Keyboard events

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 shortcut 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.

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. For more information on the event, see the UI Toolkit API.

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.

예제

The following code example prints a message to the console when the user presses a key in a TextField. This code sample highlights the event firing of both KeyUpEvent and KeyDownEvent.

To see the example in action, do the following:

1. Create a GameObject with a valid UIDocument.
2. Under Assets > Scripts, create a C# script called KeyboardEventTest.
3. Copy the example into the C# script.
4. Attach the KeyboardEventTest script to the GameObject with the UIDocument
5. Enter Play mode and type in the TextField.

using UnityEngine;
using UnityEngine.UIElements;

// Add KeyboardEventTest to a GameObject with a valid UIDocument.
// When the user presses a key, it will print the keyboard event properties to the console.
[RequireComponent(typeof(UIDocument))]
public class KeyboardEventTest : MonoBehaviour
{
    void OnEnable()
    {
        var root = GetComponent<UIDocument>().rootVisualElement;
        root.Add(new Label("Press any key to see the keyDown properties"));
        root.Add(new TextField());
        root.Q<TextField>().Focus();
        root.RegisterCallback<KeyDownEvent>(OnKeyDown, TrickleDown.TrickleDown);
        root.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);
    }
}