void Awake()
{
spritePools = new Dictionary<Sprite, SpritePool> ();
for (int i = 0; i < prefabs.Length; i++) {
var newPool = new SpritePool (prefabs[i], number);
newPool.SetOnActivate (OnActivate);
newPool.SetOnDeactivate (OnDeactivate);
spritePools.Add (prefabs [i], newPool);
}
}
