Android 如何使用Indy HTTP Get命令正确终止线程?
我的应用程序在Android 如何使用Indy HTTP Get命令正确终止线程?,android,multithreading,delphi,indy,indy10,Android,Multithreading,Delphi,Indy,Indy10,我的应用程序在FormShow事件上执行GET命令,有时用户可能会在线程启动且尚未完成后按Back并关闭表单,从而导致错误,如线程错误:无效参数(22)或线程错误:无此类进程(3) 我知道我创建的这个线程开始/结束逻辑很糟糕,我如何改进它并从显示中删除错误消息?当准备关闭表单时,如果线程仍在运行,那么您将发出终止信号,但您不会等待它完全终止,然后在窗体实际关闭时显式销毁线程对象,即使使用的是FreeOnTerminate=True 在显式销毁线程对象之前,应该调用TThread.WaitFor(
FormShow
事件上执行GET
命令,有时用户可能会在线程启动且尚未完成后按Back
并关闭表单,从而导致错误,如线程错误:无效参数(22)
或线程错误:无此类进程(3)
我知道我创建的这个线程开始/结束逻辑很糟糕,我如何改进它并从显示中删除错误消息?当准备关闭表单时,如果线程仍在运行,那么您将发出终止信号,但您不会等待它完全终止,然后在窗体实际关闭时显式销毁线程对象,即使使用的是
FreeOnTerminate=True
在显式销毁线程对象之前,应该调用TThread.WaitFor()
,但在使用FreeOnTerminate=True
时,这不起作用,这会导致您看到的错误类型。除此之外,如果线程仍在运行,并且您正在显式销毁线程对象,则TThread
析构函数会对自身调用WaitFor()
。因此,无论哪种方式,都会导致错误
因此,您需要:
- 设置
,然后等待线程完全终止,然后再显式销毁它FreeOnTerminate=False
- 设置
并且根本不手动销毁线程对象,并且在线程终止之前不关闭窗体FreeOnTerminate=True
TerminatedSet()
方法来设置一个标志,然后可以在线程内部检查该标志以中止GET
请求,例如在TIdHTTP.OnWork
事件中
使用FreeOnTerminated=True
时,请尝试以下操作:
type
TLoadListThread = class(TThread)
private
FUrl: string;
FOnLoading: TNotifyEvent;
DoAbort: Boolean;
procedure CheckAbort;
procedure DoLoading;
procedure HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
protected
procedure TerminatedSet; override;
public
constructor Create(const AUrl: String);
property OnLoading: TNotifyEvent read FOnLoading write FOnLoading;
end;
constructor TLoadListThread.Create(const AUrl: String);
begin
inherited Create(True);
FreeOnTerminate := True;
FUrl := AUrl;
end;
procedure TLoadListThread.CheckAbort;
begin
if DoAbort then SysUtils.Abort;
end;
procedure TLoadListThread.DoLoading;
begin
if Assigned(FOnLoading) then FOnLoading(Self);
end;
procedure TLoadListThread.HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
begin
CheckAbort;
end;
procedure TLoadListThread.TerminatedSet;
begin
inherited;
DoAbort := True;
end;
procedure TLoadListThread.Execute;
var
HTTP: TIdHTTP;
begin
HTTP := TIdHTTP.Create;
try
st := TStringList.Create;
try
ms := TMemoryStream.Create;
try
if Assigned(FOnLoading) then Synchronize(DoLoading);
CheckAbort;
HTTP.Get(FUrl, ms);
ms.Position := 0;
st.LoadFromStream(ms, TEncoding.UTF8);
finally
ms.Free;
end;
CheckAbort;
// Do something with st
finally
st.Free;
end;
finally
HTTP.Free;
end;
end;
或者,当使用FreeOnTerminated=False
时:
type
TLoadListThread = class(TThread)
private
FUrl: string;
FOnLoading: TNotifyEvent;
DoAbort: Boolean;
procedure CheckAbort;
procedure DoLoading;
procedure HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
protected
procedure TerminatedSet; override;
public
constructor Create(const AUrl: String);
property OnLoading: TNotifyEvent read FOnLoading write FOnLoading;
end;
constructor TLoadListThread.Create(const AUrl: String);
begin
inherited Create(True);
FreeOnTerminate := False;
FUrl := AUrl;
end;
procedure TLoadListThread.CheckAbort;
begin
if DoAbort then SysUtils.Abort;
end;
procedure TLoadListThread.DoLoading;
begin
if Assigned(FOnLoading) then FOnLoading(Self);
end;
procedure TLoadListThread.HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
begin
CheckAbort;
end;
procedure TLoadListThread.TerminatedSet;
begin
inherited;
DoAbort := True;
end;
procedure TLoadListThread.Execute;
var
HTTP: TIdHTTP;
begin
HTTP := TIdHTTP.Create;
try
st := TStringList.Create;
try
ms := TMemoryStream.Create;
try
if Assigned(FOnLoading) then Synchronize(DoLoading);
CheckAbort;
HTTP.Get(FUrl, ms);
ms.Position := 0;
st.LoadFromStream(ms, TEncoding.UTF8);
finally
ms.Free;
end;
CheckAbort;
// Do something with st
finally
st.Free;
end;
finally
HTTP.Free;
end;
end;
当准备关闭窗体时,如果线程仍在运行,则发出终止的信号,但不等待它完全终止,然后在窗体实际关闭时显式销毁线程对象,即使使用的是
FreeOnTerminate=True
在显式销毁线程对象之前,应该调用TThread.WaitFor()
,但在使用FreeOnTerminate=True
时,这不起作用,这会导致您看到的错误类型。除此之外,如果线程仍在运行,并且您正在显式销毁线程对象,则TThread
析构函数会对自身调用WaitFor()
。因此,无论哪种方式,都会导致错误
因此,您需要:
- 设置
,然后等待线程完全终止,然后再显式销毁它FreeOnTerminate=False
- 设置
并且根本不手动销毁线程对象,并且在线程终止之前不关闭窗体FreeOnTerminate=True
TerminatedSet()
方法来设置一个标志,然后可以在线程内部检查该标志以中止GET
请求,例如在TIdHTTP.OnWork
事件中
使用FreeOnTerminated=True
时,请尝试以下操作:
type
TLoadListThread = class(TThread)
private
FUrl: string;
FOnLoading: TNotifyEvent;
DoAbort: Boolean;
procedure CheckAbort;
procedure DoLoading;
procedure HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
protected
procedure TerminatedSet; override;
public
constructor Create(const AUrl: String);
property OnLoading: TNotifyEvent read FOnLoading write FOnLoading;
end;
constructor TLoadListThread.Create(const AUrl: String);
begin
inherited Create(True);
FreeOnTerminate := True;
FUrl := AUrl;
end;
procedure TLoadListThread.CheckAbort;
begin
if DoAbort then SysUtils.Abort;
end;
procedure TLoadListThread.DoLoading;
begin
if Assigned(FOnLoading) then FOnLoading(Self);
end;
procedure TLoadListThread.HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
begin
CheckAbort;
end;
procedure TLoadListThread.TerminatedSet;
begin
inherited;
DoAbort := True;
end;
procedure TLoadListThread.Execute;
var
HTTP: TIdHTTP;
begin
HTTP := TIdHTTP.Create;
try
st := TStringList.Create;
try
ms := TMemoryStream.Create;
try
if Assigned(FOnLoading) then Synchronize(DoLoading);
CheckAbort;
HTTP.Get(FUrl, ms);
ms.Position := 0;
st.LoadFromStream(ms, TEncoding.UTF8);
finally
ms.Free;
end;
CheckAbort;
// Do something with st
finally
st.Free;
end;
finally
HTTP.Free;
end;
end;
或者,当使用FreeOnTerminated=False
时:
type
TLoadListThread = class(TThread)
private
FUrl: string;
FOnLoading: TNotifyEvent;
DoAbort: Boolean;
procedure CheckAbort;
procedure DoLoading;
procedure HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
protected
procedure TerminatedSet; override;
public
constructor Create(const AUrl: String);
property OnLoading: TNotifyEvent read FOnLoading write FOnLoading;
end;
constructor TLoadListThread.Create(const AUrl: String);
begin
inherited Create(True);
FreeOnTerminate := False;
FUrl := AUrl;
end;
procedure TLoadListThread.CheckAbort;
begin
if DoAbort then SysUtils.Abort;
end;
procedure TLoadListThread.DoLoading;
begin
if Assigned(FOnLoading) then FOnLoading(Self);
end;
procedure TLoadListThread.HTTPWork(ASender: TObject; AWorkMode: TWorkMode; AWorkCount: Int64);
begin
CheckAbort;
end;
procedure TLoadListThread.TerminatedSet;
begin
inherited;
DoAbort := True;
end;
procedure TLoadListThread.Execute;
var
HTTP: TIdHTTP;
begin
HTTP := TIdHTTP.Create;
try
st := TStringList.Create;
try
ms := TMemoryStream.Create;
try
if Assigned(FOnLoading) then Synchronize(DoLoading);
CheckAbort;
HTTP.Get(FUrl, ms);
ms.Position := 0;
st.LoadFromStream(ms, TEncoding.UTF8);
finally
ms.Free;
end;
CheckAbort;
// Do something with st
finally
st.Free;
end;
finally
HTTP.Free;
end;
end;
尝试一种不同的策略:不允许窗体在完成之前关闭。使用线程安全策略:仅在执行方法中创建和使用TIDHTTP。您应该认真考虑以下实践:将线程写入自己的单元中,不使用任何表单单元,或者任何VCL单元。VCL不是线程安全的。直接从一个线程中访问表单是不符合逻辑的。它是不符合逻辑的。尝试不同的策略:不允许窗体在完成之前关闭。使用线程安全策略:仅在执行方法中创建和使用TIDHTTP;您应该认真考虑以下实践:以自己的单位编写线程。不使用任何形式单位,或任何VCL单位。VCL不是线程安全的。从一个线程中直接访问表单是非常糟糕的,这是不符合逻辑的。
procedure TForm58.FormShow(Sender: TObject);
begin
StopLoadListThread;
LListThread := TLoadListThread.Create(urlserver);
LListThread.OnLoading := LoadListThreadLoading;
LListThread.OnTerminate := LoadListThreadFinished;
LListThread.Start;
end;
procedure TForm58.StopLoadListThread;
begin
if Assigned(LListThread) then
begin
LListThread.OnLoading := nil;
LListThread.OnTerminate := nil;
LListThread.Terminate;
LListThread.WaitFor;
FreeAndNil(LListThread);
end;
end;
procedure TForm58.LoadListThreadLoading(Sender: TObject);
begin
Label1.Text := 'Loading...';
end;
procedure TForm58.LoadListThreadFinished(Sender: TObject);
var
Thread: TThread;
begin
Thread := TThread(Sender);
if Thread.FatalException = nil then
// Do something
else
// Do something else
// if using 10.1 Berlin or earlier:
TThread.CreateAnonymousThread(
procedure
begin
TThread.Queue(nil,
procedure
begin
Thread.Free;
end
);
end;
).Start;
// if using 10.2 Tokyo or later:
TThread.ForceQueue(nil,
procedure
begin
Thread.Free;
end
);
end;
procedure TForm58.CloseButtonClick(Sender: TObject);
begin
Close;
end;
procedure TForm58.FormClose(Sender: TObject; var Action: TCloseAction);
begin
StopLoadListThread;
// Do something
Action := TCloseAction.caFree;
end;