Visual C++ Tutorial文档格式.docx

Visual C++ Tutorial文档格式.docx

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Thoughyouthinkyouwanttodiverightintothecode,youreallydon'

t.Windowsprogrammingisoverwhelmingatfirst.Let'

stakeaquicklookathowWindowsworks.Thebackboneofallofyourprogrammingwillberespondingtoandsendingmessages.Whataremessages?

Messagesaresimplya32bitnumberdesignatingsomeevent.Example:

Youmovethemouse,amessage（definedasWM_MOUSEMOVE）is'

posted'

totheactivewindow.Youpressakey,amessage（WM_KEYDOWN）is'

totheactivewindow.Youresizethewindow,amessage（WM_SIZE）is'

totheactivewindow.Getthepicture?

Nowwheredothesemessagesgo?

Theygetqueuedupandawindoweventuallytakesthemoutofthequeueandreactstothem.ForinstancewhenawindowgetstheWM_MOVEmessageitchangesthecoordinatesofthewindowandredrawsitonthescreen.

Let'

smoveontoHandles.Windowsisverymuchobjectoriented.Youhaveseveralwindowobjects（likethedesktop,theprogramyourreadingthiswith,etc...）.Howdoestheprogrammerdistinguishallofthesethingsinannon-object-orientedlanguage?

Heuseshandles. 

Handlesareawaytoreferencedifferentwindowsobjects.Youcanhavehandlestowindows,handlestofiles,handlestoallocatedmemory,handlestoimages,etc. 

Youcanthinkofthemaspointers.Youmustcreatethemsomehow.Andwhenyouaredonewiththem,youmustdestroythem.Ifyoudon'

tyouwillendupwithwhatiscalledaresourceleak.Thiscouldbringyoursystemtoagrindinghalt.Sotakecaretoalwaysmakesuretheyaredestroyedatsometime.

Nowletstiethesetwothingstogether. 

Sayyouhaveawindow.Youwillhaveahandletoit（calledanHWND）.Letsnameyourhandleyour_HWND.Theoperatingsystemwantstotellyoutoredrawyourwindowbecauseitwasjustuncoveredbysomeotherwindow.Windozepassesyouamessagelikethis:

PostMessage（your_HWND,WM_PAINT,0,0）;

Thisfunctionpostsapaintmessagestothewindowwithhandleyour_HWND.Thelasttwoparametersareusedforextrainformationaboutthemessage.Don'

tworryaboutthemfornow.

Nowyourapplicationwillhaveafunctionwithabigcasestatementinittohandleallofthemessages.Forexample:

void 

HandleTheMessage（longMessage）

{

switch（Message）

{

caseWM_PAINT:

DrawWindow（）;

break;

caseWM_KEYDOWN:

etc...

}

}

Okthatisbasicallyhowwindowsworksunderthehood.ThatshouldbeenoughtogetyougoingwhenwestarttalkingaboutMFC.

IfyouwanttouseMicrosoftVisualC++,ithelpsatonifyoureallyknowC++.Everythingisaboutclasses.IfyouareusedtoplainC,youwon'

treallyseethebigdealwithclassesuntilyouusethemforawhile.Let'

sreviewwhatyouneedtoknowaboutclassestogetstartedwithVC++.

Aclassisastructureforthemostpart.Let'

sworkwithanexampleinsteadofmejusttellingyourules.Let'

smakeaclasstorepresentaline.Inthe.hfileyouwoulddefinetheclassasfollows:

classCLine

intm_nX1;

intm_nY1;

intm_nX2;

intm_nY2;

public:

//constructors

CLine（）;

CLine（intx1,inty1,intx2,inty2）;

//destructor

~CLine（）;

//setthelinedata

voidSetPoints（intx1,inty1,intx2,inty2）;

//drawtheline

voidDraw（）;

Aquickwordaboutnamingconventions.Classnamesusuallystartwith'

C'

andthemembervariablesusuallyareprefixedbya'

m_'

.Theninthemicrosoftwayyouwillhavealettertoletyouknowwhatdatatypethenameisandthenthenameofthevariable.Capitalizetheletterofallnewwordsinthename.Don'

tuseunderscoresandstufflikethat.Youmayhavethefalsebeliefthatyourcodingstyleisbetter.FromexperienceIcantellyouthatthemicrosoftwayistheway.Itmakesthingseasytoreadandeasytoremembernames（evenwhenitissomeoneelse'

scode）.Ifyouseem_pPoint,youwouldassumethisisamembervariableofaclassthatpoints（itisapointer）toapoint.IfyouseefData,youwouldassumethatitisafloating-pointvalue.

Backtoourclass.Theintvariablesaretheendpointsoftheline.Notethattheyarebeforethe'

'

part.Thismeansthataprogrammerusingthisclasswillnotbeallowedtomanipulatetheseguysdirectly.Theyarenotfor'

public'

use.Thefunctionsunderthepublicstatementareforpublicuse.Thefirstthreearecalledconstructors.ThesefunctionsarecalledanytimeanewCLineclassiscreated.Herearesomeexampleswhenthearecalled:

//thiscallsCLine（）

CLineMyLine;

//thisisapointertoaCLineclass

CLine*pMyLine;

//this 

callsCLine（）

pMyLine=newCLine;

//thiscallsCLine（intx1,inty1,intx2,inty2）

pMyLine=newCLine（0,0,10,10）;

CLineMyLine（0,0,10,10）;

Alloftheseconstructaline.Someinitializeittoitsdefaultsettingsandotherscopycoordinates.The'

new'

keywordisusedtocreatenewthingsinC++,likemallocinC.Youneedtocall'

delete'

foreverythingyousaynewto,likefreeinC.Thisgoesforclassesaswellasotherdatatypes.Icouldallocateanarrayof100integerswith:

//apointertosomeintegers

int*pNumbers;

//makememoryfor100ofthem

pNumbers=newint[100];

//setthefirstelementto0

pNumbers[0]=0;

//setthelastelementto99

pNumbers[99]=99;

//freethememory.

delete[]pNumbers;

Noticethe[]afterthedelete.Thisistotelltheprogramtodeletetheentirearray.Ifyousay'

deletepNumbers;

youwillonlyfreememoryforthefirstelement.Youwillthenbe'

leaking'

memory.Memoryleaksarewhenyouforgettodeletememory.Thismayendupcrashingyourcomputerifyouuseallthecomputersmemory.

Sorry,let'

sgetbacktotheconstructorsforCLine.Thecodefortheseconstructorfunctionswhichautomagicallygetcalledwhenanewlineiscreatedwilllooklike:

CLine:

:

CLine（）

m_nX1=0;

m_nX2=0;

m_nY1=0;

m_nY2=0;

CLine（intx1,inty1,intx2,inty2）

m_nX1=x1;

m_nX2=x2;

m_nY1=y1;

m_nY2=y2;

Noticethatthefunctiondeclarationismuchlikearegular'

functionexceptthatweputtheclassnameandtwocolonsinfrontofthefunctionname（CLine:

）.Onedifferencewithconstructorsisthattheydon'

thaveareturnvalue.Thisisthecasefordestructorsalso.AdestructoristhefunctionwhichautomagicallygetscalledwhenourCLineisdeletedorgoesoutofscope.Forinstance:

//memoryfortheclassisclearedupand~CLine（）iscalled

deletepMyLine;

//this'

}'

endsthesectionoftheprogramwhereMyLineis

//valid.~CLine（）willbecalled.（MyLinegoesoutof'

scope'

）

Forourclass,~CLine（）doesn'

tneedtodoanything.However,sometimesyoumaywanttoputyourcleanupcodehere.Likedeletinganyallocatedmemoryinyourclass.Sincewehavenothingtodooutfunctioncodeisempty:

~CLine（）

//donothing

sfillintheother2functions.

voidCLine:

SetPoints（intx1,inty1,intx2,inty2）

return;

Draw（）

//psuedocodehere,theseareoperatingsystemfunctionstodrawaline

MoveTo（m_nX1,m_nY1）;

LineTo（m_nX2,m_nY2）;

HowwouldIcallthesefunctions?

Hereareacoupleofexamples.Onewithpointersandonewithout.

CLine*pLine=newCLine（0,0,10,10）;

pLine->

Draw（）;

deletepLine;

MyLine.SetPoints（0,0,10,10）;

MyLine.Draw（）;

That'

sitfortheclass.Nowthisclasscanbeusedinotherclasses.YoucanimagineaCSquareclassthathas4Clineclassesinit:

classCSquare

CLinem_LineTop;

CLinem_LineLeft;

CLinem_LineBottom;

CLinem_LineRight;

...

Orbetteryet,thepointofallofthisclassstuff,youcanusetheCLineclasstomakeyourownclass.ThisisdoneatoninVisualC.Letssayyouwantedtodrawlinesinyourprogram,andyouthoughtthelineclassmightbenice,butitismissinganimportantfeature,itdoesn'

tletyousetthelinecolor.Insteadofwritingawholenewclass,youcansimpleinherittheCLineclass.Thiswouldlooklikethis:

classCColorLine:

publicCLine

voidDraw（longcolor）;

};

What'

sgoingonhere?

Wellwiththisclasswehaveallthefunctionalityofourotherclass,butnowwecanusethisotherDraw（）functionwhichallowsustosetthecolor.TheCPPcodewouldlooklike:

voidCColorLine:

Draw（longcolor）

SetColor（color）;

CLine: