TThread Wait for User Input

Question

I have a TThread Instance and I would like to wait for a user input. The Thread loads something, waits for the user to click a button and then continues it's task.

I was thinking about setting a global bool to true, yet this wouldn't work too well with instances I think and the thread would have to check the var state in a loop and it seems a little unprofessional.

Is there a safe method for the tthread class to wait for a user input?

Answer 1

You can use a TEvent from the SyncObjs unit.

TMyThread = class(TThread)
public
    SignalEvent : TEvent;
    procedure Execute; override;
end;


TMyForm = class(TForm)
    procedure Button1Click(Sender : TObject);
public
    myThread : TMyThread;
end;

The thread does its work, then waits for the event to be signalled by the button click event. By using a TEvent you can also specify a timeout. (or 0 to wait indefinitely).

procedure TMyForm.Button1Click(Sender : TObject);
begin
    // Tell the thread that the button was clicked.
    myThread.SignalEvent.SetEvent;
end;

procedure TMyThread.Execute;
var
    waitResult : TWaitResult;
begin
    // do stuff

    // Wait for the event to signal that the button was clicked.
    waitResult := SignalEvent.WaitFor(aTimeout);

    if waitResult = wrSignaled then
    begin
        // Reset the event so we can use it again
        SignalEvent.ResetEvent;
        // do some more stuff
    end else 
        // Handle timeout or error.
end;