vaadin-framework/documentation/advanced/advanced-shortcuts.asciidoc

---
title: Shortcut Keys
order: 5
layout: page
---

[[advanced.shortcuts]]
= Shortcut Keys

Vaadin provides simple ways to define shortcut keys for field components, as
well as to a default button, and a lower-level generic shortcut API based on
actions.

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
[classname]#UI# or a [classname]#Window# inside it.

[[advanced.shortcuts.defaultbutton]]
== Shortcut Keys for Default Buttons

You can add a __click shortcut__ to a button to set it as "default" button;
pressing the defined key, typically kbd:[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 [methodname]#setClickShortcut()#
shorthand method:


[source, java]
----
// Have an OK button and set it as the default button
Button ok = new Button("OK");
ok.setClickShortcut(KeyCode.ENTER);
ok.addStyleName(ValoTheme.BUTTON_PRIMARY);
----

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

Themes offer special button styles to show that a button is special. In the Valo
theme, you can use the [literal]#++BUTTON_PRIMARY++# style name. The result can
be seen in <<figure.advanced.shortcuts.defaultbutton>>.

[[figure.advanced.shortcuts.defaultbutton]]
.Default Button with Click Shortcut
image::img/shortcut-defaultbutton.png[]


[[advanced.shortcuts.focus]]
== Field Focus Shortcuts

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

The constructor of the [classname]#FocusShortcut# takes the field component as
its first parameter, followed by the key code, and an optional list of modifier
keys, as listed in <<advanced.shortcuts.keycodes>>.


[source, java]
----
// 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);
----

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


[source, java]
----
// A field with Alt+A bound to it, using shorthand notation
TextField address = new TextField("Address (Alt+A)");
address.addShortcutListener(
        new AbstractField.FocusShortcut(address, "&Address"));
----

This is especially useful for internationalization, so that you can determine
the shortcut key from the localized string.


[[advanced.shortcuts.actions]]
== Generic Shortcut Actions

Shortcut keys can be defined as __actions__ using the
[classname]#ShortcutAction# class. It extends the generic [classname]#Action#
class that is used for example in [classname]#Tree# and [classname]#Table# for
context menus. Currently, the only classes that accept
[classname]##ShortcutAction##s are [classname]#Window# and [classname]#Panel#.

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

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


[source, java]
----
// 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 [classname]#Action# array may be static or you can create it
dynamically for different senders according to your needs.

The constructor of [classname]#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 <<advanced.shortcuts.keycodes>>.

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


[source, java]
----
public class DefaultButtonExample extends CustomComponent
                                  implements Handler {
    // Define and create user interface components
    Panel panel = new Panel("Login");
    FormLayout formlayout = new FormLayout();
    TextField username = new TextField("Username");
    TextField password = new TextField("Password");
    HorizontalLayout buttons = new HorizontalLayout();

    // Create buttons and define their listener methods.
    Button ok = new Button("OK", event -> okHandler());
    Button cancel = new Button("Cancel", event -> cancelHandler());

    // 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 });

    public DefaultButtonExample() {
        // Set up the user interface
        setCompositionRoot(panel);
        panel.addComponent(formlayout);
        formlayout.addComponent(username);
        formlayout.addComponent(password);
        formlayout.addComponent(buttons);
        buttons.addComponent(ok);
        buttons.addComponent(cancel);

        // Set focus to username
        username.focus();

        // Set this object as the action handler
        panel.addActionHandler(this);
    }

    /**
     * Retrieve actions for a specific component. This method
     * will be called for each object that has a handler; in
     * this example just for login panel. The returned action
     * list might as well be static list.
     */
    public Action[] getActions(Object target, Object sender) {
        System.out.println("getActions()");
        return new Action[] { action_ok, action_cancel };
    }

    /**
     * Handle actions received from keyboard. This simply directs
     * the actions to the same listener methods that are called
     * with ButtonClick events.
     */
    public void handleAction(Action action, Object sender,
                             Object target) {
        if (action == action_ok) {
            okHandler();
        }
        if (action == action_cancel) {
            cancelHandler();
        }
    }

    public void okHandler() {
        // Do something: report the click
        formlayout.addComponent(new Label("OK clicked. "
                + "User=" + username.getValue() + ", password="
                + password.getValue()));
    }

    public void cancelHandler() {
        // Do something: report the click
        formlayout.addComponent(new Label("Cancel clicked. User="
                + username.getValue() + ", password="
                + password.getValue()));
    }
}
----

Notice that the keyboard actions can currently be attached only to
[classname]##Panel##s and [classname]##Window##s. This can cause problems if you
have components that require a certain key. For example, multi-line
[classname]#TextField# requires the kbd:[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.


[[advanced.shortcuts.keycodes]]
== Supported Key Codes and Modifier Keys

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

The key codes are defined in the [classname]#ShortcutAction.KeyCode# interface
and are:

Keys [parameter]#A# to [parameter]#Z#:: Normal letter keys
[parameter]#F1# to [parameter]#F12#:: Function keys

[parameter]#BACKSPACE#, [parameter]#DELETE#, [parameter]#ENTER#, [parameter]#ESCAPE#, [parameter]#INSERT#, [parameter]#TAB#:: Control keys

[parameter]#NUM0# to [parameter]#NUM9#:: Number pad keys

[parameter]#ARROW_DOWN#, [parameter]#ARROW_UP#, [parameter]#ARROW_LEFT#, [parameter]#ARROW_RIGHT#:: Arrow keys

[parameter]#HOME#, [parameter]#END#, [parameter]#PAGE_UP#, [parameter]#PAGE_DOWN#:: Other movement keys



Modifier keys are defined in [classname]#ShortcutAction.ModifierKey# and are:

[parameter]#ModifierKey.ALT#:: kbd:[Alt] key
[parameter]#ModifierKey.CTRL#:: kbd:[Ctrl] key
[parameter]#ModifierKey.SHIFT#:: kbd:[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 kbd:[Ctrl+Shift+N] key combination for a shortcut.


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

=== Supported Key Combinations

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 kbd:[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.