深入delphi编程理解之消息（二）发送消息函数及消息编号、消息结构体的理解

时间：2023-03-09 03:10:33
深入delphi编程理解之消息（二）发送消息函数及消息编号、消息结构体的理解

　　一、delphi发送消息的函数主要有以下三个：

　（一）、SendMessage函数，其原型如下：

function SendMessage(

  hWnd: HWND;        {目标句柄}

  Msg: UINT;         {要发送的消息(编号)}

  wParam: WPARAM;    {消息参数}

  lParam: LPARAM     {消息参数}

): LRESULT; stdcall; {返回处理结果}

　（二）、PostMessage函数

function PostMessage(

  hWnd: HWND;     {目标句柄}

  Msg: UINT;      {要发送的消息(编号)}

  wParam: WPARAM; {消息参数}

  lParam: LPARAM  {消息参数}

): BOOL; stdcall; {是否发送成功}

（三）、Perform 函数

function Perform(

  Msg: Cardinal;  {要发送的消息(编号)}

  WParam: WPARAM; {消息参数}

  LParam: LPARAM  {消息参数}

): LRESULT;       {返回处理结果}

　　SendMessage和PostMessage是API函数，Perform是delphi从TControl类开始定义的方法，所有从TControl继承的子类对象都可以使用。SendMessage和Perform方法，发送消息后，要等系统回馈结果后才执行下一步操作，而PostMessage函数则只管发送消息，发送消息后程序会马上执行下一步代码。

二、delphi 消息编号（Msg）规则及参数结构理解

（一）、消息编号

　　消息编号是window或者用户为各种不同消息定义唯一编号，他其实就是无符号整数（Cardinal）,为了便于理解， delphi以常量形式对每一个数字进行定义，主要有以下几种形式：

　　 1、windows消息，以WM_为前缀，如WM_CLOSE为窗口关闭消息；

2、delphi自定义消息，以CM_、CN为前缀；

　　3、用户自定义消息 以WM_USER基数，如  Const MyMessage=WM_USER+1；

定义消息编号主要作用是定位消息处理函数，作为message关键字的识别码，例如以下函数头的定义：

 procedure WMKeyDown(var Message: TWMKeyDown); message WM_KEYDOWN;

以上函数头定义了WM_KEYDOWN消息编号，其常量数值为 WM_KEYDOWN= $0100，其作用就是当窗口接受到编号为$100的消息就执行WMKeyDown这个函数。

（二）、消息结构体

　        消息结构体一般作为消息函数的参数类型出现，如上例中的TWMKeyDown就是一个消息结构体。消息结构体的标准定义如下：

PMsg = ^TMsg;

tagMSG = packed record

  hwnd: HWND;

  message: UINT;

  wParam: WPARAM;

  lParam: LPARAM;

  time: DWORD;

  pt: TPoint;

end;

TMsg = tagMSG;

MSG = tagMSG;

这种标准结构体与delphi VCL消息结构体并不兼容，所以delphi定义了自己的消息结构体。

PMessage = ^TMessage;

TMessage = packed record

  Msg: Cardinal; {消息编号}

  case Integer of

    0: (

      WParam: WPARAM;

      LParam: LPARAM;

      Result: LRESULT);

    1: (

      WParamLo: Word;

      WParamHi: Word;

      LParamLo: Word;

      LParamHi: Word;

      ResultLo: Word;

      ResultHi: Word);

end;

　　在我们实际使用中，虽然标准的结构体可以满足我们的使用，但由于使用过程中我们还要进行数据转换，为了更加便捷和易于理解，delphi在message单元文件中为我们定义大量的消息结构体，供我们直接调用。

TWMNoParams

TWMCancelMode       = TWMNoParams;

TWMChildActivate    = TWMNoParams;

TWMClear            = TWMNoParams;

TWMClose            = TWMNoParams;

TWMCopy             = TWMNoParams;

TWMCut              = TWMNoParams;

TWMDestroy          = TWMNoParams;

TWMDestroyClipboard = TWMNoParams;

TWMDrawClipboard    = TWMNoParams;

TWMFontChange       = TWMNoParams;

TWMGetDlgCode       = TWMNoParams;

TWMGetFont          = TWMNoParams;

TWMGetHotKey        = TWMNoParams;

TWMGetTextLength    = TWMNoParams;

TWMMDIGetActive     = TWMNoParams;

TWMMDIIconArrange   = TWMNoParams;

TWMMDIRefreshMenu   = TWMNoParams;

TWMNCDestroy        = TWMNoParams;

TWMPaintIcon        = TWMNoParams;

TWMPaste            = TWMNoParams;

TWMQueryDragIcon    = TWMNoParams;

TWMQueryNewPalette  = TWMNoParams;

TWMQueryOpen        = TWMNoParams;

TWMQueueSync        = TWMNoParams;

TWMRenderAllFormats = TWMNoParams;

TWMSysColorChange   = TWMNoParams;

TWMTimeChange       = TWMNoParams;

TWMQueryUIState     = TWMNoParams;

TWMUndo             = TWMNoParams;

TWMKey

TWMChar       = TWMKey;

TWMKeyDown    = TWMKey;

TWMKeyUp      = TWMKey;

TWMDeadChar   = TWMChar;

TWMSysChar    = TWMKey;

TWMSysKeyDown = TWMKey;

TWMSysKeyUp   = TWMKey;

TWMMouse

TWMLButtonDblClk = TWMMouse;

TWMLButtonDown   = TWMMouse;

TWMLButtonUp     = TWMMouse;

TWMMButtonDblClk = TWMMouse;

TWMMButtonDown   = TWMMouse;

TWMMButtonUp     = TWMMouse;

TWMMouseMove     = TWMMouse;

TWMRButtonDblClk = TWMMouse;

TWMRButtonDown   = TWMMouse;

TWMRButtonUp     = TWMMouse;

TWMMouseWheel

TMSHMouseWheel

TWMWindowPosMsg

TWMWindowPosChanged  = TWMWindowPosMsg;

TWMWindowPosChanging = TWMWindowPosMsg;

TWMScroll

TWMHScroll = TWMScroll;

TWMVScroll = TWMScroll;

TWMActivate

TWMActivateApp

TWMAskCBFormatName

TWMChangeCBChain

TWMCharToItem

TWMVKeyToItem = TWMCharToItem;

TWMChooseFont_GetLogFont

TWMCommand

TWMCompacting

TWMCompareItem

TWMCopyData

TWMCreate

TWMCtlColor

TWMCtlColorBtn       = TWMCtlColor;

TWMCtlColorDlg       = TWMCtlColor;

TWMCtlColorEdit      = TWMCtlColor;

TWMCtlColorListbox   = TWMCtlColor;

TWMCtlColorMsgbox    = TWMCtlColor;

TWMCtlColorScrollbar = TWMCtlColor;

TWMCtlColorStatic    = TWMCtlColor;

TWMDDE_Ack

TWMDDE_Advise

TWMDDE_Data

TWMDDE_Execute

TWMDDE_Initiate

TWMDDE_Poke

TWMDDE_Request

TWMDDE_Terminate

TWMDDE_Unadvise

TWMDeleteItem

TWMDevModeChange

TWMDrawItem

TWMDropFiles

TWMEnable

TWMEndSession

TWMEnterIdle

TWMEnterMenuLoop

TWMExitMenuLoop = TWMEnterMenuLoop;

TWMEraseBkgnd

TWMGetIcon

TWMGetMinMaxInfo

TWMGetText

TWMHotKey

TWMHScrollClipboard

TWMIconEraseBkgnd = TWMEraseBkgnd;

TWMInitDialog

TWMInitMenu

TWMInitMenuPopup

TWMKillFocus

TWMMDIActivate

TWMMDICascade

TWMMDICreate

TWMMDIDestroy

TWMMDIMaximize

TWMMDINext

TWMMDIRestore

TWMMDISetMenu

TWMMDITile

TWMMeasureItem

TWMMenuChar

TWMMenuSelect

TWMMouseActivate

TWMMove

TWMMoving

TWMNCActivate

TWMNCCalcSize

TWMNCCreate

TWMNCHitTest

TWMNCHitMessage

TWMNCLButtonDblClk = TWMNCHitMessage;

TWMNCLButtonDown   = TWMNCHitMessage;

TWMNCLButtonUp     = TWMNCHitMessage;

TWMNCMButtonDblClk = TWMNCHitMessage;

TWMNCMButtonDown   = TWMNCHitMessage;

TWMNCMButtonUp     = TWMNCHitMessage;

TWMNCMouseMove     = TWMNCHitMessage;

TWMNCRButtonDblClk = TWMNCHitMessage;

TWMNCRButtonDown   = TWMNCHitMessage;

TWMNCRButtonUp     = TWMNCHitMessage;

TWMNCPaint

TWMNextDlgCtl

TWMNotify

TWMNotifyFormat

TWMPaint

TWMPaintClipboard

TWMPaletteChanged

TWMPaletteIsChanging

TWMParentNotify

TWMPower

TWMQueryEndSession

TWMQuit

TWMRenderFormat

TWMSetCursor

TWMSetFocus

TWMSetFont

TWMSetHotKey

TWMSetIcon

TWMSetRedraw

TWMSetText

TWMShowWindow

TWMSize

TWMSizeClipboard

TWMSpoolerStatus

TWMStyleChange

TWMStyleChanged  = TWMStyleChange;

TWMStyleChanging = TWMStyleChange;

TWMSysCommand

TWMSysDeadChar

TWMSystemError

TWMTimer

TWMUIState

TWMChangeUIState = TWMUIState;

TWMUpdateUIState = TWMUIState;

TWMVScrollClipboard

TWMWinIniChange

TWMSettingChange

TWMHelp

TWMDisplayChange

TWMContextMenu

TWMPrint

TWMPrintClient = TWMPrint;