Check if byte array variable set

francoisg

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• Jul 20, 2011

• #1

Hi,
in the following code I am defining a byte array - afterwards I want to check if it has been set or not by checking if it is null ...


Dim data() As Byte
....
If data = Null Then ExitApplication

When I try to compile I get the following:

Compiling generated Java code. Error
B4A line: 92
If data = Null Then ExitApplication
javac 1.6.0_24
src\hawkstone\epod\actprocessdoc.java:323: incomparable types: byte[] and double
if (_data==(double)(BA.ObjectToNumber(anywheresoftware.b4a.keywords.Common.Null))) {
^

Obviously I cannot check the length as the variable value is actually null. Is there another / better way of checking if arrays has been assigned values ???

 

agraham

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• Jul 20, 2011

• #2

francoisg said:

Obviously I cannot check the length

Click to expand...

Actually you can. Basic4android will never leave a variable uninitialised so it is quite safe to check the length. In your case it will return zero as Dim a() and Dim a(0) are the same.

 

francoisg

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• Jul 20, 2011

• #3

mmm.. then I am doing something wrong - "Log(Data.Length)" gives a null pointer exception ...

 

agraham

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• Jul 20, 2011

• #4

I did check, and look at the generated code, before I posted as I always try to do but just to be sure I checked again.

B4X:

   Dim anarray() As Byte
   Log(anarray.Length)
   ToastMessageShow(anarray.Length,True)

Works fine!

 

Erel

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• Jul 20, 2011

• #5

How are you assigning the value to Data?

 

francoisg

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• Jul 20, 2011

• #6

I am getting it from the camera - if the user decides not to use the image, the data variable is null ...
One thing, the data array is part of a type defined in a code module, might this maybe have an effect at all (type abc (data() as byte, ...) ???

 

francoisg

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• Jul 20, 2011

• #7

It seems we both are correct ;-)
Local variables are assigned, global variables that is a "type" variable does not seem to be initialized ... maybe I am using it wrong, will have to experiment a bit and see ...

 

agraham

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• Jul 20, 2011

• #8

I misunderstood what you meant by set, I assumed ReDimmed. You can use a Reflector Object as a workaround.

B4X:

   Dim ba() As Byte
   ...
   Dim Obj1 As Reflector
   Obj1.Target = ba   
   If Obj1.Target = Null Then ' or If Obj1.IsNull Then
      ToastMessageShow("Null",True)
   Else
      ToastMessageShow(Obj1.Target,True)
   End If

 

agraham

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• Jul 20, 2011

• #9

francoisg said:

variables that is a "type" variable does not seem to be initialized

Click to expand...

It was initialised but you assigned null to it and lost the original zero length array.

EDIT:- Assuming that you did call Initialize on it like you should with all "type" variables.

 

Last edited: Jul 20, 2011

Erel

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• Jul 20, 2011

• #10

Once you assign the value from the camera then the previous value is discarded. So if the camera returns null then you will get a null array.
Your checking code is correct. It seems like a bug in the compiler.
The workaround is to explicitly convert the array to an object:

B4X:

Dim o As Object
o = Data
If o = Null then ...
'continue working with Data

 

agraham

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• Jul 20, 2011

• #11

:sign0161: I forgot Basic4android supported "Object" as a type - still prone to thinking in B4P terms on occasion! Getting older and older ...

 

francoisg

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• Jul 20, 2011

• #12

Erels's solutions seems to work - thanx for the workaround!!