ZK Developer's Reference/UI Patterns/Keystroke Handling

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

ENTER and ESC

To handle ENTER key pressing, you can to listen to the event:

• onOK (notice O and K are both in upper case).

To handle ESC key pressing, you can to listen to the event:

• onCancel

For example:

    <grid id="form" apply="org.zkoss.reference.developer.uipattern.KeystrokeComposer">
        <rows>
            <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>
        </rows>
    </grid>

Then, you could implement a composer as follows.

package org.zkoss.reference.developer.uipattern;

import org.zkoss.zk.ui.Component;
import org.zkoss.zk.ui.select.SelectorComposer;
import org.zkoss.zk.ui.select.annotation.*;
import org.zkoss.zul.Textbox;

public class KeystrokeComposer extends SelectorComposer<Component> {

    @Wire
    private Textbox username;
    @Wire
    private Textbox password;

    @Listen("onOK = #form")
    public void onOK() {
        //handle login
        System.out.println("ok");
    }

    @Listen("onCancel = #form")
    public void onCancel() {
        username.setValue("");
        password.setValue("");
    }
}

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 will happen.

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 that matches the combination, 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 ancestors. 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,

<vbox ctrlKeys="@c^a#f10^#f3" onCtrlKey="doSomething(event.getKeyCode())">
    <textbox/>
    <datebox/>
</vbox>

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

Allowed Control Keys

Key	Syntax	Description
Control	^[?]	[?] can be a~z, 0~9, #[?], e.g. ^k represents Ctrl+k
Alt	@[?]	[?] can be a~z, 0~9, #[?], e.g. @k represents Alt+k
Shift	$[?]	[?] can be #[?]. Note: $a ~ $z are not supported. e.g. $#down represents Shift+↓
Mac command(⌘)	%[?]	Since 8.5.0 [?] can be a~z, 0~9, #[?]. e.g. %k represents command+k
Navigation key	#[?]	the supported value of [?] are listed below:
Home	#home
End	#end
Insert	#ins
Delete	#del
←	#left
→	#right
↑	#up
↓	#down
PgUp	#pgup
PgDn	#pgdn
Backspace	#bak
function key (F1, F2,... F12)	#f1, #f2, ... #f12
Tab	#tab	Since 9.5.1

Document-level Keystrokes

Since 5.0.6

When you set the library property org.zkoss.zk.ui.invokeFirstRootForAfterKeyDown.enabled to true. If there is no widget gaining a focus when an end-user presses a keystroke, ZK can forward a key event to the first root component. For example, when visiting the following page, the div component will receive the onOK event.

<div onOK="doSomething(event)" ctrlKeys="^K" onCtrlKey="doSomething(event)" >
press enter key or ctrl+k.
<zscript><![CDATA[
public void doSomething(KeyEvent e){
	Clients.showNotification(e.getKeyCode()+"");
}
]]></zscript>
</div>

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

Nested Components

Keystrokes are propagated up from the widget gaining the focus to the first ancestor widget that handles the keystroke. For example,

<div onOK="doFirst()">
   <textbox id="t1"/>
   <div onOK="doSecond()">
       <textbox id="t2"/>
   </div>
</div>

Then, doSecond() is called if t2 is the current focus, and doFirst() is called if t1 has the focus.

Key handling and onChange event

When a onChange listener alone is registered on a component, onChange will be triggered by blur events exclusively.

However, some key events will cause a check for change value and will fire a change event if necessary.

These key events are: onOK onCancel onCtrlkeys. If a listener for any of these events is registered and triggers, an onChange event calculation will be triggered, and an onChange event will be fired if the value of the control have changed.

Version History

Version	Date	Content
5.0.6	January 2011	Document-level keystroke handling was introduced.
9.5.1	November 2020	Add Tab key support