Android Question Unexpected crash while testing my app. (Permission Error)

[tigrot]

One Beta Tester (Api 24) produced this error:

Exception java.io.FileNotFoundException: /storage/emulated/0/Android/data/it.whereami.logicdata/files/param (Permission denied)
java.io.FileOutputStream.open (FileOutputStream.java)
java.io.FileOutputStream.<init> (FileOutputStream.java:221)
anywheresoftware.b4a.objects.streams.File.OpenOutput (File.java:370)
anywheresoftware.b4a.objects.streams.File.WriteString (File.java:258)
it.whereami.logicdata.starter._jobdone (starter.java:472)
java.lang.reflect.Method.invoke (Method.java)
anywheresoftware.b4a.BA.raiseEvent2 (BA.java:186)
anywheresoftware.b4a.keywords.Common$11.run (Common.java:1144)
android.os.Handler.handleCallback (Handler.java:751)
android.os.Handler.dispatchMessage (Handler.java:95)
android.os.Looper.loop (Looper.java:154)
android.app.ActivityThread.main (ActivityThread.java:6310)
java.lang.reflect.Method.invoke (Method.java)
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:872)
com.android.internal.os.ZygoteInit.main (ZygoteInit.java:762)

The code relative to the error is a few rows(writing a parameter file)

Select Case Job.JobName
            Case "httpparam"
                Dim risp As String=Job.GetString
                securestrin=risp
                File.Writestring(File.DirDefaultExternal,"param",risp)
                startsystem
         End Select

This code worked till today for a lot of tester. I'm not sure it has been tested under Android 7+, since I've not done myself.
Does anybody tell me what is wrong?
Thank you very much

Mauro

 

[tigrot]

Forgot to write that the target in manifest is 18...

 

[Computersmith64]

In Android 6+, the user can go into the app manager & manually turn permissions on/off. Might want to check that this user hasn't done that.

- Colin.

 

[DonManfred]

You may test my first published lib...

https://www.b4x.com/android/forum/threads/storage-v1-0.49253/

Probably you can check with it if the Permission is given before you write to that folder.

 

[tigrot]

This was the first run of the App. Probably the user didn't change anything. I'm contacting the user (i have phone number of the users) just to confirm . Thank you!

 

[tigrot]

No manual intervention made from user. No visible cause for the issue...

 

[Erel]

You should check that File.ExternalWritable returns True.

 

[tigrot]

Thank you Erel!
Can you explain what could be the condition to produce this?
Mauro

 

[Erel]

Not really sure. It is probably not related but in older devices the "external" storage was locked when the device was connected to a computer.