Unity 4.3 - 2D, how to assign programmatically sprites to an object

Question

I'm trying to create an object that will be responsible of creating and showing different sprites, so I would like to access directly the assets/sprites programmatically instead of drag and drop a sprite in the hierarchy under that object.

There's a way to programmatically create a new sprite and assign what I have in the assets folder?

I also would like to have a sort of data structure with a few images loaded at the start of the game, an array or a dictionary or something like that so I can change based on some situation which images I need to show. But what confuses me since I'm new to Unity is how to create a sprite taking the reference to the sprite programmatically using the assets folder.

edit with progress:

I've created an array of sprites like this:

public Sprite[] mySprites;

in Unity I've added sprites inside the array manually (I just dragged png's inside the variable array) so actually in this Object I have a Component with this array full of sprites

inside the component I also have done this:

public SpriteRenderer renderer;
renderer = transform.GetComponent<SpriteRenderer>();
renderer.sprite = (Sprite)mySprites [0];

I got no error until I run the game, then the sprite is NOT assigned and I got this:

"PPtr cast failed when dereferencing! Castin from Texture2D to Sprite!"

I got this error even without casting (Sprite) and btw I don't know why he is telling my about Texture2D since verything is setted as sprite

Answer 1

To create a sprite programmatically might be a little too difficult to do. You'd probably need to create a Texture in memory, fill in the data, and then write that texture on the disk. After that, you should be able to read that using C#'s File, or Unity's WWW.LoadFromCacheOrDownload.

Here is how you would create a texture dynamically: http://answers.unity3d.com/questions/9919/how-do-i-create-a-texture-dynamically-in-unity.html

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To load your sprites programmatically (not the ones created dynamically though), they need to be under a folder with the name Resources (which is a special folder).

I.e. suppose you have a sprite named MySprite.png under a folder named Sprites which is under a folder named Resources. You would then load it like this:

renderer.sprite = Resources.Load<Sprite>("Sprites/MySprite");

(notice how you do not include the Resources folder and the extension of the sprite)

You can find more details in the Loading Resources at Runtime documentation.

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PPtr cast failed when dereferencing!

I did some searching and found out from this forum post that usually that happens when you had a list of one type and then changed it into another type. I.e. if mySprites was at some point GameObject[] and you linked a bunch of Sprites, and then changed it to Sprite[]. And since it specifically says Texture2D, I'm assuming that the import settings of your Sprites (or some of them) are set to Texture instead of Sprite:

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Also, all MonoBehaviours have already a field named renderer, which is of type Renderer. I would suggest you rename that field to avoid confusion, unless you only used that as an example.

Answer 2

Here is real code.. will help you

void SetSprite(UI2DSprite uiSprite, Sprite[] sprites, string strKey)
 {
     foreach (Sprite stexture in sprites)
     {
         if (stexture.name == strKey)
         {
             uiSprite.sprite2D = stexture;
             break;
         }
     }
 }

use it following the way..

UI2DSprite[] uiSprites = tmpObject.GetComponentsInChildren<UI2DSprite>();
 Sprite[] sprites = Resources.LoadAll<Sprite>("Textures");
 string resName = "icon_favorite_2";

 foreach (UI2DSprite uiSprite in uiSprites)
 {
 if(uiSprite.name = "icon")
  SetSprite(uiSprite, sprites , resName);

 }

Answer 3

Just to throw my tuppence worth in. I had this problem when I changed a SerializedField from Texture2D to Sprite in the code. The texture was already a sprite in the editor but it needed to be Sprite in the code. The field in the editor initially said type mismatch and then displayed the sprite texture again. To cure it I set the field in the editor to none and the reset it to the required sprite.