Android Question Value null in float or Integer

[rossati]

Hello

why I can assign null value to a float (or Integer) variable and I can't test it?

    Dim integer As Int = Null ' this works
    If integer = Null Then ... ' this crashes

Regards
Giovanni Rossati

 

[MarkusR]

"int" is not an object/class , so i guess it cast into value 0.
me would also expect the same behavior.
integer did not have null.
the compiler should catch this.

Logger verbunden mit: motorola XT1032
--------- beginning of main
Copying updated assets files (3)
*** Service (starter) Create ***
** Service (starter) Start **
** Activity (main) Create, isFirst = true **
** Activity (main) Resume **
Error occurred on line: 273 (Main)
java.lang.NumberFormatException: Invalid double: "null"
at java.lang.StringToReal.invalidReal(StringToReal.java:63)
at java.lang.StringToReal.initialParse(StringToReal.java:164)
at java.lang.StringToReal.parseDouble(StringToReal.java:282)
at java.lang.Double.parseDouble(Double.java:301)
at anywheresoftware.b4a.BA.ObjectToNumber(BA.java:646)
at com.rauch.test.main._null_click(main.java:633)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:710)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:339)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:249)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:139)
at anywheresoftware.b4a.BA$1.run(BA.java:325)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)

 

[rleiman]

Hi rossati,

I did some experimenting and discovered you can't assign Null to any numeric variables but you can do it to strings. For numeric variables you can only assign a number to them such as 0 or some other number. The "If" statement never got a chance to execute. I commented out the coding that will make your app crash.

Sub Activity_Create(FirstTime As Boolean)
    'Do not forget to load the layout file created with the visual designer. For example:
    'Activity.LoadLayout("Layout1")

    Dim strMyString As String = Null

    If strMyString = Null Then
        ' This works.
    End If

'  Dim lngMyLong as Long = Null

'    Dim integer As Int = Null ' this works
    
'    If integer = Null Then
'          ' this crashes
'    End If
End Sub

 

[Star-Dust]

You can assign null to variables that work by reference, all numeric variables or basic variables work by value and not by reference

Objects, classes, or non-basic variables work as references and can be assigned with null

 

[MarkusR]

yes, this basic types are exceptional case in OOP ^^

 

[rossati]

Thanks to all
I agree, the compiler should intercept this error