Delphi消息处理机制

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;

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