Opening different websites in JavaFX WebView (Update UI?) - javafx

Question

I'm trying to load different urls into a javafx webview after a given time. I have searched for a solution for at least 2 weeks but i wasn't able to find anything or wasn't able to transfer the solutions of similar problems to my code. Below are the necessary parts of the code:
Main.java
package application;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.stage.Stage;
import javafx.scene.Parent;
import javafx.scene.Scene;
public class Main extends Application {
#Override
public void start(Stage primaryStage) {
try {
Parent root = FXMLLoader.load(getClass().getResource("/application/FXML.fxml"));
primaryStage.setTitle("Window");
primaryStage.setScene(new Scene (root));
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
FXMLController.java
package application;
import java.io.File;
import java.net.URL;
import java.nio.file.Files;
import java.util.List;
import java.util.ResourceBundle;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Slider;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebView;
import javafx.stage.FileChooser;
import javafx.stage.FileChooser.ExtensionFilter;
public class FXMLController implements Initializable {
#FXML private Button btnAddUrl;
#FXML private Button btnStart;
#FXML private Slider sliderTime2NextUrl;
#FXML private WebView webviewWindow;
private WebEngine engine;
private FileChooser fileChooser;
private List<String> url;
private int urlTime;
public void initialize(URL arg0, ResourceBundle arg1) {
btnAddUrl.setOnAction(this::addUrls);
btnStart.setOnAction(this::urlLoad);
fileChooser = new FileChooser();
engine = webviewWindow.getEngine();
getsliderTime2NextUrl();
}//initialize
#FXML
private void addUrls(ActionEvent event) {
fileChooser.setTitle("Add Like List");
fileChooser.getExtensionFilters().addAll(
new ExtensionFilter("TXT Files", "*.TXT"),
new ExtensionFilter("txt Files", "*.txt"));
File file = fileChooser.showOpenDialog(null);
try {
url = Files.readAllLines(file.toPath());
} catch (Exception e) {
System.out.println("shit");
}
System.out.println(url);
}
#FXML
private void getsliderTime2NextUrl() {
sliderTime2NextUrl.valueProperty().addListener(new ChangeListener<Number>() {
#Override
public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {
System.out.println("Slider Value Changed (newValue: " + newValue.intValue() + ")");
double getTime;
getTime = sliderTime2NextUrl.valueProperty().getValue();
urlTime = (int) getTime;
}//changed
});//addListener
}//getsliderTime2NextUrl
#FXML
private void urlLoad (ActionEvent event) {
Task<Void> task = new Task<Void>() {
#Override protected Void call() throws Exception{
urlTime = urlTime * 1000 ;
System.out.println("next Url in: " + urlTime);
for(int i = 0; i < url.size(); i++) {
System.out.println("Url.size = "+ url.size());
System.out.println("Url = "+ i);
if(isCancelled()) {
updateMessage("Cancelled");
break;
}
updateMessage("Iteration " + i);
updateProgress(i, 1000);
try {
Thread.sleep(urlTime);
System.out.println("Thread Sleeps for :" + urlTime);
} catch (InterruptedException interrupted) {
if (isCancelled()) {
updateMessage("Cancelled");
break;
}
}
}
return null;
}
};
new Thread(task).start();
}
/*
#FXML
private void urlLoad (ActionEvent event) {
urlTime = urlTime * 1000 ;
System.out.println("next Url in: " + urlTime);
for(int i = 0; i < url.size(); i++) {
System.out.println("Url.size = "+ url.size());
System.out.println("Url = "+ i);
String Link = url.get(i);
engine.load(Link);
System.out.println("Url loaded = " + Link);
}
}*/
}
FXML.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.web.*?>
<?import javafx.scene.text.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<AnchorPane maxHeight="1.7976931348623157E308"
maxWidth="1.7976931348623157E308"
minHeight="400.0" minWidth="500.0"
prefHeight="500.0" prefWidth="500.0"
xmlns="http://javafx.com/javafx/8"
xmlns:fx="http://javafx.com/fxml/1"
fx:controller="application.FXMLController">
<children>
<MenuBar maxHeight="25.0" maxWidth="1920.0" prefHeight="25.0" prefWidth="500.0">
<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>
<Button fx:id="btnAddUrl" layoutX="66.0" layoutY="39.0" mnemonicParsing="false" onAction="#addUrls" prefHeight="25.0" prefWidth="69.0" text="AddUrl" />
<Button fx:id="btnStart" layoutX="36.0" layoutY="108.0" mnemonicParsing="false" onAction="#urlLoad" prefHeight="31.0" prefWidth="108.0" text="Start!">
<font>
<Font size="18.0" />
</font>
</Button>
<Slider fx:id="sliderTime2NextUrl" blockIncrement="1.0" layoutX="204.0" layoutY="39.0" majorTickUnit="2.0" max="15.0" min="3.0" minorTickCount="1" prefHeight="38.0" prefWidth="251.0" showTickLabels="true" showTickMarks="true" snapToTicks="true" value="3.0" />
<WebView fx:id="webviewWindow" layoutY="147.0" minHeight="-1.0" minWidth="-1.0" prefHeight="350.0" prefWidth="500.0" />
</children>
</AnchorPane>
I used the second "urlLoad"-Method (FXMLController.java) in the /* */ first but recognized that all Links are loaded immediately and only the last one stays active. After that I added "Thread.sleep(urlTime) + try & catch" but it freezed my whole GUI until the last URL was loaded. While searching for a solution, that was the first time I heard of workers, tasks & services.
I found out why this happened and tried to add a "Task" around the code. It was a long jorney until I found the code of the first "urlLoad"-Method in FXMLController.java. Thats exactly what my code with the Urls shoud do
![urlLoad-Method 1] there should be an image if i had 10 reputation
it gives out the numbers in the console with the given time from the slider.
Then i added my engine.load() part to the first "urlLoad"-Method
//updateMessage("Iteration " + i);
//updateProgress(i, 1000);
String Link = url.get(i);
engine.load(Link);
System.out.println("Url loaded = " + Link);
But then the method stops at the first Url and doesnt show anything:
![urlLoad-Method 1 with engine.load] there should be an image if i had 10 reputation
My assumption is, that the "urlLoad"-Method does not update the WebView Window in my GUI. I hope somebody can help me.
Thanks
Edit: After adding
task.setOnFailed((WorkerStateEvent t) -> {
throw new RuntimeException(task.getException());
});
I got the following exception:
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.IllegalStateException: Not on FX application thread; currentThread = Thread-5
at application.FXMLController.lambda$2(FXMLController.java:111)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.concurrent.EventHelper.fireEvent(EventHelper.java:219)
at javafx.concurrent.Task.fireEvent(Task.java:1356)
at javafx.concurrent.Task.setState(Task.java:707)
at javafx.concurrent.Task$TaskCallable.lambda$call$502(Task.java:1453)
at com.sun.javafx.application.PlatformImpl.lambda$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)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IllegalStateException: Not on FX application thread; currentThread = Thread-5
at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:279)
at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:423)
at javafx.scene.web.WebEngine.checkThread(WebEngine.java:1243)
at javafx.scene.web.WebEngine.load(WebEngine.java:913)
at application.FXMLController$2.call(FXMLController.java:92)
at application.FXMLController$2.call(FXMLController.java:1)
at javafx.concurrent.Task$TaskCallable.call(Task.java:1423)
at java.util.concurrent.FutureTask.run(Unknown Source)
... 1 more

Answer 1

you need to use
Platform.Runlater(()->{/*your task content here*/});
Javafx is pissy about what operations it allows you to run in which thread. Essentially, you have no business running code designated for ui control functionality on a non-ui thread... hence "thread 5" in your case.
Be careful, however, as you still need that thread.sleep routine in your background thread, as the javafx thread will sleep, and then proceed with the url.load() routine.
so...
javafxapplication thread (runs - handles its own operations)
thread 5 (runs whatever you want)
->
javafxapplication thread (runs but is idle from your POV)
thread 5 (invokes platform.runlater(/* engine.load("x") */))
->
javafxapplicationthread (executes engine.load())
thread 5 (etc etc etc)
good luck