Why is it that sometimes showing hiding forms misfires? - delphi

Question

My form1 is the mainform. I use it for login purposes and after I dont need it
I hide it. If the login is successful, on button click,form3 is called.
procedure TForm1.AdvGlowButton1Click(Sender: TObject);
begin
ABSQuery4.Active:=false;
ABSQuery4.SQL.Clear;
ABSQuery4.SQL.Add('select .....bla,bla,bla....');
ABSQuery4.Open;
if ABSQuery4.FieldByName('passsword').AsString<>''
then begin
Form3.Show;
Form1.Hide;
end else begin
cxTextedit1.Text := '';
showmessage('wrong password');
end;
end;
Now I am noticing that sometimes the event produces strange results.
Form3 is shown but Form1 remains visible also. For showing the main form
from form3 I use :
procedure TForm3.FormClose(Sender: TObject; var Action: TCloseAction);
begin
Form1.Show;
end
Since I need the application icon for Form3, I have there :
procedure TForm3.CreateParams(var Params: TCreateParams) ;
begin
inherited;
Params.ExStyle := Params.ExStyle or WS_EX_APPWINDOW;
Params.WndParent := 0;
end;
Can you tell me am I messing anything up or is there a better way to
make the forms behave properly?

Answer 1

There is a better way to do this. For a start, you should give your forms meaningful names!
Your real problem is that your main form is being hidden because you are using it as your login form. You make life needlessly difficult and complicated by doing that.
So the main piece of advice is that you should make you real main form be the Delphi main form. The Delphi main form is the first form created using Application.CreateForm. I suggest that you call Application.CreateForm exactly once, to create the main form.
This may leave you wondering how to create other forms. Well, you just create them using the standard constructor, just like any other object.
So your .dpr file code might look like this:
Application.Initialize;
LoginForm := TLoginForm.Create(nil);
try
if LoginForm.ShowModal <> mrOK then
exit;
finally
LoginForm.Free;
end;
Application.CreateForm(TMainForm, MainForm);
Application.Run;
Once you make this change you will find that you don't need to take steps to force the main form onto the taskbar.