Android Question NetworkOnMainThread exception when connecting to a WLAN Server

[DirkH]

Hello,
this is my first APP. It should transfer pictures from the android device to a WLAN Server. The following code contains the critical part and works:

#Region  Project Attributes
    #ApplicationLabel: PermissionTest
    #VersionCode: 1
    #VersionName: 1.0
    #SupportedOrientations: unspecified
    #CanInstallToExternalStorage: False
#End Region

#Region  Activity Attributes
    #FullScreen: False
    #IncludeTitle: True
#End Region

#AdditionalJar: jcifs-ng-2.1.9
#AdditionalJar: slf4j-api-1.7.25
#AdditionalJar: commons-logging-1.2
#AdditionalJar: bcpkix-jdk15on-1.68
#AdditionalJar: bcprov-jdk15on-1.68

#BridgeLogger: True

Sub Process_Globals
End Sub

Sub Globals
    Private btnTest As Button
    Private rp As RuntimePermissions
    'Dim jcifs As JavaObject
End Sub

Sub Activity_Create(FirstTime As Boolean)
    Activity.LoadLayout("layouttest")
End Sub

Sub Activity_Resume
    Log("✅ Activity_Resume startet")
    DisableStrictMode
End Sub

Sub DisableStrictMode
    Dim jo As JavaObject
    jo.InitializeStatic("android.os.Build.VERSION")
    If jo.GetField("SDK_INT") > 9 Then
        Dim policy As JavaObject
        policy = policy.InitializeNewInstance("android.os.StrictMode.ThreadPolicy.Builder", Null)
        policy = policy.RunMethodJO("permitAll", Null).RunMethodJO("build", Null)
        Dim sm As JavaObject
        sm.InitializeStatic("android.os.StrictMode").RunMethod("setThreadPolicy", Array(policy))
    End If
End Sub

Sub btnTest_Click As ResumableSub
    Sleep(0)

    Log("🟢 btnTest_Click startet")
    rp.CheckAndRequest(rp.PERMISSION_READ_EXTERNAL_STORAGE)
    Wait For Activity_PermissionResult (Permission As String, Result As Boolean)
    Log("🔁 PermissionResult: " & Permission & ", given = " & Result)
    If Result = False Then
        ToastMessageShow("❌ Access to memory refused.", True)
        Return Null
    End If

    ToastMessageShow("Permission to access given ✅", False)

    Try
        ' Local file source
        Dim localPath As String = "/storage/emulated/0/DCIM/Camera/7.jpg"
        Dim input As InputStream = File.OpenInput("", localPath)

        ' destination on NAS via SMB
        Dim remoteUrl As String = "smb://192.168.77.120/public/share_dirk/Dirk/bilderziele/ziel1/7.jpg"

        ' Authentification
        Dim auth As JavaObject
        auth.InitializeNewInstance("jcifs.smb.NtlmPasswordAuthenticator", Array("user", "PW"))

        ' Kontext with Authentification
        Dim ctxHelper As JavaObject
        ctxHelper.InitializeStatic("jcifs.context.SingletonContext")
        Dim baseContext As JavaObject = ctxHelper.RunMethod("getInstance", Null)
        Dim authContext As JavaObject = baseContext.RunMethodJO("withCredentials", Array(auth))

        ' initialize destination file
        Dim zielDatei As JavaObject
        zielDatei.InitializeNewInstance("jcifs.smb.SmbFile", Array(remoteUrl, authContext))

        ' Output-Stream
        Dim output As OutputStream = zielDatei.RunMethod("getOutputStream", Null)
        File.Copy2(input, output)

        ToastMessageShow("✅ Datei erfolgreich übertragen", False)
        Log("✅ Übertragung abgeschlossen.")
    Catch
        Log("❌ Error: " & LastException)
        ToastMessageShow("Error during transmission", True)
    End Try

    Return Null
End Sub

The manifest is:

AddManifestText(
<uses-sdk android:minSdkVersion="21" android:targetSdkVersion="32"/>
<supports-screens android:largeScreens="true"
    android:normalScreens="true"
    android:smallScreens="true"
    android:anyDensity="true"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
)
SetApplicationAttribute(android:requestLegacyExternalStorage, "true")
SetApplicationAttribute(android:icon, "@drawable/icon")
SetApplicationAttribute(android:label, "$LABEL$")
SetApplicationAttribute(android:usesCleartextTraffic, "true")
CreateResourceFromFile(Macro, Themes.LightTheme)
AddPermission(android.permission.READ_EXTERNAL_STORAGE)

It works but..
1. when I write in the manifest: android:targetSdkVersion="34"/> as recommended, it will simply not transfer data without expressing an "error message"
2. While debugging, I had to introduce the part "Sub DisableStrictMode". Otherwise I got the errorr: Network On Main Thread Exception. Now I tried again without this part in the code and it seems to work - I'm confused.

I imagine, there are more correct ways to proceed and would like to improve. I tried to transfer Code from main to Starter, but this seems to not be enough.

Thank you for any help.
Dirk

 

[Erel]

1. Never implement communication code in Activity module. Switch to B4XPages.

2. During debug mode, the compiler automatically disables strict mode as it is required for the debugger functionality. This is why it works in debug mode without you calling DisableStrictMode.

 

[DirkH]

Thank you for the valuable advice. I switched to B4XPages. New questions arising will be posted in separate threads.