Drag & drop: Cannot return object to its original position

Unity Engine
1

Hi, I am trying to return a draggable object (Image) to its original position whenever the user “drops” it. I already have a good start to the drag & drop script, but setting the original position of the object in the OnEndDrag() just puts it in the center of the screen and not in the original location. This is the drag & drop script (the commented stuff was for testing and didn’t help):

public class DragDrop : MonoBehaviour, IPointerDownHandler, IBeginDragHandler, IEndDragHandler, IDragHandler
{
    [SerializeField] private Canvas rootCanvas;
    private RectTransform rectTransform;
    private CanvasGroup canvasGroup;
    public Vector2 originalPosition;
    public Vector3 original3d;
    public int centerCardNum; // specified in Unity

    void Awake() {
        rectTransform = GetComponent<RectTransform>();
        canvasGroup = GetComponent<CanvasGroup>();

        var taggedObjects = GameObject.FindGameObjectsWithTag("rootCanvas");
        if (taggedObjects.Length == 0) {
            Debug.Log("Error: DragDrop: Awake: No objects found with tag 'rootCanvas'");
            return;
        }
        rootCanvas = taggedObjects[0].GetComponent<Canvas>();

        originalPosition = rectTransform.anchoredPosition;
        original3d = rectTransform.anchoredPosition3D;
    }

    public void OnBeginDrag(PointerEventData eventData) {
        canvasGroup.blocksRaycasts = false;
        canvasGroup.alpha = 0.6f;
    }

    public void OnDrag(PointerEventData eventData) {
        rectTransform.anchoredPosition += eventData.delta / rootCanvas.scaleFactor;
    }

    public void OnEndDrag(PointerEventData eventData) {
        canvasGroup.blocksRaycasts = true;
        canvasGroup.alpha = 1f;
       
        // GetComponent<Transform>().SetParent(GameObject.Find("CenterCardsCanvas").GetComponent<Transform>());
        // GetComponent<Transform>().SetSiblingIndex(0);
        // GetComponent<RectTransform>().SetParent(GameObject.Find("CenterCardsCanvas").GetComponent<RectTransform>());
        // GetComponent<RectTransform>().SetSiblingIndex(0);

        rectTransform.anchoredPosition3D = original3d;

    }

    public void OnPointerDown(PointerEventData eventData) {
        Debug.Log("OnPointerDown");
    }
}

Help is very much appreciated, thank you!

2

See line 21 where you mark the original positions in Awake()?

I believe you actually want to store those original positions (or make fresh equivalent variables called “PreDrag”, not sure what you want “original” to mean here) at the start of the OnBeginDrag() process.

1 Like
3

Exactly what I needed, thank you. I moved line 22 into OnBeginDrag(). I guess the issue was that the desired anchored position wasn’t available from Awake().

1 Like
4

Possibly because the Awake on the actual target hadn’t been called, or something else moved it AFTER this Awake().

Glad you’re operational. Dragging can be ticklish to get right, especially the edge cases.

5

Did you get the solution , i need the same functions too