Develop Reference

Java - custom dialogs with background threads

I am trying to raise a custom loading dialog in java and then execute some synchronous function which takes a few seconds.
I would like the dialog to be present as long as the function executes and once it finishes I would close the dialog.
My Dialog looks as follows:
public abstract class LoaderControl extends Control implements SimpleDialogInfo {
private static final StyleablePropertyFactory<LoaderControl> FACTORY = new StyleablePropertyFactory<>(Control.getClassCssMetaData());
private LoaderDialogResponse response;
private final DialogInfo dialogInfo;
private final SimpleStringProperty text = new SimpleStringProperty("");
private final SimpleBooleanProperty spinnerVisible = new SimpleBooleanProperty(true);
private UpdaterStates state;
private CloseDialogFunction onClose;
#Override
public void closeDialog(){
onClose.closeDialog();
}
#Override
public void setCloseDialog(CloseDialogFunction onClose){
this.onClose = onClose;
}
}
This is how I create it and show it:
public void createIndependentDialog(SimpleDialogInfo content, EventHandler<MouseEvent> onClose) {
Platform.runLater(() -> {
Stage stage = new Stage();
Parent p = new StackPane();
Scene s = new Scene(p);
stage.setScene(s);
MFXGenericDialog dialogContent = MFXGenericDialogBuilder.build()
.makeScrollable(true)
.setShowAlwaysOnTop(false)
.get();
MFXStageDialog dialog = MFXGenericDialogBuilder.build(dialogContent)
.toStageDialogBuilder()
.initModality(Modality.APPLICATION_MODAL)
.setDraggable(true)
.initOwner(stage)
.setTitle("Dialogs Preview")
.setOwnerNode(grid)
.setScrimPriority(ScrimPriority.WINDOW)
.setScrimOwner(true)
.get();
dialogContent.setMinSize(350, 200);
MFXFontIcon infoIcon = new MFXFontIcon(content.getDialogInfo().getIcon(), 18);
dialogContent.setHeaderIcon(infoIcon);
dialogContent.setHeaderText(content.getDialogInfo().getHeader());
dialogContent.setContent((Node) content);
MFXGenericDialog finalDialogContent = dialogContent;
MFXStageDialog finalDialog = dialog;
content.setCloseDialog(dialog::close);
convertDialogTo(String.format("mfx-%s-dialog", content.getDialogInfo().getDialogType()));
if(onClose != null)
dialogContent.setOnClose(onClose);
dialog.showAndWait();
});
}
This is how it looks like in the calling class:
DialogLoaderControlImpl preloader = new DialogLoaderControlImpl(new LoaderDialogInfo("Searching For New Versions"));
DialogsController.getInstance().createIndependentDialog(preloader);
someSynchronousMethod();
preloader.closeDialog();
The issue is that when I get to the "preloader.closeDialog()" line, the closeDialog function which should close the dialog is null (the onClose field is null).
In short:
The createIndependentDialog() method should raise a dialog and I would like to proceed to execute the method "someSynchronousMethod()" while the dialog is still shown and close it once the method finishes.
Please note that I use a Skin for the dialog which is not shown here but it works if I remove the Platform.runLater, but then it is stuck in the showAndWait() without advancing which is expected
Is there a way or a known design of some sort that will help to run tasks/methods with custom dialogs?

This can be done, but as pointed out in the comments, it is probably better to use some type of progress node. I used Alert in this example but Dialog should be very similar.
The key is closing the Alert/Dialog after the task is complete using the task's setOnSucceeded.
longRunningTask.setOnSucceeded((t) -> {
System.out.println("Task Done!");
alert.close();
});
Full Code
import javafx.application.Application;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Label;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
public class App extends Application
{
public static void main(String[] args)
{
launch();
}
#Override
public void start(Stage stage)
{
Scene scene = new Scene(new StackPane(new Label("Hello World!")), 320, 240);
stage.setTitle("Hello!");
stage.setScene(scene);
stage.show();
Task<Integer> longRunningTask = new Task<Integer>() {
#Override protected Integer call() throws Exception {
int iterations;
for (iterations = 0; iterations < 100000; iterations++) {
if (isCancelled()) {
break;
}
System.out.println("Iteration " + iterations);
}
return iterations;
}
};
Alert alert = new Alert(Alert.AlertType.INFORMATION);
Button okButton = (Button)alert.getDialogPane().lookupButton(ButtonType.OK);
okButton.setDisable(true);
longRunningTask.setOnSucceeded((t) -> {
System.out.println("Task Done!");
alert.close();
});
new Thread(longRunningTask).start();
alert.setTitle("Hello World");
alert.setHeaderText("Hello");
alert.setContentText("I will close when the long running task ends!");
alert.showAndWait();
}
}
Altered code from https://docs.oracle.com/javase/8/javafx/interoperability-tutorial/concurrency.htm.
One pitfall I can see is someone closing the Alert/Dialog before the task finishes.

JavaFX - Why does changing the header text of a dialog make the button bar invisible?

Here is a small sample from my custom dialog, which is meant to display the progress of a running javafx.concurrent.Task.
DialogPane pane = this.getDialogPane()
pane.getButtonTypes().addAll(ButtonType.CANCEL);
pane.headerTextProperty().bind(task.titleProperty());
pane.contentTextProperty().bind(task.messageProperty());
For some reason, the buttons in the button bar disappeared, but only after some text updated. After further investigation, I found that binding the header text of a dialog seems to remove all the buttons in the button bar. Why would this happen, and what would I do to stop the buttons from being hidden?
EDIT: Here's an MCVE demonstrating the problem.
import javafx.application.Application;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.concurrent.Task;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.StackPane;
import javafx.stage.Modality;
import javafx.stage.Stage;
public class MCVE extends Application {
public static class CustomDialog extends Dialog<ButtonType> {
public CustomDialog(Task<?> task) {
this.initModality(Modality.APPLICATION_MODAL);
DialogPane pane = this.getDialogPane();
{
pane.getButtonTypes().addAll(ButtonType.CANCEL);
pane.headerTextProperty().bind(task.titleProperty());
}
setOnCloseRequest(event -> {
if (task.isRunning()) event.consume();
});
}
}
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage stage) {
StackPane root = new StackPane();
Button starter = new Button("Showcase");
starter.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
root.getChildren().add(starter);
Scene scene = new Scene(root, 500, 500);
stage.setScene(scene);
stage.show();
starter.setOnAction(event -> {
Task<Void> task = new Task<>() {
#Override
protected Void call() throws Exception {
updateTitle("Before loop");
try {
Thread.sleep(1000);
} catch (InterruptedException ignored) {
if (isCancelled()) return null;
}
for (int i = 1; i <= 20; i++) {
updateTitle("loop " + i);
try {
Thread.sleep(1000);
} catch (InterruptedException ignored) {
if (isCancelled()) return null;
}
}
return null;
}
};
Thread worker = new Thread(task);
worker.start();
new CustomDialog(task).showAndWait();
});
}
}

It appears that the issue needs fixing on JavaFX's end. In fact, the button bar is simply pushed out of view. There is a relatively decent workaround though. Dialog internally uses a styled GridPane to display header text and graphics, so I simply replicated that using an external GridPane and instead bound to the textProperty() of a Label.
public static class CustomDialog extends Dialog<ButtonType> {
public CustomDialog(Task<?> task) {
DialogPane pane = this.getDialogPane(); {
pane.getButtonTypes().addAll(ButtonType.CANCEL);
//construct custom header
GridPane headerRoot = new GridPane(); {
Label headerText = new Label();
//headerText is the label containing the header text
headerText.textProperty().bind(task.titleProperty());
headerRoot.add(headerText, 0, 0);
}
headerRoot.getStyleClass().addAll("header-panel");
pane.setHeader(headerRoot);
pane.setContentText("Placeholder content");
pane.getScene().getWindow().setOnCloseRequest(event -> {
if (!task.isDone()) {
event.consume();
}
});
}
}
It looks exactly the same as a default dialog, without the issue mentioned in the question above.

Passing reference to javafx.application.Application

Consider a non-fx existing application, let's call it Business.
Business exposes a Model object, which in turn exposes some properties. Model also accepts listeners to those properties.
My question is about adding JavaFx gui to such application. The GuiApp obviously extends javafx.application.Application and will need a reference to a Model object.
Searching for a solution for passing a non-String parameter to GuiApp I found several different approaches:
Static approach : for example have Business initialize a static reference to Model in GuiApp. One example of the use of statics can be seen here .
JavaFx 9 approach: as demonstrated here you can launch JavaFx application without extending Application.
Change workflow approach: change the existing workflow to have GuiApp initialize BusinessApp . One example of such workflow can be seen here.
Are there another viable approaches ? Best practice ?

I'll try to demonstrate some different approaches for passing a reference between a java program, and a java-fx program.
I post it in hope it will help some future readers having similar need. I also hope it may encourage other answers with additional solutions.
The posted code should not be considered proper implementation, but rather a short code aiming to clarify the different approaches. For this purpose I'll introduce a simple listening interface :
interface Observe{ void update(int i); }
A java class, that represents an exiting business application :
public class JavaApp {
private Observe observer; private int counter = 0;
JavaApp(Observe observer){ //not null safe
this.observer = observer;
}
void process() {
new Timer().scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
observer.update(counter >=100 ? 0 : ++counter);
}
}, 1000,1000);
}
}
A java-fx application that should be added to the existing business application, listen to it and serve as view:
public class JavaFxApp extends Application implements Observe{
private Label label;
#Override public void start(Stage stage) {
label = new Label("waiting");
BorderPane pane = new BorderPane(label);
Scene scene = new Scene(pane, 100, 100);
stage.setScene(scene);
stage.show();
}
#Override public void update(int i) {
Platform.runLater(()-> label.setText(String.valueOf(i)));
}
}
How do we share a reference, in this case a reference to Observe instance, between the two applications ?
Approach 1: Consider the start() method as the entry point to the application (see James_D answer)
This is simple and straight forward if you want to tie the existing java application with java-fx and use java-fx Application as the entry point:
public class JavaFxApp extends Application implements Observe{
private Label label;
#Override public void start(Stage stage) {
JavaApp main = new JavaApp(this);
label = new Label("waiting");
BorderPane pane = new BorderPane(label);
Scene scene = new Scene(pane, 100, 100);
stage.setScene(scene);
stage.show();
new Thread(()-> { main.process();}).start(); //launch the business process
}
#Override public void update(int i) {
Platform.runLater(()-> label.setText(String.valueOf(i)));
}
public static void main(String[] args) { launch(); }
}
Approach 2: Use JavaFX 9 Platform#startup
This is the best solution I found, when you can not use the Application#start method as the entry point to the application.
As demonstrated in fabians answer, as off java-fx 9 you can launch without extending Application. All you have to do is modify the main of the java application:
public class JavaApp {
private Observe observer; private int counter = 0;
JavaApp(Observe observer){//not null safe
this.observer = observer;
}
void process() {
new Timer().scheduleAtFixedRate(new TimerTask() {
#Override public void run() {
observer.update(counter >=100 ? 0 : ++counter);
}
}, 1000,1000);
}
public static void main(String[] args) {
JavaFxApp view = new JavaFxApp(); //initialize JavaFx application
JavaApp main = new JavaApp(view);
Platform.startup(() -> {//launch JavaFx application
Stage stage = new Stage();
try {
view.start(stage);
} catch (Exception ex) {ex.printStackTrace();}
});
main.process(); //run business process
}
}
Approach 3: Use Static members
For example introduce a static getter in the java-fx application :
public class JavaFxApp extends Application {
private static Label label = new Label("waiting");
#Override public void start(Stage stage) {
BorderPane pane = new BorderPane(label);
Scene scene = new Scene(pane, 100, 100);
stage.setScene(scene);
stage.show();
}
static Observe getObserver() {
return JavaFxApp::update;
}
private static void update(int i) {
Platform.runLater(()-> label.setText(String.valueOf(i)));
}
}
and use it in the java application:
public class JavaApp {
private Observe observer; private int counter = 0;
JavaApp(Observe observer){//not null safe
this.observer = observer;
}
void process() {
new Timer().scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
observer.update(counter >=100 ? 0 : ++counter);
}
}, 1000,1000);
}
public static void main(String[] args){
new Thread(()-> Application.launch(JavaFxApp.class)).start();
Observe observer = JavaFxApp.getObserver(); //get static observer reference
JavaApp main = new JavaApp(observer);
main.process();
}
}
A better approach to get a static reference might be (based on this answer) :
public class JavaFxApp extends Application implements Observe{
private static final CountDownLatch latch = new CountDownLatch(1);
private static Observe observer = null;
private Label label;
#Override public void init() {
observer = this;
latch.countDown();
}
#Override public void start(Stage stage){
label = new Label("waiting");
BorderPane pane = new BorderPane(label);
Scene scene = new Scene(pane, 100, 100);
stage.setScene(scene);
stage.show();
}
#Override public void update(int i) {
Platform.runLater(()-> label.setText(String.valueOf(i)));
}
static Observe getObserver() {
try {
latch.await();
} catch (InterruptedException e) { e.printStackTrace(); }
return observer;
}
}

How to get a scheduled event to interact with JavaFX GUI

I'm a beginner Java programmer trying to figure this out. I have a piece of code that does some calculation and updates a label in my JavaFX GUI. It runs every 100ms using a ScheduledExecutorService and a Runnable. The problem is it cannot update the Label of the GUI. I have spent yesterday looking for a way to do it and most of the topics seem to be solved with the use of Platform.runLater but even putting my code into the runLater runnable seems to still not work. Another thing I have found is using the Java concurrency framework, but I don't know how to use that for a repeating scheduled service like this. Here's how I wrote the code:
ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
Runnable loop = new Runnable() {
public void run() {
Platform.runLater(new Runnable() {
#Override public void run() {
double result = calculation();
labelResult.setText("" + result);
}
});
}
};
executor.scheduleAtFixedRate(loop, 0, 100, TimeUnit.MILLISECONDS);
How could I do this?
EDIT:
I'm including a full example.
Main class:
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import javafx.application.Application;
import javafx.application.Platform;
public class Main{
private static long value = 0;
private static Gui gui;
public static void main(String[] args){
ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
Runnable loop = new Runnable() {
public void run() {
Platform.runLater(new Runnable() {
#Override public void run() {
calculate();
}
});
}
};
executor.scheduleAtFixedRate(loop, 0, 100, TimeUnit.MILLISECONDS);
Application.launch(Gui.class, args);
}
public static void calculate(){
double result = value++;
gui.setResult(result);
}
public static void setGui(Gui ref){
gui = ref;
}
}
Gui class:
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
public class Gui extends Application{
private Stage window;
private Scene scene;
private HBox layout = new HBox();
private Label result = new Label("TEST");
#Override
public void start(Stage stage) throws Exception {
window = stage;
layout.getChildren().addAll(result);
Main.setGui(this);
scene = new Scene(layout, 1280, 720);
window.setTitle("Example");
window.setResizable(false);
window.setScene(scene);
window.show();
}
public void setResult(double res){
result.setText("" + res);
}
}

The overall structure of your application is wrong. The reason that your scheduled executor service is failing is that you attempt to start it before you launch the JavaFX application, and consequently your first call to Platform.runLater(...) happens before the FX toolkit has been started and before the FX Application Thread is running.
If you wrap the call to Platform.runLater() in a try block and catch the exception:
Runnable loop = new Runnable() {
public void run() {
try {
Platform.runLater(new Runnable() {
#Override
public void run() {
calculate();
}
});
} catch (Exception e) {
e.printStackTrace();
}
}
};
you will see the exception:
java.lang.IllegalStateException: Toolkit not initialized
at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:273)
at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:268)
at javafx.application.Platform.runLater(Platform.java:83)
at Main$1.run(Main.java:17)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
(Incidentally, handling the exception will also allow the executor to continue, so eventually it will "recover" as the toolkit will be started at some point. You may also see other exceptions, because, e.g. there are race conditions on the gui field: some iterations of the executor may get called before gui is initialized.)
You should think of the Application.start() method essentially as the entry point for the application. When you call launch() (or when it is called for you, which happens in most final deployment scenarios), the FX Toolkit is started, then an instance of the Application subclass is created, and start() is invoked on that instance on the FX Application Thread.
So the way to structure this is to drive it all from the start() method. Create an instance of your GUI class there, create an instance of the class that is running your scheduled executor, tie them together, and then just display the UI in the provided stage. Here's one possible example of this refactoring:
Main.java:
import javafx.application.Application;
import javafx.stage.Stage;
public class Main extends Application{
private Stage window;
#Override
public void start(Stage stage) throws Exception {
window = stage;
Gui gui = new Gui();
UpdateService service = new UpdateService(gui);
service.startService();
window.setTitle("Example");
window.setResizable(false);
window.setScene(gui.getScene());
window.show();
}
public static void main(String[] args) {
launch(args);
}
}
UpdateService.java:
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import javafx.application.Platform;
public class UpdateService {
private long value = 0;
private final Gui gui;
public UpdateService(Gui gui) {
this.gui = gui;
}
public void startService() {
// create executor that uses daemon threads;
ScheduledExecutorService executor = Executors.newScheduledThreadPool(1, runnable -> {
Thread t = new Thread(runnable);
t.setDaemon(true);
return t;
});
Runnable loop = new Runnable() {
public void run() {
Platform.runLater(new Runnable() {
#Override
public void run() {
calculate();
}
});
}
};
executor.scheduleAtFixedRate(loop, 0, 100, TimeUnit.MILLISECONDS);
}
public void calculate() {
double result = value++;
gui.setResult(result);
}
}
Gui.java:
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
public class Gui {
private Scene scene;
private HBox layout = new HBox();
private Label result = new Label("TEST");
public Gui() {
layout.getChildren().addAll(result);
scene = new Scene(layout, 1280, 720);
}
public Scene getScene() {
return scene ;
}
public void setResult(double res){
result.setText("" + res);
}
}
Finally, note that a cleaner way to get regularly-repeating functionality that runs on the FX Application Thread is to use the Animation API (as in JavaFX periodic background task):
public void startService() {
Timeline timeline = new Timeline(new KeyFrame(Duration.millis(100), e -> calculate()));
timeline.setCycleCount(Animation.INDEFINITE);
timeline.play();
}

Thread communication: How to signal that a key was clicked? java.lang.IllegalMonitorStateException

i have a simple JavaFX stage with a TextField. What i want to do is: when user inserts letters into the TextField, i want to print "now" (just to look if it works). Im using a Thread because later i want to scan a dictonary to see, if the letters the user entered are part of words from the dictionary.
But i get: java.lang.IllegalMonitorStateException
Any ideas? I don't seem to understand the whole concept of Condition.await and Multithreading..
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class DictionaryThreading extends Application {
private static Lock lock = new ReentrantLock();
public static Condition condition = lock.newCondition();
public static void main(String[] args) {
launch();
}
private static class ScanWords implements Runnable{
#Override
public void run() {
lock.lock();
try{
while(true){
this.wait();
System.out.println("clicked");
}
} catch (Exception e){
e.printStackTrace();
} finally{
lock.unlock();
}
}
}
#Override
public void start(Stage primaryStage) throws Exception {
StackPane pane = new StackPane();
new ScanWords().run();
TextField tf = new TextField("Please enter a word");
tf.setOnKeyPressed(e -> {});
pane.getChildren().add(tf);
Scene scene = new Scene(pane);
primaryStage.setScene(scene);
primaryStage.show();
}
}

There is no need to create a thread that does nothing other than wait for user events. The JavaFX framework already provides this for you (it is one of the fundamental pieces of functionality of any UI toolkit). All you need to do to respond to changes in the text in a text field is register a change listener with the text field's text property:
public void start(Stage primaryStage) throws Exception {
StackPane pane = new StackPane();
TextField tf = new TextField("Please enter a word");
tf.textProperty().addListener((obs, oldText, newText) -> {
System.out.println("text changed");
});
pane.getChildren().add(tf);
Scene scene = new Scene(pane);
primaryStage.setScene(scene);
primaryStage.show();
}
If the thing you need to do in response to the text changing takes a long time, then you should launch that process in a background thread in the listener on the text field. If you are searching something large, you probably want to cancel any existing search, so that you don't end up with a large number of searches all running concurrently. The JavaFX Service class provides the functionality you need for this:
public class SearchService extends Service<List<String>> {
// modify and access only on FX Application Thread:
private String searchString ;
#Override
protected Task<List<String>> createTask() {
final String s = searchString ;
return new Task<List<String>>() {
#Override
protected List<String> call() throws Exception {
List<String> matches = new ArrayList<>();
// do search for strings matching s
// be sure to check isCancelled() regularly
return matches ;
}
};
}
public String getSearchString() {
checkThread();
return searchString ;
}
public void setSearchString(String searchString) {
checkThread();
this.searchString = searchString ;
}
private void checkThread() {
if (! Platform.isFxApplicationThread()) {
throw new IllegalStateException("Not on FX Application Thread");
}
}
}
Then you can do
public void start(Stage primaryStage) throws Exception {
StackPane pane = new StackPane();
SearchService searchService = new SearchService();
searchService.setOnSucceeded(e -> {
List<String> matches = searchService.getValue();
// do whatever you need with search results...
// this is called on FX application thread
});
TextField tf = new TextField("Please enter a word");
tf.textProperty().addListener((obs, oldText, newText) -> {
searchService.cancel();
searchService.setSearchText(newText);
searchService.restart();
});
pane.getChildren().add(tf);
Scene scene = new Scene(pane);
primaryStage.setScene(scene);
primaryStage.show();
}

I don't use JavaFX, but I think you need to use EventListener. Try to use TextListener or InputMethodListener. For example:
StackPane pane = new StackPane();
TextField tf = new TextField("Please enter a word");
tf.addTextListener(e -> System.out.println("Pushed"));
pane.getChildren().add(tf);
Scene scene = new Scene(pane);
primaryStage.setScene(scene);
primaryStage.show();

wait method should be executed within synchronized block:
try{
while(true){
synchronized(this){
this.wait();
System.out.println("clicked");
}
}
} catch (Exception e){
e.printStackTrace();
} finally{
lock.unlock();
}