multithreading - 在TThread执行中引发异常？

Question

我只是意识到我的异常没有在我的线程中显示给用户!

最初，我在线程中使用了此方法来引发异常，该异常不起作用:

except on E:Exception do
begin
  raise Exception.Create('Error: ' + E.Message);
end;

IDE向我显示了异常，但我的应用程序却没有!

我到处寻找解决方案，这是我发现的结果:

Delphi thread exception mechanism

http://www.experts-exchange.com/Programming/Languages/Pascal/Delphi/Q_22039681.html

这些都不对我有用。

这是我的线程单元:

unit uCheckForUpdateThread;

interface

uses
  Windows, IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient,
  IdHTTP, GlobalFuncs, Classes, HtmlExtractor, SysUtils, Forms;

type
  TUpdaterThread = class(TThread)
  private
    FileGrabber : THtmlExtractor;
    HTTP : TIdHttp;
    AppMajor,
    AppMinor,
    AppRelease : Integer;
    UpdateText : string;
    VersionStr : string;
    ExceptionText : string;
    FException: Exception;
    procedure DoHandleException;
    procedure SyncUpdateLbl;
    procedure SyncFinalize;
  public
    constructor Create;

  protected
    procedure HandleException; virtual;

    procedure Execute; override;
  end;

implementation

uses
  uMain;

{ TUpdaterThread }

constructor TUpdaterThread.Create;
begin
  inherited Create(False);
end;

procedure TUpdaterThread.Execute;
begin
  inherited;
  FreeOnTerminate := True;

  if Terminated then
    Exit;

  FileGrabber           := THtmlExtractor.Create;
  HTTP                  := TIdHTTP.Create(nil);
  try
    try
      FileGrabber.Grab('http://jeffijoe.com/xSky/Updates/CheckForUpdates.php');
    except on E: Exception do
    begin
      UpdateText := 'Error while updating xSky!';
      ExceptionText := 'Error: Cannot find remote file! Please restart xSky and try again! Also, make sure you are connected to the Internet, and that your Firewall is not blocking xSky!';
      HandleException;
    end;
    end;

    try
      AppMajor      := StrToInt(FileGrabber.ExtractValue('AppMajor[', ']'));
      AppMinor      := StrToInt(FileGrabber.ExtractValue('AppMinor[', ']'));
      AppRelease    := StrToInt(FileGrabber.ExtractValue('AppRelease[[', ']'));
    except on E:Exception do
    begin
      HandleException;
    end;
    end;

    if (APP_VER_MAJOR < AppMajor) or (APP_VER_MINOR < AppMinor) or (APP_VER_RELEASE < AppRelease) then
    begin
      VersionStr := Format('%d.%d.%d', [AppMajor, AppMinor, AppRelease]);
      UpdateText := 'Downloading Version ' + VersionStr;
      Synchronize(SyncUpdateLbl);
    end;

  finally
    FileGrabber.Free;
    HTTP.Free;
  end;
  Synchronize(SyncFinalize);
end;

procedure TUpdaterThread.SyncFinalize;
begin
  DoTransition(frmMain.TransSearcher3, frmMain.gbLogin, True, 500);
end;

procedure TUpdaterThread.SyncUpdateLbl;
begin
  frmMain.lblCheckingForUpdates.Caption := UpdateText;
end;

procedure TUpdaterThread.HandleException;
begin
  FException := Exception(ExceptObject);
  try
    Synchronize(DoHandleException);
  finally
    FException := nil;
  end;
end;

procedure TUpdaterThread.DoHandleException;
begin
  Application.ShowException(FException);
end;

end.

如果您需要更多信息，请告诉我。

再次:IDE捕获了所有异常，但是我的程序没有显示它们。

编辑:最终，这是Cosmin的解决方案起作用的-最初之所以不起作用的原因是，因为我没有添加ErrMsg变量，而是我只是将变量中包含的任何内容放入Synchronize中，这将不起作用，但是我不知道为什么。当我没有其他想法时，我就意识到了这一点，然后我就弄乱了解决方案。

和往常一样，这个笑话在我身上。 = P

Answer 1

这是我对此问题的非常简短的“总结”。它仅适用于Delphi 2010+(因为该版本引入了匿名方法)。与已经发布的更复杂的方法不同，我的仅显示错误消息，仅此而已。

procedure TErrThread.Execute;
var ErrMsg: string;
begin
  try
    raise Exception.Create('Demonstration purposes exception');
  except on E:Exception do
    begin
      ErrMsg := E.ClassName + ' with message ' + E.Message;
      // The following could be all written on a single line to be more copy-paste friendly  
      Synchronize(
        procedure
        begin
          ShowMessage(ErrMsg);
        end
      );
    end;
  end;
end;