Delphi 包的应用英文Word文件下载.docx

Delphi 包的应用英文Word文件下载.docx

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3.DropabuttononForm1andaddthefollowingcodetotheOnClickeventhandler:

4.withTForm2.Create（Application）do

5.begin

6.ShowModal;

7.Free;

end;

8.RemembertoaddUnit2toUnit1'

susesclause.

9.Saveandruntheproject.

Wehavecreatedasimpleapplicationthatshowsaformwithabuttonthatshowsanotherformwhenitisclicked.

ButwhatifwewantedtocreateForm2inareusablemodule?

Theansweris--PACKAGES!

TocreateapackageforForm2wewill:

1.Opentheprojectmanager（View|ProjectManager）

2.Right-clickontheProjectGroupandselect"

AddNewProject..."

3.Select"

Package"

fromthe"

New"

itemslist.

4.YoushouldnowseethePackageeditor.

5.Selectthe"

Contains"

itemandpressthe"

Add"

button.

6.Nowusethe"

Browse..."

buttontoselect"

Unit2.pas."

7.Thepackageshouldnowcontaintheunit"

8.Nowsaveandcompilethepackage.

Thepackageisnowcomplete.Youshouldhaveafilecalled"

package1.bpl"

inyourProjectsBPLdirectory.（TheBPListheBorlandPackageLibrary;

theDCPistheDelphiCompiledPackage--sortofliketheDCUofaPASfile.）

That'

sallthatneedtobedonetothepackage.Wenowneedtocompiletheoriginalapplicationwiththepackageoptionswitchedon.

1.Selecttheproject"

Project1.exe"

fromtheProjectManagerbydouble-clickingonit.

2.Right-clickandselect"

Options..."

（YoucanalsoselectProject|Options...fromthemenu.

3.Selectthe"

Packages"

tab.

4.Checkthe"

Buildwithruntimepackages"

checkbox.

5.Edittheedit-boxinthe"

Runtimepackages"

sectiontoread:

"

Vcl50;

Package1"

andOKtheoptions. 

6.NOTE:

DonotremoveUnit2fromtheapplication.

7.Saveandruntheapplication.

Theapplicationwillrunandbehavejustlikebefore--thedifferencecanbeseeninthefilesize.Project1.exeisnowonly14Kasapposedtotheoriginal293K.IfyouusearesourceexplorertoviewthecontentsoftheEXEandtheBPLyouwillfindthatboththeDFMandthecodeforForm2nowresideinthepackage.

Delphiachievesthisbystaticallylinkinginthepackageatcompiletime.（That'

swhyyoushouldn'

tremovetheunitfromtheEXEproject.）

Justthinkofwhatcanbeachievedbydoingthis:

Onecouldcreatedatamodulesinpackagesandquicklymodifytheirsourceandonlydistributethenewpackagewhenourdata-accessruleshavechanged,likewhenwemovefromBDEbasedconnectivitytoADO.Or,wecouldcreateafromthatshow'

sa"

thisoptionisnotavailableinthisversion"

messageinonepackage,andthenasimilarlynamedformthathasfunctionalityinasame-namedpackage.Wewillthenhavea"

Pro"

and"

Enterprise"

versionofourproductwithoutmucheffort.

Dynamicloadandunloadofpackages

StaticallylinkedDLLsandBPLsworkfineinmostcases,butwhatifwedecidenottodeploytheBPL?

Wewouldgeta"

ThedynamiclinklibraryPackage1.bplcouldnotbefoundinthespecifiedpath..."

errorandourapplicationwouldstopfunctioning.Orwhatif,inourmodularapplication,wewantedtohavenumerousplug-inlikemodules?

WeneedawaytodynamicallylinktotheBPLatruntime.

WithDLLsthisisasimpleprocessofusingtheLoadLibraryfunction.

functionLoadLibrary（

lpLibFileName:

PChar）:

HMODULE;

stdcall;

OncetheDLLisloadedwecancallexportedfunctionsandprocedureswithintheDLLbyusingtheGetProcAddressfunction.

functionGetProcAddress（hModule:

lpProcName:

LPCSTR）:

FARPROC;

WefinallyunloadthedllbyusingtheFreeLibraryfunction.

functionFreeLibrary（hLibModule:

HMODULE）:

BOOL;

InthisexamplewewilldynamicallyloadMicrosoft'

sHtmlHelplibrary:

functionTForm1.ApplicationEvents1Help（

Command:

Word;

Data:

Integer;

varCallHelp:

Boolean）:

Boolean;

type

TFNHtmlHelpA=function（hwndCaller:

HWND;

pszFile:

PAnsiChar;

uCommand:

UINT;

dwData:

DWORD）:

var

HelpModule:

HModule;

HtmlHelp:

TFNHtmlHelpA;

begin

Result:

=False;

HelpModule:

=LoadLibrary（'

HHCTRL.OCX'

）;

ifHelpModule<

>

0then

begin

@HtmlHelp:

=GetProcAddress（HelpModule,

'

HtmlHelpA'

if@HtmlHelp<

nilthen

=HtmlHelp（Application.Handle,

PChar（Application.HelpFile）,

Command,

Data）<

0;

FreeLibrary（HelpModule）;

end;

CallHelp:

DynamicallyloadedBPLs

BPLsarejustassimple.Wellalmost.

WedynamicallyloadthepackagebyusingtheLoadPackagefunction.

functionLoadPackage（constName:

string）:

WecreateTPersistentClassoftheclasswewishtoinstantiatebyusingtheGetClassfunction.

functionGetClass（constAClassName:

TPersistentClass;

Instantiateanobjectoftheloadedclassanduseit.

Andwhenwearedone,unloadthepackageusingtheUnloadPackageprocedure.

procedureUnloadPackage（Module:

HMODULE）;

Letusgobacktoourexampleandmakeafewchanges:

1.Select"

fromtheprojectmanager.

4.Remove"

edit-boxsectionandOKtheoptions.

5.OnDelphi'

stoolbar,clickonthe"

Removefilefromproject"

6.Select"

Unit2|Form2"

fromthelistandthen"

OK."

7.Nowgotothe"

Unit1.pas"

sourceandremoveUnit2fromitsusesclause.（ThesestepsarerequiredtoremoveanylinktoUnit2andthepackagewewishtoloaddynamically.）

8.GotothesourceofButton1'

sOnClickevent.

9.AddtwovariablesoftypeHModuleandTPersistentClass.

10.var

11.PackageModule:

AClass:

12.LoadthepackagePackage1byusingtheLoadPackagefunction.

PackageModule:

=LoadPackage（'

Package1.bpl'

13.CheckthatthePackageModuleisnot0（zero）.

14.CreateapersistentclassusingtheGetClassfunction,passingitthenameoftheformwithinthepackageasitsparameter:

AClass:

=GetClass（'

TForm2'

15.Ifthepersistentclassisnotnil,createanduseaninstanceoftheclassjustabefore.

16.withTComponentClass（AClass）.Create（Application）

17.asTCustomFormdo

18.begin

19.ShowModal;

20.Free;

21.Finally,unloadthepackageusingtheUnloadPackageprocedure:

UnloadPackage（PackageModule）;

22.Savetheproject.

HereisthecompletelistingoftheOnClickevent:

procedureTForm1.Button1Click（Sender:

TObject）;

PackageModule:

ifPackageModule<

ifAClass<

withTComponentClass（AClass）.Create（Application）

asTCustomFormdo

ShowModal;

Free;

Unfortunatelythat'

snottheendofit.

TheproblemisthattheGetClassfunctionrequirestheclasstoberegisteredbeforethefunctioncanfindit.Usuallyformclassesandcomponentclassesthatarereferencedinaformdeclaration（instancevariables）areautomaticallyregisteredwhentheformisloaded.Buttheformisn'

tloadedyet.Sowhereshouldweregistertheclass?

Theanswer:

inthepackage.Eachunitinthepackageisinitializedwhenthepackageisloadedandfinalizedwhenthepackageisunloaded.

Let'

sreturntoourexampleandmakeafewchanges:

1.Double-clickon"

Package1.bpl"

intheprojectmanager;

thiswillactivatethepackageeditor.

2.Clickonthe+symbolnextto"

Unit2"

inthe"

section.Thiswillexpandtheunittree.

3.Double-clickon"

Unit2.pas"

toactivatetheunit'

ssourcecode.

4.Scrolldowntotheendofthefileandaddaninitializationsection.