Android Question Service locking activity

advansis · May 5, 2014

Hi guys,
I wrote a service that starts each minute by calling 'StartServiceAt' (at the end of each Service_Start routine).
It must manage a long process: it must parse big data coming from a web-service (about 1-2Mb).
The Service_Start routine calls the parsing one, inside there's a loop that works for about 2-3 minutes; during this loop the service-start time is delayed.

The first problem is:

During the running of the loop, the user interface hangs (activities take about 10 seconds to load) and sometimes the screen gets blank. Android, also tries to kill my application (asks me...)

What I've tried:
1) Set the attribute: #StartCommandReturnValue: android.app.Service.START_STICKY
2) Put a 'DoEvents' statement inside the loop (BetterDialogs' inputbox by Informatix won't work in this case: dialogs are closed automatically after loaded...)
3) Created 2 services, one catching HttpUtils2 JobDone events and the other parsing the results each minute
4) Did a prayer

but nothing seems to work.
After exiting from the loop, the application runs normally.

The second problem is: during the loop I cannot refresh the UI because timer's tick are not fired...

Any clue ? Thanks in advance.

G. Pizzuto

thedesolatesoul · May 5, 2014

Long operations should always be done in a thread. And 2-3 minutes is a long time.
You will have to parse it on a thread, or break it down into smaller chunks and then parse it.

advansis · May 5, 2014

Thanks for replying...
Before your answer, I tought services were called in separate threads from the UI. So I'll give a try.
Is there some basic approach in b4a or shell I use the threading library provided from agraham ?

thedesolatesoul · May 5, 2014

Usually it is upto the library to do the work in a thread. What do you use to parse the data?
Otherwise you may have to use agraham's library.

advansis · May 5, 2014

I get data through HttpUtils2 and SaxParser. Then I use Sql library to insert the data inside my db (a FOR cycle with UPDATE and INSERT statements).
Both Receiving and Db-Inserts are done inside a service (running each minute, HttpUtils saves it's data in a global string).

thedesolatesoul · May 5, 2014

Is there a way you can find out which process takes longer, the sax parsing or the sql inserts?
My guess would be sax is serial so taking a long time.
Maybe you can use XOM parser instead, although I am not sure if it parses on a thread.

advansis · May 5, 2014

Sax is very fast, as data are very simple. The long process is the one performing the 'UPSERT' in the db (update or insert dipending on the existance of the record or not). Anyway I'm trying agraham's library. Still writing. Tanks a lot.

advansis · May 5, 2014

The agraham's library is not working for me... Cannot start the thread because of "Exception : wrong number of arguments; expected 3, got 0".
As I understand, it's an unresolved problem (and Erel gets angry each time someone talks about threadings...)
So, is there a simple library to manage very simple threads (neither arguments nor semaphores) ?

DonManfred · May 6, 2014

have you tried to wrap sql-insert into a begintransaction/endtransaction?

B4X:

Sub InsertManyRows
    SQL1.BeginTransaction
    Try
        For i = 1 To 500
            SQL1.ExecNonQuery2("INSERT INTO table1 VALUES ('def', ?, ?)", Array As Object(i, i))
        Next
        SQL1.TransactionSuccessful
    Catch
        Log(LastException.Message)
    End Try
    SQL1.EndTransaction
End Sub

advansis · May 6, 2014

Yes, I did after your post. Seems to be more responsive, probably i must check all over the code...

Android Question Service locking activity

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