Delphi 如何实现一个简单的消息队列?
我想在一个新线程中实现一个消息队列,就像主线程一样。我在这里找到了,但我不需要显示窗口。因此,示例中的Delphi 如何实现一个简单的消息队列?,delphi,message-queue,delphi-10.3-rio,Delphi,Message Queue,Delphi 10.3 Rio,我想在一个新线程中实现一个消息队列,就像主线程一样。我在这里找到了,但我不需要显示窗口。因此,示例中的RegisterClass和CreateWindow对我来说是不需要的。无论如何,我没有这些信息可以传递给那些程序。我只想注册一个窗口过程AllocateHWnd(PrivateWndProc)然后使用GetMessage和DispatchMessage进行循环。我不知道这是否有意义…我构建了一个演示,向您展示如何创建一个工作线程,它的工作原理与主线程非常相似 要使用演示,请创建一个带有3个按钮
RegisterClass
和CreateWindow
对我来说是不需要的。无论如何,我没有这些信息可以传递给那些程序。我只想注册一个窗口过程AllocateHWnd(PrivateWndProc)
然后使用GetMessage
和DispatchMessage
进行循环。我不知道这是否有意义…我构建了一个演示,向您展示如何创建一个工作线程,它的工作原理与主线程非常相似
要使用演示,请创建一个带有3个按钮和备忘录的表单。然后将代码粘贴到下面。看一下我给组件的名称,它们可以执行相同的操作并关联正确的事件处理程序
您可能需要添加更多错误检查。我做了一些快捷方式,使代码更容易阅读。你可能应该检查所有可能失败的东西
在实际应用程序中,如果您有多个工作线程,请从我的TMyThread类派生所有线程,以便它们继承消息队列和消息泵
由于线程无法访问VCL,为了简单起见,我让工作线程使用OutputDebugString显示消息。在Delphi调试器下运行演示时,这些消息将显示在事件视图(Ctrl+Alt+V)中
unit ThreadDemoMain;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Classes,
Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;
type
TMyThread = class(TThread)
private
FWinHandle : HWND;
procedure AllocateHWnd; virtual;
procedure DeallocateHWnd; virtual;
procedure WndProc(var MsgRec: TMessage); virtual;
public
procedure Execute; override;
property WinHandle : HWND read FWinHandle;
end;
TThreadDemoForm = class(TForm)
StartThreadButton: TButton;
Memo1: TMemo;
StopThreadButton: TButton;
PostMessageButton: TButton;
Label1: TLabel;
procedure StartThreadButtonClick(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure StopThreadButtonClick(Sender: TObject);
procedure PostMessageButtonClick(Sender: TObject);
private
FWorkerThread : TMyThread;
procedure WorkerThreadTerminate(Sender: TObject);
end;
var
ThreadDemoForm: TThreadDemoForm;
implementation
{$R *.dfm}
procedure TThreadDemoForm.PostMessageButtonClick(Sender: TObject);
begin
if not Assigned(FWorkerThread) then begin
Memo1.Lines.Add('Worker thread not running');
Exit;
end;
PostMessage(FWorkerThread.FWinHandle, WM_USER + 2, 0, 0);
end;
procedure TThreadDemoForm.StartThreadButtonClick(Sender: TObject);
begin
if Assigned(FWorkerThread) then begin
Memo1.Lines.Add('Worker thread already running');
Exit;
end;
Memo1.Lines.Add('Ask worker thread to start...');
FWorkerThread := TMyThread.Create(TRUE);
FWorkerThread.FreeOnTerminate := TRUE;
FWorkerThread.OnTerminate := WorkerThreadTerminate;
FWorkerThread.Start;
end;
procedure TThreadDemoForm.StopThreadButtonClick(Sender: TObject);
begin
if not Assigned(FWorkerThread) then begin
Memo1.Lines.Add('Worker thread not running');
Exit;
end;
Memo1.Lines.Add('Asking the worker thread to terminate...');
PostMessage(FWorkerThread.FWinHandle, WM_QUIT, 0, 0);
end;
procedure TThreadDemoForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
if Assigned(FWorkerThread) then begin
FWorkerThread.OnTerminate := nil; // Cancel event handling
// Ask the worker thread to terminate
PostMessage(FWorkerThread.FWinHandle, WM_QUIT, 0, 0);
FWorkerThread := nil;
// Let the workerthread breath
Sleep(250);
end;
end;
procedure TThreadDemoForm.WorkerThreadTerminate(Sender : TObject);
begin
Memo1.Lines.Add('Worker thread Terminated');
FWorkerThread := nil;
end;
{ TMyThread }
var
GWndHandlerCritSect : TRTLCriticalSection;
const
WorkerThreadWindowClassName = 'WorkerThreadWindowClass';
// WndControlWindowsProc is a callback function used for message handling
function WndControlWindowsProc(
ahWnd : HWND;
auMsg : UINT;
awParam : WPARAM;
alParam : LPARAM): LRESULT; stdcall;
var
Obj : TObject;
MsgRec : TMessage;
begin
// When the window was created, we stored a reference to the object
// into the storage space we asked windows to have
{$IFDEF WIN64}
Obj := TObject(GetWindowLongPtr(ahWnd, 0));
{$ELSE}
Obj := TObject(GetWindowLong(ahWnd, 0));
{$ENDIF}
// Check if the reference is actually our object type
if not (Obj is TMyThread) then
Result := DefWindowProc(ahWnd, auMsg, awParam, alParam)
else begin
// Internally, Delphi use TMessage to pass parameters to his
// message handlers.
MsgRec.Msg := auMsg;
MsgRec.wParam := awParam;
MsgRec.lParam := alParam;
TMyThread(Obj).WndProc(MsgRec);
Result := MsgRec.Result;
end;
end;
procedure TMyThread.AllocateHWnd;
var
TempClass : TWndClass;
NewWndClass : TWndClass;
ClassRegistered : Boolean;
begin
// Nothing to do if hidden window is already created
if FWinHandle <> 0 then
Exit;
// We use a critical section to be sure only one thread can check if a
// class is registered and register it if needed.
// We must also be sure that the class is not unregistered by another
// thread which just destroyed a previous window.
EnterCriticalSection(GWndHandlerCritSect);
try
// Check if the window class is already registered
NewWndClass.hInstance := HInstance;
NewWndClass.lpszClassName := WorkerThreadWindowClassName;
ClassRegistered := GetClassInfo(HInstance,
NewWndClass.lpszClassName,
TempClass);
if not ClassRegistered then begin
// Not registered yet, do it right now !
NewWndClass.style := 0;
NewWndClass.lpfnWndProc := @WndControlWindowsProc;
NewWndClass.cbClsExtra := 0;
NewWndClass.cbWndExtra := SizeOf(Pointer);
NewWndClass.hIcon := 0;
NewWndClass.hCursor := 0;
NewWndClass.hbrBackground := 0;
NewWndClass.lpszMenuName := nil;
if Winapi.Windows.RegisterClass(NewWndClass) = 0 then
raise Exception.Create(
'Unable to register hidden window class.' +
' Error: ' + SysErrorMessage(GetLastError));
end;
// Now we are sure the class is registered, we can create a window using it
FWinHandle := CreateWindowEx(WS_EX_TOOLWINDOW,
NewWndClass.lpszClassName,
'', // Window name
WS_POPUP, // Window Style
0, 0, // X, Y
0, 0, // Width, Height
0, // hWndParent
0, // hMenu
HInstance, // hInstance
nil); // CreateParam
if FWinHandle = 0 then
raise Exception.Create(
'Unable to create hidden window. ' +
' Error: ' + SysErrorMessage(GetLastError)); { V8.62 tell user real error. probably no memory }
// We have a window. In the associated data, we record a reference
// to our object. This will later allow to call the WndProc method to
// handle messages sent to the window.
{$IFDEF WIN64}
SetWindowLongPtr(FWinHandle, 0, INT_PTR(Self));
{$ELSE}
SetWindowLong(FWinHandle, 0, Longint(Self));
{$ENDIF}
finally
LeaveCriticalSection(GWndHandlerCritSect);
end;
end;
procedure TMyThread.DeallocateHWnd;
begin
if FWinHandle = 0 then
Exit; // Already done
{$IFDEF WIN64}
SetWindowLongPtr(FWinHandle, 0, 0);
{$ELSE}
SetWindowLong(FWinHandle, 0, 0);
{$ENDIF}
DestroyWindow(FWinHandle);
FWinHandle := 0;
end;
procedure TMyThread.Execute;
var
MsgRec : TMsg;
begin
// We cannot access the VCL from a thread, so use system function.
// The message will be shown in the debugger in the events view.
OutputDebugString('Thread Starting');
AllocateHWnd;
// Put a first message into the message queue
PostMessage(FWinHandle, WM_USER + 1, 0, 0);
// Message loop
// If GetMessage retrieves the WM_QUIT, the return value is FALSE and
// the message loop is broken.
while (not Terminated) and GetMessage(MsgRec, 0, 0, 0) do begin
TranslateMessage(MsgRec);
DispatchMessage(MsgRec)
end;
DeallocateHWnd;
OutputDebugString('Thread Ending');
end;
procedure TMyThread.WndProc(var MsgRec: TMessage);
begin
case MsgRec.Msg of
WM_USER + 1 : OutputDebugString('WM_USER + 1');
WM_USER + 2 : OutputDebugString('WM_USER + 2');
else
MsgRec.Result := DefWindowProc(FWinHandle, MsgRec.Msg,
MsgRec.wParam, MsgRec.lParam);
end;
end;
initialization
InitializeCriticalSection(GWndHandlerCritSect);
finalization
DeleteCriticalSection(GWndHandlerCritSect);
end.
unitthreaddemomain;
接口
使用
Winapi.Windows、Winapi.Messages、System.SysUtils、System.class、,
图形、控件、窗体、对话框、stdctrl;
类型
TMyThread=class(TThread)
私有的
FWinHandle:HWND;
程序分配wnd;事实上的
程序DeallocateHWnd;事实上的
程序WndProc(var MsgRec:TMessage);事实上的
公众的
程序执行;推翻
属性WinHandle:HWND read FWinHandle;
结束;
tthreademoform=class(TForm)
开始线程按钮:t按钮;
备忘录1:TMemo;
停止线程按钮:t按钮;
PostMessageButton:TButton;
标签1:TLabel;
过程开始线程按钮单击(发送方:ToObject);
过程FormClose(发送方:ToObject;var操作:TCloseAction);
程序停止线程按钮单击(发送方:ToObject);
过程PostMessageButton单击(发件人:ToObject);
私有的
FWorkerThread:TMyThread;
程序WorkerThreadTerminate(发送方:ToObject);
结束;
变量
ThreadDemoForm:tthreademoform;
实施
{$R*.dfm}
过程TThreadDemoForm.PostMessageButtonClick(发件人:ToObject);
开始
如果未分配(FWorkerThread),则开始
Memo1.Lines.Add('工作线程未运行');
出口
结束;
PostMessage(FWorkerThread.FWinHandle,WM_USER+2,0,0);
结束;
过程TThreadDemoForm.StartThreadButtonClick(发送方:ToObject);
开始
如果已分配(FWorkerThread),则开始
Memo1.Lines.Add('工作线程已在运行');
出口
结束;
Memo1.Lines.Add('Ask worker thread to start…');
FWorkerThread:=TMyThread.Create(TRUE);
FWorkerThread.FreeOnTerminate:=真;
FWorkerThread.OnTerminate:=WorkerThreadTerminate;
FWorkerThread.启动;
结束;
过程TThreadDemoForm.StopThreadButton单击(发送方:ToObject);
开始
如果未分配(FWorkerThread),则开始
Memo1.Lines.Add('工作线程未运行');
出口
结束;
Memo1.Lines.Add('请求工作线程终止…');
PostMessage(FWorkerThread.FWinHandle,WM_QUIT,0,0);
结束;
过程TThreadDemoForm.FormClose(发送方:ToObject;变量操作:TCloseAction);
开始
如果已分配(FWorkerThread),则开始
FWorkerThread.OnTerminate:=nil;//取消事件处理
//请求工作线程终止
PostMessage(FWorkerThread.FWinHandle,WM_QUIT,0,0);
FWorkerThread:=零;
//让工作线程呼吸
睡眠(250);
结束;
结束;
过程TThreadDemoForm.WorkerThreadTerminate(发送方:ToObject);
开始
Memo1.Lines.Add('Worker thread Terminated');
FWorkerThread:=零;
结束;
{TMyThread}
变量
GWndHandlerCritSect:TRTLCriticalSection;
常数
WorkerThreadWindowClassName='WorkerThreadWindowClass';
//WndControlWindowsProc是用于消息处理的回调函数
函数WndControlWindowsProc(
ahWnd:HWND;
auMsg:UINT;
awParam:WPARAM;
alParam:LPARAM):LRESULT;stdcall;
变量
对象:对象;
MsgRec:TMessage;
开始
//创建窗口时,我们存储了对对象的引用
//进入我们要求windows提供的存储空间
{$IFDEF WIN64}
对象:=TObject(GetWindowLongPtr(ahWnd,0));
{$ELSE}
Obj:=TObject(GetWindowLong(ahWnd,0));
{$ENDIF}
//检查引用是否实际上是我们的对象类型
如果不是(Obj是TMyThread),则
结果:=DefWindowProc(ahWnd、auMsg、awParam、alParam)
否则开始
//在内部,Delphi使用TMessage将参数传递给his
//消息处理程序。
MsgRec.Msg:=auMsg;
MsgRec.wParam:=awParam;
MsgRec.lParam:=alParam;
TMyThread(Obj).WndProc(MsgRec);
结果:=MsgRec.Result;
结束;
结束;
程序TMyThread.AllocateHWnd;
变量
临时班:TWndClass;
NewWndClass:TWndClass;
类注册:布尔;
开始
//如果已创建隐藏窗口,则无需执行任何操作
如果FWinHandle为0,则
出口
//我们使用临界部分来确保只有一个线程可以检查
//类进行注册,并在需要时进行注册。
//我们还必须确保该类没有被其他类注销
//刚刚破坏前一个窗口的线程。
肠危重科(GWndHandlerCritSect);
尝试
//检查窗口类是否已注册
NewWndClass.hInstance:=hInstance;
NewWndClass.lpszClassName:=WorkerThreadWindowClassName;
ClassRegistered:=GetClassInfo(HInstance,