A modular and easily customisable Unity MonoBehaviour for handling swipe and pinch motions on mobile.

PanAndZoom.cs

using UnityEngine;
using System;
using System.Collections.Generic;
using UnityEngine.EventSystems;

/// <summary> A modular and easily customisable Unity MonoBehaviour for handling swipe and pinch motions on mobile. </summary>
public class PanAndZoom : MonoBehaviour {

    /// <summary> Called as soon as the player touches the screen. The argument is the screen position. </summary>
    public event Action<Vector2> onStartTouch;
    /// <summary> Called as soon as the player stops touching the screen. The argument is the screen position. </summary>
    public event Action<Vector2> onEndTouch;
    /// <summary> Called if the player completed a quick tap motion. The argument is the screen position. </summary>
    public event Action<Vector2> onTap;
    /// <summary> Called if the player swiped the screen. The argument is the screen movement delta. </summary>
    public event Action<Vector2> onSwipe;
    /// <summary> Called if the player pinched the screen. The arguments are the distance between the fingers before and after. </summary>
    public event Action<float, float> onPinch;

    [Header("Tap")]
    [Tooltip("The maximum movement for a touch motion to be treated as a tap")]
    public float maxDistanceForTap = 40;
    [Tooltip("The maximum duration for a touch motion to be treated as a tap")]
    public float maxDurationForTap = 0.4f;

    [Header("Desktop debug")]
    [Tooltip("Use the mouse on desktop?")]
    public bool useMouse = true;
    [Tooltip("The simulated pinch speed using the scroll wheel")]
    public float mouseScrollSpeed = 2;

    [Header("Camera control")]
    [Tooltip("Does the script control camera movement?")]
    public bool controlCamera = true;
    [Tooltip("The controlled camera, ignored of controlCamera=false")]
    public Camera cam;

    [Header("UI")]
    [Tooltip("Are touch motions listened to if they are over UI elements?")]
    public bool ignoreUI = false;

    Vector2 touch0StartPosition;
    Vector2 touch0LastPosition;
    float touch0StartTime;

    bool cameraControlEnabled = true;

    bool canUseMouse;

    /// <summary> Has the player at least one finger on the screen? </summary>
    public bool isTouching { get; private set; }

    /// <summary> The point of contact if it exists in Screen space. </summary>
    public Vector2 touchPosition { get { return touch0LastPosition; } }

    void Start() {
        canUseMouse = Application.platform != RuntimePlatform.Android && Application.platform != RuntimePlatform.IPhonePlayer && Input.mousePresent;
    }

    void Update() {

        if(useMouse && canUseMouse) {
            UpdateWithMouse();
        } else {
            UpdateWithTouch();
        }
    }

    void UpdateWithMouse() {
        if(Input.GetMouseButtonDown(0)) {
            if(ignoreUI || !IsPointerOverUIObject()) {
                touch0StartPosition = Input.mousePosition;
                touch0StartTime = Time.time;
                touch0LastPosition = touch0StartPosition;

                isTouching = true;

                if(onStartTouch != null) onStartTouch(Input.mousePosition);
            }
        }

        if(Input.GetMouseButton(0) && isTouching) {
            Vector2 move = (Vector2) Input.mousePosition - touch0LastPosition;
            touch0LastPosition = Input.mousePosition;

            if(move != Vector2.zero) {
                OnSwipe(move);
            }
        }

        if(Input.GetMouseButtonUp(0) && isTouching) {

            if(Time.time - touch0StartTime <= maxDurationForTap
               && Vector2.Distance(Input.mousePosition, touch0StartPosition) <= maxDistanceForTap) {
                OnClick(Input.mousePosition); 
            }

            if (onEndTouch != null) onEndTouch (Input.mousePosition);
            isTouching = false;
            cameraControlEnabled = true;
        }

        if(Input.mouseScrollDelta.y != 0) {
            OnPinch(1, Input.mouseScrollDelta.y < 0 ? (1 / mouseScrollSpeed) : mouseScrollSpeed, Vector2.right);
        }
    }

    void UpdateWithTouch() {
        int touchCount = Input.touches.Length;

        if(touchCount == 1) {
            Touch touch = Input.touches[0];

            switch(touch.phase) {
                case TouchPhase.Began: {
                    if(ignoreUI || !IsPointerOverUIObject()) {
                        touch0StartPosition = touch.position;
                        touch0StartTime = Time.time;
                        touch0LastPosition = touch0StartPosition;

                        isTouching = true;

                        if(onStartTouch != null) onStartTouch(touch0StartPosition);
                    }

                    break;
                }
                case TouchPhase.Moved: {
                    touch0LastPosition = touch.position;

                    if(touch.deltaPosition != Vector2.zero && isTouching) {
                        OnSwipe(touch.deltaPosition);
                    }
                    break;
                }
                case TouchPhase.Ended: {
                    if(Time.time - touch0StartTime <= maxDurationForTap
                        && Vector2.Distance(touch.position, touch0StartPosition) <= maxDistanceForTap
                        && isTouching) {
                        OnClick(touch.position);
                    }

                    if(onEndTouch != null) onEndTouch(touch.position);
                    isTouching = false;
                    cameraControlEnabled = true;
                    break;
                }
                case TouchPhase.Stationary:
                case TouchPhase.Canceled:
                break;
            }
        } else if(touchCount == 2) {
            Touch touch0 = Input.touches[0];
            Touch touch1 = Input.touches[1];

            if(touch0.phase == TouchPhase.Ended || touch1.phase == TouchPhase.Ended) return;

            isTouching = true;

            float previousDistance = Vector2.Distance(touch0.position - touch0.deltaPosition, touch1.position - touch1.deltaPosition);

            float currentDistance = Vector2.Distance(touch0.position, touch1.position);

            if(previousDistance != currentDistance) {
                OnPinch(previousDistance, currentDistance, (touch1.position - touch0.position).normalized);
            }
        } else {
            if(isTouching) { 
                if(onEndTouch != null) onEndTouch(touch0LastPosition);
                isTouching = false;
            }

            cameraControlEnabled = true;
        }
    }

    void OnClick(Vector2 position) {
        if (onTap != null && (ignoreUI || !IsPointerOverUIObject())) {
            onTap (position);
        }
    }
    void OnSwipe(Vector2 deltaPosition) {
        if (onSwipe != null) {
            onSwipe (deltaPosition);
        }

        if (controlCamera && cameraControlEnabled) {
            if (cam == null) cam = Camera.main;

            cam.transform.position -= (cam.ScreenToWorldPoint (deltaPosition) - cam.ScreenToWorldPoint(Vector2.zero));
        }
    }
    void OnPinch(float oldDistance, float newDistance, Vector2 touchDelta) {
        if (onPinch != null) {
            onPinch (oldDistance, newDistance);
        }

        if (controlCamera && cameraControlEnabled) {
            if (cam == null) cam = Camera.main;

            if(cam.orthographic) {
                cam.orthographicSize = Mathf.Max(0.1f, cam.orthographicSize * oldDistance / newDistance);
            } else {
                cam.fieldOfView = Mathf.Clamp(cam.fieldOfView * oldDistance / newDistance, 0.1f, 179.9f);
            }
        }
    }

    /// <summary> Checks if the the current input is over canvas UI </summary>
    public bool IsPointerOverUIObject() {

        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;
    }

    /// <summary> Cancels camera movement for the current motion. Resets to use camera at the end of the touch motion.</summary>
    public void CancelCamera() {
        cameraControlEnabled = false;
    }
}