This file is primarily for reference when converting Visual Basic 6 source code to B4A.
VB6 B4A
=== ===
controls Views (button, edittext, label, etc.)
In the VB6 code window, the top left drop-down list contains all
the controls you have placed in the current form and the right list
contains all the events for each control. The equivalent in B4A can
be found by clicking on Designer - Tools - Generate Members. Once
you have created Subs in the program coding window, the tab "Modules"
on the right side will list each of the Subs.
In B4A, you start by typing "Sub [viewName]" followed by a space and
follow the prompts, pressing Enter after each selection until B4A
ends with "EventName" highlighted. This is where you would type in
the name of the Sub.
editBox = string editBox.Text = string
In VB6, you can leave ".Text" off the names of controls when assigning
text to them, but this is not allowed in B4A.
Dim/ReDim:
---------
Dim Array(n) Dim Array(n+1)
While "n" is the last index number in VB6, it indicates the number
of array elements when used in B4A. For example, to Dim an array
with 0-32 elements in VB6, you would say Dim A(32), while to convert
this to B4A, you need to change it to Dim A(33), yet index #33 is
never used (doing so would cause an out-of-range error).
ReDim Preserve Use a List.
ReDim Array() Dim Array(n+1) -- to clear an array, just Dim it again.
[Dim a Int: Dim b as Boolean]
If Not b Then... If Not(b) Then...
If b Then... same
If b = True Then same
If a Then... If a > 0 Then...
B4A does not treat any non-zero value as True like VB6.
a = a + b If b = True Then a = a - 1
Boolean's value cannot be used in a math function in B4A.
Global Const x=1 B4A does not have a Global Const function.
In Sub Globals, you can say Dim x as Int: x = 1
but x is not a constant (it's value can be changed).
Loops, If-Then, Select Case:
---------------------------
Do [Until/While] same
Loop [Until/While] Loop [Until/While not allowed.]
For - Next same
For i... - Next i The loop variable (i) is not allowed with Next.
Exit Do/For Exit
If - Then - Else same, except VB's ElseIf is "Else If" in B4A; ditto EndIf
--- Continue [Skips to Next in For-Next loop]
For i = 1 to 6 For i = 1 to 6
If i <> 4 Then If i = 4 Then Continue
...code... ...code...
End If ...
Next Next
Select Case [expr] Select [value]
Colors:
------
L1.BackColor = L1.Color = Colors.Red
vbRed
L1.ForeColor = L1.TextColor = Colors.Black
vbBlack
Calling a sub:
-------------
SubName x, y SubName(x, y)
Sub SubName() Sub SubName() As Int/String/etc. -- a Global variable cannot be
a parameter, so say that "player" is a Global variable, you
cannot say: PlayCard(player). Instead you have to say:
i=player: PlayCard(i)
Function FName() Sub FName() As [var.type]
As [var.type] In B4A, any Sub can be used like a Function by adding a
variable type such as
Sub CheckX(x As Int) As Boolean
...optional code...
If x = [desired value] Then Return True
...optional code...
End Sub
If no Return is given, then zero/False/"" is returned, but
the IDE will give a warning, so it is better to Return 0/False/"".
The calling code does not have to reference the returned
value, so that while "If CheckX(x) = True..." is valid,
so is just "CheckX(x)"
Exit Sub Return
Exit Function Return [value]
General:
-------
CInt
DoEvents same, except that Erel says:
"Calling DoEvents in a loop consumes a lot of resources and
it doesn't allow the system to process all waiting messages
properly." This was in response to my pointing out that while
in a Do Loop with DoEvents in it, WebView could not be loaded
or if loaded, would not process a hyperlink click. And Agraham
says: "Looping is bad practice on mobile devices. The CPU will
be constantly executing code and using battery power as the
code will never get back to the OS idle loop where the hardware
power saving measures are invoked."
Format() NumberFormat & NumberFormat2 [see documentation]
InputBox($) InputList(Items as List, Title, CheckedItem as Int) as Int
can list multiple Shows list of choices with radio buttons. Returns index.
choices for which CheckedItem is the default.
the user enters a InputMultiList(Items as List, Title) As List
number to choose. User can select multiple items via checkboxes.
Returns list with the indexes of boxes checked.
MsgBox "text" MsgBox("text", "title")
i=MsgBox() MsgBox2(Message, Title, Positive, Cancel, Negative, Icon) as Int
Displays three buttons with text to display for buttons
(Positive, Cancel, Negative)
Icon is displayed near the title and is specified like:
LoadBitmap(File.DirAssets, "[filename].gif")
--- ToastMessageShow(text, b) [where b=True for long duration]
Following is a Sub from Pfriemler which acts like InputBox:
Sub InputBox(Prompt As String, Title As String, Default As String, Hint As String) As String
Dim Id As InputDialog
Id.Hint = Hint
Id.Input = Default
ret = Id.Show(Prompt, Title, "OK", "","Abbrechen", Null)
If ret = -1 Then Return Id.Input Else Return ""
End Sub
Rnd is < 1 Rnd(min, max) is integer >= min to < max
Rnd(-#) RndSeed(#) - causes Rnd to generate the same random number series
for the same # entered.
Randomize Not needed in B4A to randomize Rnd.
Round(n) same, or Round2(n, x) where x=number of decimal places
i = Val(string) If IsNumber(string) Then i = string Else i = 0 --
An attempt to use i=string "throws an exception" if the string is
not numbers, even if the string starts with numbers. For example,
t = "10:45"
i = Val(t) sets i=10 but causes an error in B4A.
Instead,
i = t.SubString2(0, 2) = 10
control.SetFocus view.RequestFocus
n / 0 : error n / 0 = 2147483647 -- B4A does not "throw an exception" for
division by 0, but it does return 2147483647 no matter
what the value of "n" is.
x = Shell("...") See "Intent". This is not a complete replacement, but allows
code such as the following from the B4A forum (by Erel):
Dim pi As PhoneIntents
StartActivity (pi.OpenBrowser("[URL]file:///sdcard/yourfile.html[/URL]"))
t = Timer t = DateTime.Now ' Ticks are number of milliseconds since 1-1-70
TabIndex:
--------
In VB6, TabIndex can be set to control the order in which controls get focus
when Tab is pressed. According to Erel, in B4A:
"Android handles the sequence according to their position. You can set
EditText.ForceDone = True in all your EditTexts. Then catch the
EditText_EnterPressed event and explicitly set the focus to the next
view (with EditText.RequestFocus)."
Setting Label Transparency:
--------------------------
Properties - Back Style Designer - Drawable - Alpha
Constants:
---------
"" Quote = Chr$(34)
vbCr CRLF = Chr$(10)
vbCrLf none
String "Members":
----------------
VB6 uses a character position pointer starting with 1.
B4A uses a character Index pointer starting with 0.
VB6 B4A
Mid$("abcde", 1, 1) = "a" = letter array index 0 -- "a" = "abcde".CharAt(0)
Mid$("abcde", 2, 1) = "b" = letter array index 1
Mid$("abcde", 3, 1) = "c" = letter array index 2
Mid$("abcde", 4, 1) = "d" = letter array index 3
Mid$("abcde", 5, 1) = "e" = letter array index 4
VB6 B4A
=== ===
Mid$(text, n, 1) text.CharAt(n-1)
Mid$(text, n) text.SubString(n-1)
Mid$(text, n, x) [x=length wanted] text.SubString2(n-1, n+x-1) [n+x-1=end position]
Mid$(text, n, x) = text2 text = text.SubString2(0, n-2) & _
text2.SubString2(0, x-1) & _
text.SubString(n-1 + z) where...
z = Min(x, text2.length)
Left$(text, n) [n=num.of chars.] text.SubString2(0, n)
Right$(text, n) text.SubString(text.Length - n + 1)
If a$ = b$... If a.CompareTo(b)...
If Right$(text, n) = text2... If text.EndsWith(text2)...
If Left$(text, n) = text2... If text.StartsWith(text2)...
If Lcase$(text) = Lcase$(text2)... If text.EqualsIgnoreCase(text2)...
Following are some subs from NeoTechni which take the place of VB6
string functions:
Sub Left(Text As String, Length As Long)As String
If length>text.Length Then length=text.Length
Return text.SubString2(0, length)
End Sub
Sub Right(Text As String, Length As Long) As String
If length>text.Length Then length=text.Length
Return text.SubString(text.Length-length)
End Sub
Sub Mid(Text As String, Start As Int, Length As Int) As String
Return text.SubString2(start-1,start+length-1)
End Sub
Sub Split(Text As String, Delimiter As String) As String()
Return Regex.Split(delimter,text)
End Sub
x = Len(text) x = text.Length
text = Replace(text, str, str2) text.Replace(str, str2)
Lcase(text) text.ToLowerCase
Ucase(text) text.ToUpperCase
Trim(text) text.Trim
(no LTrim or RTrim in B4A)
Instr(text, string) text.IndexOf(string)
Instr(int, text, string) text.IndexOf2(string, int)
Returns -1 if not found.
Returns char. index, not position.
Starts search at "int".
InStrRev(text, str, start, case) text.LastIndexOf(string)
Searches from end of string, text.LastIndexOf(string, start)
optionally from "start". Cannot specify case sensitivity.
case = 0 = case-sensitive
case = 0 = case-insensitive
A boolean form of IndexOf is -
If text.Contains(string) = True Then...
If Lcase$(x) = Lcase$(y)... If x.EqualsIgnoreCase(y)...
text = Left$(text, n) & s & text.Insert(n, s)
Right$(Text, y)
Asc(s) [where s = a character] same
Error Trapping:
--------------
VB6:
===
Sub SomeSub
On [Local] Error GoTo ErrorTrap
...some code...
On Error GoTo 0 [optional end to error trapping]
...optional additional code...
Exit Sub [to avoid executing ErrorTrap code]
ErrorTrap:
...optional code for error correction...
Resume [optional: "Resume Next" or "Resume [line label]".
End Sub
B4A:
===
Sub SomeSub
Try
...some code...
Catch [only executes if error above]
Log(LastException) [optional]
...optional code for error correction...
End Try
...optional additional code...
End Sub
WIth B4A, if you get an error caught in the middle of a large subroutine, you can
NOT make a correction and resume within the code you were executing. Only the code
in "Catch" gets executed, plus any code following "End Try".
Try-Catch in place of GoTo:
--------------------------
Try-Catch can be used as a substitute for GoTo [line label] for forward, but not
backward, jumps. It cannot be used to replace GoSub, for which B4A has no equivalent.
Start the code with "Try" and replace the [line label] with "Catch".
Replace "GoTo [line label]" with code which will create an exception, which causes
a jump to "Catch", such as OpenInput("bad path", "bad filename").
"Immediate Window" vs "Logs" Tab
--------------------------------
Comments, variable values, etc., can be displayed in VB6's Immediate
Window by entering into the code "Debug.Print ...".
In the B4A environment, the Logs tab on the right side of the IDE is a
way to show the values of variables, etc., while the code is running.
Both VB6 and (now) B4A allow single-stepping through the code while it
is running and viewing the values of variables. VB6 also allows changing
the value of variables, changing the code, jumping to other lines from
the current line, etc. Because B4A runs on a PC while the app runs on
a separate device, B4A is currently unable to duplicate all of these
VB6 debug features.