B4J Tutorial [B4XPages] Save the pages size and position

Add to B4XMainPage:
Type PagePosition (Left As Int, Top As Int, Width As Int, Height As Int, IsIconified As Boolean)
Private kvs As KeyValueStore
Public Sub SavePagePosition (Page As Object)
    Dim f As Form = B4XPages.GetNativeParent(Page)
    If f = Null Or f.IsInitialized = False Then Return
    kvs.Put(B4XPages.GetPageId(Page), FormToPP(f))    
End Sub

Public Sub LoadPagePosition (Page As Object)
    Dim f As Form = B4XPages.GetNativeParent(Page)
    Dim pp As PagePosition = kvs.Get(B4XPages.GetPageId(Page))
    If pp = Null Then Return
    SetFormFromMap(pp, f)
End Sub

Private Sub FormToPP (f As Form) As PagePosition
    Return CreatePagePosition(f.WindowLeft, f.WindowTop, f.WindowWidth, f.WindowHeight, f.As(JavaObject).GetFieldJO("stage").RunMethod("isIconified", Null))
End Sub

Private Sub SetFormFromMap(pp As PagePosition, f As Form)
    f.WindowLeft = pp.Left
    f.WindowTop = pp.Top
    f.WindowWidth = pp.Width
    f.WindowHeight = pp.Height
    Dim iconified As Boolean = pp.IsIconified
    If iconified Then
        Dim jo As JavaObject = f
        jo.GetFieldJO("stage").RunMethod("setIconified", Array(iconified))
    End If
    'check that left and top are in screen boundaries
    Dim goodLeft, goodTop As Boolean
    Dim fx As JFX
    For Each screen As Screen In fx.Screens
        If f.WindowLeft >= screen.MinX And f.WindowLeft <= screen.MaxX Then
            goodLeft = True
        End If
        If f.WindowTop >= screen.MinY And f.WindowTop <= screen.MaxY Then
            goodTop = True
        End If
    If Not(goodLeft) Then f.WindowLeft = 0
    If Not(goodTop) Then f.WindowTop = 0
End Sub

Private Sub CreatePagePosition (Left As Int, Top As Int, Width As Int, Height As Int, IsIconified As Boolean) As PagePosition
    Dim t1 As PagePosition
    t1.Left = Left
    t1.Top = Top
    t1.Width = Width
    t1.Height = Height
    t1.IsIconified = IsIconified
    Return t1
End Sub

Add to each page:
'at the end of B4XPage_Created
Private Sub B4XPage_Background
End Sub


  • Project.zip
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Last edited:


Licensed User
Longtime User
I was wondering: "save the position of a page?" 😲

"Fortunately", then I realized that you are talking about B4J and therefore about Forms 😁