While loop freezes game in Unity3D

问题

I've always struggled with while loops because they barely ever work for me. They always cause my Unity3D application to freeze, but in this instance I really need it to work:

bool gameOver = false;
bool spawned = false;
float timer = 4f;

void Update () 
{
    while (!gameOver)
    {
        if (!spawned)
        {
            //Do something
        }
        else if (timer >= 2.0f)
        {
            //Do something else
        }
        else
        {
            timer += Time.deltaTime;
        }
    }
}

Ideally, I want those if statements to run as the game runs. Right now it crashes the program and I know it's the while loop which is the problem because it freezes anytime I uncomment it out.

回答1:

Update() is called every frame, so you should not use a while loop in it except in exceptional circumstances. This is because the game screen freezes until the loop is exited.

Further reading: https://docs.unity3d.com/Manual/ExecutionOrder.html

Instead, either use a coroutine as @Programmer has done, or use an if/switch statement instead, with a boolean check.

i.e.

bool gameOverActionDone = false;
void Update () 
{
    if (!gameOver && !gameOverActionDone)
    {
        if (!spawned)
        {
            //Do something
            gameOverActionDone = true;
        }
        else if (timer >= 2.0f)
        {
            //Do something else
            gameOverActionDone = true;
        }
        else
        {
            timer += Time.deltaTime; //either keep this here, or move it out if the if condition entirely
        }
    }
}

回答2:

If you want to use a variable to control a while loop and wait in that while loop then do it in a coroutine function and yield after each wait. If you don't yield, it will wait too much and Unity will freeze. On mobile devices like iOS, it would crash.

void Start()
{
    StartCoroutine(sequenceCode());
}

IEnumerator sequenceCode()
{
    while (!gameOver)
    {
        if (!spawned)
        {
            //Do something
        }
        else if (timer >= 2.0f)
        {
            //Do something else
        }
        else
        {
            timer += Time.deltaTime;
        }

        //Wait for a frame to give Unity and other scripts chance to run
        yield return null;
    }
}

来源：https://stackoverflow.com/questions/49525038/while-loop-freezes-game-in-unity3d

标签

unity3d

while-loop