Android Question Query and use a class variable in Designer?

Filippo · Mar 9, 2026

Hi,

how can I query and use a variable from a class in Designer? Is that even possible? If so, how?

Specifically, it concerns this code here:

B4X:

Private Sub StatusBarHeight As Int
    Dim sHeight As Int
    Dim jo As JavaObject
    jo.InitializeContext
    
    Try
        Dim res As JavaObject = jo.RunMethod("getResources", Null)
        Dim resourceId As Int = res.RunMethod("getIdentifier", Array("status_bar_height", "dimen", "android"))
        
        If resourceId > 0 Then
            sHeight = res.RunMethod("getDimensionPixelSize", Array(resourceId))           
        End If
    Catch
        Log("Fehler beim Verschieben: " & LastException.Message)
    End Try
    Return sHeight
End Sub

I want to use the height of “StatusBarHeight” in the designer so that my toolbar adjusts accordingly.

Chris2 · Mar 9, 2026

Sounds like a job for.....

[B4X] [DSE] Designer Script Extensions

The soon to be released versions of B4A, B4i and B4J include a new feature named: designer script extensions. The new feature allows calling B4X code from the visual designer scripts. Note that the B4X code is not executed at design time. I believe that over time this new feature, with a...

www.b4x.com

Filippo · Mar 9, 2026

Chris2 said:
Sounds like a job for.....

That's what I thought, but I don't know how it would work; the whole thing doesn't look very intuitive.

Chris2 · Mar 9, 2026

I rarely use B4A, but certainly in B4J I've found it to be far more straight forward than it first appeared.

You'd basically just create a class with your StatusBarHeight sub and a sub with whatever you want to do with it :

Desinger Script Claa:

'Class named DSE_SBH'

'Parameters: panel that you want to adjust
Private Sub SetPanelBasedOnSHeight(DesignerArgs As DesignerArgs)

    Dim Panel As B4XView = DesignerArgs.GetViewFromArgs(0)
    Panel.Top = StatusBarHeight     'for example

End Sub

Private Sub StatusBarHeight As Int

    Dim sHeight As Int
    Dim jo As JavaObject
    jo.InitializeContext

    Try

        Dim res As JavaObject = jo.RunMethod("getResources", Null)
        Dim resourceId As Int = res.RunMethod("getIdentifier", Array("status_bar_height", "dimen", "android"))

        If resourceId > 0 Then

            sHeight = res.RunMethod("getDimensionPixelSize", Array(resourceId))           

        End If

    Catch

        Log("Fehler beim Verschieben: " & LastException.Message)

    End Try

    Return sHeight

End Sub

Then call it from the layout's script:

In layout script:

DSE_SBH.SetPanelBasedOnSHeight(Panel1)

Or something like that (code written on the fly)!

Filippo · Mar 9, 2026

I am receiving this error:

B4A Version: 13.40
Parsing code. (0.40s)
Java Version: 19
Building folders structure. (0.09s)
Compiling code. (0.39s)
Compiling layouts code. Error
Unassigned variable: 'clsstatusbar'
Error File: layToolBar.bal

Go to the designer script page to debug this error.

Designer-script:

B4X:

If ActivitySize > 6.5 Then
    pnlToolBar.Height = 64dip
Else
    If Portrait Then
        pnlToolBar.Height = 56dip
    Else
        pnlToolBar.Height = 48dip
    End If
End If

DDD.AddClass(fsToolBar)
fsToolBar.SetStatusBarHeight(pnlToolBar, pnlToolBar.Height)

Classe fsToolBar:

B4X:

Private Sub SetStatusBarHeight(DesignerArgs As DesignerArgs)
    Dim Panel As B4XView = DesignerArgs.GetViewFromArgs(0)
    Panel.Height = StatusBarHeight + DesignerArgs.GetViewFromArgs(1)
End Sub

Private Sub StatusBarHeight As Int
    Dim sHeight As Int
    Dim jo As JavaObject
    jo.InitializeContext
    
    Try
        Dim res As JavaObject = jo.RunMethod("getResources", Null)
        Dim resourceId As Int = res.RunMethod("getIdentifier", Array("status_bar_height", "dimen", "android"))
        
        If resourceId > 0 Then
            sHeight = res.RunMethod("getDimensionPixelSize", Array(resourceId))           
        End If
    Catch
        Log("Fehler beim Verschieben: " & LastException.Message)
    End Try
    Return sHeight
End Sub

Chris2 · Mar 9, 2026

Change:

B4X:

Private Sub SetStatusBarHeight(DesignerArgs As DesignerArgs)
    Dim Panel As B4XView = DesignerArgs.GetViewFromArgs(0)
    Panel.Height = StatusBarHeight + DesignerArgs.GetViewFromArgs(1)
End Sub

To:

B4X:

Private Sub SetStatusBarHeight(DesignerArgs As DesignerArgs)
    Dim Panel As B4XView = DesignerArgs.GetViewFromArgs(0)
    Dim pnlToolBarHeight As Int = DesignerArgs.Arguments.Get(1)
    Panel.Height = StatusBarHeight + pnlToolBarHeight
End Sub

Chris2 · Mar 9, 2026

I may be wrong, but in this case I also don't think you need the line DDD.AddClass(fsToolBar).

Filippo · Mar 9, 2026

If I don't use this line, I get this error when compiling:

java.lang.Exception: Sub initialize signature does not match expected signature.
public static anywheresoftware.b4a.pc.RemoteObject fg.cronomillemiglia.fstoolbar_subs_0._initialize(anywheresoftware.b4a.pc.RemoteObject,anywheresoftware.b4a.pc.RemoteObject,anywheresoftware.b4a.pc.RemoteObject,anywheresoftware.b4a.pc.RemoteObject) throws java.lang.Exception
class anywheresoftware.b4a.pc.RemoteObject, class anywheresoftware.b4a.pc.RemoteObject,

Chris2 · Mar 9, 2026

Filippo said:
java.lang.Exception: Sub initialize signature does not match expected signature.

What does the Initialize sub in your class look like?
Remember that the Initialize sub of Designer Script Extension classes must not include any parameter.

Filippo · Mar 9, 2026

Chris2 said:
Remember that the Initialize sub of Designer Script Extension classes must not include any parameter.

Now I understand that there should be no parameters in “Initialize” in the class.
Now there are no errors, but the height of the “pnlToolBar” panel is not changed.

Chris2 · Mar 9, 2026

I'd suggets you test the code in SetStatusBarHeight , calling it from a button or something to make sure that it works separately from the Designer Script.
Maybe try calling Pane1.SetLayoutAnimated instead of directly setting the height only with Panel.Height = StatusBarHeight + pnlToolBarHeight.

Filippo · Mar 9, 2026

I don't think the designer script is the solution to my problem.
I need to continue editing the new panel-height in Designer, and it looks like it won't work with that.

Chris2 · Mar 9, 2026

Fair enough. Maybe someone else who has more experience with using Designer Scripts in B4A can step in and help better than I can, or provide an alternative to DSE.
Having said that....

Filippo said:
I need to continue editing the new panel-height in Designer, and it looks like it won't work with that.

If you're talking about this bit:

B4X:

If ActivitySize > 6.5 Then
    pnlToolBar.Height = 64dip
Else
    If Portrait Then
        pnlToolBar.Height = 56dip
    Else
        pnlToolBar.Height = 48dip
    End If
End If

... then I would think that you can do that in the SetStatusBarHeight sub too:

B4X:

'Parameters: Panel, ActivitySize, Portrait'
Private Sub SetStatusBarHeight(DesignerArgs As DesignerArgs)
    Dim pnlToolBar As B4XView = DesignerArgs.GetViewFromArgs(0)
    Dim ActivitySize As Double = DesignerArgs.Arguments.Get(1)
    Dim Portrait As Boolean = DesignerArgs.Arguments.Get(2)
   
    If ActivitySize > 6.5 Then
        pnlToolBar.Height = 64dip
    Else
           If Portrait Then
            pnlToolBar.Height = 56dip
        Else
                pnlToolBar.Height = 48dip
        End If
    End If
   
    pnlToolBar.Height = StatusBarHeight + pnlToolBar.Height
End Sub

designer script:

DDD.AddClass(fsToolBar)
fsToolBar.SetStatusBarHeight(pnlToolBar, ActivitySize, Portrait)

[Again, this is untested 'guesstimate' code. Someone with a greater knowledge of B4A may need to correct it]

Filippo · Mar 9, 2026

Thank you very much for your efforts, but unfortunately that doesn't work either.
The variable “pnlToolBar.Height” is not modified in the Designer.

Filippo · Mar 9, 2026

It works!

My mistake was that I called the “SetStatusBarHeight” procedure from Designer in the fsTootlBar class, but you should call the procedure from Designer in the main layout.

designer script:

clsStatusBar.SetStatusBarHeight(ToolBar1)

B4X:

'Parameters: Panel
Private Sub SetStatusBarHeight(DesignerArgs As DesignerArgs)
    Dim ToolBar As B4XView = DesignerArgs.GetViewFromArgs(0)
  
    ToolBar.Height = StatusBarHeight + ToolBar.Height
    Log("ToolBar.Height=" & ToolBar.Height)
End Sub

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