Check key press when OnTriggerStay() is called

问题

I have an NPC that my player can talk to when the players collider is colliding with the NPC, I do that using this piece of code:

private void OnTriggerStay2D(Collider2D other)
{
    if (other.gameObject.tag == "InteractiveArea")
    {
        if (Input.GetKeyDown(KeyCode.E))
        {
            Debug.Log("PRESSED NPC");
            CreateAndShowDialog();
        }
    }
}

However, this gets called really randomly, sometimes the first time I press "E", sometimes the second or third time, etc.

My rigidbodies:

The colliders I use are standard BoxCollider2D, my players collider is a trigger, the NPCs is not.

Why are some key press not detected in the OnTriggerStay function?

回答1:

OnTriggerStay2D is called randomly. This is why you should never check for Input inside of it.

Set to a flag to true and false in the OnTriggerEnter2D and OnTriggerExit2D functions then check for that flag and input in the Update function which is called every frame. Also, always use CompareTag instead of other.gameObject.tag to compare tags.

private void Update()
{
    if (Input.GetKeyDown(KeyCode.E) && triggerStay)
    {
        //
    }
}

bool triggerStay = false;

void OnTriggerEnter2D(Collider2D collision)
{
    Debug.Log("Entered");
    if (collision.gameObject.CompareTag("InteractiveArea"))
    {
        triggerStay = true;
    }
}

void OnTriggerExit2D(Collider2D collision)
{
    Debug.Log("Exited");
    if (collision.gameObject.CompareTag("InteractiveArea"))
    {
        triggerStay = false;
    }
}

回答2:

My guess would be because the value returned by Input.GetKeyDown is only true for the single (Update()) frame that the key was pressed, whereas physics (including OnTriggerStay) are called during physics frames, i.e. FixedUpdate()

Doing a bit of research I pull up this question which suggests:

I've been struggling with this issue all afternoon!

My OnTriggerStay and Update/FixedUpdate methods were not in sync resulting is split-second undesired effects.

I finally found the solution when I read in the OnTriggerStay docs that this function can be a co-routine. I simply added a WaitForFixedUpdate in the correct location in my OnTriggerStay and it worked. They now both run in sync with each other. This even corrects the issue in Update.

Another question has this as a solution (Programmer's answer):

OnTriggerStay will not call on every frame. One way to get around this is to have OnTriggerEnter, and OnTriggerExit set a bool. Then execute your code in the FixedUpdate().

While the documentation no longer says what this post says,

OnTriggerStay gets called every FixedUpdate.

"Note: OnTriggerStay function is on the physics timer so it wont necessary run every frame. "

That confirms my guess and that the documentation was changed to no longer include this note, for some unexplained reason.

来源：https://stackoverflow.com/questions/44684522/check-key-press-when-ontriggerstay-is-called

标签

unity3d

unity5