How can I change my button background color from test.fxml programmatically in my HelloConroller.java?
I would like to change button1 background color from null to white if I click the enter button, but I am always getting an error "this.button1" is null after I clicked enter, even though I called them by their fxml id's.
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml@18.0.1/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1857)
at javafx.fxml@18.0.1/javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1724)
at javafx.base@18.0.1/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at javafx.base@18.0.1/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
at javafx.base@18.0.1/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base@18.0.1/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base@18.0.1/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base@18.0.1/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base@18.0.1/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base@18.0.1/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base@18.0.1/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base@18.0.1/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base@18.0.1/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base@18.0.1/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.base@18.0.1/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics@18.0.1/javafx.scene.Node.fireEvent(Node.java:8797)
at javafx.controls@18.0.1/javafx.scene.control.Button.fire(Button.java:203)
at javafx.controls@18.0.1/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:208)
at javafx.controls@18.0.1/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
at javafx.base@18.0.1/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
at javafx.base@18.0.1/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at javafx.base@18.0.1/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
at javafx.base@18.0.1/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base@18.0.1/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base@18.0.1/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base@18.0.1/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base@18.0.1/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base@18.0.1/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base@18.0.1/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base@18.0.1/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base@18.0.1/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base@18.0.1/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base@18.0.1/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics@18.0.1/javafx.scene.Scene$MouseHandler.process(Scene.java:3881)
at javafx.graphics@18.0.1/javafx.scene.Scene.processMouseEvent(Scene.java:1874)
at javafx.graphics@18.0.1/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2607)
at javafx.graphics@18.0.1/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:411)
at javafx.graphics@18.0.1/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:301)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at javafx.graphics@18.0.1/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:450)
at javafx.graphics@18.0.1/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
at javafx.graphics@18.0.1/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:449)
at javafx.graphics@18.0.1/com.sun.glass.ui.View.handleMouseEvent(View.java:551)
at javafx.graphics@18.0.1/com.sun.glass.ui.View.notifyMouse(View.java:937)
at javafx.graphics@18.0.1/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics@18.0.1/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:116)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:77)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at javafx.base@18.0.1/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml@18.0.1/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:84)
at javafx.fxml@18.0.1/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1854)
... 46 more
Caused by: java.lang.NullPointerException: Cannot invoke "javafx.scene.control.Button.setStyle(String)" because "this.button1" is null
at com.example.demo/com.example.demo.HelloController.onClick(HelloController.java:14)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
... 53 more
Process finished with exit code 0
HelloApplication.java:
package com.example.demo;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.stage.Stage;
import java.io.IOException;
public class HelloApplication extends Application {
@Override
public void start(Stage stage) throws IOException {
FXMLLoader fxmlLoader = new FXMLLoader(HelloApplication.class.getResource("hello-view.fxml"));
Scene scene = new Scene(fxmlLoader.load(), 320, 240);
stage.setTitle("Hello!");
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch();
}
}
HelloController.java:
package com.example.demo;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.stage.Stage;
import java.io.IOException;
public class HelloController {
@FXML
public void switchToTest(ActionEvent event) throws IOException {
FXMLLoader fxmlLoader = new FXMLLoader(HelloApplication.class.getResource("test.fxml"));
Scene scene = new Scene(fxmlLoader.load());
Stage stage = (Stage)((Node)event.getSource()).getScene().getWindow();
stage.setScene(scene);
stage.setResizable(false);
stage.show();
}
}
testController.java
package com.example.demo;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
public class testController {
@FXML
private Button button1, button2;
protected void onClick() {
button1.setStyle("-fx-background-color: white");
}
}
test.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<VBox alignment="CENTER" prefHeight="200.0" prefWidth="200.0" spacing="20.0" style="-fx-background-color: black;" xmlns="http://javafx.com/javafx/17.0.2-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.example.demo.testController">
<padding>
<Insets bottom="20.0" left="20.0" right="20.0" top="20.0" />
</padding>
<Button fx:id="button1" style="-fx-background-color: null;" text="Button1" textFill="WHITE" />
<Button fx:id="button2" mnemonicParsing="false" style="-fx-background-color: null;" text="Button2" textFill="WHITE" />
</VBox>
hello-view.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<VBox alignment="CENTER" prefHeight="200.0" prefWidth="200.0" spacing="20.0" style="-fx-background-color: black;" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/17.0.2-ea" fx:controller="com.example.demo.HelloController">
<padding>
<Insets bottom="20.0" left="20.0" right="20.0" top="20.0" />
</padding>
<Button onAction="#onClick" text="enter" />
</VBox>