Develop Reference

JavaFX: Why do I have to press the button several times before the background changes?

In my programm I want to switch dark mode on and off via a MenuItem. And it's is working, but I've a little problem and I don't understand what causes this problem.
The problem is, that I've to select the CheckMenuItem serveral times before the selectedProperty is doing something.
If you run my mvce, you should see it (I think you have to click it 3 times).
But after the selectedProperty was active for the first time, it works without any problems until you restart the application.
MVCE
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.CheckMenuItem;
import javafx.scene.control.MenuButton;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
public class DarkModeMVCE extends Application {
public static void main(String[] args) {
Application.launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
BorderPane pane = new BorderPane();
Scene scene = new Scene(pane, 500, 500);
MenuButton menuButton = new MenuButton("Menu");
CheckMenuItem checkMenuItem = new CheckMenuItem("Darkmode");
checkMenuItem.setSelected(false);
checkMenuItem.setOnAction(aE -> checkMenuItem.selectedProperty().addListener((obs, wasSelected, isSelected) -> {
if (isSelected) {
pane.setStyle("-fx-background-color: black");
}
else {
pane.setStyle("-fx-background-color: white");
}
}));
menuButton.getItems().add(checkMenuItem);
pane.setCenter(menuButton);
primaryStage.setScene(scene);
primaryStage.setTitle("MVCE");
primaryStage.show();
}
}
Can anyone please explain why this is happening?
Is this a bug or an error in the code?

setOnAction() listener listen to any action applies on the MenuItem so when you click the menuItem it execute the code inside the listener
which at this point assign a new listener to the property of selection on the menuItem which gonna listen if the menuItem is gonna be selected or not next time any action is applied so the first action is not counted the next you do is deselect the menuItem whchi in your case do nothing and re-select it again make the desired action so no need to make two listener to the same property you can just make a listener to the change of the selection property
checkMenuItem.selectedProperty().addListener((obs, wasSelected, isSelected) -> {
if (isSelected) {
pane.setStyle("-fx-background-color: black");
}
else {
pane.setStyle("-fx-background-color: white");
}
});

This is the simple way to achieve this :-)
checkMenuItem.setOnAction(event -> {
if (checkMenuItem.isSelected()) {
pane.setStyle("-fx-background-color: black");
} else {
pane.setStyle("-fx-background-color: white");
}
});

JavaFX mouse drag events not firing

I tried almost everything, but the mouse drag events are not firing, like explained here:
https://openjfx.io/javadoc/11/javafx.graphics/javafx/scene/input/MouseDragEvent.html
Here is a minimal example, so you can try it out (I am using Java 11 with JavaFX 11.0.2):
import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.*;
import javafx.stage.Stage;
public class Main extends Application {
private double mouseClickPositionX, mouseClickPositionY, currentRelativePositionX, currentRelativePositionY;
#Override
public void start(Stage primaryStage) throws Exception{
primaryStage.setTitle("Hello World");
BorderPane mainBorderPane = new BorderPane();
BorderPane centerBorderPane = new BorderPane();
FlowPane flowPane = new FlowPane();
GridPane gridPane = new GridPane();
Button button1 = new Button("button1");
gridPane.add(button1, 0, 0);
flowPane.getChildren().add(gridPane);
centerBorderPane.setCenter(flowPane);
HBox hbox = new HBox();
TilePane tilePane = new TilePane();
Button button2 = new Button("button2");
tilePane.getChildren().add(button2);
hbox.getChildren().add(tilePane);
mainBorderPane.setCenter(centerBorderPane);
centerBorderPane.setBottom(hbox);
// button2 event handlers
button2.setOnMousePressed(event -> {
mouseClickPositionX = event.getSceneX();
mouseClickPositionY = event.getSceneY();
currentRelativePositionX = button2.getTranslateX();
currentRelativePositionY = button2.getTranslateY();
button2.setMouseTransparent(true);
});
button2.setOnMouseDragged(event -> {
button2.setTranslateX(currentRelativePositionX + (event.getSceneX() - mouseClickPositionX));
button2.setTranslateY(currentRelativePositionY + (event.getSceneY() - mouseClickPositionY));
});
button2.setOnDragDetected(event -> {
button2.startFullDrag();
});
button2.setOnMouseReleased((event) -> {
button2.setMouseTransparent(false);
});
// button1 event handlers
button1.setOnMouseDragReleased((event) -> {
System.out.println("it works in button1");
});
// gridPane event handlers
gridPane.setOnMouseDragReleased((event) -> {
System.out.println("it works in gridPane");
});
primaryStage.setScene(new Scene(mainBorderPane, 300, 275));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
I want to get the reference of button2 either in button1 or in gridPane via setOnMouseDragReleased. There are many nested panes etc. because I wanted to maintain the original project layout structure. I did this because I am not sure if this also can be a reason for the non functioning.
Thanks in advance.

I've ended up manually triggering the events from centerBorderPane to gridPane, using node.fireEvent(event). Also implemented a helper function, which returns the right child node:
private Optional<Node> findNode(Pane pane, double x, double y) {
return pane.getChildren().stream().filter(n -> {
Point2D point = n.sceneToLocal(x, y);
return n.contains(point.getX(), point.getY());
}).findAny();
}
Don't forget to consume the events, so you won't get into an infinite loop.

MOUSE_DRAG_RELEASED fires when a drag ends on this node. For example
centerBorderPane.setOnMouseDragReleased((event) -> {
System.out.println("centerBorderPane drag released");
});
should fire when you drag button2 and the drag ends on centerBorderPane.
To fire an event when the mouse is dragged over button1 use button1.setOnMouseDragged
If you want to propagate a mouse event from parent to its children see this

How to properly implement the Action Listener in a bullseye animation

This program first displays a bullseye created by three different sized circles.
Once the animate me button is clicked, the function animation() will make the existing circles shrink inwards until the size of the circles is zero.
Once the user presses the button named "Press to stop", the animation will then stop. If the user presses the button again, it will then keep going from the state it was stopped from, so on so forth.
Currently, this is not working as intended. It only creates about 9 circles (including the nine circles that the program began with). I know I will need to use the action listener in order to make the program run, but I'm having a hard time in terms of the documentation of the action listener. What am I supposed to put in the parameters of the listener? If you see any other ways around this, please feel free to let me know.
package target;
import javafx.animation.ScaleTransition;
import javafx.animation.Timeline;
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.util.Duration;
public class Target extends Application
{
Circle[] cir = new Circle[7];
Button btn = new Button("Animate me!");
StackPane root = new StackPane();
public static void main(String[] args)
{
launch(args);
}
/**
* start method will create the target and the start button first
* displayed on-screen to the user
*/
#Override
public void start(Stage primaryStage)
{
root.setStyle("-fx-border-color:black;");
cir[0] = new Circle(400, 250, 200);
cir[0].setFill(Color.RED);
cir[0].setStyle("-fx-border-color:black;");
cir[1] = new Circle(315, 165, 115);
cir[1].setFill(Color.WHITE);
cir[1].setStyle("-fx-border-color:black;");
cir[2] = new Circle(230, 80, 30);
cir[2].setFill(Color.RED);
cir[2].setStyle("-fx-border-color:black;");
root.getChildren().addAll(cir[0], cir[1], cir[2]);
root.getChildren().add(btn);
primaryStage.setScene(new Scene(root));
primaryStage.show();
btn.setOnAction(e ->
{
animation();
btn.setText("Press to Stop");
});
}
public void animation()
{
//Timeline animation = new Timeline(
//)
ScaleTransition[] st = new ScaleTransition[7];
boolean recycleCircles = false;
st[0]= new ScaleTransition(Duration.seconds(7), cir[0]);
st[0].setToX(0.0f);
st[0].setToY(0.0f);
st[0].play();
st[1] = new ScaleTransition(Duration.seconds(5.5), cir[1]);
st[1].setToX(0.0f);
st[1].setToY(0.0f);
st[1].play();
st[2] = new ScaleTransition(Duration.seconds(4), cir[2]);
st[2].setToX(0.0f);
st[2].setToY(0.0f);
st[2].play();
// int delayInc = 1;
int delay = 1;
//will create circles (will rotate between white and red) and then add
//to scaleTransitions
//while(btn.isPressed() == false)
{
for(int i = 3; i<st.length; i++)
{
if(recycleCircles == true)
{
i = 0;
recycleCircles = false;
}
if(i % 2 == 1)
{
cir[i] = new Circle(400,250,200);
cir[i].setFill(Color.WHITE);
cir[i].setStyle("-fx-border-color:black;");
root.getChildren().add(cir[i]);
cir[i].toBack();
st[i] = new ScaleTransition(Duration.seconds(7), cir[i]);
st[i].setDelay(Duration.seconds(delay));
delay++;
st[i].setToX(0.0f);
st[i].setToY(0.0f);
st[i].play();
}
else if(i%2==0)
{
cir[i] = new Circle(400, 250, 200);
cir[i].setFill(Color.RED);
cir[i].setStyle("-fx-border-color:black;");
root.getChildren().add(cir[i]);
cir[i].toBack();
st[i] = new ScaleTransition(Duration.seconds(7), cir[i]);
st[i].setDelay(Duration.seconds(delay));
delay++;
st[i].setToX(0.0f);
st[i].setToY(0.0f);
st[i].play();
}
if(i == 6)
recycleCircles = true;
}
}
//btn.pressedProperty().addListener(listener);
btn.setOnMousePressed(event ->
{
});
btn.setOnMouseReleased(event ->
{
for(int y = 0; y<st.length;y++)
{
}
});
}
}

Not sure whether you have any specific use case with each circle. If your are using the circles only for the purpose of alternating row colors, then you can get similar effect with radial gradient's repeat option.
To the extent I understand the question, below program is what I can think of. May be this can help you.
Just to let you know, the overall effect is slightly different from your program. The main difference in effects is, your program gives an effect/impression that each circle are shrinking towards center, as the distance between each circle is always same till it shrinked completely.
My program gives the effect/.impression like the entire board is moving away from your sight till it vanishes. In my program the distance between each circle decreases proportianally till it shrinks.
import javafx.animation.ScaleTransition;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.util.Duration;
public class TargetAnimation extends Application {
Button btn = new Button("Animate me!");
StackPane root = new StackPane();
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) {
root.setPrefSize(400, 400);
root.setStyle("-fx-border-color:black;");
Circle board = new Circle();
board.setRadius(200);
board.setStyle("-fx-fill:radial-gradient(focus-angle 0deg , focus-distance 0% , center 50% 50% , radius 21% , repeat, red 44% , white 46% );-fx-stroke-width:1px;-fx-stroke:black;");
root.getChildren().addAll(board, btn);
primaryStage.setScene(new Scene(root));
primaryStage.show();
ScaleTransition transition = new ScaleTransition(Duration.seconds(7), board);
transition.setToX(0);
transition.setToY(0);
btn.setOnAction(e -> {
switch (transition.getStatus()) {
case RUNNING:
transition.pause();
break;
case PAUSED:
transition.play();
break;
default:
board.setScaleX(1);
board.setScaleY(1);
transition.playFromStart();
}
});
}
}

The code given to setOnAction is an EventHandler, which is a #FunctionalInterface with the single method handle. That means that you can give it a lambda expression instead. The method takes an argument, which is the ActionEvent of clicking the button (created for you by JavaFX), and runs the code you give it.
If you want to pause the animation, call Animation#pause, and if you want to resume it, call Animation#play. I suggest that you create a ParallelTransition with all of your ScaleTransitions as its children. Then call the above methods on the ParallelTransition in the event handler.
That means that the setup code, like naming the button and creates the animations, goes outside of the event handler.

JavaFX, MouseEvent problems

I am currently making a paint application and have created several tools which are working, but I encountered a problem when trying to create a
"Draw straight line" tool
So I basically draw a line from point A to B and it works, the line is there, however, when I toggle my other tools (Draw circle, rectangle etc) the shapes are being drawn at the same time as the straight-line despite the "Draw Line" button being toggled off.
The code below will allow you to draw straight-lines and you can try toggling on and off the different buttons, the straight line will still be drawn when you drag the cursor across the pane.
Anyone know what kind of mistake I did, and any possible fixes and/or alternate solutions?
(The event handler is there so that I can select the drawn shapes change them later if needed, this code is a stripped-down version of my paint application)
public class DrawLine extends Application {
#Override
public void start(Stage primaryStage) {
ToggleButton lineButton = new ToggleButton ("Draw Line");
ToggleButton Button = new ToggleButton ("Button with no function");
BorderPane pane = new BorderPane();
ToolBar toolbar = new ToolBar();
Scene scene = new Scene(pane, 1200, 800);
pane.setLeft(toolbar);
toolbar.getItems().addAll(lineButton, Button);
// Draw Line
scene.addEventHandler(MouseEvent.MOUSE_CLICKED, me -> {
if(lineButton.isSelected() & me.getButton().equals(MouseButton.PRIMARY) ) {
scene.setOnMousePressed(event -> {
Line line = new Line();
line.setStartX(event.getX());
line.setStartY(event.getY());
scene.setOnMouseDragged(e->{
line.setEndX(e.getX());
line.setEndY(e.getY());
});
pane.getChildren().add(line);
});
}
});
primaryStage.setTitle("Paint App");
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch();
}
}

You only check if the lineButton is selected inside the MOUSE_CLICKED (which is a press-then-release gesture, by the way) handler. Inside this handler you add a MOUSE_PRESSED handler and inside that handler you add a MOUSE_DRAGGED handler. You don't check if the lineButton is selected inside the MOUSE_PRESSED or MOUSE_DRAGGED handlers.
What this all means is that, after the if condition inside the MOUSE_CLICKED handler evaluates to true, you'll have a MOUSE_PRESSED and MOUSE_DRAGGED handler that operate independently of your MOUSE_CLICKED handler. Now, whenever you press any mouse button it will create a Line and add it to the parent. Then the newly added MOUSE_DRAGGED handler will alter the Line.
You're fortunate, in a way, that you're using the onXXX properties instead of using addEventHandler. The properties replace the old EventHandler when set. If that didn't happen (such as with addEventHandler) you'd have many (one more each time) EventHandlers drawing Lines.
You just need to register all the appropriate EventHandlers once and do the logic inside of them.
Here's a small example:
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.ToggleButton;
import javafx.scene.control.ToggleGroup;
import javafx.scene.control.ToolBar;
import javafx.scene.input.MouseButton;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Line;
import javafx.stage.Stage;
public class Main extends Application {
private ToggleGroup toggleGroup;
private ToggleButton lineBtn;
private Group group;
private Line currentLine;
#Override
public void start(Stage primaryStage) {
toggleGroup = new ToggleGroup();
lineBtn = new ToggleButton("Line");
ToggleButton noneBtn = new ToggleButton("None");
toggleGroup.getToggles().addAll(lineBtn, noneBtn);
toggleGroup.selectToggle(noneBtn);
group = new Group();
BorderPane root = new BorderPane(new Pane(group), new ToolBar(lineBtn, noneBtn), null, null, null);
root.getCenter().setOnMousePressed(this::handleMousePressed);
root.getCenter().setOnMouseDragged(this::handleMouseDragged);
root.getCenter().setOnMouseReleased(this::handleMouseReleased);
primaryStage.setScene(new Scene(root, 800, 600));
primaryStage.setTitle("Draw Shape Example");
primaryStage.show();
}
private void handleMousePressed(MouseEvent event) {
if (lineBtn.equals(toggleGroup.getSelectedToggle())
&& event.getButton() == MouseButton.PRIMARY) {
currentLine = new Line(event.getX(), event.getY(), event.getX(), event.getY());
group.getChildren().add(currentLine);
}
}
private void handleMouseDragged(MouseEvent event) {
if (currentLine != null) {
currentLine.setEndX(event.getX());
currentLine.setEndY(event.getY());
}
}
private void handleMouseReleased(MouseEvent event) {
if (currentLine != null
&& currentLine.getStartX() == currentLine.getEndX()
&& currentLine.getStartY() == currentLine.getEndY()) {
// The line has no length, remove it
group.getChildren().remove(currentLine);
}
currentLine = null;
}
}

Wait for and then receive textfield input without freezing GUI

I hope I'm not duplicating a question, but I couldn't find one specifically for my issue.
I'm developing a small math flash card application, using JavaFX to create the GUI. The program should runs as follow:
user selects settings, then presses start button.
gui displays question and textfield for user input.
user inputs answer within X amount of seconds or gui automatically move onto the next question - alternatively, user can move onto next question immediately by pressing next button.
GUI displays score and average.
The problems is getText() from user textfield is processed as soon as start button is pressed, without giving the user a chance to enter an answer. How do I make the program wait for X amount of seconds or for the next button to be clicked before processing the user's answer? Here's my code:
//start button changes view and then runs startTest()
start.setOnAction(e -> {
setLeft(null);
setRight(null);
setCenter(test_container);
running_program_title.setText(getDifficulty().name() + " Test");
buttons_container.getChildren().clear();
buttons_container.getChildren().addAll(next, quit, submit);
startTest();
});
Here is the problem code... at least how I see it.
//startTest method calls askAdd() to ask an addition question
void startTest() {
int asked = 0;
int correct = 0;
while (asked < numberOfQuestions) {
if(askAdd()){
correct++;
asked++;
}
}
boolean askAdd() {
int a = (int) (Math.random() * getMultiplier());
int b = (int) (Math.random() * getMultiplier());
//ask question
question.setText("What is " + a + " + " + b + "?");
//code needed to pause method and wait for user input for X seconds
//retrieve user answer and return if its correct
return answer.getText().equalsIgnoreCase(String.valueOf(a+b));
}
I've tried using Thread.sleep(X) but that freezes the gui for however long I specify and then goes through the addAsk() method and the loop before going to the test screen. (I know because I had the program set up to print the questions and answer input to the console). It shows the last question and that's all.
I didn't include the next button code because I can't get the gui to go to the test page anyway.
Any help on any of the code is appreciated.

This can be achieved by various methods.
PauseTransition is one of the many apt solution present. It waits for X time interval and then performs a Task. It can start, restart, stop at any moment.
Here is an example of how it can used to achieve a similar result.
Complete Code
import javafx.animation.PauseTransition;
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javafx.util.Duration;
import java.util.stream.IntStream;
public class Main extends Application {
int questionIndex = 0;
int noOfQuestions = 10;
#Override
public void start(Stage stage) {
VBox box = new VBox(10);
box.setPadding(new Insets(10));
Scene scene = new Scene(new ScrollPane(box), 500, 200);
ObservableList<String> questions =
FXCollections.observableArrayList("1) Whats your (full) name?",
"2) How old are you?",
"3) Whats your Birthday?",
"4) What starsign does that make it?",
"5) Whats your favourite colour?",
"6) Whats your lucky number?",
"7) Do you have any pets?",
"8) Where are you from?",
"9) How tall are you?",
"10) What shoe size are you?");
ObservableList<String> answers = FXCollections.observableArrayList();
final PauseTransition pt = new PauseTransition(Duration.millis(5000));
Label questionLabel = new Label(questions.get(questionIndex));
Label timerLabel = new Label("Time Remaining : ");
Label time = new Label();
time.setStyle("-fx-text-fill: RED");
TextField answerField = new TextField();
Button nextQuestion = new Button("Next");
pt.currentTimeProperty().addListener(new ChangeListener<Duration>() {
#Override
public void changed(ObservableValue<? extends Duration> observable, Duration oldValue, Duration newValue) {
time.setText(String.valueOf(5 - (int)newValue.toSeconds()));
}
});
box.getChildren().addAll(questionLabel, answerField, new HBox(timerLabel, time), nextQuestion);
nextQuestion.setOnAction( (ActionEvent event) -> {
answers.add(questionIndex, answerField.getText());
//Check if it is the last question
if(questionIndex == noOfQuestions-1) {
pt.stop();
box.getChildren().clear();
IntStream.range(0, noOfQuestions).forEach(i -> {
Label question = new Label("Question : " + questions.get(i));
question.setStyle("-fx-text-fill: RED");
Label answer = new Label("Answer : " + answers.get(i));
answer.setStyle("-fx-text-fill: GREEN");
box.getChildren().addAll(question, answer);
});
}
// All other time
else {
//Set new question
questionLabel.setText(questions.get(++questionIndex));
answerField.clear();
pt.playFromStart();
}
});
pt.setOnFinished( ( ActionEvent event ) -> {
nextQuestion.fire();
});
pt.play();
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}

For the timer you should (IMO) use a Timeline. Here is an example:
public class MultiGame extends Application {
ProgressBar progressBar;
final int allowedTime = 5; //seconds
final DoubleProperty percentOfTimeUsed = new SimpleDoubleProperty(0);
final Timeline timer =
new Timeline(
new KeyFrame(
Duration.ZERO, new KeyValue(percentOfTimeUsed, 0)),
new KeyFrame(
Duration.seconds(allowedTime), new KeyValue(percentOfTimeUsed, 1))
);
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) {
BorderPane root = new BorderPane();
progressBar = new ProgressBar();
progressBar.progressProperty().bindBidirectional(percentOfTimeUsed);
root.setTop(progressBar);
Button answer = new Button("Answer");
answer.setOnAction(ae -> restart());// the on answer handler
Button skip = new Button("Skip");
skip.setOnAction(ae -> restart());// the skip question handler
HBox mainContent = new HBox(15,
new Label("Your Question"), new TextField("The answer"), answer, skip);
root.setCenter(mainContent);
timer.setOnFinished(ae -> restart());// the end of timer handler
primaryStage.setScene(new Scene(root));
primaryStage.show();
restart();
}
void restart() { timer.stop(); timer.playFromStart(); }
void pause() { timer.pause(); }
void resume() { timer.play(); }
}
You just need to capture the text from the input in between the starting of the timeline and the restart method.