Move a player along Y axis using touch location

Question

I'm trying to move a player when the screen is tapped to where the screen is tapped, but only along the Y axis. I've tried this:

Vector2 touchPosition;
        [SerializeField] float speed = 1f;   

void Update() {

            for (var i = 0; i < Input.touchCount; i++) {

                if (Input.GetTouch(i).phase == TouchPhase.Began) {

                    // assign new position to where finger was pressed
                    transform.position = new Vector3 (transform.position.x, Input.GetTouch(i).position.y, transform.position.z);

                }
            }    
        }

But the player disappears rather than moves. What am I doing wrong?

Answer 1

You need to convert the touch position from Screen to World. This is very easy to do, I've just knocked this quick script together, hopefully it helps:

using UnityEngine;
using System.Collections;

public class TouchSomething : MonoBehaviour 
{
    public GameObject thingToMove;

    public float smooth = 2;

    private Vector3 _endPosition;

    private Vector3 _startPosition;

    private void Awake()
    {
        _startPosition = thingToMove.transform.position;
    }

    private void Update()
    {
        if(Application.platform == RuntimePlatform.Android || Application.platform == RuntimePlatform.IPhonePlayer)
        {
            _endPosition = HandleTouchInput();
        }
        else
        {
            _endPosition = HandleMouseInput();
        }

        thingToMove.transform.position = Vector3.Lerp(thingToMove.transform.position, new Vector3(_endPosition.x, _endPosition.y, 0), Time.deltaTime * smooth);
    }

    private Vector3 HandleTouchInput()
    {
        for (var i = 0; i < Input.touchCount; i++) 
        {
            if (Input.GetTouch(i).phase == TouchPhase.Began) 
            {
                var screenPosition = Input.GetTouch(i).position;
                _startPosition = Camera.main.ScreenToWorldPoint(screenPosition);
            }
        }

        return _startPosition;
    }

    private Vector3 HandleMouseInput()
    {
        if(Input.GetMouseButtonDown(0))
        {
            var screenPosition = Input.mousePosition;
            _startPosition = Camera.main.ScreenToWorldPoint(screenPosition);
        }

        return _startPosition;
    }
}

This allows you to also test in the editor as well.

I hope this helps.