Android Question B4XPages and ResumableSub

RB Smissaert · Dec 31, 2022

Just starting with B4XPages and noticed that ResumableSub is not behaving the same as in a non B4XPages project.
In an activity based project I can run this from Main with no problem:

B4X:

    Dim rs As ResumableSub = CSV2List(File.DirRootExternal & "/PhonePats", "menu_props2.csv", True, 44, 34, True, 10, -1)
    Wait For (rs) Complete (lstCSV As List)
    
    Log(lstCSV.Size)

and I can use the produced list fine.

In a B4XPages project though I get this error:
java.lang.ClassCastException: java.util.ArrayList cannot be cast to anywheresoftware.b4a.BA$ResumableSub

If I run this not as a ResumableSub:

B4X:

    Dim lstCSV As List
    
    lstCSV = CSV2List(File.DirRootExternal & "/PhonePats", "menu_props2.csv", True, 44, 34, True, 10, -1)

    Log(lstCSV.Size)

There is no problem.
Is this a known limitation of B4XPages or am I doing something wrong?

RBS

klaus · Jan 1, 2023

You might replace the line above by this one.

B4X:

'Ctrl + click to export as zip: ide://run?File=%B4X%\Zipper.jar&Args=\%PROJECT_NAME%.zip

%PROJECT_NAME% is a reserved word for the project name.
I use it it in all my B4XPages projects.

RB Smissaert · Jan 1, 2023

RB Smissaert said:
OK, wasn't aware of that and attached a new file, which is indeed a bit larger.

RBS

Just fixed a minor bug to do with Sub btnMenu_Click in B4XMainPage.
Nil to do with the ResumableSub problem.

RBS

RB Smissaert · Jan 1, 2023

RB Smissaert said:
Just fixed a minor bug to do with Sub btnMenu_Click in B4XMainPage.
Nil to do with the ResumableSub problem.

RBS

Another minor bug fix, to do with the text of the menu title label.

RBS

Sagenut · Jan 1, 2023

The app crash because it cannot find the CSV file in the position where it search for.
The only way I got to make it work is to follow @LucaMs solution to copy the CSV file from ASSETS to DIRINTERNAL.
In this way I got the list created by CSV2LIST (maybe with other changes, but now I downloaded your last version).
Anyway in ASSETS we have menu_props, while you search for menu_props2.
Are we missing something?
And anyway it throw an error on item 29 or 30 of the list while parsing it because of an EMPTY STRING.
Of course I can't analize all your app to understand what it should do. ?

RB Smissaert · Jan 1, 2023

Sagenut said:
The app crash because it cannot find the CSV file in the position where it search for.
The only way I got to make it work is to follow @LucaMs solution to copy the CSV file from ASSETS to DIRINTERNAL.
In this way I got the list created by CSV2LIST (maybe with other changes, but now I downloaded your last version).
Anyway in ASSETS we have menu_props, while you search for menu_props2.
Are we missing something?
And anyway it throw an error on item 29 or 30 of the list while parsing it because of an EMPTY STRING.
Of course I can't analize all your app to understand what it should do. ?

RB Smissaert · Jan 1, 2023

Ignore the .csv files in dirassets. I am testing only with the file that I copied to that phonepats folder via Windows file explorer via the USB connection. There are no empty strings in the .csv I posted.

RBS

Sagenut · Jan 1, 2023

OK, I missed the post where you posted that file.
Created the PhonePats folder, copied the file................. It works.

RB Smissaert · Jan 1, 2023

Sagenut said:
OK, I missed the post where you posted that file.
Created the PhonePats folder, copied the file................. It works.

I made it work by making the Sub MakeMenuArray Resumable. With me if I make that Sub non-Resumable I get the problem as mentioned.

RBS

Sagenut · Jan 1, 2023

The fact is that MakeMenuArray contain a Wait For instructions.
Any Sub that contain a Sleep or a Wait For become a Resumable Sub (check Here).
So to return a value it's needed the

B4X:

as ResumableSub

at the end.

RB Smissaert · Jan 1, 2023

Sagenut said:
The fact is that MakeMenuArray contain a Wait For instructions.
Any Sub that contain a Sleep or a Wait For become a Resumable Sub (check Here).
So to return a value it's needed the

B4X:

as ResumableSub

at the end.

OK, thanks, I think that might be the solution. I thought that in the non B4XPages project it worked, but that must be wrong. Will check that in bit.

RBS

RB Smissaert · Jan 1, 2023

Sagenut said:
The fact is that MakeMenuArray contain a Wait For instructions.
Any Sub that contain a Sleep or a Wait For become a Resumable Sub (check Here).
So to return a value it's needed the

B4X:

as ResumableSub

at the end.

I checked in the other non-B4XPages project and there are Subs that contain a Wait For and those Subs are called normally (not as ResumableSub) and that is fine
if that Sub with the Wait For doesn't return a value. In the MenuTest project the Sub MakeMenuArray wasn't returning a value, but still I was unable to call it as a non-ResumableSub. This is the difference. So, it seems to me that if a Sub contains a Wait For that Sub can be called as a non-ResumableSub, provided that Sub returns no value.
So, still not sure why it fails in this B4XPages project.

RBS

RB Smissaert · Jan 1, 2023

RB Smissaert said:
I checked in the other non-B4XPages project and there are Subs that contain a Wait For and those Subs are called normally (not as ResumableSub) and that is fine
if that Sub with the Wait For doesn't return a value. In the MenuTest project the Sub MakeMenuArray wasn't returning a value, but still I was unable to call it as a non-ResumableSub. This is the difference. So, it seems to me that if a Sub contains a Wait For that Sub can be called as a non-ResumableSub, provided that Sub returns no value.
So, still not sure why it fails in this B4XPages project.

RBS

[B4X] Resumable subs that return values (ResumableSub)

Remember that that a call to Sleep or Wait For in a resumable sub causes the code flow to return to the parent. Example: Sub Button1_Click Sum(1, 2) Log("after sum") End Sub Sub Sum(a As Int, b As Int) Sleep(100) 'this will cause the code flow to return to the parent Log(a + b) End Sub...

www.b4x.com

>> - You can wait for resumable subs in other modules (in B4A it is relevant for classes only).

As a B4XPage is class, maybe this is relevant.

RBS

Sagenut · Jan 1, 2023

Your Sub in the end contain a
Return True
If this it's not needed I think that you can remove it and then probably you can even remove the
as ResumableSub
suffix.

RB Smissaert · Jan 1, 2023

Sagenut said:
Your Sub in the end contain a
Return True
If this it's not needed I think that you can remove it and then probably you can even remove the
as ResumableSub
suffix.

I only added the Return True when I made it a Resumable Sub. Without making MakeMenuArray a ResumableSub I couldn't get it to work.
Can you make it work without making MakeMenuArray a ResumableSub and with CSV2List being a ResumableSub?

RBS

LucaMs · Jan 1, 2023

It's not possible to use your project exactly as it is, because we don't have the file in DirRootExternal (that's not the right way to access it, by the way).

However, in general:

if a sub contains a Wait For or a Sleep, it automatically becomes of type ResumableSub. It is possible to call it both with and without "Wait For" but you must bear in mind that the project flow will continue after its invocation.

Anyway, change the name to one of the two ResumableSub variables; they are both RS, inside the same Sub(B4XPage_Created), so the second one redefines the other.

RB Smissaert · Jan 1, 2023

LucaMs said:
It's not possible to use your project exactly as it is, because we don't have the file in DirRootExternal (that's not the right way to access it, by the way).

However, in general:

if a sub contains a Wait For or a Sleep, it automatically becomes of type ResumableSub. It is possible to call it both with and without "Wait For" but you must bear in mind that the project flow will continue after its invocation.

Anyway, change the name to one of the two ResumableSub variables; they are both RS, inside the same Sub(B4XPage_Created), so the second one redefines the other.

I posted the .csv file

> that's not the right way to access it, by the way
How should it be done instead?

> change the name to one of the two ResumableSub variables
OK, wasn't aware that could be a problem, will change that.

RBS

LucaMs · Jan 1, 2023

RB Smissaert said:
I posted the .csv file

I know but I don't have it in the same dir as yours, of course. As you know, I copied it to DirInternal with success.

RB Smissaert said:
> that's not the right way to access it, by the way
How should it be done instead?

GetSafeDirDefaultExternal

RB Smissaert · Jan 1, 2023

LucaMs said:
I know but I don't have it in the same dir as yours, of course. As you know, I copied it to DirInternal with success.

GetSafeDirDefaultExternal

> GetSafeDirDefaultExternal
OK, will have a look at that.

RBS

LucaMs · Jan 1, 2023

(but using File.DirInternal)

Sagenut · Jan 1, 2023

Correct me if I am wrong.
In this part of your code

B4X:

If bDone Then
       
        '----------
        'this works
        '----------
        Dim rs As ResumableSub = MakeMenuArray
        Wait For (rs) Complete (dDoneMenuArray As Boolean)
       
        '-----------------
        'this doesn't work
        '-----------------
'        MakeMenuArray

        For i = iButtonStartIndex To arrMenuButtons.Length - 1 'overflow button has no bitmap
            arrMenuButtons(i).SetBitmap(arrMenu(i).bmpIconBitMap1) '<<<<< java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
        Next

    End If

after the MakeMenuArray you have a For cycle that need

B4X:

arrMenu(i).bmpIconBitMap1

to be ready. This is done by MakeMenuArray.
Calling MakeMenuArray as a normal Sub seems not to leave enough time to the Sub to complete its job before the next operations.
This is why using it as a Resumable Sub solve the problem.
As a confirmation, if you put a Sleep to let it complete

B4X:

If bDone Then
       
        '----------
        'this works
        '----------
'        Dim rs As ResumableSub = MakeMenuArray
'        Wait For (rs) Complete (dDoneMenuArray As Boolean)
       
        '-----------------
        'this doesn't work
        '-----------------
        MakeMenuArray
       
        Sleep(1000) 'Let us give time to MakeMenuArray to complete (exagerated value)
       
        For i = iButtonStartIndex To arrMenuButtons.Length - 1 'overflow button has no bitmap
            arrMenuButtons(i).SetBitmap(arrMenu(i).bmpIconBitMap1) '<<<<< java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
        Next

    End If

then you can have your Sub like this

B4X:

Sub MakeMenuArray
    'Do things
    'More things
    'Yet more things
End Sub

But honestly I would prefer a Resumable Sub that just wait for the exact time needed by the Sub to complete.

Android Question B4XPages and ResumableSub

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