Can't write file to SHARED directories on API31 (Android 12)

[rkuba]

Hi,
Could anybody suggest any working on API31 combination of path, context of file component and default context of application (on Screen1) to write and read file in shared folders (Documents or Download) please?
I use file component to File1.SaveFile.

And Yes, I have searched this forum, tried multiple combinations of App/Shared context of both Screen1 and File component as well as short/full path styles for the path (/Download/, /storage/emulated/0/Download/ and file:///storage/emulated/0/Download/) . I do not want you to analyse my blocks - either anybody has tried and knows combination of these 3 parameters (Application default context, file component context, path) or not

[Anke]

Access to non-media & media files on Android 11+

Access to non-media files on Android 11+ On Android 11+, non-media files (like txt, pdf, csv, ...) can be accessed if and only if the text files are in the → ASD or in the → Private dir (i.e. were saved there), or the text files are in one of the Shared folders /Documents or /Download and these files were created by the app itself, or SAF is used, or MANAGE_EXTERNAL_STORAGE* permission is requested and granted. *` This is not really an option, because an app that requests this permi…

[Anke]

See also here:

MFile - a modified version of Sunny's `EFile` extension - Shared folders - storage permissions - Android 11+

Here is a modified version of Sunny's EFile extension, which added some methods that are needed (among others things) for testing purposes with Companion & AKP. Because if you try to save in one of the Shared folders (/Documents or /Download) first with Companion it is not possible to do this without deleting the saved text file before testing with the APK and vice versa (at least on Android 11+). So the Delete & FileExists & API level methods are needed. The Delete method exists with the File …

[rkuba]

Thanks a lot for help and MFile component.
This allows me to restore writing to Shared folders on API29-API31.

I did not understand point on necessity to delete files + I can't make MFile delete /Download/MyTempFolder (File component did have recursive flag allowing me to clean-up...) but these are not really my top priorities for a while

Thanks again !

[Taifun]

@rkuba

I did not understand point on necessity to delete files +

Because your app is not able to overwrite files from other apps

Taifun

[Anke]

@rkuba

I can't make MFile delete /Download/MyTempFolder

[rkuba]

Thanks for all the explanations. I've done some tests on API30 and API31:

1. Deleting non-empty directories requires knowing the content (->Delete for each file in TaifunFile.FileList),
2. On devices shared by 2 people (Settings->Users and ...->Users), root folder may not be /storage/emulated/0/ - replace zero by what u find in e.g. MFile.ApplicationSpecificDirPath
   Best regards

[Anke]

@rkuba

Deleting non-empty directories requires knowing the content

@rkuba

On devices shared by 2 people (Settings->Users and ...->Users), root folder may not be /storage/emulated/0/ - replace zero by what u find in e.g. MFile.ApplicationSpecificDirPath

I don't understand both points, but I should if they were worded in an understandable way.

[Taifun]

@rkuba

I've done some tests on API30 and API31:

what you are trying to say is, you tested on an Android 11 and Android 12 device
the target sdk for App Inventor apps is always SDK30...

@rkuba

Deleting non-empty directories requires knowing the content (->Delete for each file in TaifunFile.FileList),

yes, this is how my file extension works... if there are files inside a directory you first have to delete the files before you are able to delete the directory

Taifun

[Anke]

@Taifun

this is how my file extension works... if there are files inside a directory you first have to delete the files before you are able to delete the directory

Yes, and this is the same with the File component.
But the FileTools extension can also delete a non-empty folder.

@rkuba

requires knowing the content

Knowing the content is irrelevant, it just has to be files (content) that the app created itself.

[rkuba]

I new in Android so so things obvious to You are not to me ... Part of my problem was that Download folder was not in " /storage/emulated/0/Download" but in "/storage/emulated/10/Download" instead. I did not find a function "getSharedFoldersRoot" giving "/storage/emulated/0/" or /storage/emulated/10/ or whatever is appropriate on given device (so I've put together some blocks ). Thanks for all the support.

[TIMAI2]

Something like this:

[rkuba]

Thanks. Unfortunatelly I've deleted my question .... so here I re-crete it:
...

One more : what is proper way to append rows sequentially in the loop ? Scenario is simple: I have a header string ending \n (generated by _AdifHeader function) and a list (log). I create file writing Header MFile.Save and I iterate list using _AdifRow function that renders string ended by "\n" (lines) and write these using MFile.Append. It looks to me that subsequent Appends neither wait for file operations before them nor make sure thay are written sequentially. Sometimes they are out of order, sometimes (as now) first appended line looks live overriden by preceding SaveFile operation. I've found it only now ... I'll try to reproduce it with File component... Help me please.
...
Anyway:

1. is it safe in AppInventor to call from within AfterFileSave another save ?
2. it requires use of global variables (counter and buffer) and accessing it implicitly - I want to avoid it as much as possible in my code as it makes any change/debuging extremely difficult and code gets error-prone
3. What is safe lenght of Text (so that I create veeeeeeery long text having all lines and write it at once) ?

[TIMAI2]

@rkuba

is it safe in AppInventor to call from within AfterFileSave another save ?

Yes. This ensures that each item in your list is appended to the file and saved before the next item.

@rkuba

it requires use of global variables (counter and buffer) and accessing it implicitly - I want to avoid it as much as possible in my code as it makes any change/debuging extremely difficult and code gets error-prone

Don't see this as an issue. You won't be accessing the file whilst you add items from your list ? Using a counter means it has to be a global variable. Not sure what you mean by buffer ?

@rkuba

What is safe lenght of Text (so that I create veeeeeeery long text having all lines and write it at once) ?

Length of lines in a text file, size of a text file, and size of data stored in a tinydb are generally limited by the storage memory capacity of the device. Others have stored entire books/novels in a single file, and displayed then in a single label.

[rkuba]

Thanks for all the explanations, patience and great help.