windows消息处理（强烈推荐，收藏）

由于看了一下，比较好理解，暂时先放到这里，待有空再翻译。只是在每节后大致介绍一下讲的内容。

感觉写的比较全，无论从消息的原理还是从MFC操作上来说，值得一看，我也在此做个收藏。
（一）
说明：以下首先对消息进行介绍，然后在消息处理中，使用类向导创建消息循环，这个操作是在vc6.0（或者之下版本）操作的。

Introduction

PerhapsoneofthemostimportantmeansofcommunicationinwindowsisMessages.Thetraditionalprogramstartsatyour

main()

function,movesdownline-by-lineinyourcode,andeventuallyexits.
TheWindowsconceptisdifferent.Thewayyouprograminwindowsisbyrespondingtoevents.Theseeventsarecalledmessages.

Messagescansignalmanyevents,causedbytheuser,theoperatingsystem,oranotherprogram.Aneventcouldbecausedbyamousemove,akey-press,orbyyourwindowgettingresized.Thereare2kindsofmessages:awindowmessage,orathreadmessage.
SinceThreadsareanadvancedissue,I'llreferonlytowindowmessages.

WindowMessages:

Ingeneral,amessagemustbesenttoawindow.AllthemessagessenttoyouarestoredinaMessageQueue,aplaceinthememorywhichstoresmessagewhicharetransferredbetweenapplications.

MessageLoop:

thewayyouretrievemessagesfromtheMessageQueueisbycreatingaMessageLoop.AMessageLoopisaloopthatchecksformessagesintheMessageQueue.onceamessageisreceived,theMessageLoopdispatchesthemessagebycallingaMessageHandler,
afunctiondesignedtohelptheMessageLoopatprocessingthemessage.

TheMessageLoopwillendwhena

WM_QUIT

messageisreceived,signalingtheapplicationtoend.ThismessagecouldbesentbecausetheuserselectedExitfromyourFilemenu,clickedonthe
closebutton(theXsmallbuttonintheupperrightcornerofyourwindow),orpressedAlt+F4.WindowshasdefaultMessageHandlersforalmostallthemessages,givingyourwindowthedefaultwindowbehavior.Infact,allthestandardcontrolsaresimplywindows
withMessagehandlers.TakeaButtonforexample.Whenitgetsa

WM_PAINT

messageitwilldrawthebutton.WhenyouLeft-clickthebutton,itgetsa

WM_LBUTTONDOWN

message,anditdrawsthepressed-button.Whenyouletgoofthemousebuttonitreceivesa

WM_LBUTTONUP

message,andrespectivelydrawsthebutton.

Windowsdefinesmanydifferentmessagetypes(whicharestoredasUINTs).Theyusuallybeginwiththeletters"WM"andanunderscore,asin

WM_CHAR

and

WM_SIZE

.
Thenamesofthemessageareusuallyagoodindicatorofwhattheyrepresent.

WM_SIZE

forsizingmessages,

WM_CHAR

forcharacterentry
messagesandsoon.ThenamingconventioninMFCformessagehandlerfunctionsistotakeawaythe"WM_"andreplaceitwith"On",sothemessagehandlerfor

WM_SIZE

isusuallycalled

OnSize

.

Amessagecomeswith2parametersthatgiveyoumoreinformationabouttheevent.Eachparameterisa32-bitvalue:lParamandwParam.Forexample:

WM_MOUSEMOVE

willgiveyouthemousecoordinates
inoneparamter,andintheothersomeflagsindicatingthestateoftheALT,Shift,CTRLandmousebuttons.

AMessagemayalsoreturnavaluewhichallowsyoutosenddatabacktothethesendingprogram.Forexample,the

WM_QUERYENDSESSION

messagesentbywindowsbeforethecomputerisshutdown,expects
youtoreturnaBooleanvalue.Ifyourapplicationcanterminateconveniently,itshouldreturnTRUE;otherwise,itshouldreturnFALSE.Othermessagesuchasthe

WM_CTLCOLOR

messagesexpectyou
toreturnan

HBRUSH

.

Note:IntherestofthetutorialIwillfocusonMFCforsimplicityreasons.AlltheinformationaboveappliestobothSDKprograms,andMFCprograms.

MessageHandlers:

Fortunately,MFCwillgiveallthecodeneededforthemessageloop,Oneofthe

CWinApp

memberfunctionscalledbyWinMain—Run—providesthemessageloopthatpumpsmessagestotheapplication's
window.TheonlythingyouneedtodosoyoucanreceivemessagesistocreateMessageHandlers,andinformMFCofthem.So,howdoyoucreateaMessageHandler?OnceyouhaveanMFCC++classthatencapsulatesawindow,youcaneasilyuseClassWizardtocreate
MessageHandlers.

UsingClassWizardtocreateMessageHandlers:

PressCtrl+WtostarttheClassWizard,orrightclicktheAddbuttonandselectClassWizardfromthecontextmenu.OpenClassWizard,selectMessageMapstab.InClassnameselectthenameofyourC++class.onObjectIDsselecteithertheIDofamenu
item(formessagescausedbytheuserinteractingwithamenu),theIDofacontrol(formessagescausedbytheuserinteractingwithacontrol),orthefirstoptiontohandlemessagesothermessages.ChoosethemessagefromtheMessageslist,

WM_SIZE

forexample,andClickonAddFunction.ClickOK,thenclickEditCode.ClassWizardwillwriteanewemptyfunction(

OnSize

forexample)withtheproperprototypeintheclassheader.Thecode
generatedshouldlooksimilartothis:

voidCAboutWindow::OnSize(UINTnType,intcx,intcy)
{
CDialog::OnSize(nType,cx,cy);
//TODO:Addyourmessagehandlercodehere

//Hereiswhereyoucanresizecontrolsinyourwindow,change
//thesizeofabitmapinit,ordowhateveryoucanthinkof.
}

That'sit,nowyoucanhandlemessages.Ifyouwanttohandleamessageandthenletthedefaultmessagehandlerhandlethemessage,youshouldcallthebaseclassmemberfunctionthatcorrespondswiththemessage.Takethefollowing

WM_CLOSE

MessageHandlerasanexample:

voidCAboutWindow::OnClose()
{
//TheUseroranotherprogramistryingtocloseourwindow...
//Ifyoudon'taddcodetoclosethewindow,yourwindowwillneverclose
}

Ifyouwantwindowstogetashotatthemessage,youshouldcallthebaseclassmemberfunctionOnClose:

voidCAboutWindow::OnClose()
{
MessageBox(_T("Closingthewindow!"))
//CalltheBaseclassmemberfunction,whichwillclosethewindow.
CWnd::OnClose()
}

Youcouldusethisbehaviortoscreen-outevents.Forexample,aprogramthatpromptstheuserifheissurethathewantstoclosethewindow:

voidCAboutWindow::OnClose()
{
intRet=MessageBox(_T("Areyousureyouwanttoclosethewindow?"),
_T("CloseWindow?"),MB_YESNO);
if(Ret==IDYES){
//TheUserissure,closethewindowbycallingthebaseclass
//member
CWnd::OnClose()
}
else{
//Theuserpressedno,screenoutthemessagebynotcalling
//thebaseclassmember

//Donothing
}
}

SendingMessages:

Besidesreceivingmessages,youwilloftenfindyourselfsendingmessages.Youmightwanttosendmessagestocommunicatebetweentowindowsinyourprogram,ortocommunicatebetweendifferentprograms.Inordertosendamessageyouneedapointerto
ac++windowclass.Thiscanberetrievedusingvariousfunctions,including

CWnd::FindWindow,GetDlgItem(),GetParent(),

andmore.The

CWnd

classhasa

SendMessage()

memberfunctionwhichallowsyoutosendmessagestoit'swindow.Forexample,Let’ssayyouhaveaCWndpointertotheCalculator,andyouwanttocloseit.Whatyoushoulddoissenda

WM_CLOSE

message,whichwillnotifytheCalculatorthatitshouldclose.Youcanusethefollowingcode.InordertogetapointertoCalculator,Iusethestatic

CWnd::FindWindow()

functionandpassthetitleofthewindow,whichinourcaseis"Calculator".

CWnd*pCalc;
//Getapointertothe"Calculator"Window
pCalc=CWnd::FindWindow(NULL,_T("Calculator));
if(pCalc==NULL){
//Couldn'tfindCalculator
}
else{
pCalc->SendMessage(WM_CLOSE);
//Presto!TheCalculatorshouldclose.
}

（二）

HowdoMFCmessagehandlerswork?

Wheneveryourwindowreceivesamessage,MFCwillcallamemberfunctionofyourclass.ButhowdoesMFCknowwhatfunctiontocall?

MFCusesatechniquecalledMessageMaps.AMessageMapisatablethatassociatesmessageswithfunctions.Whenyoureceiveamessage,MFCwillgothroughyourMessageMapandsearchforacorrespondingMessageHandler.IhaveshowedinPart1howyouadd
aMessageHandlertotheMessageMapbyusingClassWizard,butwhatreallyhappenscode-wise?

MFCusesalargesetofrathercomplicatedmacrosthataddtheMessageMaptoyourclasses.WhenyouuseClassWizardtocreateaMessageHandler,itwillfirstaddthefunctiontoyourclass,andaddthecorrespondingmacrotoyourMessageMap.Forexample,
examinethefollowingClassWizardgenerated

WM_CLOSE

handler:

第一步：消息映射---MessageMap:locatedintheclassimplementation

BEGIN_MESSAGE_MAP(CAboutDlg,CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
ON_WM_CLOSE()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

第二步：函数声明---FunctionDeclaration:locatedintheclassdeclaration.

protected:
//{{AFX_MSG(CAboutDlg)
afx_msgvoidOnClose();
//}}AFX_MSG
DECLARE_MESSAGE_MAP()

第三步：函数执行---FunctionImplementation:locatedintheclassimplementation

voidCAboutDlg::OnClose()
{
//TODO:Addyourmessagehandlercodehereand/orcalldefault

CDialog::OnClose();
}

Byaddinga

DECLARE_MESSAGE_MAP

statementtotheclassdeclaration,MFCaddstherequiredcodetodeclarethemessagemap.The

BEGIN_MESSAGE_MAP

tellsMFCwheretheMessageMapbegins,andidentifiesyourclassandit'sbaseclass.ThereasonitneedsthebaseclassisbecauseMessageHandlersarepassedthroughc++inheritance,justlikeanyotherfunction.

END_MESSAGE_MAP

obviously,tellsMFCwheretheMessageMapends.InbetweenthesetwomacrosiswhereyourdeclaretheMessageMapentryforyourMessageHandler.MFChasmanypredefinedmacros,whichassociatemessageswithyourmemberfunction.Takethethe

ON_WM_CLOSE

macroasanexample:Itassociatesthe

WM_CLOSE

messagewithyour

OnClose()

memberfunction.Themacrotakesnoparameterssinceit
alwaysexpectsafunctioncalled

OnClose()

whichisprototypedas

afx_msgvoidOnClose()

.Thismethodgivesyou2advantages:

ItiseasytokeeptrackofMessageHandlersandthemessagestheyhandle
MFCscreensoutanyirrelevantandwillbreakuplParamandwParamtoparametersrelevanttothemessage.

Alsothereturnvalueissimplified,andtheMessageHandlerisprototypedaccordingtothemessage.Forexample:Ifthevalueshouldalwaysbezero,MFCsimplifiestheprocessandallowsyoutodeclarethefunctionasa

void

,
andMFCwillberesponsibleforreturning0.TofindthenameofthemessagehandlerthatcorrelateswithagivenMessageHandlermacroyoushouldlookitupintheMFCdocumentation.

TherearesomemessagesthatClassWizarddoesn'tsupport,butyoucanmanualyaddyourmessagehandlerbyaddingthefunctionandMessageMapmacroasdescribedabove.Ifyouaddmessage-mapentriesmanually,youmaynotbeabletoeditthemwithClassWizard
later.Ifyouaddthemoutsidethebracketingcomments

//{{AFX_MSG_MAP(classname)

and

//}}AFX_MSG_MAP

,ClassWizardcannoteditthem
atall.NotethatbythesametokenClassWizardwillnottouchanyentriesyouaddoutsidethecomments,sofeelfreetoaddmessagesoutsidethecommentsifyoudonotwantthemtobemodified.MessagesthatarenotrecognizedbyClassWizard,suchasmessage-map
ranges,mustbeaddedoutsidethecomments.

TheallmightyON_MESSAGE

SometimesyouwillfindyourselftryingtohandleamessagethatClassWizarddoesn'tsupport,anditdoesn'thaveaMessageMapmacro.MFChasagenericmacrojustforthiskindofsituation

ON_MESSAGE

.

ON_MESSAGE

allowsyoutohandleanymessagethatexists.TheprototypeofMessageHandlersthatuse

ON_MESSAGE

is

afx_msgLRESULTOnMessage(WPARAMwParam,LPARAMlParam);

where

OnMessage

isthenameofyourhandlerfunction.The

ON_MESSAGE

macrotakes2parameters:Theaddressofthehandler,and
themessageitshouldhandle.Forexample:ThefollowingstatementMaps

WM_GETTEXTLENGTH

to

OnGetTextLength()

:

ON_MESSAGE(WM_GETTEXTLENGTH,OnGetTextLength)

OnGetTextLength

isprototypedas

afx_msgLRESULTOnGetTextLength(WPARAMwParam,LPARAMlParam);

说明：以上部分还是接第一部分的类向导，通过ctrl+w快捷键进入，选择之后，vc6会自动把上文标注的三步骤放到相应的位置，下边自定义的消息（在类向导中没有的消息，自己定义的消息），则可以参考上文的三步骤，在和它们对应的位置添加，注意这个需要定义一个消息宏（下面红色标注），WM_APP现在应该为WM_USER，自定义消息只需要在WM_USER之上加上一个数字，因为一般WM_USER之前的消息，是系统消息（ctrl+w中看到的鼠标点击消息、键盘消息】重绘消息等）。

User-definedmessages

Sometimes,youwillneedtocommunicatebetween2windowsinyourapplicationorbetween2windowsfromdifferentapplications.AneasywaytodothisisbyusingUser-definedmessages.Thename"User-defined"canbeconfusingatfirst;youdefineaUser-defined
messageandnottheuserofyourprogram.IhavestatedinPart1thatmessagesareidentifiedbynumbers,andthatWindowspredefinesstandardmessages.Thewayofusingpredefinedmessagesistosimplyuseanumber.Tomakesurethatyoudon'tconflictwith
thesystemdefinedmessagesyoushoulduseanumberintherangeof

WM_APP

through0xBFFF:

#defineWM_DELETEALLWM_APP+0x100
//...
pYourDialog->SendMessage(WM_DELETEALL,0,0);

Handlingauser-definedmessageisdonewiththe

ON_MESSAGE

macro:

#defineWM_DELETEALLWM_APP+0x100
//...
//MessageMapentry:
ON_MESSAGE(WM_DELETEALL,OnDeleteAll)
//OnDeleteAllisprototypedas
afx_msgLRESULTOnDeleteAll(WPARAMwParam,LPARAMlParam);
//Andisimplementedas
LRESULTOnDeleteAll(WPARAMwParam,LPARAMlParam){
//DoWhateveryouwant
returnsomevalue;
}

RegisteredWindowsMessages

The

RegisterWindowMessage

functionisusedtodefineanewwindowmessagethatisguaranteedtobeuniquethroughoutthesystem.Themacro

ON_REGISTERED_MESSAGE

isusedtohandlethesemessages.Thismacroacceptsanameofa

UINT

variablethatcontainstheregisteredWindowsmessageID.Forexample:

classCMyWnd:publicCMyParentWndClass
{
public:
CMyWnd();

//{{AFX_MSG(CMyWnd)
afx_msgLRESULTOnFind(WPARAMwParam,LPARAMlParam);
//}}AFX_MSG

DECLARE_MESSAGE_MAP()
};

staticUINTWM_FIND=RegisterWindowMessage("YOURAPP_FIND_MSG");

BEGIN_MESSAGE_MAP(CMyWnd,CMyParentWndClass)
//{{AFX_MSG_MAP(CMyWnd)
ON_REGISTERED_MESSAGE(WM_FIND,OnFind)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

Therangeofuserdefinedmessagesusingthisapproachwillbeintherange0xC000to0xFFFF.Andyousenditusingtheregular

SendMessage()

method:

staticUINTWM_FIND=RegisterWindowMessage("YOURAPP_FIND_MSG");
//...
pFindWindow->SendMessage(WM_FIND,lParam,wParam);

（三）

说明：这部分才是消息处理的底层部分，前面MFC只是在这部分之上包了一层，所以你在那层看不到消息处理的本质。

HandlingMessagesinSDKapplications

ThisarticleassumesyouarefamiliarwithcreatingawindowinanSDKprogram.TheDialogpartassumesyouarefamiliarwithcreatingmodalandmodelessdialoginaSDKprogram.

HandlingmessagesinSDKapplicationsisatotallydifferentprocessthanMFC.NoClassWizardormacrostohelpyou.No

CWinApp

toimplementtheMessageLoopforyou.It'salluptoyou.

WindowsClassesandWindowProcedures

Window"classes"intraditionalprogrammingforWindowsdefinethecharacteristicsofa"class"(notaC++class)fromwhichanynumberofwindowscanbecreated.Thiskindofclassisatemplateormodelforcreatingwindows.InWindows,everywindowhas
aWindowClassthatdefinestheattributesofawindowsuchasthewindow'sicon,thewindow'sbackgroundandthewindow'sprocedure.TocreateaWindowclass,youcall

RegisterClass

thataccepts
a

WNDCLASS

structuredefiningthepropertiesoftheWindowclass.Everywindowmusthaveawindowclass,sotypically,

RegisterClass

is
calledin

WinMain

.

Usually,theMessageLoopisimplementedasabasic

while

loop:

MSGmsg;
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
returnmsg.wParam;

The

MSG

structureisastructurethatholdsalltheinformationaboutthemessage:Thewindowitwassentto,themessageidentifier,the2

lParam

/

wParam

parametersthatcomewiththemessage,thetimeatwhichthemessagewassent,andthepositionofthemousewhenthemessagewassent.

Thecallto

GetMessage

tellswindowstoretrievethefirstmessageintheMessageQueue.IfthereisnomessageintheMessageQueue,

GetMessage

willnotreturnuntilthereis.Thereturnvaluefrom

GetMessage

dependsonthemessageitretrieved:Ifitwasa

WM_QUIT

message
itwillreturn

FALSE

,ifitwasn't,itwillreturn

TRUE

.The

TranslateMessage

functiontranslatesvirtual-keymessagesintocharactermessages.Thecharactermessagesarepostedtothecallingthread'sMessageQueue,tobereadthenexttimethethreadcallsthe

GetMessage

function.Forexample,ifyougeta

WM_KEYDOWN

message,

TranslateMessage

willadda

WM_CHAR

messagetoyourMessageQueue.Thisisveryusefulbecausethe

WM_KEYDOWN

willonlytellyouwhatkeyhasbeenpressed,notthecharacteritself.A

WM_KEYDOWN

for

VK_A

couldmean"a"or"A",dependingonthestateoftheCapsLockandShiftkey.

TranslateMessage

willdotheworkofchecking
ifitshouldbecapitalforyou.Thecallto

DispatchMessage

willcalltheWindowProcedureassociatedwiththewindowthatreceivedthemessage.That'stheSDKMessageLoopinanutshell.

AWindowProcedureisafunctioncalledbytheMessageLoop.Wheneveramessageissenttoawindow,theMessageLooplooksatthewindow'sWindowClassandcallstheWindowProcedurepassingthemessage'sinformation.AWindowProcedureisprototypedas:

LRESULTCALLBACKWindowProc(
HWNDhwnd,//handletowindow
UINTuMsg,//messageidentifier
WPARAMwParam,//firstmessageparameter
LPARAMlParam//secondmessageparameter
);

The

HWND

isthehandletothewindowthatreceivedthemessage.Thisparameterisimportantsinceyoumightcreatemorethanonewindowusingthesamewindowclass.

uMsg

isthemessageidentifier,andthelast2parametersaretheparameterssentwiththemessage.

Typically,aWindowProcedureisimplementedasasetof

switch

statements,andacalltothedefaultwindowprocedure:

LRESULTCALLBACKWndProc(HWNDhwnd,UINTuMsg,
WPARAMwParam,LPARAMlParam){
switch(uMsg)
{
caseWM_CREATE:
//Dosomeinitialization,Playasoundorwhateveryouwant
return0;
caseWM_PAINT:
//HandletheWM_PAINTmessage
return0;
caseWM_DESTROY:
PostQuitMessage(0);
return0;
}
returnDefWindowProc(hwnd,message,wParam,lParam);
}

The

switch

-

case

blockinspectsthemessageidentifierpassedinthe

uMsg

parameterandrunsthecorrespondingmessagehandler.The

PostQuitMessage

callwillsenda

WM_QUIT

messagetotheMessageLoop,causing

GetMessage()

toreturn

FALSE

,andtheMessageLooptohalt.

DefWindowProc

AsIstatedinPart1,Windowsshouldhandleanymessageyoudon'thandle.Thecallto

DefWindowProc()

givesWindowsashotatthemessage.Somemessagessuch
as

WM_PAINT

and

WM_DESTROY

mustbehandledinyourWindowProcedure,andnotin

DefWindowProc

.

Puttingitalltogether:AllToGether.C（这个是核心的处理函数，入口函数）

#include<windows.h>
//DeclaretheWindowProcedure
LRESULTCALLBACKWndProc(HWND,UINT,WPARAM,LPARAM);

intWINAPIWinMain(
HINSTANCEhInstance,//handletocurrentinstance
HINSTANCEhPrevInstance,//handletopreviousinstance
LPSTRlpCmdLine,//pointertocommandline
intnCmdShow//showstateofwindow
){
staticTCHARlpszClassName[]=TEXT("AllTogether");
HWNDhwndMainWindow;
MSGmsg;
WNDCLASSwndclass;//窗口类，窗口显示的样式
//FillintheWindowclassdata
wndclass.cbClsExtra=0;
wndclass.cbWndExtra=0;
//Thedefaultwindowbackground
wndclass.hbrBackground=COLOR_WINDOW;
//Thesystem,IDC_ARROWcursor
wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
//ThesystemIDI_APPLICATIONicon
wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
wndclass.hInstance=hInstance;
wndclass.lpfnWndProc=WndProc;
//Thenameoftheclass,neededforCreateWindow
wndclass.lpszClassName=lpszClassName;
wndclass.lpszMenuName=NULL;
wndclass.style=CS_HREDRAW|CS_VREDRAW;

RegisterClass(&wndclass);//注册类，下面是创建窗体
hwndMainWindow=
CreateWindow(lpszClassName,//pointertoregisteredclassname
TEXT("LetsPutitalltogether"),//pointertowindowname
WS_OVERLAPPEDWINDOW,//windowstyle
CW_USEDEFAULT,CW_USEDEFAULT,//positionofwindow
CW_USEDEFAULT,CW_USEDEFAULT,//sizeofwindow
NULL,//handletoparentorownerwindow
NULL,//handletomenu
hInstance,//handletoapplicationinstance
NULL);//pointertowindow-creationdata
ShowWindow(hwnd,nCmdShow);
UpdateWindow(hwnd);

while(GetMessage(&msg,NULL,0,0))//消息循环
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
returnmsg.wParam;
}

LRESULTCALLBACKWndProc(HWNDhwnd,UINTuMsg,
WPARAMwParam,LPARAMlParam){
switch(uMsg)
{
caseWM_CREATE:
//Dosomeinitialization,Playasoundorwhateveryouwant
return0;
caseWM_PAINT:
//HandletheWM_PAINTmessage
return0;
caseWM_DESTROY:
PostQuitMessage(0);
return0;
}
returnDefWindowProc(hwnd,message,wParam,lParam);
}

SendingMessages

Besidesreceivingmessages,youwilloftenfindyourselfsendingmessages.Youmightwanttosendmessagestocommunicatebetweentwowindowsinyourprogram,ortocommunicatebetweendifferentprograms.Inordertosendamessage,youneedahandleto
thetargetwindow.Thiscanberetrievedusingavarietyoffunctions,including

FindWindow()

,

GetDlgItem()

,

GetParent()

,

EnumWindows()

andmanymore.TheSDKhasa

SendMessage()

functionwhichallowsyoutosendmessagestoawindow.Forexample,let'ssayyouhaveahandletotheCalculator,andyouwanttocloseit.Whatyoushoulddoissenda

WM_CLOSE

message,which
willnotifytheCalculatorthatitshouldclose.Youcanusethefollowingcode.InordertogetapointertoCalculator,Iusethe

FindWindow()

functionandpassthetitleofthewindow,which
inourcaseis"Calculator":

HWNDhWndCalc;
//Getahandletothe"Calculator"Window
hWndCalc=FindWindow(NULL,TEXT("Calculator));
if(hWndCalc==NULL)
{
//Couldn'tfindCalculator
}
else
{
SendMessage(hWndCalc,WM_CLOSE,0,0);
//Presto!TheCalculatorshouldclose.
}

LOWORDandHIWORDmacros:SplituplParamandwParam

Often,oneormoreofthe32-bit

lParam

and

wParam

parametersareactuallymadeoftwo16-bitparameters.Onecaseisthe

WM_MOUSEMOVE

message.MSDNstatesthatthe

lParam

forthismessageisactually2values:theXpositionofthemouse,andtheYpositionofthemouse.Buthowdoyouretrievethevaluesfromthe

lParam

?
TheSDKhas2macrosdesignedforexactlythispurpose:

LOWORD()

and

HIWORD()

.The

LOWORD

macroretrievesthelow-orderwordfromthegiven32-bitvalue,andthe

HIWORD()

macroretrievesthehigh-orderword.So,given
an

lParam

of

WM_MOUSEMOVE

,youcanretrievethecoordinatesusingthefollowingcode:

WORDxPos=LOWORD(lParam);//horizontalpositionofcursor
WORDyPos=HIWORD(lParam);//verticalpositionofcursor

MAKELPARAMandMAKEWPARAMmacros:concatenatetwo16-bitvalues

LOWORD

and

HIWORD

arefineifyouwanttosplituptheparameters,butwhatifyouwanttocreatea32-bitvalueforuseasan

lParam

or

wParam

parameterinamessage?TheSDKhas2macrosforthissituationalso:

MAKELPARAM

and

MAKEWPARAM

bothcombinetwo16-bitvaluesinto
a32-bitvalue,thatisusableformessages.Forexample,thefollowingcodesendsa

WM_MOUSEMOVE

messagetoawindow(

HWNDhWndTarget

)
withthe

fFlags

parameterasthe

wParam

,andthex/ycoordinatesasthe

lParam

:

SendMessage(hWndTarget,WM_MOUSEMOVE,fFlags,MAKELPARAM(x,y));

Dialogs

Handlingamessageinadialogisverysimilartohandlingamessageinanormalwindow.WindowshaveWindowProcedures,DialogshaveDialogProcedures.Onemajordifferenceisthatyoudon'tspecifyawindowclassforadialog.Whenyoucreateadialog
usingoneofthe

CreateDialog...

functionsorthe

DialogBox...

functions,youpassaDialogProcedureasoneoftheparameters.A
DialogProcedureisprototypedas:

BOOLCALLBACKDialogProc(
HWNDhwndDlg,//handletodialogbox
UINTuMsg,//message
WPARAMwParam,//firstmessageparameter
LPARAMlParam//secondmessageparameter
);

YoumighthavenoticedthattheDialogProcedurelooksverysimilartotheWindowProcedure,butitisn'tarealWindowProcedure.TheWindowProcedureforthedialogislocatedinsidewindows.ThatWindowProcedurecallsyourDialogProcedurewhenvarious
messagesaresenttoyourwindow.Becauseoftheabove,therearemessagesthatyouwillreceiveinaWindowProcedurethatyouwon'treceiveinaDialogProcedure.ThereareafewmajordifferencesbetweenaWindowProcedureandaDialogProcedure:

ADialogProcedurereturnsa

BOOL

,aWindowProcedurereturnsa

LRESULT

.
ADialogProceduredoesn'tneedtohandle

WM_PAINT

or

WM_DESTROY

.
ADialogProceduredoesn'treceivea

WM_CREATE

message,butrathera

WM_INITDIALOG

message
AWindowProcedurecalls

DefWindowProc()

formessagesitdoesnothandle.ADialogProcedureshouldreturn

TRUE

ifithandled
themessageor

FALSE

ifnotwithoneexception:ifyousettheinputfocustoacontrolin

WM_INITDIALOG

,youshouldreturn

FALSE

.

User-definedmessages

Sometimes,youwillneedtocommunicatebetween2windowsinyourapplicationorbetween2windowsfromdifferentapplications.AneasywaytodothisisbyusingUser-definedmessages.Thename"User-defined"canbeconfusingatfirst;youdefineaUser-defined
messageandnottheuserofyourprogram.IhavestatedinPart1thatmessagesareidentifiedbynumbers,andthatWindowspredefinesstandardmessages.Thewayofusinguser-definedmessagesistosimplyuseanumber.Tomakesurethatyoudon'tconflict
withthesystemdefinedmessages,youshoulduseanumberintherangeof

WM_APP

through0xBFFF:

#defineWM_DELETEALLWM_APP+0x100
//...
SendMessage(hWndYourDialog,WM_DELETEALL,0,0);

Youhandleauser-definedmessagejustlikeyouhandlearegularmessage:

#defineWM_DELETEALLWM_APP+0x100
//WindowProcedure
LRESULTCALLBACKWndProc(HWNDhwnd,UINTuMsg,WPARAMwParam,LPARAMlParam)
{
switch(uMsg)
{
caseWM_DELETEALL:
//We'vegottheuser-definedmessage,letsDeleteAll
return0;
caseWM_CREATE:
//Dosomeinitialization,Playasoundorwhateveryouwant
return0;
caseWM_PAINT:
//HandletheWM_PAINTmessage
return0;
caseWM_DESTROY:
PostQuitMessage(0);
return0;
}
returnDefWindowProc(hwnd,message,wParam,lParam);
}

RegisteredWindowsMessages

The

RegisterWindowMessage

functionisusedtodefineanewwindowmessagethatisguaranteedtobeuniquethroughoutthesystem.Likeuser-definedmessages,RegisteredMessagesarehandledlike
regularmessages:

staticUINTWM_FIND=RegisterWindowMessage(TEXT("YOURAPP_FIND_MSG");
//WindowProcedure
LRESULTCALLBACKWndProc(HWNDhwnd,UINTuMsg,WPARAMwParam,LPARAMlParam)
{
switch(uMsg)
{
caseWM_FIND:
//We'vegottheregisteredmessage,letsstartFinding.
return0;
caseWM_CREATE:
//Dosomeinitialization,Playasoundorwhateveryouwant
return0;
caseWM_PAINT:
//HandletheWM_PAINTmessage
return0;
caseWM_DESTROY:
PostQuitMessage(0);
return0;
}
returnDefWindowProc(hwnd,message,wParam,lParam);
}

Theregisteredmessageidentifiersusingthisapproachwillbeintherangeof0xC000to0xFFFF.Andyousenditusingtheregular

SendMessage()

method:

staticUINTWM_FIND=RegisterWindowMessage(TEXT("YOURAPP_FIND_MSG"));
//...
SendMessage(hWndFindWindow,WM_FIND,lParam,wParam);

（四）

这部分没研究，可以看看，原文：http://www.codeproject.com/Articles/600/Windows-Message-Handling-Part-4

Introduction

Subclassingisatechniquethatallowsanapplicationtointerceptandprocessmessagessentorpostedtoaparticularwindowbeforethewindowhasachancetoprocessthem.ThisistypicallydonebyreplacingtheWindowProcedureforawindowwithapplication-defined
windowprocedure.Iwilldevidethisarticleinto3:

Whysubclass?

Sometimesyouwanttotakethefunctionalityofacontrolandmodifyitslightly.Oneexampleisreplacingthemenuinaneditcontrol,Anotherisaddingacontextmenuwhenyoupressonabutton.OneofthemostcommonquestionsIencounteris"HowdoI
screenoutcharactersfromaneditcontrol?".IwillshowthesolutiontothisfromanMFCapproachandfromanSDKapproach,whileItrytoexplainSubclassing.

TheneedforsubclassingcomesfromthefactthatthecodefortheWindowscontrolsiswithinWindows,meaningyoucannoteditthecode.Althoughyoucannoteditthecodeofthecontrolitself,youinterceptthemessagessenttoit,andhandlethemyour
self.Youdosobysubclassingthecontrol.SubclassinginvolvesreplacingtheMessageHandlersofthecontrol,andpassinganyunprocessedmessagetothecontrolsMessageHandler.

SDKSubclassing

AlthoughtheMessageProcedureforthecontrolislocatedwithinwindows,youcanretrieveapointertoitbyusingthe

GetWindowLong

functionwiththe

GWL_WNDPROC

identifier.Likewise,youcancall

SetWindowLong

andspecifyanewWindowProcedureforthecontrol.ThisprocessiscalledSubclassing,andallowsyoutohookintoawindow/controlandintercept
anymessageitgets.SubclassingistheWindowstermforreplacingtheWindowProcedureofawindowwithadifferentWindowProcedureandcallingtheoldWindowProcedurefordefault(superclass)functionality.Remember

DefWindowProc()

?
insteadofcalling

DefWindowProc

fordefaultMessageHandlingyouusetheoldWindowProcedureasthedefaultMessageHandler.

ImplementingSDKSubclassing

So,letstrytosolvetheclassicquestion"HowdoIscreenoutcharactersfromaneditcontrol?",or"HowdoIcreatealetter-onlyeditcontrol?"

Firstletsanalyzehowaneditcontrolworks:

Aneditcontrolisawindow.It'swindowprocedurelieswithinwindows.Amongotherthings,wheneveritgetsa

WM_CHAR

messageitaddsthecharactertothetextitcontains.Nowthatweknow
that,wecansimplysubclasstheeditcontrol,andinterceptthe

WM_CHAR

messages.Wheneverthe

WM_CHAR

messageisaletterorakey
likespacebarorbackspacewe'llpassthemessagetotheeditcontrol.Ifitisn'toneoftheabove,we'lljust"Swallow"themessage,blockingitfromreachingtheEditControl.

Thefirststeptosubclassingistoaddaglobal/static

WNDPROC

variablethatwillstoretheaddressoftheeditcontrol'sWindowProcedure.

WNDPROCg_OldEdit;

ThesecondstepistocreateanewWindowProcedurefortheeditcontrol:

LRESULTCALLBACKNewEditProc(HWNDhwnd,UINTmessage,
WPARAMwParam,LPARAMlParam)
{

TCHARchCharCode;
switch(message)
{
caseWM_CHAR:
chCharCode=(TCHAR)wParam;
if(chCharCode>0x20&&!IsCharAlpha(chCharCode))
return0;
break;
}
returnCallWindowProc(g_OldEdit,hwnd,message,wParam,lParam);
}

The

IsCharAlpha

functiondetermineswhetheracharacterisanalphabeticcharacter.Thisdeterminationisbasedonthesemanticsofthelanguageselectedbytheuserduringsetuporbyusing
ControlPanel.

Moreinterestingisthe

CallWindowProc

function.The

CallWindowProc

functionpassesmessageinformationtothespecifiedWindow
Procedure.Acallto

CallWindowProc

willallowyoutocalltheoldWindowProcedurewithanymessageyoureceive,thusprovidingdefaultmessagehandling

ThethirdstepistoreplacetheWindowProcedurefortheeditcontrol,andtostoretheoldoneing_OldEdit.Forexample,ifyouwanttosubclassaneditcontrolthatresidesinadialog(hDlg)andhastheIDof

IDC_EDIT1

youwouldusethefollowingcode:

hwndhWndEdit=GetDlgItem(hDlg,IDC_EDIT1);<BR>//ReplacetheWindowProcedureandStoretheOldWindowProcedure
g_OldEdit=(WNDPROC)SetWindowLong(hWndEdit,GWL_WNDPROC,(LONG)NewEditProc);

Thecontrolisnowsubclassed.Anymessagetotheeditcontrolwillfirstgothroughthe

NewEditProc

WindowProcedure,whichwilldecideifthemessageshouldgototheeditcontrol'sWindow
Procedure.

MFCSubclassing

SubclassinginbothMFCandSDKprogramsisdonebyreplacingthemessagehandlersofacontrol.ItisrathereasytosubclassinaMFCprogram.Firstyouinherityourclassfromaclassthatencapsulatesthefunctionalityofathecontrol.InClassWizard,
clickon"AddClass",then"New".Forthebaseclass,choosetheMFCControlclassyouarederivingfrom,inourcase,

CEdit

.



UsingMFCrelievesyoufromhavingtocalltheoldMessageHandlers,sinceMFCwilltakecareofitforyou.

ThesecondstepistoaddMessageHandlerstoyournewclass.Ifyouhandleamessageandyouwantthecontrol'smessagehandlertogetashotatit,youshouldcallthebaseclassmemberfunctionthecorrespondswiththemessage.thisisthesubclassed

WM_CHAR

handler:

voidCLetterEdit::OnChar(UINTnChar,UINTnRepCnt,UINTnFlags)
{
if(nChar<=0x20||IsCharAlpha((TCHAR)nChar))<BR>{
//Callbaseclassmember,whichwillcall<BR>//thecontrol'smessagehandler
CEdit::OnChar(nChar,nRepCnt,nFlags);
//Ifnot,themessageisblocked<BR>}
}

Thethirdandfinalstageistoassociatethewindowwithaninstanceofournewclass.InadialogthisisdonesimplybyusingClassWizardtocreateacontrolmembervariableofyourclassinthewindow'sparent,andassociateitwiththe
control.



Inanon-dialogparentyoushouldaddamembervariableinstanceofyourcontroltoit,andcalloneofthetwo

CWnd

Subclassingfunctions:

CWnd::SubclassWindow
orCWnd::SubclassDlgItem

.Bothroutinesattacha

CWnd

objecttoanexistingWindows

HWND

.

SubclassWindow

takesthe

HWND

directly,and

SubclassDlgItem

isahelperthattakesacontrolIDandtheparentwindow(usuallyadialog).

SubclassDlgItem

is
designedforattachingC++objectstodialogcontrolscreatedfromadialogtemplate.

FurtherReading

ForamoreindepthtreatmentofMFCsubclassingseeChrisMaunder'sarticle:"Createyourowncontrols-theartofsubclassing".

ReflectedMessages-MFC4.0+

Whenyousubclassacontrol,besideshandlingthemessageitreceives,inMFCyoucanalsohandlethenotificationsitsendstoit'sparentwindow.ThistechniqueiscalledMessageReflecting.Windowscontrolsoftensendnotificationstotheirparents,for
example,aButtonwillsenda

WM_COMMAND

messagetellingit'sparentithasbeenclicked.Usuallyitistheparent'sjobtohandlethesemessages,butMFCwillalsoallowyoutohandlethemin
thecontrolitself.InClassWizardthesemessagesappearwithan"="signbeforethem,indicatingtheyareReflectedMessages.Youhandlethemjustlikeanyothermessage.Themacrosforthesemessagesaresimilartotheregularmessages,buthave

_REFLECT

addedtotheendofthemacro.Forexample,

ON_NOTIFY()

becomes

ON_NOTIFY_REFLECT()

.