layoutX="445.0" layoutY="182.0" text="=" />
<Label layoutX="160.0" layoutY="26.0" text="Bob Marley"
textAlignment="CENTER">
<font>
<Font name="HelveticaNeueLTStd-Lt" size="74.0" />
</font>
</Label>
</children>
</AnchorPane>
</children>
</VBox>
我收到错误消息：
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
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:8413)
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:198)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.Trampoline.invoke(Unknown Source)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
... 48 more
Caused by: java.lang.NullPointerException
at application.Controller.handleButtonAction(Controller.java:53)
... 58 more
感谢您的帮助！ 路德维希