Android Question Read file and Math Function

[Tilesoft]

Hi,
My app must Download a file > then read it (a number) > then (number+1=result) > write result to same file.
But i get some errors. My code is:

Sub Globals
    Dim NumberVar As Int
    Dim NumberMath As Int
End Sub

Sub Button1_Click
    Dim j As HttpJob 'redim and initialize
    j.Initialize("", Me)
    j.Download("https://x.ir/number.txt")
    Wait For (j) JobDone(j As HttpJob)
    If j.Success Then
        Dim out1 As OutputStream = File.OpenOutput(File.DirInternal, "number.txt", False)
        File.Copy2(j.GetInputStream, out1)
        out1.Close '<------ very important
        If File.Exists(File.DirInternal, "number.txt") = True Then
            Log("yes")
            NumberVar=File.ReadString(File.DirInternal, "number.txt")
            Log(NumberVar)
            NumberMath=NumberVar+1
            File.WriteString(File.DirInternal, "number.txt", NumberMath)
            Log(NumberMath)
        End If
        'StartActivity(Post_Publish)
    End If
    j.Release
End Sub

And errors:

number_download$ResumableSub_Button1_Clickresume (java line: 450)
java.lang.NumberFormatException: empty String
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1842)
    at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    at java.lang.Double.parseDouble(Double.java:538)
    at lila.project.number_download$ResumableSub_Button1_Click.resume(number_download.java:450)
    at anywheresoftware.b4a.BA.checkAndRunWaitForEvent(BA.java:267)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:207)
    at anywheresoftware.b4a.keywords.Common$11.run(Common.java:1178)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:224)
    at android.app.ActivityThread.main(ActivityThread.java:7561)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:995)

 

[Brian Dean]

What does this line show in the Log ...

            Log(NumberVar)

It looks as though it is not finding the numerical value that you expect. That would explain this error message ...

java.lang.NumberFormatException: empty String

 

[Erel]

Strange code.

Correct code:

Dim s As String = Job.GetString
If IsNumber(s) Then
 Dim n As Int = s
 File.WriteString(XUI.DefaultFolder, "number.txt", n + 1)
Else
 Log("not a number!!!")
End If