正确进行线程化 FTP 下载 (Indy/Android)
Correctly making a threaded FTP download (Indy/Android)
我已经创建了一个 IdFTP 来从我的 FTP 服务器下载文件,但是当我尝试将其线程化时,它卡在了 "Resolving hostname..." in Android OS.
没有线程(工作正常):
uses ..., IdFTPCommon;
var
RecordDownload: TMemoryStream;
uses System.IOUtils;
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
try
IdFTP1.Connect();
IdFTP1.Get('00001.m4a',TPath.GetDocumentsPath + PathDelim + '00001.m4a',True,False);
except
IdFTP1.Disconnect;
end;
end;
procedure TForm1.IdFTP1AfterGet(ASender: TObject; AStream: TStream);
begin
IdFTP1.Disconnect;
end;
procedure TForm1.IdFTP1WorkEnd(ASender: TObject; AWorkMode: TWorkMode);
begin
if FileExists(TPath.GetDocumentsPath + PathDelim + '00001.m4a') then
begin
ShowMessage('Downloaded!');
end;
end;
以及我在 this solution 之后制作的线程代码:
uses ..., IdFTPCommon;
type
TLoadThread = class(TThread)
public
constructor Create; reintroduce;
protected
procedure Execute; override;
end;
type
TForm1 = class(TForm)
...
procedure ThreadTerminated(Sender: TObject);
var
RecordDownload: TMemoryStream;
Loading: Boolean = False;
zLThread: TLoadThread = nil;
uses System.IOUtils;
constructor TLoadThread.Create;
begin
inherited Create(True);
FreeOnTerminate := True;
end;
procedure TLoadThread.Execute;
begin
try
Form1.IdFTP1.Connect();
Form1.IdFTP1.Get('00001.m4a',TPath.GetDocumentsPath + PathDelim + '00001.m4a',True,False);
except
Form1.IdFTP1.Disconnect;
end;
end;
procedure TForm1.ThreadTerminated(Sender: TObject);
begin
zLThread := nil;
Loading := False;
FloatAnimation1.Enabled := False;
FloatAnimation2.Enabled := False;
Arc3.StartAngle := -90;
Arc3.EndAngle := 0;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
zLThread := TLoadThread.Create;
zLThread.OnTerminate := ThreadTerminated;
zLThread.Start;
Loading := True;
FloatAnimation1.Enabled := True;
FloatAnimation2.Enabled := True;
end;
procedure TForm1.IdFTP1AfterGet(ASender: TObject; AStream: TStream);
begin
IdFTP1.Disconnect;
end;
procedure TForm1.IdFTP1WorkEnd(ASender: TObject; AWorkMode: TWorkMode);
begin
Form1.FloatAnimation1.Enabled := False;
Form1.FloatAnimation2.Enabled := False;
Form1.Arc3.StartAngle := -90;
Form1.Arc3.EndAngle := 0;
if FileExists(TPath.GetDocumentsPath + PathDelim + '00001.m4a') then
begin
ShowMessage('Downloaded!');
end;
end;
procedure TForm1.IdFTP1Status(ASender: TObject; const AStatus: TIdStatus;
const AStatusText: string);
begin
Memo1.Lines.Add(AStatusText);
Application.ProcessMessages;
end;
然后 FTP 状态显示它卡在 "Resolving hostname ..."。如何正确穿线?
没有理由按照您使用它们的方式使用 OnAfterGet
和 OnWorkEnd
事件。 Indy 是同步的。 TIdFTP.Get()
在传输完成之前不会 return,如果发生错误,则会引发异常。
因此,摆脱两个事件处理程序,使用 try/finally
而不是 try/except
来调用 Disconnect()
,并且仅在 Get()
未引发时才处理下载。
OnWorkEnd
和 OnStatus
事件在调用 Connect()
、Disconnect()
和 Get()
的同一线程的上下文中触发。因此,在您的线程示例中,这将是工作线程,而不是主线程。但是您的事件处理程序没有同步对 UI 控件的访问。这可能会导致各种问题,包括您遇到的冻结。您必须同步(TThread.OnTerminated
事件同步)。
话虽如此,试试这个:
非线程:
uses
..., IdFTPCommon;
...
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
try
IdFTP1.Connect;
try
IdFTP1.Get('00001.m4a', TPath.GetDocumentsPath + PathDelim + '00001.m4a', True, False);
finally
IdFTP1.Disconnect;
end;
ShowMessage('Downloaded!');
except
ShowMessage('Error while downloading!');
end;
end;
线程化:
uses
..., IdFTPCommon;
type
TLoadThread = class(TThread)
public
constructor Create; reintroduce;
protected
procedure Execute; override;
end;
type
TForm1 = class(TForm)
...
IdFTP1: TIdFTP;
procedure ThreadTerminated(Sender: TObject);
...
private
Loading: Boolean;
zLThread: TLoadThread;
end;
...
constructor TLoadThread.Create;
begin
inherited Create(True);
FreeOnTerminate := True;
end;
procedure TLoadThread.Execute;
begin
Form1.IdFTP1.Connect;
try
Form1.IdFTP1.Get('00001.m4a', TPath.GetDocumentsPath + PathDelim + '00001.m4a', True, False);
finally
Form1.IdFTP1.Disconnect;
end;
end;
procedure TForm1.ThreadTerminated(Sender: TObject);
begin
zLThread := nil;
Loading := False;
FloatAnimation1.Enabled := False;
FloatAnimation2.Enabled := False;
Arc3.StartAngle := -90;
Arc3.EndAngle := 0;
If TThread(Sender).FatalException = nil then
ShowMessage('Downloaded!')
else
ShowMessage('Error while Downloading!');
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
zLThread := TLoadThread.Create;
zLThread.OnTerminate := ThreadTerminated;
zLThread.Start;
Loading := True;
FloatAnimation1.Enabled := True;
FloatAnimation2.Enabled := True;
end;
procedure TForm1.IdFTP1Status(ASender: TObject; const AStatus: TIdStatus; const AStatusText: string);
begin
TThread.Queue(nil,
procedure
begin
Memo1.Lines.Add(AStatusText);
end
);
end;
我已经创建了一个 IdFTP 来从我的 FTP 服务器下载文件,但是当我尝试将其线程化时,它卡在了 "Resolving hostname..." in Android OS.
没有线程(工作正常):
uses ..., IdFTPCommon;
var
RecordDownload: TMemoryStream;
uses System.IOUtils;
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
try
IdFTP1.Connect();
IdFTP1.Get('00001.m4a',TPath.GetDocumentsPath + PathDelim + '00001.m4a',True,False);
except
IdFTP1.Disconnect;
end;
end;
procedure TForm1.IdFTP1AfterGet(ASender: TObject; AStream: TStream);
begin
IdFTP1.Disconnect;
end;
procedure TForm1.IdFTP1WorkEnd(ASender: TObject; AWorkMode: TWorkMode);
begin
if FileExists(TPath.GetDocumentsPath + PathDelim + '00001.m4a') then
begin
ShowMessage('Downloaded!');
end;
end;
以及我在 this solution 之后制作的线程代码:
uses ..., IdFTPCommon;
type
TLoadThread = class(TThread)
public
constructor Create; reintroduce;
protected
procedure Execute; override;
end;
type
TForm1 = class(TForm)
...
procedure ThreadTerminated(Sender: TObject);
var
RecordDownload: TMemoryStream;
Loading: Boolean = False;
zLThread: TLoadThread = nil;
uses System.IOUtils;
constructor TLoadThread.Create;
begin
inherited Create(True);
FreeOnTerminate := True;
end;
procedure TLoadThread.Execute;
begin
try
Form1.IdFTP1.Connect();
Form1.IdFTP1.Get('00001.m4a',TPath.GetDocumentsPath + PathDelim + '00001.m4a',True,False);
except
Form1.IdFTP1.Disconnect;
end;
end;
procedure TForm1.ThreadTerminated(Sender: TObject);
begin
zLThread := nil;
Loading := False;
FloatAnimation1.Enabled := False;
FloatAnimation2.Enabled := False;
Arc3.StartAngle := -90;
Arc3.EndAngle := 0;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
zLThread := TLoadThread.Create;
zLThread.OnTerminate := ThreadTerminated;
zLThread.Start;
Loading := True;
FloatAnimation1.Enabled := True;
FloatAnimation2.Enabled := True;
end;
procedure TForm1.IdFTP1AfterGet(ASender: TObject; AStream: TStream);
begin
IdFTP1.Disconnect;
end;
procedure TForm1.IdFTP1WorkEnd(ASender: TObject; AWorkMode: TWorkMode);
begin
Form1.FloatAnimation1.Enabled := False;
Form1.FloatAnimation2.Enabled := False;
Form1.Arc3.StartAngle := -90;
Form1.Arc3.EndAngle := 0;
if FileExists(TPath.GetDocumentsPath + PathDelim + '00001.m4a') then
begin
ShowMessage('Downloaded!');
end;
end;
procedure TForm1.IdFTP1Status(ASender: TObject; const AStatus: TIdStatus;
const AStatusText: string);
begin
Memo1.Lines.Add(AStatusText);
Application.ProcessMessages;
end;
然后 FTP 状态显示它卡在 "Resolving hostname ..."。如何正确穿线?
没有理由按照您使用它们的方式使用 OnAfterGet
和 OnWorkEnd
事件。 Indy 是同步的。 TIdFTP.Get()
在传输完成之前不会 return,如果发生错误,则会引发异常。
因此,摆脱两个事件处理程序,使用 try/finally
而不是 try/except
来调用 Disconnect()
,并且仅在 Get()
未引发时才处理下载。
OnWorkEnd
和 OnStatus
事件在调用 Connect()
、Disconnect()
和 Get()
的同一线程的上下文中触发。因此,在您的线程示例中,这将是工作线程,而不是主线程。但是您的事件处理程序没有同步对 UI 控件的访问。这可能会导致各种问题,包括您遇到的冻结。您必须同步(TThread.OnTerminated
事件同步)。
话虽如此,试试这个:
非线程:
uses
..., IdFTPCommon;
...
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
try
IdFTP1.Connect;
try
IdFTP1.Get('00001.m4a', TPath.GetDocumentsPath + PathDelim + '00001.m4a', True, False);
finally
IdFTP1.Disconnect;
end;
ShowMessage('Downloaded!');
except
ShowMessage('Error while downloading!');
end;
end;
线程化:
uses
..., IdFTPCommon;
type
TLoadThread = class(TThread)
public
constructor Create; reintroduce;
protected
procedure Execute; override;
end;
type
TForm1 = class(TForm)
...
IdFTP1: TIdFTP;
procedure ThreadTerminated(Sender: TObject);
...
private
Loading: Boolean;
zLThread: TLoadThread;
end;
...
constructor TLoadThread.Create;
begin
inherited Create(True);
FreeOnTerminate := True;
end;
procedure TLoadThread.Execute;
begin
Form1.IdFTP1.Connect;
try
Form1.IdFTP1.Get('00001.m4a', TPath.GetDocumentsPath + PathDelim + '00001.m4a', True, False);
finally
Form1.IdFTP1.Disconnect;
end;
end;
procedure TForm1.ThreadTerminated(Sender: TObject);
begin
zLThread := nil;
Loading := False;
FloatAnimation1.Enabled := False;
FloatAnimation2.Enabled := False;
Arc3.StartAngle := -90;
Arc3.EndAngle := 0;
If TThread(Sender).FatalException = nil then
ShowMessage('Downloaded!')
else
ShowMessage('Error while Downloading!');
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
IdFTP1.Host := 'motoristaajudante.ddns.net';
IdFTP1.Port := 2121;
IdFTP1.DataPortMin := 50100;
IdFTP1.DataPortMax := 51100;
IdFTP1.Username := 'anonymous';
IdFTP1.TransferType := IdFTPCommon.TIdFTPTransferType.ftBinary;
IdFTP1.Passive := True;
zLThread := TLoadThread.Create;
zLThread.OnTerminate := ThreadTerminated;
zLThread.Start;
Loading := True;
FloatAnimation1.Enabled := True;
FloatAnimation2.Enabled := True;
end;
procedure TForm1.IdFTP1Status(ASender: TObject; const AStatus: TIdStatus; const AStatusText: string);
begin
TThread.Queue(nil,
procedure
begin
Memo1.Lines.Add(AStatusText);
end
);
end;