Hi Mark

howdy, Frank

I need some help understanding how to get UI updates from a service to the UI Thread

I have a service that needs to send out updates say every second

why?

it is monitoring "real-time" data.

like heart-rate

ok

is the issue getting the data to an activity?

I had it broadcasting, but I think that was overkill. And then I tried Handlers, but I still don't like that

you can use callbacks

(a.k.a., listener objects)

ok. What if there were several activities (ie in a tabhost) that needed to do the same exact thing

they all have a common "hud" on each tab

well, I wouldn't have several activities in a TabHost, but that's a separate issue

either have the TabHost register the listener, or have all interested tabs register listeners

I would like to use the TabHost, but was having issues including other views in the same XML file as the tabhost. It was ignoring all of them

it would ignore everything besides the "tabs" and the "content frame"

you would need to have the TabHost be inside some other container (e.g., RelativeLayout) and have the non-tab-widgets be part of the outer container

ok. I will make sure to try that again

so when the listener gets an update say sharedpreferenceupdate. I can just schedule for the UI thread to redraw my HudView using the new sharedpreference values

well, I wouldn't use shared preferences as the conduit of the data

Step #1: Have the service implement registerSomethingListener() and unregisterSomethingListener()

so bundle them up in an intent

Step #2: Have the service hold onto a collection of those listeners

ok

Step #3: have the service iterate over the collection calling a method on the listeners when the event occurs

Step #4: have the activities call register...() and unregister...() when appropriate

you'll see an example of this pattern in _Android Programming Tutorials_

specifically tutorials 17 and 18

Ok. Thanks I will look over them. What type of application would you want to use Handlers or something like AIDL

Handlers are orthogonal to your problem

Handlers are one way to get control from a background thread to the main application thread

your activity might use a Handler to have the listener update the UI

I usually only use AIDL for remote services, where the service and its clients are in separate applications

ahhh. That helps me make sense of things. I was trying to use RemoteViews to update and it was messing me all up.

RemoteViews are mostly for app widgets, and secondarily for customized entries in the notification drawer

Yes. I was trying to design this thing where the "hud" in the activities could be used an app widget

but I think that's a whole different problem that I will have to face later after I get the activities in the tabs working

So we have been teaching a class on Android Programming at Florida State University. Would you mind if I used some of your examples in class and in exchange we will put your ware subscription as the "required text"

if the course is listed in the FSU course catalog

here is a link to the page I created last semester ww2.cs.fsu.edu/~sposaro/mobile

then I can give you Warescriptions for your students for free

yes. It is in the course catalog

it it listed as CIS4930: Mobile Programming

typically we only have 1 class in the spring with around 30 computer science students

I'm confused -- I see lots of CIS4930 classes (multi-core programming, systems & network administration)

yeah. That's a generic title

oh, wait, some of those are past years

I suppose if the class sticks around for another year then we will get our unique listing

so are you running the CIS4930 Mobile Programming one this fall?

or in the spring?

no. It will be in the spring

OK

when enrollment settles out, send me an email reminding me of all of this, along with the count of students, and I can send you Warescription coupons for them

So when the time comes. I will just contact you with more information then

thank you

in terms of the sample code, that's all Apache 2 licensed, so you can do with it what you want

Hey Mark. 1 more question before you go. I just looked at those examples. How would your store the data that the service generates for the View update

what do you mean by "store"?

getting the data values to the UI to update

ummm...an object?

not in a shared preference because of the frequency

oh, you mean you want to persist the data?

if the data is updated every second, I don't know why you need to persist it

just put it in an object

pass the object to the listener

listener passes the object to the activity

activity does really cool stuff

:-)

lol. Will I have to have a handler in the activity to actually scheduel the UI update

I usually use post(), available on View (so, any widget or container), to schedule a Runnable to do the work

or, runOnUiThread(), available on Activity

but you can use a Handler -- there's an example of that in _The Busy Coder's Guide to Android Development_

I have runonuithread now, but I think using post will be better since I'm creating a custom view for the hud

all runOnUiThread() does is see if you're presently running on the main application thread, and if not, it does the same stuff as post()

Hence, I don't know that it's worth changing

I am collecting HeartRate data and wanted to offer it along with calories burned etc. So that was the reason for persistence. But I want to log a history of it so I'll worry about filling in a content provider later on

well thanks for the help. I have been very happy with me Commonsware subscription :)

glad you like it

have a pleasant day/evening/whatever!

lol. I'm on the east cost too

goodbye