How to load one of Unity's built-in UI Sprites at runtime?

Question

I have some code that creates objects with an Image component, in which I want to replace the Source Image with one of the default built-in sprites, through the code.

Example:

Code:

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

public class PotionManager : MonoBehaviour {

    Image sourceImage;
    private float timer=25;
    static int COUNT_OF_ORDERS = 0;
    public Transform parent;
    public List<PotionAsset> potionList = new List<PotionAsset>();
    private float posX,posY,posZ;

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update()
    {
        timer += Time.deltaTime;
        if (timer >= 30)
        {
            CreateOrderHolder();
        }
    }

    void CreateOrderHolder()
    {
        posX = 160 * COUNT_OF_ORDERS + 80;
        posY = -70;
        posZ = 0;

        COUNT_OF_ORDERS++;

        GameObject temp = new GameObject("Potion Order " + COUNT_OF_ORDERS, typeof(RectTransform));
        temp.transform.SetParent(parent);
        temp.transform.localPosition = new Vector3(posX, posY, posZ);
        temp.transform.localScale = new Vector3(1.5f, 1.5f, 1.5f);
        temp.GetComponent<RectTransform>().anchorMax = new Vector2(0, 1);
        temp.GetComponent<RectTransform>().anchorMin = new Vector2(0, 1);

        CreatePotionHolder(temp.transform);

        timer = 0;
    }

    void CreatePotionHolder(Transform parent)
    {
        posX = 0;
        posY = 13.5f;
        posZ = 0;

        GameObject temp = new GameObject("PotionHolder", typeof(RectTransform), typeof(Image));

        temp.transform.SetParent(parent);
        temp.transform.localPosition = new Vector3(posX, posY, posZ);
        temp.transform.localScale = new Vector3(1, 1, 1);
        temp.GetComponent<RectTransform>().sizeDelta = new Vector2(100,50);

        sourceImage = temp.GetComponent<Image>();
        sourceImage.sprite = Resources.Load<Sprite>("Resources/unity_builtin_extra/UISprite");
        Debug.Log(sourceImage.sprite);
    }

}

In the end, sourceImage.sprite returns null. I tried to add at the end of the file path the file extension like png, psd, but this did not help.

Answer 1

You can access the built in Extra Resources in the editor. I believe if you make a public reference to the UI sprite it will create a replica to use for runtime somewhere along the way.

Otherwise the path to the sprite is 'UI/Skin/UISprite.psd'

example

sourceImage = temp.GetComponent<Image>();
sourceImage.sprite = UnityEditor.AssetDatabase.GetBuiltinExtraResource<Sprite>("UI/Skin/UISprite.psd");

I'd suggest using Sprite.Create(); during runtime and you can create a texture for it also so you have no need to load their default one.