A Unity helper class to check if the player's pointer is over the UI. Useful to avoid doing world actions if the pointer is over a bit of UI. Works on desktop and mobile.

IsPointerOverUI.cs

using System.Collections.Generic;

using UnityEngine;
using UnityEngine.EventSystems;

public static class IsPointerOverUI {

    public static bool Check() {
        if (EventSystem.current == null) return false;
        PointerEventData eventDataCurrentPosition = new PointerEventData(EventSystem.current);
        eventDataCurrentPosition.position = new Vector2(Input.mousePosition.x, Input.mousePosition.y);
        List<RaycastResult> results = new List<RaycastResult>();
        EventSystem.current.RaycastAll(eventDataCurrentPosition, results);
        return results.Count > 0;
    }
}