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unit ThreadServerCheck;

interface

uses
  Classes;

type
  TServerCheckThread = class(TThread)
  private
    { private declarations }
  protected
    ServerFound: Boolean;
    procedure Execute; override;
    procedure UpdateMainForm;
  end;

implementation

uses SysUtils, MainForm, ZConnection, DatenmodulDM, Graphics;

{ Important: Methods and properties of objects in the VCL or CLX can
   only be used in methods, that call Synchronize, for example:

      Synchronize(UpdateCaption);

   where UpdateCaption could look like this:

    procedure TServerCheckThread.UpdateCaption;
    begin
      Form1.Caption := 'Changed in a thread';
    end; }

{ TServerCheckThread }

procedure TServerCheckThread.Execute;
var
  Connection: TZConnection;
  Result: Boolean;
begin
  Result := True;
  // create your own separate connection
  Connection := TZConnection.Create(nil);
  //configure your connection object here
  try
    Connection.Connect;
    // you could do some additional checks here. 
    // You should create your own separate queries here.
    Connection.Disconnect;
  except
    Result := False;
  end;
  FreeAndNil(Connection);

  if Result Then Synchronize(UpdateMainForm); // important: Use Synchronize for calling methods, that do changes in the main thread!
end;

procedure TServerCheckThread.UpdateMainForm;
begin
  // here you can do operations in the context of your main thread. I use it for
  // changing a static text. But you also could set a flag for your main thread to
  // to instruct it to change the database whenever it is convenient to do so.
  frmMain.ConnStateLbl.Caption := frmMain.ConnStateLbl.Caption + ', Server aber vorhanden';
  frmMain.ConnStateLbl.Font.Color := clRed;
  frmMain.ConnStateWarningTxt.Visible := True; 
end;

end.

Code: Select all

procedure TfrmMain.FormCreate(Sender: TObject);
var
  X: TServerCheckThread;
begin
   X := TServerCheckThread.Create(false);
  // from here the server check is running in the background while your main
  // application continues to run
end;