Cancel Form Opening 1

[lespaul]

If I have a process in the OnShow procedure and want to exit and not show the form, how can I accomplish this? For example, I have a form that is used to Record Courtroom Use, however, if someone tries to perform that function and there are no Trials currently in progress, how can I abort the showing of the form?

thanks!

leslie

 

[TonHu]

You should move the check to initiate the display to somewhere before the OnShow event. The code should be more general, like a function AreTrialsInProgress(eCourtroom: enCourtrooms) : boolean; and call that in the OnClick event of the button that should open the form.

HTH
TonHu

 

[lespaul]

that's kinda what I'm doing now, but wanted to see if there was another way.

thanks!
leslie

 

[schu]

you just close it after the check,
it still pops up if the system is slow, but will immediately close.

 

[sggaunt]

agree with schu, yes its 'messy' but I have a couple of 'check somthing' at startup type things that do just that.
I have also noticed several 'lots of money' type apps that 'flash' a startup window at you, before opening properly, not quite the same thing, but with todays fast machines.



Steve: Delphi a feersum engin indeed.

 

[lespaul]

Thanks for the additional confirmation!

leslie

 

[Zathras]

Some questions:

1. Is this the main form?
2. Is this a modal dialog or modeless?
3. Is Delphi creating the form (auto-create) or are you?
4. Are you using an MDI architecture?

 

[lespaul]

1. No it is not the main form.

2. It is not currently a modal form, but that is certainly possible to do.

3. I am creating the form.

4. No, no MDI.

Thanks!

leslie

 

[Zathras]

Using a modal dialog is simplest. The way I do it is to make a global function to encapsulate all of the necessary code. This allows the calling unit to work simply with one line of code.

For example, the main routine might have a line of code like this:

  if MyCustomDialog( SomeInputParm, SomeOutputParm )= mrOk then
    GoNextStep( SomeOutputParm );

And the second unit would define the global function and implement it something like this:

interface

  function MyCustomDialog(AInput:string; var AOutput:string ):TModalResult;

type
  TModalResult = class(TForm)
  private
    FInput:string;
    FOutput:string;
    :
    :
  public
    :
    :
  end;

implementation

  function MyCustomDialog(AInput:string; var AOutput:string ):TModalResult;
  begin
    if DataExist(AInput) then
      with TMyCustomDialog.Create do
        begin
          FInput := AInput;
          ShowModal;
          AOutput := FOutput;
          Result := ModalResult;  // mrOk or mrCancel
          Free;
        end
    else
      Result := mrNo;
  end;

The OnShow event would use the value in FInput to initialize the form.

If it is time-consuming to retrieve the data for the form, you could use one of the techniques available that can show the form first, before fetching data. One way is to use a timer and populate the dialogwith the OnTimer event. Another way is to define your own message and post it to the dialog, then use a message handler event to populate the dialog.

 

[lespaul]

That's pretty cool, I'll give it a try!

Thanks,
Leslie