ImageViews MouseEvent not working on a javaFX application

Question

I have a javaFX application with ImageView, what i need to do is to be able to drag an ImageView, drop it on an another ImageView and replace them both by an another single ImageView. My problem is that the event i set, work well for some ImageView, but not for others.

Example : example, i can drag and drop the red arrow image on the green, but not the green on the red, I can't drop the green one on the others ( the two axes and the wood )

I'm loading the GUI from a FXML file, here is my controller class :

public class PartieGUI {

    @FXML
    Pane gamePane;

    static ArrayList elements = new ArrayList<>() {{
        add( new ElementGUI( "OAK_LOG" ) );
        add( new ElementGUI( "STONE_AXE" ) );
        add( new ElementGUI( "IRON_AXE" ) );
        add( new ElementGUI( "DIAMOND_ORE" ) );
        add( new ElementGUI( "DIAMOND_PICKAXE" ) );
    }};

    private static final int HEIGHT = 100;
    private static final int WIDTH = 100;

    @FXML
    public void initialize() {

        gamePane.setOnDragOver( event -> { // for moving the dragged ImageView
            if( event.getGestureSource() instanceof ImageView ) {
                ImageView draggedImageView = ( (ImageView) event.getGestureSource() );
                draggedImageView.setX( event.getX() - WIDTH / 2 );
                draggedImageView.setY( event.getY() - HEIGHT / 2 );
            }
        } );

        for( ElementGUI elementGUI : elements ) {
            setEvents( elementGUI );
            gamePane.getChildren().add( elementGUI.imageView );
        }

    }

    private void setEvents( ElementGUI elementGUI ) {
        ImageView imageView = elementGUI.imageView;

        imageView.setOnDragDetected( event -> {
            Dragboard db = imageView.startDragAndDrop( TransferMode.ANY );
            ClipboardContent content = new ClipboardContent();
            content.putImage( imageView.getImage() );
            content.putString( elementGUI.ID ); ;
            db.setContent( content );
        } );

        imageView.setOnDragOver( event -> {
            Dragboard db = event.getDragboard();
            if( db.hasImage() && !db.getString().equals( elementGUI.ID ) 
                    && event.getGestureSource() instanceof ImageView ) {
                ImageView draggedImageView = ( (ImageView) event.getGestureSource() );
                if( imageView != draggedImageView ) { // prevent that  it drag and drop on itself
                    System.out.println( "dragging over" );
                    event.acceptTransferModes( TransferMode.ANY );
                }
            }
        } );

        imageView.setOnDragDropped( event -> {
            Dragboard db = event.getDragboard();
            if( db.hasImage() && !db.getString().equals( elementGUI.ID ) 
                    && event.getGestureSource() instanceof ImageView ) {
                ImageView draggedImageView = ( (ImageView) event.getGestureSource() );
                if( imageView == draggedImageView )
                    return;
                elements.removeIf( element -> element.imageView == draggedImageView );
                elements.removeIf( element -> element.imageView == imageView );
                ElementGUI newElement = new ElementGUI( "DIAMOND", imageView.getX(), imageView.getY() );
                setEvents( newElement );
                elements.add( newElement );
                refreshGamePane();
            }
        } );
    }

    public void refreshGamePane() {
        gamePane.getChildren().clear();
        for( ElementGUI elementGUI : elements )
            gamePane.getChildren().add( elementGUI.imageView );
    }

    private static class ElementGUI {

        protected String ID;
        protected ImageView imageView;

        ElementGUI( String ID ) {
            this.ID = ID;
            this.imageView = new ImageView(
                      new Image( PartieGUI.class.getResource( "/Textures/" + ID + ".png" )
                    .toString(), 100, 100, false, false )
            );
            this.imageView.setX( new Random().nextInt( 500 ) ); // tmp
            this.imageView.setY( new Random().nextInt( 200 ) );
        }

        public ElementGUI( String ID, double x, double y ) {
            this.ID = ID;
            this.imageView = new ImageView(
                      new Image( PartieGUI.class.getResource( "/Textures/" + ID + ".png" )
                    .toString(), 100, 100, false , false )
            );
            this.imageView.setX( x );
            this.imageView.setY( y );
        }

    }

}

My application class, followed by the FXML file, if you want to test ( don't ask why the Pane is in a BorderPane, i need it to be like this )

public class Executor extends Application {
    
    public static void main( String[] args ) {
        launch();
    }

    @Override
    public void start( Stage primaryStage ) throws IOException {
        primaryStage.setScene( new Scene( FXMLLoader.load( 
                Executor.class.getResource( "/GUIs/PartieGUI.fxml" ) 
        ) ) ); // load FXML file
        primaryStage.show();
    }
}

Since someone said that all this information is not enought for "minimal reproducible example", here are the images i used : https://imgur.com/a/sb3nmKC

Also the build.gradle ( i have JDK 11 who don't have javaFX libraries integrated, so i must use gradle) :

plugins {
    id 'java'
    id 'application'
    id 'org.openjfx.javafxplugin' version '0.0.9'
    id "com.github.johnrengelman.shadow" version "6.1.0"
}

repositories {
    mavenCentral()
}

mainClassName = 'Executor'
archivesBaseName = 'MoriaMines'

shadowJar {
    archiveFileName = archivesBaseName + ".jar"
    manifest {
        attributes 'Main-Class': mainClassName
    }
}

javafx {
    version = "15.0.1"
    modules = ['javafx.controls', 'javafx.fxml']
}

arbi12321 · Accepted Answer

Answer by kleopatra : calling imageView.toBack(); in setOnDragDetected fixed it

ImageViews MouseEvent not working on a javaFX application

Answers (1)

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