Required a number in text box in Inno Setup - inno-setup

Question

I found a code here that I needed. To only allow write numbers in a text box. But I still wanted more, which does not offer up the "Next" button without write the number in this text box.
Can help me?
procedure NumbersOnly(Sender: TObject; var Key: Char);
var
S: string;
begin
S := ('1234567890'#8);
if Pos(Key, S) = 0 then
Key := #0;
end;

Answer 1

You can setup the next button to be enabled or disabled in the CurPageChanged event when the user reaches the page where resides your edit box. Except that you need to monitor changes of that edit box to enable or disable the next button according to whether there's something entered in that edit box. For this you need to write a handler for the OnChange event. Here is an example:
[Setup]
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program
[Code]
var
MyEdit: TNewEdit;
MyPage: TWizardPage;
procedure MyEditChange(Sender: TObject);
begin
{ enable the next button if the edit box is not empty; disable otherwise }
WizardForm.NextButton.Enabled := MyEdit.Text <> '';
end;
procedure MyEditKeyPress(Sender: TObject; var Key: Char);
var
KeyCode: Integer;
begin
{ allow only numbers }
KeyCode := Ord(Key);
if not ((KeyCode = 8) or ((KeyCode >= 48) and (KeyCode <= 57))) then
Key := #0;
end;
procedure InitializeWizard;
begin
MyPage := CreateCustomPage(wpWelcome, 'Caption', 'Description');
MyEdit := TNewEdit.Create(WizardForm);
MyEdit.Parent := MyPage.Surface;
MyEdit.Left := 0;
MyEdit.Top := 0;
MyEdit.Width := 150;
MyEdit.OnChange := #MyEditChange;
MyEdit.OnKeyPress := #MyEditKeyPress;
end;
procedure CurPageChanged(CurPageID: Integer);
begin
{ if the currently turned wizard page is the one with the edit box, enable }
{ the next button if the edit box is not empty; disable otherwise }
if CurPageID = MyPage.ID then
WizardForm.NextButton.Enabled := MyEdit.Text <> '';
end;

Answer 2

There are two flaws in the #TLama's answer:
A user can bypass the check by using Paste command from edit box context menu (and possibly by other kinds of input methods).
To fix this, you can introduce a last resort check in NextButtonClick.
I would also suggest adding the check for an empty input there, instead of MyEditChange, as it allows providing feedback to the user, explaining what is wrong.
On the other hand, Ctrl+C, Ctrl+V and Ctrl+X keys are not working. Particularly a lack of Ctrl+V is not comfortable.
To fix this, allow these control characters in the MyEditKeyPress.
[Code]
var
MyEdit: TNewEdit;
MyPage: TWizardPage;
procedure ValidateMyEdit;
begin
{ enable the next button if the edit box is not empty; disable otherwise }
WizardForm.NextButton.Enabled := (MyEdit.Text <> '');
end;
procedure MyEditChange(Sender: TObject);
begin
ValidateMyEdit;
end;
function IsDigit(C: Char): Boolean;
begin
Result := (C >= '0') and (C <= '9')
end;
procedure MyEditKeyPress(Sender: TObject; var Key: Char);
begin
if not ((Key = #8) or { Tab key }
(Key = #3) or (Key = #22) or (Key = #24) or { Ctrl+C, Ctrl+V, Ctrl+X }
IsDigit(Key)) then
begin
Key := #0;
end;
end;
procedure InitializeWizard;
begin
MyPage := CreateCustomPage(wpWelcome, 'Caption', 'Description');
MyEdit := TNewEdit.Create(WizardForm);
MyEdit.Parent := MyPage.Surface;
MyEdit.Left := 0;
MyEdit.Top := 0;
MyEdit.Width := 150;
MyEdit.OnChange := #MyEditChange;
MyEdit.OnKeyPress := #MyEditKeyPress;
end;
procedure CurPageChanged(CurPageID: Integer);
begin
if CurPageID = MyPage.ID then
begin
ValidateMyEdit;
end;
end;
function NextButtonClick(CurPageID: Integer): Boolean;
var
I: Integer;
begin
Result := True;
if CurPageID = MyPage.ID then
begin
for I := 1 to Length(MyEdit.Text) do
begin
if not IsDigit(MyEdit.Text[I]) then
begin
MsgBox('Only numbers are allowed', mbError, MB_OK);
Result := False;
Break;
end;
end;
end;
end;

Answer 3

This is the way I use based on keys from ASCII code:
procedure justNumbers(Sender: TObject; var Key: Char);
begin
if not ((Key = #8) or (Key = #43) or ((Key >= #48) and (Key <= #57)))
then
begin
Key := #0;
end;
end;
Could work for validate others characters too.