Multiple event cases ?

I hear people saying do not use multiple event cases.
is this in reference to multiple event cases in the same loop?
is it ok to use 1 event structure per parallel loop?
what happens if you have two parallel loops reacting to the same event?
- James
Using LV 2012 on Windows 7 64 bit

James R wrote:
I hear people saying do not use multiple event cases.
Who are these people??! There is nothing wrong with an event structure containing multiple event cases.
James R wrote:
is this in reference to multiple event cases in the same loop?
Yes, you should only have one event structure per loop, but that event structure can have multiple cases.
James R wrote:
is it ok to use 1 event structure per parallel loop?
Yes. What makes you think otherwise?
James R wrote:
what happens if you have two parallel loops reacting to the same event?
Nothing unusual. They will both fire whenever that associated event occurs. No problem!
LabVIEW Champion . Do more with less code and in less time .

Similar Messages

Can I have multiple event structures with the same event cases?

Hello,
I'm doing an application that reproduces the front panel of the HP6675A power supply. To achieve this, I have done a state machine with different states
(initialize, measures, voltage, current, ocp, ov, store, recall, etc). In each state, should have an event structure that catches the events of the buttons, like for example: if the current state is the Voltage mode and the user press the current button the next state will be the Current mode. For this in each state of the state machine should be the same event structure with the same events.
My problem is that the Vi doesn't work properly when I have multiple event structures with the same event cases. There are some possibily to do this, and how? Or is impossible to have multiple events? I have been reading some posts, but I don't find solutions.
Any help is appreciated.
Thank you very much.
Solved!
Go to Solution.

natasftw wrote:
Or as others mentioned, make two parallel loops. In one loop, have your state machine. In the other, have just the Event Handler. Pass the events from the handler to the state machine by way of queues.
A proper state machine will not need the second loop. The "Wait For Event" or "Idle" state (whatever you want to call it) is all you really need in order to catch the user button presses. The setup is almost there. Maybe add a shift register to keep track of which state to go to in the case of a timeout on the Event Structure.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Multiple events handled in a case, variant type newval

Hi!
I use an event case structure, and one case handles two value change events. One is a button's, the other is a cluster of controls'.
I would like to distinguish, whether the source was the button, or one of the controls in the cluster, but i get back the new-val and old-val in a variant type.
How could i get the appropriate values back?
Thanks
Solved!
Go to Solution.

For this, you would use the "ctlref" event terminal, not the "newval".
If you only have two controls, create a control reference for one and compare it with the ctlref event terminal. If they are equal, that was the control, else the other one. Place the terminal of both controls inside the event to get the values of each.
(If you have more than two controls, create an array of control references and use "search array" for the ctrlref output)
If your controls have unique names, you could also use the ctlref to get the control label, for example.
LabVIEW Champion . Do more with less code and in less time .

Using Multiple Event Listeners

Hi,
I have a movielcip (A) class in which I have used a Tween class effect on a child movieclip (B) scrollRect. The (B) Movieclip in turn has several movieclips whose have tween class effect being executed on thier child movieclips.
the tweens are all unique to each movieclip
and the event listeners are taken off once completed.
This works all well and good in FLASH IDE...
My problem arises when I try to view this in a browser on a Windows XP
it doesnt work in
Opera Version 9.63
Firefox 2.0
and Google Chrome 2.0
The only browser it works fluently in is
Internet Explorer 7.0.5
What is happening in most cases it that the animation appears to "stick" but i think what may be happening is the listening or removal of the event listeners. The animations are left incompleted.
Is there any rule of thumb when using multiple event listeners?
here is a snippet of some of my code
on click event from movieclip (A)
private function scrollToSlidePrev(e:MouseEvent) {
               if (((slideIndex - 1) >= 0)) {
                    nextButton.mouseEnabled = nextButton.enabled = previousButton.enabled = previousButton.mouseEnabled = false;
                    var position:Number = 0-SLIDEAREA.width;
                    var slide1:TileListSlide = slides[slideIndex] as TileListSlide;
                    var slide2:TileListSlide = slides[--slideIndex] as TileListSlide;
                    scrollSlide(position,slide1,slide2);
tween animation in movieclip (A) on (B)
private function scrollSlide(pos:int,slide1:TileListSlide,slide2:TileListSlide) {
               slide1.resizeSlideTo(0.6); // execute tween on child movie clips in B
               slide2.resizeSlideTo(1); // same as above;
               var rect:Rectangle = sliderMc.scrollRect;
               var tween1:Tween = new Tween(rect,"x",Regular.easeOut,rect.x,rect.x + pos,3,true);
               tween1.addEventListener(TweenEvent.MOTION_CHANGE,setSliderScroll,false,4);
               tween1.addEventListener(TweenEvent.MOTION_FINISH,toggleButtonEnabled,false,3);
tween animation in movieclip (B) children
public function resizeSlideTo(sc) {
               var m:Matrix = tileList.transform.matrix as Matrix;
               var p:Point = new Point (m.a, 0);
               var tween2:Tween = new Tween(p,"x",Regular.easeOut,p.x,sc,3,true);
               if (numericStepper != null) {
                    if (sc != 1) {
                         numericStepper.visible = false;
                         tween2.removeEventListener(TweenEvent.MOTION_FINISH,showStepper);
                    if (sc === 1) {
                         tween2.addEventListener(TweenEvent.MOTION_FINISH,showStepper,false,2);
               tween2.addEventListener(TweenEvent.MOTION_CHANGE,setScaleOnScroll,false,3);
here is the link
http://visual_admin.web.aplus.net/ticker/ticker_widget.html
the effect disables and re-enables the buttons when its done.... then the listeners are removed.
each one with the exception cretes its own unique tween (obviously this is a custom class built as each clip)
i really don't know what to make of it guys

apparantly making the tween a property of the class rather than a random variable in a function worked.....go figure

Is it possible to handle multiple events using Jscript for a button in Apex

Hi,
I've application wherein in one of the pages for a button, I need to trigger 2 events as: 1. redirect to a new page upon 'click' of the button
2. display a set of values on 'mouse over' that button.
I'm able to handle both separately, but not in one button. I would like to know if there is any limitation in Apex that we cant handle multiple events? Currently I've put a text item near the button, and called the Jscript for mouse over event in that as a temporary workaround. Can someone let me know if this is feasible? If not any other alternative to handle this?
Thanks in advance,
gsachidh

Hi Gsachidh,
well interesting problem you're facinng. Indeed, it can't be specified using the 'Button Attributes' So we have to come up with an workaround.
A quick en dirty solution would be to specify it with the 'Optional URL Redirect options'. In a normal button, with processing on same page, this would be 'no target'. but in case of additional things to be done this can be used, using an target URL. I used this many times, in example with popUp windows for refreshing the caller object when changes are made. In your case we have to add next to the href an onmouseover event. this can be done with;
Target set to => URL
URL - target => javascript:doSubmit('<button_name>');" onMouseOver="javascript:showTooltip('tooltip');"
Here the " is the key, letting ApEx know the target (href) is doSubmit('<button_name>'), just like when no target would be specified and adding a new javascript event; onMouseOver.
Although this is a dirty solution in my opinion, it is the best i could come up with. I have another idea in how to do this, that is by adding this event dynamically with javascript with an addEvent. But i don't have an example at the moment for this scenario.
Simon
Message was edited by:
S1M0N

Repeat every X minutes w/o multiple events

Is there any way to get an event to repeat faster than 1 day? For example. I want something to repeat every 10 minutes. Is there a way to do this without creating multiple events?

I'm seeing this behaviour, too. In my case, it happens with a recurring meeting.

Multiple event receivers with a list

Hi All,
If there are two item event receivers attached with a list and event is cancelled by event receiver that trigger first, will second event receiver be invoked? As per my understanding that second event receiver will not be invoked.
I have a requirement where in case first event receiver cancel the event, second event recever should still be invoked.
do anyone has any idea aroound it?
Regards Amit

Hi, Amit KM.
http://msdn.microsoft.com/en-us/library/gg749858.aspx
Notice the following details:
Synchronous event receivers are called in sequential order based on the sequence number specified during event binding. This applies to both Before and After synchronous events.
Asynchronous After event receiver threads are initiated in sequential order based on the sequence number. However, there is no guarantee that they will finish in that same order.
An asynchronous After event can start at any time after its associated user action is performed. It may start before, at the same time as, or after the Web request is completed.
After a user initiates an action in the SharePoint user interface, and before SharePoint Foundation executes the user action, the synchronous Before events are raised. If there are multiple synchronous Before events, they are raised in the order specified
by their sequence number. Similarly, synchronous After events are raised after SharePoint Foundation executes the user action. These, too, are raised in the order specified by sequence number. As you can see, all synchronous events are processed in the same
thread as that in which the user action occurs.
Asynchronous After events, however, are processed on secondary threads.
So you're completely right that if the first event receiver has cancelled the operation, the second event receiver will never been executed.
In your case if you want second event receiver(B) to be invoked regardless of the first event receivers'
(A) result you can easily swap the sequence numbers for those event receivers.
Event Receiver Sequence
The event receiver sequence specifies the order in which an event receiver is executed in cases where an event triggers multiple event receivers. For example, if you have two
ItemAdded event receivers bound to the same list (one from Assembly "1" and the other from Assembly "2"), the event receiver that is bound with a lower sequence number is executed first. A practical example is adding an event receiver to a
system list that already has a system event receiver bound to it. In that case, you assign the new event receiver a higher sequence number.
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
<Receivers ListUrl="Lists/Tasks">
<Receiver>
<Assembly>MyReceiverAssembly, Version=1.0.0.0, Culture=Neutral,
PublicKeyToken=12e5e5525fb3d28a</Assembly>
<Class>MyReceiverAssembly.MyReceiverClass</Class>
<Type>ItemAdded</Type>
<Name>My ItemAdded Event Receiver</Name>
<Synchronization>Synchronous</Synchronization>
<SequenceNumber>1000</SequenceNumber>
</Receiver>
</Receivers>
</Elements>
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SharePoint Managed Metadata Claims Provider project

Lock front panel until the event case for this event completes

A Dynamic Event is a filtered event? Is this why "Lock front panel until the event case for this event completes" is not shown on Edit Event window dialog? I use Dynamic Event so I can subvi the event structure.
I need stop my app from locking the FP whenever the user double clicks on the numerical array value (<-- the FP freezes the mouse and renders it useless) and stops the value from ever being changed. This event is registered for Value Change (not mouse up or down) and I get a locked mouse. As yet in the UI, no value changed occurs but I get a locked mouse. A LV bug?
Trying to KISS, I can see this fixing this by moving ONLY the value change event to the top level VI instead of a dynamic registered event in a subVI. This will give me the option to NOT "Lock front panel until the event case for this event completes" .
Solved!
Go to Solution.

richjoh wrote:
Thx, Ben that fixed the problem when I unchecked "Lock panel...".
So it appears LV locks the panel during runtime once the Dynamic Reg Events is on BD and it doesn't matter if your case to handle the Reg Events is created or NOT... interesting. That's why my mouse persisted to "freeze up" although I deleted the case for my FP array.
Its situation like what you described that has given me many insights into how LV actually works. In one of my bbuggy VI's I found that a class wire can run a million miles through multiple sub-VI queues etc but the data itself is only touched when it has to be touched. in my case it was a crash while trying to write bogus class dat to a TDMS file.
I am glad you are back on course.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Multiple events in firePartialAction

I have two event handlers, A and B. How can I fire both events from one <firePartialAction>?

johnsold wrote:
You cannot change all the buttons at once, but you can still use the OR nature of the event structure with multiple events for one case.
Create a case for the three buttons' Value Changed events. Inside the case read all three buttons. AND the result. Wire the AND to a case structure. In the True case activate the code you want for all the buttons. In the False case do nothing.
Lynn
You will need to pay attention to the mechanal action of the buttons. If they clear when read this will not work.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot

Multiple event structures in one program

I know it's not good practice to have one event structure inside another event structure (I don't know exactly why). But if another event structure is in the subvi, is it safe? Please comment.

guangdew1 wrote:
I know it's not good practice to have one event structure inside another event structure (I don't know exactly why).
This is because of dataflow and the way event structures work. If you have an event structure inside an event structure, both event structures will accumulate events whenever one occurs, but it is unlikely that they can be handled in the order they occur or at all. By default, event structure are set to lock the front panel until the event completes, meaning that if an inner event gets triggered first, the code will lock up, because it will no longer be possible to trigger one of the outer events. If the outer event occurs first, it cannot complete, because it requires a later firing of one of the inner events before it is ready to handle the next event that occurs in the UI. Even if it marginally works if the panels don't get locked, you are requiring the user to trigger events in a certain order. How is he supposed to know what's allowed or not?
If this is not exactly clear to you, you need to start with a few tutorial and learn about dataflow, Then start using a single event structure and see how things work by programming scenarios and see what happens.
guangdew1 wrote:
But if another event structure is in the subvi, is it safe? Please comment.
Event structures are only useful inside interactive subVIs that show their front panel. even then I strongly advise against calling anything interactive, or anything that takes excessively long, inside a main event structure. You end up with code that can become unpredictable, can deadlock, is hard to debug and flies in the face of all good programming guidelines.
Obviously, you have some specific application in mind where you think something like that is useful, I can guarantee you that there is a much better solution is you think about this a bit longer. If you need help, please describe exactly what the program should do and how it should react to user interactions at the various stages.
A program should always be approached from the code and UI needs. Don't start with a harebrained code construct (events inside events) and then look for a use. It does not exist!
Event structure only belong in toplevel loops. They should never be hidden insde squences or case structures (or other event structures as already mentioned above). If you have multiple toplevel loops that run in parallel, it is safe to place up to one event structure inside each. Each event structure can have an unlimited number of event cases. This should be sufficient to handle any programming need you might have.
LabVIEW Champion . Do more with less code and in less time .

Multiple event structures in one VI

I have two event structures in a single VI, one that handles events that freeze the user interface and one for events that don't. The latter group are all triggered acquisition tasks, where you arm the data acquisition, but possibly might want to abort it (or do other things, while waiting for the data to come. Obviously you need a stop button to be active and responsive. In retrospect, using two loops was possibly a poor choice, but one I made because it never occured to me that these things would only fire once and have to be put in a while loop to be kept active. No other language does that as far as I know. Anyway, the question is how do I keep both active? Do I enclose both in a single while loop? Do I give each there own while loop. Do I give up and merge the two event structures into one. For clarity I would like to keep them seperate, but that is not essential. I'ld like to know what my options are.
Solved!
Go to Solution.

rossu wrote:
If they are in sperate while loops will they both run. If they are in one loop will the loop recycle if one structue is still waiting for an event to occur?
The answer to this is fundamental to how LabVIEW works. A loop will not proceed to the next cycle until everything inside it completes. If you have two event structures in the same loop, both of them need to process an event (or a timeout) before the loop will iterate.
You can have multiple event structures in the same VI.
By "freeze the UI," do you mean the "Lock front panel..." checkbox in the event dialog? There is no problem with having some events that do lock the front panel and some that do not in the same event structure. I'm not sure that this is what you mean by "freezing" the UI, though.
EDIT: and one more comment. Generally you should not put long-running tasks (like data acquisition) inside an event structure. Instead, the event case should pass those tasks off to a separate loop (for example using a queue) so that the event structure can quickly go back to listening for other events.

Multiple event structure in a while loop

Dear All,
               I had a multiple event structure inside a while loop. The purpose of doing so is because I had a few 2D picture on the front panel. I would like to detect which 2D pictures had been click using the mouse down event structure for 8 of my 2D pictures.
              The problem that I faced now is that when I of the event case or one of the 2D pictures had been click, it will not exit the while loop. I had to click on all the 8 2D pictures before it will exit the loop.
              I had uncheck the under the "Edit Event" --> "Lock Front Panel (defer processing of user action) until this event case completes". But I am still stuck inside the loop.
              Each 2D picture will perform different action therefore I cannot have an event case of all 2D pictures inside else I would know which 2D picture had been click.
             Is there any other way out of this situation? Pls help. Thanks a lot

A producer/consumer architecture (look at the examples that ship with LabVIEW) is comprised of two parallel while loops. One loop contains the event structure. The other contains your consumer which is basically a queued state machine. It receives messages from the producer via a queue. Your event structure can register a separate event for each 2D picture control or it can use a single event that would determine which spefic controls was clicked on. This is a more general approach and expands easily. Here is a basic example of what I am talking about.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot
Attachments:
Event Producer-Consumer.vi ‏14 KB

DAQmx in Event structure / avoid multiple events

Hi all
I've started creating program for acquisition and analysis of data . I don't have much experience in LabVIEW, but it's important to me to start creating this application in good way. Can you give me some advice about things below?
I prepared template with Event structure, based on some article .
First question is how exactly place DAQmx blocks in it. Now they are all on one state of case structure "test", but I'm not sure that's correct because most of the example on NI side have initialization (like sample rate, number of saple) outside of the loop? It's important to make it possible to change parameter between measurements.
Second. How to avoid multiple events. In example: button TEST is pressed, measurement is taken. This measurement take a long time. I've started bored, and some other buttons (maybe TEST ) accidentally were pressed. When measurement is completed it would be good idea to destroy this events associated with accidently pressed buttons. It is possible to do it? What's the best way when there's a lot of buttons(when analysis part of program will be added)?
Best Regards
PS. sorry about my english
Attachments:
pgm.vi ‏33 KB
Enum_Events.ctl ‏5 KB

Dear Finch!
Welcome to NI Forums!
My first advice regarding your code would be to use shift registers instead of Queues as your state storage, since (as you've said) there is no reason to store multiple events that have happened. The state machine design pattern, which I strongly recommend in this scenario is built into LabVIEW, you can use it as a template if you go to the New.. menu.
Please check out these materials for further discussion about state machines.
You are correct in that most of the DAQmx VIs can be placed outside of the loop, only DAQmx Read (the function we actually use more then once) must be placed inside the loop, the rest can stay out. If you want to modify some parameters (like Timing) mid-execution, you only have to stop the task, set them, then start it again.
This can be easily done in a different state, which can execute only when some parameters have changed.
Also, if you want your user to be unable to interact with certain controls while the test is being taken, you can programmatically disable them with a Property Node.
Please get back to me if you have any other questions.
Best regards:
Andrew Valko
NI Hungary
Andrew Valko
National Instruments Hungary

Event Structure: Multiple Events ??

All
I have a project where I have an event structure handling about 10 individual events. Would it be possible to fire multiple events at the same time ? For instance, if my event 3 is triggered and the corresponding process is running, can I trigger an event 7 to have it's process running ?
Kudos always welcome for helpful posts

Edit your event and make sure to uncheck "Lock front panel until the event case for this event completes", else you won't be able to do much.
Attached is a simple example using two event structures. (All that said, maybe there is a better solution than using two events, just re-think your code).
LabVIEW Champion . Do more with less code and in less time .
Attachments:
2events.vi ‏42 KB

How do I select multiple events in iCal 8.0?

In OSX Mavericks, I used to be able to select multiple events in iCal in the event list view. I could select the initial event in the span of events to be selected. Then hold Shift while selecting the final even in the span of events. As a result, all of the events in that span would be selected.
in OSX Yosemite, this is no longer possible. There appears to be no list view, and holding the Shift button does not allow me to select a span of events.
What is the best way to select a span of events, say as much as 30 events?
Thank you.

Empty Caches
1. Safari > Preference > Advanced
    Checkmark the box for "Show Develop menu in menu bar".
    "Develop" menu will appear in the Safari menu bar.
    Click Develop and select "Empty Caches" from the dropdown.
2. Quit Safari if open.
    Option click the "Go" menu in the Finder menu bar.
    Select "Library" and then "Caches".
    Look for the folder 'com.apple.Safari"
    Right click "com.apple.Safari" and select "Move to Trash"
    Relaunch Safari.

Multiple event cases ?

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