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B4A Library Threading library

Discussion in 'Additional libraries, classes and official updates' started by agraham, Dec 7, 2010.

  1. agraham

    agraham Expert Licensed User

    This library lets you run Basic4android Subs on separate threads to the main GUI thread. It also contains a Lock (semaphore) object that can be used for resource access arbitration and thread synchronisation.

    Included is also an enhanced Exception object to give more information on any Exception caught. This can also rethrow those caught Exceptions and can create new Exceptions to throw.

    EDIT :- Version 1.1 posted. See post #13 for details.

    Attached Files:

    Last edited: Jun 23, 2012
  2. sdaly

    sdaly New Member Licensed User



    Do you have any examples for threading? I'm looking to start a thread to process files and update a progress bar from this thread in the gui....
  3. agraham

    agraham Expert Licensed User

    There's a demo in the archive. Threading in Android can be tricky because of activity lifecycle considerations. Have you considered the non-modal ProgressDialog in Basic4ppc which will let you do your stuff on the main thread or using a ProgressBar and DoEvents to keep it updated?
    ahorro1 likes this.
  4. sdaly

    sdaly New Member Licensed User


    Thanks, got the new thread working....

    Progress bar still doesn't update until the end of processing. I'm using as below...

    pbval = pbval + 1
    Dim Params(1) As Object
    Params(0) = pbval
    th.RunOnGuiThread("updatePb", Params)
  5. agraham

    agraham Expert Licensed User

    I can't see anything from that fragment. This works fine for me.
    Sub ThreadSub2
    Dim Count As Int
    Dim Params(1As Object
    Do While Count < 1000
    ' instead of locking like Thread1 we could crudely just wait for the GUI to update
          ' some messages may be lost but this may not matter in some applications
          Count = Count + 1
    0) = Count
    "Update2", Params)
    End Sub

    Sub Update2(count As Int)
       EditText2.Text = count
       ProgressBar1.Progress = count /
    End Sub
  6. spillermarco

    spillermarco Member Licensed User

    Thread1.RunOnGuiThread .....

    Hello, I use this library to read some data from a network device view.
    the problem is that sometimes, in the opening application, the program stops saying "application terminated unexpectedly .." .
    If the program starts successfully continued without stopping.
    I discovered that an error is generated:

    Thread1.RunOnGuiThread ("Update1", Params)

    if I take off this command, the program no longer exits.

    I did all the tests possible, I also recalled a sub empty, passing one parameter fixed, it should be equally in error.

    By removing the filters from the log window that read:

    threadid = 1: thread exiting with Uncaught exception (group = 0x40015560)

    How can I do to see what went wrong?

    Thanks in advance

  7. corwin42

    corwin42 Expert Licensed User

    I tried to create a new thread in a class but it doesn't seem to work.

    It seems that the thread sub gets never called and the Ended event is raised with endedOK = false imediately.

    Am I doing something wrong? Attached is a small example which shows the problem.

    Attached Files:

    Last edited: Jun 22, 2012
  8. agraham

    agraham Expert Licensed User

    Your posted code doesn't compile without changes. Note that a Thread traps and saves any exception. You can see where it occurred with
    Dim e As ExceptionEx
    e = t.Exception
    In this case Thread expects to invoke a static Java method (Sub) as all Subs in Basic4android modules so far have been static. However Subs in a class are normal instance methods and so the invoke fails because no Class instance is passed to the method invocation - hence the mention of "null" in the logged error message.

    I am very rusty on Android and Java but can't immediately think of an elegant way to use both static and instance methods as the Runnable for a thread. I'll think about it. Perhaps Erel might have an idea.
  9. corwin42

    corwin42 Expert Licensed User

    Sorry, I noticed this and uploaded the correct version 5 minutes after the first one. You are just too fast. :)

    Ok, thank you for explaining it. Hopefully you or Erel will find a solution for it.
  10. agraham

    agraham Expert Licensed User

    I've got it working by passing the class instance to Start using the new Me parameter available in version 2.0. This will also work for Subs in Activities and Services.
    t.Start("GetAsyncDataThreadSub", Me, Array As Object(pId, pMap))
    However there is a somewhat non-obvious Java typing issue to do with wrapping (or not) underlying Java objects that I need to discuss with Erel and try to clarify in the XML help.
  11. JakeBullet70

    JakeBullet70 Well-Known Member Licensed User

    I have been following this thread as I have a need for threads in classes.

    t.Start("GetAsyncDataThreadSub", Me, Array As Object(pId, pMap))
    This code wont compile as I get an error saying 'Too many parameters'

    Ideas anybody?
  12. agraham

    agraham Expert Licensed User

    As I tried to imply in my last post I've got it working but I need to decide how to document or solve some typing issues before posting a modified library.
  13. agraham

    agraham Expert Licensed User

    Version 1.1 now posted adds a parameter to Start (a breaking change I'm afraid) to enable Class instance methods to be used as Thread Subs. The additional help for Start is posted below

    Dim MyMap as Map
    "AsyncSetMap"Array As Object(myMap))
    Private Sub AsyncSetMap(MapObj As Object)
    Dim Map1 As Map
           Map1 = MapObj
    'Add some Data to the map
          Map1.Put("A Key""Some Data")
    End Sub
    Milton FS Santos and lemonisdead like this.
  14. JakeBullet70

    JakeBullet70 Well-Known Member Licensed User

    Sorry, I misunderstood.

    Thanks for the update!!!!!!!
  15. corwin42

    corwin42 Expert Licensed User

    Works as expected now. Thank you very much.
  16. tcgoh

    tcgoh Active Member Licensed User

    I'm trying to use your Thread Libraries to show a progressbar when the code below is converting a large data.text file to SQL.

    Its takes about 2mins to convert the 2-3 mb file. Is it possible to show a progressbar or dialog during this 2mins?
    Sub button1_click
    end sub

    Sub convert
    "CREATE TABLE CREW (s1 TEXT , s2 TEXT, s3 TEXT, s4 TEXT, s5 TEXT, s6 TEXT, s7 TEXT, s8 TEXT, s9 TEXT, s10 TEXT )"
    Dim line3 As String
    Dim i As Int

          line3 = reader.ReadLine
    Do While line3 <> Null 
    Dim CC() As String  'CC is column content
          CC = Regex.Split(",", line3)
    "INSERT INTO " & DBTableName & " VALUES (?,?,?,?,?,?,?,?,?,?)"Array As  Object (CC(0), CC(1), CC(2), CC(3),CC(4), CC(5), CC(6), CC(7),CC(8),CC(9)))
           i = i + 
                    line3 = reader.ReadLine
    Msgbox(i & " Records in text file were imported to ".ToUpperCase & DBTableName, "T E X T  F I L E")
    End Sub
    Thanks and regards
  17. Mahares

    Mahares Well Known Member Licensed User

    Perhaps, As another solution, according to Erel, you can improve the import performance of the text file into the table dramatically if you properly use begin and end transaction. I have not taken full advantage of them because my files are small. Please try and let us know how much time you save. For more details see the following post: http://www.basic4ppc.com/forum/basi...placement-transaction-keywords.html#post94614. See below code where to place them:
    'do all the SQL statements here.
        'loop should start and end here.

    Log(LastException.Message) 'no changes will be made
    End Try
  18. tcgoh

    tcgoh Active Member Licensed User

    Thanks Mahares for coming to my rescues again.

    Yes I'm now using the SQL1.BeginTransaction , endTransaction and it cuts down the time taken from 100sec to only 15sec for about 38k of records.

    I've also used the

    If j mod 1000 = 0 then DoEvents

    to show a progressdialogshow in between. Works nicely.

    Now my next question, how do I show something like Doevents for

    Do While line <> Null
    Thanks and regards
  19. Erel

    Erel Administrator Staff Member Licensed User

    It is better to start a new thread for a new question.
  20. Informatix

    Informatix Expert Licensed User

    I started a thread in a service and it seems that changing its priority during its run doesn't change anything. Confirmation ?
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