Keystroke Handling

From Documentation

Keystroke Handling

Keystroke handling is generic. Any component inherited from XulElement can handle the key event in the same way.


To handle ENTER, you could listen to the onOK event (notice O and K are both in upper case). To handle ESC, you could listen to the onCancel event. For example,

<grid id="form" apply="foo.Login">
        <row>Username: <textbox id="username"/></row>
        <row>Password: <textbox id="password" type="password"/></row>
        <row><button label="Login" forward="form.onOK"/><button label="Reset" forward="form.onCancel"/></row>

Then, you could implement a composer as follows.

package foo;
import org.zkoss.zul.*;
public class Login extends org.zkoss.zk.ui.util.GenericForwardComposer {
    Textbox username;
    Textbox password;
    public void onOK() {
        //handle login
    public void onCancel() {

Notice that the onOK and onCancel events are sent to the nearest ancestor of the component that has the focus. In other words, if you press ENTER in a textbox, then ZK will look up the textbox, its parent, its parent's parent and so on to see if any of them has been registered a listener for onOK. If found, the event is sent to it. If not found, nothing happens.

Also notice that, if a button gains the focus, ENTER will be intercepted by the browser and interpreted as pressed. For example, if you move the focus to the Reset button and press ENTER, you will receive onCancel rather than onOK (since onClick will be fired and it is converted to onCancel because of the forward attribute specified).

Control Keys

To handle the control keys, you have to specify the keystrokes you want to handle with XulElement.setCtrlKeys(String). Then, if any child component gains the focus and the user presses a keystroke matches the combination, then the onCtrlKey will be sent to the component with an instance of KeyEvent.

Like ENTER and ESC, you could specify the listener and the ctrlKeys property in one of the ancestor. ZK will search the component having the focus, its parent, its parent's parent and so on to find if any of them specifies the ctrlKeys property that matches the keystroke.

For example,

<vlayout ctrlKeys="@c^a#f10^#f3" onCtrlKey="doSomething(event.getKeyCode())">

As shown, you could use KeyEvent.getKeyCode() to know which key was pressed.

Allowed Control Keys

The control key, i.e., Ctrl+k, where k can be a~z, 0~9, #n and ~n.
The alt key, i.e., Alt+k, where k can be a~z, 0~9, #n and ~n.
The shift key, i.e., Shift+k, can k could be #n and ~n.
A special key as follows.

A function key. #f1, #f2, ... #f12 for F1, F2,... F12.

Document-level Keystrokes

If there is no widget gaining a focus when the end user presses a keystroke, ZK will try to locate the first root component and then forward the event to it. For example, when visiting the following page, the div component will receive the onOK event.

<div onOK="doSomething()">

In other words, doSomething() will be called if the user presses ENTER, even though no widget ever gains the focus.

Version History

Last Update : 2011/01/28

Version Date Content
5.0.6 January 2011 Document-level keystroke handling was introduced.

Last Update : 2011/01/28

Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.