12.6. Shortcut Keys

You can add or set a click shortcut to a button to set it as "default" button; pressing the defined key, typically Enter, in any component in the window causes a click event for the button.

You can define a click shortcut with the setClickShortcut() shorthand method:

// Have an OK button and set it as the default button
Button ok = new Button("OK");
ok.setClickShortcut(KeyCode.ENTER);
ok.addStyleName("primary");

You can define a shortcut key that sets the focus to a field component (any component that inherits AbstractField) by adding a FocusShortcut as a shortcut listener to the field.

// A field with Alt+N bound to it
TextField name = new TextField("Name (Alt+N)");
name.addShortcutListener(
        new AbstractField.FocusShortcut(name, KeyCode.N,
                                        ModifierKey.ALT));
layout.addComponent(name);

// A field with Alt+A bound to it
TextField address = new TextField("Address (Alt+A)");
address.addShortcutListener(
        new AbstractField.FocusShortcut(address, KeyCode.A,
                                        ModifierKey.ALT));
layout.addComponent(address);

Shortcut keys can be defined as actions using the ShortcutAction class. ShortcutAction extends the generic Action class that is used for example in Tree and Table for context menus. Currently, the only classes that accept ShortcutActions are Window and Panel.

To handle key presses, you need to define an action handler by implementing the Handler interface. The interface has two methods that you need to implement: getActions() and handleAction().

The getActions() method must return an array of Action objects for the component, specified with the second parameter for the method, the sender of an action. For a keyboard shortcut, you use a ShortcutAction. The implementation of the method could be following:

// Have the unmodified Enter key cause an event
Action action_ok = new ShortcutAction("Default key",
        ShortcutAction.KeyCode.ENTER, null);

// Have the C key modified with Alt cause an event
Action action_cancel = new ShortcutAction("Alt+C",
        ShortcutAction.KeyCode.C,
        new int[] { ShortcutAction.ModifierKey.ALT });

Action[] actions = new Action[] {action_cancel, action_ok};

public Action[] getActions(Object target, Object sender) {
    if (sender == myPanel)
        return actions;

    return null;
}

The returned Action array may be static or you can create it dynamically for different senders according to your needs.

The shortcut key definitions require a key code to identify the pressed key and modifier keys, such as Shift, Alt, or Ctrl, to specify a key combination.

The key codes are defined in the ShortcutAction.KeyCode interface and are:

Modifier keys are defined in ShortcutAction.ModifierKey and are:

All constructors and methods accepting modifier keys take them as a variable argument list following the key code, separated with commas. For example, the following defines a Ctrl+Shift+N key combination for a shortcut.

TextField name = new TextField("Name (Ctrl+Shift+N)");
name.addShortcutListener(
        new AbstractField.FocusShortcut(name, KeyCode.N,
                                        ModifierKey.CTRL,
                                        ModifierKey.SHIFT));