Question

Editable JavaFx ComboBoxes works well but the left-arrow key is interpreted as Shift-TAB.

As you can see the focus is set to the ComboBox and the insertion point is in the middle of its field. Pressing the left arrow key move the focus to the first control, the TextField on the left of the image when pressing right arrow key move the insertion one character right as expected like in any TextField.

How can I catch events to reproduce the behavior of a TextField in an editable ComboBox?

I’ve tried to catch key events via ComboBox.setOnKeyPressed() and event.consume() but without success.

Here is a minimal program to reproduce this unexpected behavior:

@Override
public void start( Stage stage ) {
   stage.setTitle( "Editable ComboBox and left-arrow key" );

   ComboBox<String> cmbBx = new ComboBox<>();
   cmbBx.getItems().addAll( "A", "B", "C", "D", "E" );
   cmbBx.setMinWidth( 150 );
   cmbBx.setEditable( true );
   cmbBx.setOnKeyPressed( new EventHandler<KeyEvent>(){
      @Override public void handle( KeyEvent event ) {
         System.err.println( event );
         event.consume(); }}); // Consuming left arrow key is inoperant

   GridPane grid = new GridPane();
   grid.setVgap( 4 );
   grid.setHgap( 4 );
   grid.setPadding( new Insets( 4, 4, 4, 4 ));

   grid.add( new Label( "TextField:" ), 0, 0 );
   grid.add( new TextField()          , 1, 0 );
   grid.add( new Label( "ComboBox:" ) , 2, 0 );
   grid.add( cmbBx                    , 3, 0 );

   stage.setScene( new Scene( grid ));
   stage.show();
}

Answer 1

The answer is around key bindings like shown in this SO post “key bindings in javafx”.

This code catch the LEFT event:

  cmbBx.addEventFilter( KeyEvent.ANY, new EventHandler< KeyEvent >() {
     @Override public void handle(KeyEvent event ) {
        if( event.getCode() == KeyCode.LEFT ) {
           event.consume(); }}});

And that’s all, but I’m surprised because the left arrow key move the insertion point as expected, only the undesired behavior is removed. Why?