Unity5：有没有想法在没有协程的情况下编写代码FadeIn / Out？

Question

I'm thinking to make FadeIn/Out effect by C#.

// so, If there's a code like this :

    float targetAlpha = 0.7f;
    Color targetColor = new Color();

    public void FadeIn() {
    if(color.a < targetAlpha) { color.a += Time.deltaTime; }
    sprite.color = targetColor;
    }

1) I don't want to put FadeIn() in Update() because I don't use this FadeIn() function often.

2) I don't want to use Coroutine because StartCoroutine() makes garbage. I will set active on/off this object very often.

3) Animator... There's no way, right?

So I'm going to make 1 event, which will always work on Update(), and then I will put everything in that event. (add when OnEnable(), remove when OnDisable())

Is there a better solution?

Answer 1

If you don't want to put it in update because it won't be used often, maybe you can consider a state machine approach. I would only consider this if performance really is more important than readability. Because this approach will add a lot of additional code.

For simplicity the code below is more verbose than it has to be.

public interface IState
{
    void Update();
}

public class FadeInState : IState
{
    private readonly float targetAlpha;
    private readonly Sprite sprite;
    private readonly Action onComplete;

    public FadeInState(Sprite sprite, float targetAlpha, Action onComplete)
    {
        this.targetAlpha = targetAlpha;
        this.sprite = sprite;
        this.onComplete = onComplete;
    }

    public void Update()
    {
        // Your fade-in code
        if (sprite.color.a < targetAlpha)
        {
            Color tmp = sprite.color;
            tmp.a += Time.deltaTime;
            sprite.color = tmp;
        }
        else
        {
            this.onComplete.Invoke();
        }
    }
}

public class FadeOutState : IState
{
    private readonly float targetAlpha;
    private readonly Sprite sprite;
    private readonly Action onComplete;

    public FadeOutState(Sprite sprite, float targetAlpha, Action onComplete)
    {
        this.targetAlpha = targetAlpha;
        this.sprite = sprite;
        this.onComplete = onComplete;
    }

    public void Update()
    {
        // Your fade-out code
        if (sprite.color.a > targetAlpha)
        {
            Color tmp = sprite.color;
            tmp.a -= Time.deltaTime;
            sprite.color = tmp;
        }
        else
        {
            this.onComplete.Invoke();
        }
    }
}

public class DoNothingState : IState
{
    public void Update()
    {
        // Do nothing
    }
}

public class YourClass : MonoBehaviour
{
    private IState currentState;

    void Awake()
    {
        this.currentState = new DoNothingState();
    }

    void Update()
    {
        this.currentState.Update();
    }

    public void FadeIn(Sprite sprite, float targetAlpha)
    {
        this.currentState = new FadeInState(sprite, targetAlpha,
            () =>
            {
                this.currentState = new DoNothingState();
            });
    }

    public void FadeOut(Sprite sprite, float targetAlpha)
    {
        this.currentState = new FadeOutState(sprite, targetAlpha,
            () =>
            {
                this.currentState = new DoNothingState();
            });
    }
}

Initially your class is in the DoNothing state. So update will effectively do nothing.

If someone calls FadeIn , your FadeInState will do your fading logic as if it were in the MonoBehaviour.Update() .

The state takes an Action in the constructor that is executed when it is finished. This way you can control what happens after the animation completes from within YourClass . In the example I just set the state to DoNothing but you can probably disable the gameObject.

If you go with this approach and you start using it for other things, you should just look into some better StateMachine implementations. Otherwise you will eventually end up with tons of state classes. This one is decent.