Queues and Coroutines

Unity Engine
1

Hey

I tried to implement a short message queue where I can add messages via a button (1 click = 1 msg to add). These messages are stored in smsQueue of type Queue.

In Start() I will call my forever looping coroutine displayShortMessageLoop.

/** add sms to the list of sms to be displayed */
public void addShortMessage(ShortMessage sms){
    smsQueue.Enqueue(sms);
}

/** while true loop that displays a short message from smsQueue that disappears after a few seconds */
private IEnumerator displayShortMessageLoop(){
    ShortMessage sms;
    while(true){
        if(smsQueue.Count == 0){
            yield return new WaitForSeconds(0.1f)
            continue; // check again in 0.1s if no message present
        } else {
            if(lastSMSSpawnTime + 2.9f >= Time.time ) yield return new WaitForSeconds((lastSMSSpawnTime + 2.9f) - Time.time);
            Debug.Log ("smsQueue " + smsQueue.Count);
            sms = smsQueue.Dequeue();
            // do a lot of stuff, set text and image
            smsGO.GetComponent<MoveOverTime>().StartCoroutine("begin");
        }
    }
}

MoveOverTime looks like this

public override void Start () {
    base.Start();
    originalPos = gameObject.transform.position;
}

public IEnumerator begin() {
    foreach(MoveOverTimeContainer cont in moveDirections){
        yield return new WaitForSeconds(cont.waitAtStart);
        StartCoroutine(moveWithinTime(cont.target, cont.timeToTarget));
        yield return new WaitForSeconds(cont.timeToTarget); // wait the time until processing the next cont
    }
    yield return null;
}

/** move to target position within timetoMove seconds */
public IEnumerator moveWithinTime(Vector3 target, float timeToMove){
    Vector3 currentPos = gameObject.transform.position;
    target += originalPos;
    float t = 0f;
    while(t < 1) {
        t += Time.deltaTime / timeToMove;
        gameObject.transform.position = Vector3.Lerp(currentPos, target, t);
        yield return null;
    }
}

MoveOverTimeContainer:

/** initial waiting time */
public float waitAtStart = 0f;
/** move to this point */
public Vector3 target;
/** within this timeframe */
public float timeToTarget = 2f;

Now, what I want to achieve is that no matter when the message is added, the following should happen:

If the message has not fully reached its 1st target position (because that is what happens during begin()), wait until that happens. If the message is fully on the screen, make sure it is displayed for at least the waiting delay of the second cont object (2s). From that point on, it is allowed to override the movement so that a message that has being added between second 0 and second timeToMove+2s will stay at the first target position so that the message field stays where it is while the text is being changed. I know this is confusing to I tried to visualize this:

1924276--124265--IRQSMS.png
1924276--124265--IRQSMS.png779×1005 58.9 KB

I have problems understanding the scope of a coroutine I think. The moving UI object with his MoveOverTime will always be the same, only the text and image are changed in a message. I can’t really make this work because of that and need some clarification

The MoveOverTimeContainers:
1: wait 0s, move to left within 0.9s
2: wait 2s, move to 0/0 (original) within 0.6s

When I click the button 4 times rapidly, I want to scroll it to the left within 0.9s, show msg1 for 2s, then msg2 for 2s, then msg3 for 2s, then msg4 for 2s, then go back to original pos. If I add the message while it is already moving back, interrupt that and move to position1 and continue normally.

Any help appreciated :slight_smile:

2

:slight_smile:

3

"

  • public IEnumerator begin() {
  • foreach(MoveOverTimeContainer cont in moveDirections){
  • yield return new WaitForSeconds(cont.waitAtStart);
  • StartCoroutine(moveWithinTime(cont.target, cont.timeToTarget));
  • yield return new WaitForSeconds(cont.timeToTarget); // wait the time until processing the next cont
  • }
  • yield return null;
  • }

"

you need this line

yield return null;
inside the curly brakets, because its not returning a null IEnumator :slight_smile:

1 Like
4

hmmmm why do I need a yield return null when I have a
yield return new WaitForSeconds(cont.timeToTarget) ?

5

,Because the ‘Yield’ keyword means Wait. so you Say ‘Yield’ (wait) For Seconds. WaitForSeconds(time);

well thats a good but you need to yield return null do make a ‘null’ IEnumeratorso It will resume the code execution at the foreach loop once the update starts again. :slight_smile: Thats the best i can tell ya :smile:

I.E :

public IEnumerator Begin()
{
foreach(MoveOverTimeContainer cont in MoveOverTimeContainer)
{
yield return new WaitForSeconds(cont.timeToTarget);

StartCoroutine(moveWithinTime(cont.target, cont.timeToTarget));

yield return new WaitForSeconds(cont.timeToTarget); // wait the time until processing the next cont

yield return null; //Returns a null IEnumerator so that the code execution can resume a the givin spot
}
}

6

Nope any yield will do that, a null just yields until the next frame, a waitforseconds wont resume execution of the coroutine until the time has passed.

7

It’s returning the IEnumator null :stuck_out_tongue: So it will execute the code again :stuck_out_tongue: at the next frame :stuck_out_tongue:

By the way… Watch the video… You’ll know what I meant

8

actually my problem is more of the nature that I don’t know how to “stop” the current movement if there is a new one, since everything I tried with local and global variables I tried failed. That’s what I meant with “scope”. The code itselfs runs fine concerning the movement in a standard, non-interrupting situation, no yield return null is needed imho.

9

If it’s working then I’m not sure. Good job and Good luck with you’r project! :slight_smile: