Shortcut Keys

    A shortcut is an action that is executed when a key or key combination is pressed within a specific scope in the UI. The scope can be the entire UI or a Window inside it.

    You can add a click shortcut to a button to set it as “default” button; pressing the defined key, typically Enter, in any component in the scope (sub-window or UI) causes a click event for the button to be fired.

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

    Java

    The setClickShortcut() is a shorthand method to create, add, and manage a ClickShortcut, rather than to add it with addShortcutListener().

    Themes offer special button styles to show that a button is special. In the Valo theme, you can use the BUTTON_PRIMARY style name. The result can be seen in Default Button with Click Shortcut.

    Default Button with Click Shortcut

    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.

    The constructor of the FocusShortcut takes the field component as its first parameter, followed by the key code, and an optional list of modifier keys, as listed in .

    Java

    2. TextField name = new TextField("Name (Alt+N)");
    3. name.addShortcutListener(
    4.         new AbstractField.FocusShortcut(name, KeyCode.N,
    5.                                         ModifierKey.ALT));

    See the on-line example.

    You can also specify the shortcut by a shorthand notation, where the shortcut key is indicated with an ampersand ( &).

    Java

    See the .

    Shortcut keys can be defined as actions using the ShortcutAction class. It 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:

    Java

    1. // Have the unmodified Enter key cause an event
    2. Action action_ok = new ShortcutAction("Default key",
    3.         ShortcutAction.KeyCode.ENTER, null);
    5. // Have the C key modified with Alt cause an event
    6. Action action_cancel = new ShortcutAction("Alt+C",
    7.         ShortcutAction.KeyCode.C,
    8.         new int[] { ShortcutAction.ModifierKey.ALT });
    10. Action[] actions = new Action[] {action_cancel, action_ok};
    11. public Action[] getActions(Object target, Object sender) {
    13.         return actions;
    15.     return null;
    16. }

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

    The constructor of ShortcutAction takes a symbolic caption for the action; this is largely irrelevant for shortcut actions in their current implementation, but might be used later if implementors use them both in menus and as shortcut actions. The second parameter is the key code and the third a list of modifier keys, which are listed in Supported Key Codes and Modifier Keys.

    The following example demonstrates the definition of a default button for a user interface, as well as a normal shortcut key, Alt+C for clicking the Cancel button.

    Java

    Notice that the keyboard actions can currently be attached only to Panels and Windows. This can cause problems if you have components that require a certain key. For example, multi-line TextField requires the Enter key. There is currently no way to filter the shortcut actions out while the focus is inside some specific component, so you need to avoid such conflicts.

    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:

    Keys A to Z

    Normal letter keys

    F1 to F12

    Function keys

    Control keys

    NUM0 to NUM9

    Number pad keys

    ARROW_DOWN, ARROW_UP, ARROW_LEFT, ARROW_RIGHT

    Arrow keys

    HOME, END, PAGE_UP, PAGE_DOWN

    Other movement keys

    Modifier keys are defined in ShortcutAction.ModifierKey and are:

    ModifierKey.ALT

    Alt key

    ModifierKey.CTRL

    Ctrl key

    ModifierKey.SHIFT

    Shift key

    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.

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

    The actual possible key combinations vary greatly between browsers, as most browsers have a number of built-in shortcut keys, which can not be used in web applications. For example, Mozilla Firefox allows binding almost any key combination, while Opera does not even allow binding Alt shortcuts. Other browsers are generally in between these two. Also, the operating system can reserve some key combinations and some computer manufacturers define their own system key combinations.