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Keyboard events

Events that occur when the user presses a key.
Read time 4 minutesLast updated a month ago
Keyboard events occur when you press or release keys on the keyboard. Each event includes information about the modifier, text character, and related key code for the event.
Many standard controls use the 
KeyDownEvent
to encode shortcuts or accessibility behaviors. The following examples all use keyboard events:
  • The 
    Toggle
    and 
    Button
    classes listen for 
    Enter
    and 
    Spacebar
    key presses as replacement actions for mouse clicks.
  • The ScrollView and Slider controls use directional arrow key presses to modulate their values.
  • The TextField control looks at both the 
    keyCode
    property and the character property to execute special actions or to accept text.
The base class for all keyboard events is KeyboardEventBase.
The following table describes the keyboard events and their propagation phases:

Event

Description

Trickles down

Bubbles up

Cancellable

KeyDownEventSent when the user presses a key on the keyboard.YesYesYes
KeyUpEventSent when the user releases a key on the keyboard.YesYesYes

Unique properties

keyCode
: The 
keyCode
property returns a character key that corresponds directly to a physical key on an input device, such as a keyboard or joystick. The difference between the 
character
property and the 
keyCode
property is that 
keyCode
represents a physical key, while 
character
represents the entry of a specific character. For example, both 
a
and 
A
return 
keyCode=KeyCode.A
during a 
keyDownEvent
.
character
: The 
character
property returns a character code during a 
keyDownEvent
.
modifiers
: The 
modifiers
property returns which modifier key is held down. Some examples of modifier keys are the 
Shift
, 
Ctrl
, or 
Alt
keys.
For more information, see the Modifier keys section of the MDN documentation.

Event List

The following list provides the name, description, and target of each event in the event family.
By default, a visual element doesn't receive keyboard events. Only elements that are focusable and currently in focus are targeted for keyboard events. This is because keyboard events trickle down and bubble up, allowing parent elements to receive them as well.
In summary, to begin receiving keyboard events, you must mark the element as 
focusable=true
and explicitly give it focus using 
element.Focus()
. This ensures that the element is eligible to receive keyboard events.

KeyDownEvent

A KeyDownEvent is sent each time you press a key on the keyboard. The key pressed contains the 
keyCode
property for that event. If that key press has text input associated with it, additional events are sent for each character of text input. The 
character
property contains the character for those events.
When you press and release 
a
, UI Toolkit sends the following events:
KeyDownEvent { keyCode=KeyCode.A }KeyDownEvent { character=’a’ }KeyUpEvent { keyCode=KeyCode.A }
When you press and release 
Ctrl+a
, UI Toolkit sends the following events:
KeyDownEvent { keyCode=KeyCode.LeftControl, modifiers=EventModifiers.Control }KeyDownEvent { keyCode=KeyCode.A, modifiers=EventModifiers.Control }KeyUpEvent { keyCode=KeyCode.A, modifiers=EventModifiers.Control }KeyUpEvent { keyCode=KeyCode.LeftControl }
target
: The visual element that has focus. If no element has focus, the root visual element of the panel.

KeyUpEvent

A KeyUpEvent is sent when you release a key on the keyboard. The keyCode property for that event contains the key being released. 
KeyDownEvent
has additional events sent when a keystroke has an associated text input.
When you press and release 
a
, UI Toolkit sends the following events:
KeyDownEvent { keyCode=KeyCode.A }KeyDownEvent { character=’a’ }KeyUpEvent { keyCode=KeyCode.A }
When you press and release 
Ctrl+a
, UI Toolkit sends the following events:
KeyDownEvent { keyCode=KeyCode.LeftControl, modifiers=EventModifiers.Control }KeyDownEvent { keyCode=KeyCode.A, modifiers=EventModifiers.Control }KeyUpEvent { keyCode=KeyCode.A, modifiers=EventModifiers.Control }KeyUpEvent { keyCode=KeyCode.LeftControl }
target
: The visual element that has focus. If no element has focus, the root visual element of the panel.

Examples

The following code example prints a message to the console when you press a key in a TextField. This code sample highlights the event firing of both 
KeyUpEvent
and 
KeyDownEvent
.
  1. Create a Unity project with any template.
  2. In the SampleScene, select
    GameObject

    ?

    > UI Toolkit > Panel Renderer.
  3. Create a C# script named 
    KeyboardEventTest.cs
    with the following contents:
    using UnityEngine;using UnityEngine.UIElements;// Add KeyboardEventTest to a GameObject with a valid PanelRenderer.// When the user presses a key, it will print the keyboard event properties to the console.[RequireComponent(typeof(PanelRenderer))]public class KeyboardEventTest : MonoBehaviour{    void OnEnable()    {        GetComponent<PanelRenderer>().RegisterUIReloadCallback(OnUIReload);    }    void OnDisable()    {        GetComponent<PanelRenderer>().UnregisterUIReloadCallback(OnUIReload);    }    private void OnUIReload(PanelRenderer panelRenderer, VisualElement rootElement, int version)    {        rootElement.Add(new Label("Press any key to see the keyDown properties"));        rootElement.Add(new TextField());        rootElement.Q<TextField>().Focus();        rootElement.RegisterCallback<KeyDownEvent>(OnKeyDown, TrickleDown.TrickleDown);        rootElement.RegisterCallback<KeyUpEvent>(OnKeyUp, TrickleDown.TrickleDown);    }    void OnKeyDown(KeyDownEvent ev)    {        Debug.Log("KeyDown:" + ev.keyCode);        Debug.Log("KeyDown:" + ev.character);        Debug.Log("KeyDown:" + ev.modifiers);    }    void OnKeyUp(KeyUpEvent ev)    {        Debug.Log("KeyUp:" + ev.keyCode);        Debug.Log("KeyUp:" + ev.character);        Debug.Log("KeyUp:" + ev.modifiers);    }}
  4. Select the PanelRenderer GameObject in the Hierarchy window.
  5. Drag 
    KeyboardEventTest.cs
    to Add Component in the Inspector window.
  6. Enter Play mode and type in the TextField.

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