Basic TThread doesn't work

[alzaimar]

This is a bit tricky. Here's a simple example:

Delphi-Quellcode:

Type
  TMythread = Class (TThread)
  private
     fLabelMsg : String; // a private field to display in the main form from within a thread
     procedure DoShowMessage;
  Protected
     Procedure Execute; Override;
  End;
Procedure TMyThread.DoShowMessage;
Begin
  MainForm.MyLabel.Caption := fLabelMsg;
End;

Procedure TMyThread.Execute;
Begin
  ....
  fLabelMsg :='Show this!'; // Write what you want to display in your private fields
  Synchronize (DoShowMessage); // Call the method which actually talks to the VCL via Synchronize
  ...
// The Thread terminates automatically, when the Execute-Method is exited.
End;

Bear in mind that ANY access to VCL-Controls (not only on the main form) must be wrapped in a Synchronize call, otherwise your app will hang.