How can I terminate thread directly outside of thread in delphi? - multithreading

Question

I want to terminate thread by clicking the button. If the thread normally works without user interruption it is OK but sometimes user needs to abort thread and that's the question that how user abort the thread.
Here is my code that I tested:
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, mmsystem, ExtCtrls;
type
TForm1 = class(TForm)
Image1: TImage;
procedure Image1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
end;
type
hangth = class(TThread)
private
{ Private declarations }
protected
procedure Execute; override;
procedure play;
end;
var
Form1: TForm1;
played: boolean;
szalhang: hangth;
implementation
{$R *.dfm}
procedure hangth.play;
begin
played := true;
szalhang.Terminate;
end;
procedure hangth.Execute;
begin
played := false;
SndPlaySound(pchar('hang.wav'), SND_SYNC);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
played := true;
end;
procedure TForm1.Image1Click(Sender: TObject);
begin
if played = true then begin
szalhang := hangth.Create(true);
szalhang.Resume;
end else begin
szalhang.Terminate();
// here i want to terminate thread, but it doesn't want to be killed.
end;
end;
end.

Answer 1

When you call TThread.Terminate(), it sets the TThread.Terminated property to true and does nothing else. It is the responsibility of your TThread.Execute() code to look at the TThread.Terminated property periodically and exit gracefully when it is True. However, in this situation, that is not possible because SndPlaySound() is blocking the thread, and there is no way to interrupt SndPlaySound() when it is running in SND_SYNC mode. Your only option would be to use the Win32 API TerminateThread() function to perform a brute-force termination of the thread.
Since you obviously need more control over the playback of the audio, and detection of when the audio is finished playing, then SndPlaySound() is not the best solution for your needs. You have a TForm, you might consider using Delphi's TMediaPlayer component, for example:
unit Unit1;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls, Vcl.MPlayer;
type
MPlayerState = (mpsClosed, mpsOpened, mpsPlaying);
TForm1 = class(TForm)
Image1: TImage;
MediaPlayer1: TMediaPlayer;
procedure MediaPlayer1Notify(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure Image1Click(Sender: TObject);
private
{ Private declarations }
State: MPlayerState;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm56.FormCreate(Sender: TObject);
begin
State := mpsClosed;
MediaPlayer1.FileName := 'C:\full path to\hang.wav';
end;
procedure TForm56.MediaPlayer1Notify(Sender: TObject);
begin
case MediaPlayer1.Mode of
mpStopped, mpPlaying:
State := mpsOpened;
end;
end;
procedure TForm1.Image1Click(Sender: TObject);
begin
if State = mpsClosed then
begin
MediaPlayer1.Notify := False;
MediaPlayer1.Wait := True;
MediaPlayer1.Open;
State := mpsOpened;
end;
if State = mpsOpened then
begin
MediaPlayer1.Notify := True;
MediaPlayer1.Wait := False;
MediaPlayer1.Play;
if MediaPlayer1.Error = 0 then
State := mpsPlaying
end else
begin
MediaPlayer1.Notify := False;
MediaPlayer1.Wait := True;
MediaPlayer1.Stop;
State := mpsOpened;
MediaPlayer1.Notify := False;
MediaPlayer1.Wait := True;
MediaPlayer1.Close;
State := mpsClosed;
end;
end;
end.