This page includes frequently asked questions for using the event systemA way of sending events to objects in the application based on input, be it keyboard, mouse, touch, or custom input. The Event System consists of a few components that work together to send events. More info
See in Glossary and the input system with UI(User Interface) Allows a user to interact with your application. Unity currently supports three UI systems. More info
See in Glossary Toolkit.
You can do this by two methods:
First method
Add an Event System component in your sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary the same way as you create GameObject-based UI content from the com.unity.uGUI package.
Use the EventSystem.current.IsPointerOverGameObject method, which returns true if the pointer is over UI content from either uGUI or from UI Toolkit.
Use the EventSystem.current.RaycastAll method to see what visual element is under the mouse.
Intersected UI Toolkit Panels are represented in the Event System’s environment through a GameObjectThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary:
PanelRaycaster and PanelEventHandler. Both components have a panel property that returns the IPanel it targets.After you find the panel under the pointer, call the panel.Pick method to find what visual element lies at the pointer’s position.
You must use the RuntimePanelUtils.ScreenToPanel method to transform the pointer’s screen coordinates into panel coordinates.
uGUI’s screen coordinate system uses a bottom-left origin whereas UI Toolkit screen coordinates are expressed from the top-left. Conversion between the two systems requires that you mirror the Y coordinate with yTopLeft = Screen.height - yBottomLeft, and vice versa.
Second method
UIDocument.rootVisualElement property from one UIDocument per distinct PanelSettings used to get the list of all the runtime panels that could be under the pointer, which you can gatherpanel.Pick on each of them successively until you find one that returns a visual element.To remap basic UI actions:
com.unity.uGUI package.Note: The actions mapped to Tab and Shift+Tab inputs can’t be remapped because they’re not exposed through the Event System input modules.
You can configure directional navigation to have other targets other than the default ones.
The following code example allows element A to navigate to elements U, D, L, R when navigating up, down, left, and right respectively:
A.RegisterCallback <NavigationMoveEvent>(e =>
{
switch(e.direction)
{
case NavigationMoveEvent.Direction.Up: U.Focus(); break;
case NavigationMoveEvent.Direction.Down: D.Focus(); break;
case NavigationMoveEvent.Direction.Left: L.Focus(); break;
case NavigationMoveEvent.Direction.Right: R.Focus(); break;
}
e.StopPropagation(); // Prevent further processing of the event
A.focusController.IgnoreEvent(e); // Prevent default navigation
});
Yes. You can use the EventSystem’s StandaloneInputModule or InputSystemUIInputModule fields in the Inspector window to control what input maps to each action. However, since these actions are shared with uGUI input, this also changes the uGUI controls.
To remap UI Toolkit inputs without affecting uGUI controls, disable UI Toolkit’s runtime event handling and send all events manually to panels. To do so, call EventSystem.SetUITookitEventSystemOverride(null, true, false); before the start method of your current EventSystem kicks in, such as the Awake method of the component of your scene. For more information about this uGUI method, see SetUITookitEventSystemOverride.
It’s possible that no element or panel is in focus at a given time, such as when loading your game scene for the first time. In this case, keyboard navigation doesn’t start from a predictable first element. This can be a problem for a game that plays entirely without a mouse.
To allow a predictable navigation behavior from the start, add a C# script and attach it to the same GameObject as the UIDocument responsible for the element that you choose to get the initial focus.
Assume your script is named FirstFocus and your initial focused element is named as first-focused. In your script’s Start() method, add a line to focus that element as the following:
public class FirstFocus : MonoBehaviour
{
void Start()
{
FocusFirstElement();
}
public void FocusFirstElement()
{
GetComponent<UIDocument>().rootVisualElement.
Q<VisualElement>("first-focused").Focus();
}
}
Note: If you disable the UIDocument’s GameObject, all its underlying hierarchy is recreated from scratch. Therefore, you must run your custom FocusFirstElement() method again after you re-enable the GameObject.