/// <summary>
/// 设置背景（淡入）
/// </summary>
/// <param name="fadein">新图淡入的时间，默认0.3s</param>
public EffectPiece FadeinBackground(string spriteName, float fadein = 0.3f)
{
Queue <NewImageEffect> effects = new Queue <NewImageEffect>();
effects.Enqueue(NewEffectBuilder.SetBackSprite(spriteName));
effects.Enqueue(NewEffectBuilder.FadeInBackSprite(fadein));
return(new EffectPiece(id++, effects));
}
