Dim str1, str2 As String
Dim i As Int
str1 = "abcdef"
For i = str1.Length - 1 To 0 Step -1
str2 = str2 & str1.CharAt(i)
Next
Msgbox(str1 & CRLF & str2, "Reversed")
I know it's old, but I was looking for this but the sub above appeared unoptimized so I made one
B4X:
Sub StrReverse(Text As String) As String
Dim tempstr As StringBuilder,temp As Int
tempstr.Initialize
For temp = Text.Length-1 To 0 Step -1
tempstr.Append( Text.CharAt(temp) )
Next
Return tempstr.ToString
End Sub