Touch support

Touch support is divided into:

Note: You should not use Touchscreen for polling. If you want to read out touches similar to UnityEngine.Input.touches, see EnhancedTouch. If you read out touch state from Touchscreen directly inside of the Update or FixedUpdate methods, your app will miss changes in touch state.

Touch input is supported on Android, iOS, Windows, and the Universal Windows Platform (UWP).

Touchscreen Device

At the lowest level, a touch screen is represented by an InputSystem.Touchscreen Device which captures the touch screen's raw state. Touch screens are based on the Pointer layout.

To query the touch screen that was last used or last added, use Touchscreen.current.

Controls

Additional to the Controls inherited from Pointer, touch screen Devices implement the following Controls:

Control Type Description
primaryTouch TouchControl A touch Control that represents the primary touch of the screen. The primary touch drives the Pointer representation on the Device.
touches ReadOnlyArray<TouchControl> An array of touch Controls that represents all the touches on the Device.

A touch screen Device consists of multiple TouchControls. Each of these represents a potential finger touching the Device. The primaryTouch Control represents the touch which is currently driving the Pointer representation, and which should be used to interact with the UI. This is usually the first finger that touches the screen.

primaryTouch is always identical to one of the entries in the touches array. The touches array contains all the touches that the system can track. This array has a fixed size, regardless of how many touches are currently active. If you need an API that only represents active touches, see the higher-level EnhancedTouch.Touch class.

Each TouchControl on the Device, including primaryTouch, is made up of the following child Controls:

Control Type Description
position Vector2Control Absolute position on the touch surface.
delta Vector2Control The difference in position since the last frame.
startPosition Vector2Control The position where the finger first touched the surface.
startTime DoubleControl The time when the finger first touched the surface.
press ButtonControl Whether the finger is pressed down.
pressure AxisControl Normalized pressure with which the finger is currently pressed while in contact with the pointer surface.
radius Vector2Control The size of the area where the finger touches the surface.
touchId IntegerControl The ID of the touch. This allows you to distinguish individual touches.
phase TouchPhaseControl A Control that reports the current TouchPhase of the touch.
tap ButtonControl A button Control that reports whether the OS recognizes a tap gesture from this touch.
tapCount IntegerControl Reports the number of consecutive tap reports from the OS. You can use this to detect double- and multi-tap gestures.

Using touch with Actions

You can use touch input with Actions, like any other Pointer Device. To do this, bind to the pointer Controls, like <Pointer>/press or <Pointer>/delta. This gets input from the primary touch, and any other non-touch pointer Devices.

However, if you want to get input from multiple touches in your Action, you can bind to individual touches by using Bindings like <Touchscreen>/touch3/press. Alternatively, use a wildcard Binding to bind one Action to all touches: <Touchscreen>/touch*/press.

If you bind a single Action to input from multiple touches, you should set the Action type to pass-through so the Action gets callbacks for each touch, instead of just one.

EnhancedTouch.Touch Class

The EnhancedTouch.Touch class provides a polling API for touches similar to UnityEngine.Input.touches. You can use it to query touches on a frame-by-frame basis.

Because the API comes with a certain overhead due to having to record touches as they happen, you must explicitly enable it. To do this, call EnhancedTouchSupport.Enable():

    using UnityEngine.InputSystem.EnhancedTouch;
    // ...
    // Can be called from MonoBehaviour.Awake(), for example. Also from any
    // RuntimeInitializeOnLoadMethod code.
    EnhancedTouchSupport.Enable();

Note: Touchscreen does not require EnhancedTouchSupport to be enabled. You only need to call EnhancedTouchSupport.Enable() if you want to use the EnhancedTouch.Touch API.

The EnhancedTouch.Touch API is designed to provide access to touch information along two dimensions:

  1. By finger: Each finger is defined as the Nth contact source on a Touchscreen. You can use Touch.activeFingers to get an array of all currently active fingers.

  2. By touch: Each touch is a single finger contact with at least a beginning point (PointerPhase.Began) and an endpoint (PointerPhase.Ended or PointerPhase.Cancelled). Between those two points, an arbitrary number of PointerPhase.Moved and/or PointerPhase.Stationary records exist. All records in a touch have the same touchId. You can use Touch.activeTouches to get an array of all currently active touches. This lets you track how a specific touch moves over the screen, which is useful if you want to implement recognition of specific gestures.

See EnhancedTouch.Touch API documentation for more details.

Note: The Touch and Finger APIs don't generate GC garbage. The bulk of the data is stored in unmanaged memory that is indexed by wrapper structs. All arrays are pre-allocated.

Touch Simulation

Touch input can be simulated from input on other kinds of Pointer devices such as Mouse and Pen devices. To enable this, you can either add the TouchSimulation MonoBehaviour to a GameObject in your scene or simply call TouchSimulation.Enable somewhere in your startup code.

    void OnEnable()
    {
        TouchSimulation.Enable();
    }

In the editor, you can also enable touch simulation by toggling "Simulate Touch Input From Mouse or Pen" on in the "Options" dropdown of the Input Debugger.

TouchSimulation will add a Touchscreen device and automatically mirror input on any Pointer device to the virtual touchscreen device.