I am using the following code

libraryCombo.setOnKeyPressed(new EventHandler<KeyEvent>(){
            @Override
            public void handle(KeyEvent t) {
                if (t.getCode() == KeyCode.ENTER) {
                    btn_OkAction.requestFocus();
                    makeOKAction(null);
                }
            }
        });

Where libraryCombo is the object of ComboBox

But this code is not working for Enter Key but for Other Keys it os working properly.

I also tried this but has the same behavior

libraryCombo.getEditor().addEventHandler(KeyEvent.KEY_PRESSED, new EventHandler<KeyEvent>(){
            @Override
            public void handle(KeyEvent t) {
                if (t.getCode() == KeyCode.ENTER) {
                    btn_OkAction.requestFocus();
                    makeOKAction(null);
                }
            }
        });

Please have a look.

Thanks