Delphi关于线程的消息处理

在平时写程序时,总是碰到窗体（TForm）与线程（TThread）消息通信问题。令人烦恼的是窗体不能向线程（TThread）发送消息（线程没有窗口句柄）。经过几天的折腾，想出二种解决方案，拿出来跟大家探讨探讨。

第一。我们知道VC++ 中的MFC类库是自已封装了消息处理（BEGINMESSAGE, ENDMESSAGE），在MFC中对消息的处理是通过建立一张消息映射表，而把方法（function）或过程（PRocedure）的地址保存到映射表里（消息处理实质上是方法或过程的调用）,再加上一个消息分发机制，来实现消息的接收发送 <详见VC++技术内幕>。所以我们只要为线程里建立一张消息映射表，并建立相应的消息分发机制。这样就可以处理窗体发送到线程的消息。以下代码是实现消息映射表和消息分发的类（详见 <../消息处理设计(线程)1/MessageHandle.pas> 中 ）

unit MessageHandle;

interface

uses messages,Classes,SysUtils,Dialogs;

const PMSG_BASE = $BE00; //自定义消息基址;

PMSG_NUM = 200; //消息表大小；

{**自定义消息处理类

*;功能 = 建立自定义消息表，处理线程之间

* 以及与主窗体之间的自定义消息(宏观)

*}

//消息处理句柄

TMessageHandle = procedure(var Message: TMessage) of Object;

TPDispatcher = class(TObject)

private

//消息对应表(消息ID为数组下标);

MessageHandles: array of TMessageHandle;

//从消息ID得到数组ID

function GetIndexFromMsgID(const aMessageID: cardinal): Integer;

public

constructor Create;

destructor Destroy;

//发送消息

procedure SendMessage(var Message: TMessage); overload;

//添加自定义消息到消息对应表;

procedure AddHandle(const aMessageID: cardinal; aMessageHandle: TMessageHandle);

end;

//

implementation

{ TPDispatcher }

constructor TPDispatcher.Create;

var i: Integer;

begin

SetLength(MessageHandles,PMSG_NUM); //200个消息的消息对应表

//初始化消息队列;

for i := 0 to Pred(PMSG_NUM) do

MessageHandles[i] := nil;

end;

destructor TPDispatcher.Destroy;

begin

{释放消息对应表}

FreeAndNil(MessageHandles);

end;

procedure TPDispatcher.AddHandle(const aMessageID: cardinal;

aMessageHandle: TMessageHandle);

var tID: Integer;

begin

tID := GetIndexFromMsgID(aMessageID);

Assert((tID > 0) or (tID < Pred(PMSG_NUM)) );

Assert(Assigned(aMessageHandle));

MessageHandles[tID] := aMessageHandle;

end;

function TPDispatcher.GetIndexFromMsgID(const aMessageID: cardinal): Integer;

begin

Result := aMessageID - PMSG_BASE;

end;

procedure TPDispatcher.SendMessage(var Message: TMessage);

var tID: Integer;

tMsgHandle: TMessageHandle;

begin

tID := GetIndexFromMsgID(Message.Msg);

Assert((tID > 0) or (tID < Pred(PMSG_NUM)));

tMsgHandle := MessageHandles[tID];

if Assigned(tMsgHandle) then

tMsgHandle(Message);

end;

现在我们只需要注册一下自定义的消息，然后通过消息分发类（TPDispatcher），实现对线程消息的处理。代码如下<详见../消息处理设计(线程)1/test/unit1.pas>：

Unit unit1

const

{自定久线程消息}

MY_MESSAGE2 = PMSG_BASE + 02;

type

TForm1 = class(TForm)

AddMsgList: TButton;

SendThead: TButton;

sendForm: TButton;

sendOther: TButton;

procedure SendTheadClick(Sender: TObject); //发送消息

procedure FormCreate(Sender: TObject);

procedure FormDestroy(Sender: TObject);

private

Fdispatcher: TPDispatcher; 消息映射表类

Fhandle: TPHandler;

FThread: TPTHread; 自定义线程类

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.SendTheadClick(Sender: TObject);

var aMessage: TMessage;begin

aMessage.Msg := MY_MESSAGE2;

aMessage.WParam := 1;

Fdispatcher.SendMessage(aMessage);

end;

end;

procedure TForm1.FormCreate(Sender: TObject);

begin

{创建消息映射表类}

Fdispatcher := TPDispatcher.Create;

Fhandle := TPHandler.Create;

{创建线程}

FThread := TPThread.Create(false);

{向映射表中增加消息}

Fdispatcher.AddHandle(MY_MESSAGE2,FThread.DoMessage);

end;

procedure TForm1.FormDestroy(Sender: TObject);

var i: Integer;

begin

FreeAndNil(Fdispatcher);

FreeAndNil(Fhandle);

for i:= 0 to 3 do

FreeAndNil(FThread[i]);

end;

第二。窗口可以处理消息是因为它有窗口句柄。为了使线程也能处理消息，我们可以通过为线程加上一个相应窗口类的窗口名柄。（源码在 <../消息处理设计(线程)2 / pThread.pas >中）

unit pThread;

interface

uses classes,sysutils,Windows,Messages,Dialogs;

const MY_MESSAGE1 = $BD00 + 01;

Type

{** 消息处理线程类

*;功能 = 添加线程处理消息能力，

*}

TPMsgThread = class(TThread)

private

//窗口句柄

FWndHandle: HWND;

//窗口数据信息

FWndClass: WNDCLASS;

//指向窗口回调函数的指针

FObjectInstance: Pointer;

//初始化窗口数据

procedure InitWnd;

//创建隐藏窗口

procedure CreateWnd;

//注册隐藏窗口

procedure RegistWnd;

procedure DestroyWnd;

//窗口回调函数

procedure pWndProc(var Message: TMessage); virtual;

protected

procedure Execute; override;

procedure DoTerminate; override;

public

constructor Create(CreateSuspended: Boolean); virtual;

property WndHandle: HWND read FWndHandle write FWndHandle;

end;

implementation

const WND_NAME = 'PY20';

{ TPMsgThread }

constructor TPMsgThread.Create(CreateSuspended: Boolean);

begin

inherited Create(CreateSuspended);

FWndHandle := Integer(nil);

InitWnd;

RegistWnd;

CreateWnd;

end;

procedure TPMsgThread.CreateWnd;

begin

if(WndHandle = Integer(nil)) then

WndHandle := CreateWindow(FWndClass.lpszClassName, FWndClass.lpszClassName,

WS_POPUP or WS_CAPTION or WS_CLipSIBLINGS or WS_SYSMENU

or WS_MINIMIZEBOX,

GetSystemMetrics(SM_CXSCREEN) div 2,

GetSystemMetrics(SM_CYSCREEN) div 2,

0, 0, 0, 0, FWndClass.hInstance, nil);

//置换窗口回调函数

SetWindowLong(WndHandle, GWL_WNDPROC, Longint(FObjectInstance));

end;

procedure TPMsgThread.DestroyWnd;

begin

UnregisterClass(FWndClass.lpszClassName,FWndClass.hInstance);

DestroyWindow(WndHandle);

end;

procedure TPMsgThread.DoTerminate;

begin

inherited;

DestroyWnd;

end;

procedure TPMsgThread.Execute;

begin

end;

procedure TPMsgThread.InitWnd;

begin

FwndClass.lpszClassName := PChar(WND_NAME);

FWndClass.hInstance := Handle;

FWndClass.lpfnWndProc := @DefWindowProc;

end;

procedure TPMsgThread.pWndProc(var Message: TMessage);

begin

end;

procedure TPMsgThread.RegistWnd;

begin

FObjectInstance := Classes.MakeObjectInstance(pWndProc);

if(FWndClass.hInstance <> Integer(nil)) then

RegisterClass(FWndClass);

end;