Demonstration of an On-Screen-Keyboard with JavaFx. http://stackoverflow.com/questions/42286960/prevent-javafx-scene-from-gaining-focus-onscreen-keyboard

OskFx.java

package com.isp.stackoverflow;

import static java.util.stream.IntStream.concat;
import static java.util.stream.IntStream.rangeClosed;
import static javafx.geometry.Orientation.HORIZONTAL;

import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.Robot;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

import javafx.application.Platform;
import javafx.embed.swing.JFXPanel;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.FlowPane;

/**
 * @author okr
 * @date 17.02.2017
 *
 */
public class OskFx
{
  /**
   * Number of rows of keyboard keys.
   */
  private static final int    PREF_ROW_COUNT = 3;
  /**
   * Some height for the keyboard. Needs refac for hidpi.
   */
  private static final int OSK_HEIGHT     = 300;

  /**
   * Spacing between keyboard keys.
   */
  private static final double PADDING = 16.0;

  private static Robot MARVIN;


  private static void initAndShowGUI()
  {
    try
    {
      MARVIN = new Robot();
    }
    catch ( final AWTException __ )
    {
      // TODO(okr): Explain the why!
    }

    // This method is invoked on Swing thread
    final JFrame frame = new JFrame( "FX" );
    frame.setUndecorated( true );
    frame.setFocusableWindowState( false );
    frame.setFocusable( false );
    frame.enableInputMethods( false );
    frame.setAlwaysOnTop( true );


    final Dimension screenSize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();

    frame.setSize( (int) screenSize.getWidth(), OSK_HEIGHT );
    frame.setLocation( 0, (int) (screenSize.getHeight() - OSK_HEIGHT) );

    final JFXPanel fxPanel = new JFXPanel();
    frame.add( fxPanel );
    frame.setVisible( true );

    Platform.runLater( () -> fxPanel.setScene( initFxScene() ) );
  }

  private static Scene initFxScene()
  {
    final FlowPane root = new FlowPane( HORIZONTAL, PADDING / 2, PADDING / 2 );
    root.setPadding( new Insets( PADDING ) );
    final Scene scene = new Scene( root );

    //The constant values for characters from 0 to 9 and A to Z in KeyEvent are incidentally the ASCII values.
    concat( rangeClosed( '0', '9' ), rangeClosed( 'A', 'Z' ) )
        .forEach( character ->
        {
          //This cast is safe, as long we iterate over only ASCII values...
          final Button keyboardButton = new Button( Character.toString( (char) character ) );

          keyboardButton.setOnMousePressed( __ -> MARVIN.keyPress( character ) );

          keyboardButton.setPrefWidth( OSK_HEIGHT / PREF_ROW_COUNT - PADDING );
          keyboardButton.setPrefHeight( OSK_HEIGHT / PREF_ROW_COUNT - PADDING );
          root.getChildren().add( keyboardButton );
        } );

    return scene;
  }

  /**
   * @param args ignored.
   */
  public static void main( final String[] args )
  {
    SwingUtilities.invokeLater( () -> initAndShowGUI() );
  }
}