Simple joystick script for mobile use. Dynamic position joystick and has a public member "value"(v2) to store the input value. To use: Create image for the outer circle as a UI object. Create child image for the inner circle. Slap the script on your parent image and you're good to go.

Joystick.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Joystick : MonoBehaviour
{
	//Public Variables
	public Image centerImg;
	[Tooltip("This field does not need to be filled")]
	public Text debugText;
	public float radius = 50;
	public float fadeSpeed = 2;
	[HideInInspector]
	public Vector2 value;

	//Private Varaibles
	private RectTransform center;
	private RectTransform rt;
	private Image img;
	private float stAlpha;
	private float stCenterAlpha;
	private bool isDebug;

	void Start()
	{
		//Get components
		rt = GetComponent<RectTransform>();
		center = centerImg.GetComponent<RectTransform>();
		img = GetComponent<Image>();

		//Record stating alphas
		stAlpha = img.color.a;
		stCenterAlpha = centerImg.color.a;

		//Check if debugging
		if (debugText != null)
			isDebug = true;
	}

	void Update()
	{
		if (Input.GetMouseButtonDown(0))
		{
			//Set entire joystick pos
			rt.position = Input.mousePosition;
		}

		if (Input.GetMouseButtonUp(0))
		{
			//Reset value
			value = Vector2.zero;

			//Debug
			if (isDebug)
				debugText.text = "(" + value.x + ", " + value.y + ")";
		}

		if (Input.GetMouseButton(0))
		{
			//Move small joystick
			Vector2 pos = ToV2(rt.position) - ToV2(Input.mousePosition);
			pos = Vector2.ClampMagnitude(pos, radius);
			center.position = ToV2(rt.position) - pos;

			//Calculate the value
			value = -(pos / radius);

			//Debug
			if (isDebug)
				debugText.text = "(" + value.x + ", " + value.y + ")";

			//Fade in
			if (img.color.a < stAlpha)
				img.color = Fade(img.color, fadeSpeed * Time.deltaTime);

			if (centerImg.color.a < stCenterAlpha)
				centerImg.color = Fade(centerImg.color, fadeSpeed * Time.deltaTime);
		}
		else
		{
			//Fade out
			if (img.color.a > 0)
				img.color = Fade(img.color, -fadeSpeed * Time.deltaTime);

			if (centerImg.color.a > 0)
				centerImg.color = Fade(centerImg.color, -fadeSpeed * Time.deltaTime);
		}
	}

	Vector2 ToV2(Vector3 v3)
	{
		return new Vector2(v3.x, v3.y);
	}

	Color Fade(Color color, float amount)
	{
		return new Color(color.r, color.g, color.b, color.a + amount);
	}
}