HK_LongZhiMeng/Assets/Scripts/DragCamera2D.cs

using UnityEngine;
using UnityEngine.EventSystems;

public class DragCamera2D : MonoBehaviour
{
    public Camera cam;

    [Header("Panning")]
    public bool panningEnabled = true;
    [Range(-5, 5)]
    public float panSpeed = -0.06f;
    public bool keyboardInput = false;
    public bool inverseKeyboard = false;

    [Header("Zoom")]
    public bool zoomEnabled = true;
    public bool linkedZoomDrag = true;
    public float maxZoom = 10;
    [Range(0.01f, 10)]
    public float minZoom = 0.5f;
    [Range(0.1f, 10f)]
    public float zoomStepSize = 0.5f;

    void Start() {
        if (cam == null) {
            cam = Camera.main;
        }
    }

    void Update() {
        if (panningEnabled) {
            panControl();
        }

        if (zoomEnabled) {
            zoomControl();
        }
    }

    //click and drag
    public void panControl() {
        // if mouse is down
        if (Input.GetMouseButton(2)) {
            if (!EventSystem.current.IsPointerOverGameObject())
            {
                float x = Input.GetAxis("Mouse X") * panSpeed;
                float y = Input.GetAxis("Mouse Y") * panSpeed;

                if (linkedZoomDrag)
                {
                    x *= Camera.main.orthographicSize;
                    y *= Camera.main.orthographicSize;
                }

                transform.Translate(x, y, 0);

            }
                
        }

        // if keyboard input is allowed
        if (keyboardInput) {
            float x = -Input.GetAxis("Horizontal") * panSpeed;
            float y = -Input.GetAxis("Vertical") * panSpeed;

            if (linkedZoomDrag) {
                x *= Camera.main.orthographicSize;
                y *= Camera.main.orthographicSize;
            }

            if (inverseKeyboard) {
                x = -x;
                y = -y;
            }
            transform.Translate(x, y, 0);
        }
    }

    // managae zooming
    public void zoomControl() 
    {
        if (!EventSystem.current.IsPointerOverGameObject())
        {
            if ((Input.GetAxis("Mouse ScrollWheel") > 0) && Camera.main.orthographicSize > minZoom) // forward
            {
                Camera.main.orthographicSize = Camera.main.orthographicSize - zoomStepSize;

                // Keep soze above 0 or error.
                if (Camera.main.orthographicSize < 0.01f)
                {
                    Camera.main.orthographicSize = 0.01f;
                }
            }

            if ((Input.GetAxis("Mouse ScrollWheel") < 0) && Camera.main.orthographicSize < maxZoom) // back            
            {
                Camera.main.orthographicSize = Camera.main.orthographicSize + zoomStepSize;
            }
        }
            
    }

}