howdy, Brent!

how can I help you today?

Evening Mark

Well, I've been studying services and methods of communicating information between them and activities

and I'm hoping to glean some wisdom on how best to provide that communication.

so that said...

Is it ok to both start and then bind a service?

that's unusual, but supported

I'm writing a file manager app

why would a file manager app need any sort of service?

and I want to offload file operations onto a background service in order to better handle long running file operations

ah, OK

So the service needs to persist past binding

why do you want to both bind and start?

just in case the app UI thread gets destroyed

That would be the reason for starting (to my understanding)

if "the app UI thread gets destroyed", your process was terminated, and your service is gone too

Hmm

the main application ("UI") thread is created when the process starts and lives until the process is terminated

Am I getting mixed up between processes and activities?

perhaps

I can't read your mind :-)

It's possible for the activity to be recycled while the service persists, correct?

if you use startService() (and only startService()) the service is independent of any activity

if you bind to a service, you need to unbind before the activity goes away

personally, I can't conceive of a scenario where it makes sense to both start and bind

Fair enough

in your case, using an IntentService (or a regular Service with a thread pool) for background ops makes sense, but I'd just use start

Best not to use an intent service, since I'd like to allow for concurrent operations

then a Service and either a passel of AsyncTasks or your own thread pool

Although, now that I'm thinking about it, concurrent file operations might create issues with simultaneous access...

but regardless

If what I'm aiming for is the reliable completion of long running file operations, even if the user closes the app, I should go for starting a service?

(as opposed to binding)

you definitely need to use startService() for your scenario

and, if you bind to a service, you need to unbind cleanly (e.g., bind in onCreate()/unbind in onDestroy() of an activity)

that's if you want to both start *and* bind

which I don't know why you would want to do

Are there concievable communication advantages with bind?

for some definition of "conceivable", perhaps

I would phrase it more as "use startService() alone, and mix in bindService() if and only if you have a clear need for it"

and, off the cuff, I have no idea what that need would be

I'm going to assume that means the use of both is far outside normal/best practices and focus on starting my service

Ok. Now I already know how operation completion will be handled (via the ordered broadcast you helped me with previously)

it's pretty unusual

yup

BTW, that's covered in greater detail in the Advanced Android update I released yesterday

I'll check that out.

So now I just need to get a handle on how best to allow the UI activity to provide realtime completion stats.

In addition to keeping track of file operation history (likely via a db)

what will be in the "realtime completion stats"?

A progress bar, basically

oh

Maybe some accompanying numbers

Like percentages or bytes moved, etc

off the cuff, there, I'd use the Messenger approach I demonstrate in _The Busy Coder's Guide to Android Development_

pass a Messenger, tied to your activity's Handler, in an Intent extra on the "yo, download this, buddy" command you pass to the Service

Service updates the activity via the Messenger

Sounds like what I'm looking for.

for events the user needs to know about beyond that, use the ordered broadcast, or try the Messenger and raise a Notification if you get the RemoteObjectException

another possibility, if you want to stick to broadcast, is to use a LocalBroadcastManager instead of the Messenger

that's also covered in yesterday's update to the Advanced Android book

ok

you don't want to use true broadcasts for frequent stuff, as there is IPC overhead on each broadcast, so it gets a bit expensive

That's kinda what I was thinking

so I wouldn't update byte counts using a regular sendBroadcast()

but a LocalBroadcastManager, or Messenger, are cheap

That is exactly the info I was looking for

I love all of the sample code that you provide. There is no substitute for reading the code of experienced programmers

best way to actually understand best practices

glad it's proving useful

On a side note, not sure if you keep up with the progress on ActionBarSherlock, but it's rapidly approaching completion

yup, it's going to be a key piece of The Big Book Reboot

I feel like Jake is singlehandedly matching Google's efforts towards encouraging the modernization of new and existing apps.

Jake is awesome

Here's another question for you:

I'm going to be faced with passing complex packages of data from my activity over to my service

Like a list of files to be copied and the destination directory, for example

I'm assuming communication would be via intent?

with startService(), yes, you package your command as extras on the Intent

And if so, How can I package that information into something that can be handled via intent?

for complex structures, either use stuff that go in Intent extras (e.g., string arrays), or use Bundle, or make a class that implements Parcelable

From what I have been able to learn so far, I think Parcelable might be my ticket

Is that basically like serializing the object?

yes, though the results cannot be persisted

basically, they skip the versioning info

assuming it's only being used temporarily

hmmm

I'd like the service to be working with it's own instance of the data, in order to be separate from the activity

That possible?

if you are passing stuff via the Intent, they will be copied

Even an entire object parcel?

yes

That works then

I'm thinking of gathering all relevant information, flags and files into "pasteRequest" and "zipRequest" objects

that are passed over and used by paste and zip operations

within the service

Time to take the backseat

Hey Samuel

howdy, Samuel!

Hello

Samuel: do you have a question?

Yes. I got this error : 'close() was never explicitly called on database '/data/data/com.samuel.find_resto/databases/Resto' but it's happen when I query data from web server using REST. If I delete the query the error is gone. The application still running normally even though the error exist.

Can I ignore it?

first, it is a warning, not an error -- it should be colored yellow-orange, not red

It's red

I have never seen that reported as an error

I would simply try to close the database when you are done with it

if your database is managed by a ContentProvider, you won't be able to do that

but if you are accessing a SQLiteDatabase outside of a ContentProvider, call close() on it when you are done with it and any Cursors you retrieved from it

I use sqllite and I'm sore I have closed it because if I pass the the code for querying data from web server, the error will not raise.

then I cannot help you

Ok, thanks for your time. I think I'll ignore it.

God bless you all.

It's enough for now.

Bye

Samuel: have a pleasant day!

Brent: do you have another question?

Trying to think if I'm forgetting anything

Ooo! yes. Is it possible to use both a background color overlaid with a semi-transparent striped png on the action bar?

beats me

I have never tried styling the action bar

Haha, ok

that being said, you can only have one background, in all likelihood

which means you will need to use a LayerListDrawable if you really want those alpha-composited

how well that will work when styling an action bar's background, though, I can't say

stripes, though, sound a bit retro :-)

Probably not that well

The action bar is a bit of a black box

and it's not too retro, lol

well, you could use Theme.Holo.Light, in which case it's a bit of a white box :-)

Nice classy diagonal pinstripes

har har :-)

that's the canonical documentation for action bar styling AFAIK

(http://developer.android.com/guide/topics/… also has stuff, but it's a bit light on prose)

I've been able to get that far

Not sure if you can view this, but: https://mail-attachment.googleusercontent.…

no, sorry, that's an attachment in your Gmail inbox AFAICT

If you notice the colored highlights, I was thinking of ways to make it easily user configurable.

fortunately for you, I can't read your mail

There we go

seems awful black for a file named blue

Well, when the little bit of blue is the only distinguishing feature of the blue, green, gold and transparent versions, you gotta work with what you got

setBackgroundDrawable() exists on ActionBar

in principle, calling that with a LayerListDrawable (to blend your color and stripes) could work

I'll look into that

probably not the most critical element of my development

well, that depends

if your APK might be a bit large, they say stripes can cause a slimming effect... :-)

(of course, I think that's for vertical stripes)

any other questions from either of you?

I think that's it for me

You've given me weeks of things to think about

well, that's a wrap for today's chat

next one is Thursday, also at 7:30pm Eastern

have a pleasant day!

Thanks Mark!