Why would something fail in FormCreate, but work fine in FormShow?

I'm using Delphi 7. When I try to create an object in FormCreate, it fails (actually it just hangs). When I try to do the same thing in FormShow, it works. Please note, I'm not talking about creating a visual component like a TEdit. It's a database abstraction object. Any ideas why this might happe开发者_开发知识库n? Are there any guidelines about this topic?

1) The reason is because on FormCreate, the handle to Form is not created yet.

If your database object needs a form handle, do this:

Self.HandleNeeded; // on FormCreate time.

2) The other reason is maybe your database component needs to be connected and it's only connected on DFM?

My first guess is that you're accessing a DataModule hasn't been created yet. If your project's source looks like the following:

begin
    Application.Initialize;
    Application.CreateForm(TForm1, Form1);
    Application.CreateForm(TDataModule1, DataModule1);
    Application.Run;
end.

And your TForm1.FormCreate looks like the following:

begin
    DataModule1.AddUsersToStringList(Self.ComboBox1.Items);
end;

Then FormCreate going to fail because it's is being run as part of the Application.CreateForm(TForm1, Form1); line, and your Data Module hasn't been created yet.

There's 2 solutions:

1. Defer your processing/initialization until after all the forms and data modules have been created.
2. Create all the data modules before creating any of your forms. The Application's "Main Form" in Delphi is the first TCustomForm descendant created by Application.CreateForm, not the first object.