Qt WebKit中英文翻译.docx

Qt WebKit中英文翻译.docx

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QtWebKit中英文翻译

原文：

QtWebKit

1.QWebElement

TheQWebElementclassprovidesconvenientaccesstoDOMelementsinaQWebFrame.

AQWebElementobjectallowseasyaccesstothedocumentmodel,representedbyatree-likestructureofDOMelements.TherootofthetreeiscalledthedocumentelementandcanbeaccessedusingQWebFrame:

:

documentElement（）.

SpecificelementscanbeaccessedusingfindAll（）andfindFirst（）.TheseelementsareidentifiedusingCSSselectors.ThecodesnippetbelowdemonstratestheuseoffindAll（）.

QWebElementdocument=frame->documentElement（）;

/*Assumethedocumenthasthefollowingstructure:

Intro

Snippets

Content

Here

*/

QWebElementCollectionallSpans=document.findAll（"span"）;

QWebElementCollectionintroSpans=document.findAll（"p.introspan"）;

Thefirstlistcontainsallspanelementsinthedocument.Thesecondlistcontainsspanelementsthatarechildrenofp,classifiedwithintro.

UsingfindFirst（）ismoreefficientthancallingfindAll（）,andextractingthefirstelementonlyinthelistreturned.

AlternativelyyoucantraversethedocumentmanuallyusingfirstChild（）andnextSibling（）:

frame->setHtml（"

FirstParagraph

SecondParagraph

QWebElementdoc=frame->documentElement（）;

QWebElementbody=doc.firstChild（）;

QWebElementfirstParagraph=body.firstChild（）;

QWebElementsecondParagraph=firstParagraph.nextSibling（）;

Individualelementscanbeinspectedorchangedusingmethodssuchasattribute（）orsetAttribute（）.Forexamle,tocapturetheuser'sinputinatextfieldforlateruse（auto-completion）,abrowsercoulddosomethinglikethis:

QWebElementfirstTextInput=document.findFirst（"input[type=text]"）;

QStringstoredText=firstTextInput.attribute（"value"）;

Whenthesamepageislaterrevisited,thebrowsercanfillinthetextfieldautomaticallybymodifyingthevalueattributeoftheinputelement:

QWebElementfirstTextInput=document.findFirst（"input[type=text]"）;

textInput.setAttribute（"value",storedText）;

Anotherusecaseistoemulateaclickeventonanelement.ThefollowingcodesnippetdemonstrateshowtocalltheJavaScriptDOMmethodclick（）ofasubmitbutton:

QWebElementdocument=frame->documentElement（）;

/*Assumethatthedocumenthasthefollowingstructure:

*/

QWebElementbutton=document.findFirst（"input[type=submit]"）;

button.evaluateJavaScript（"click（）"）;

TheunderlyingcontentofQWebElementisexplicitlyshared.CreatingacopyofaQWebElementdoesnotcreateacopyofthecontent.Instead,bothinstancespointtothesameelement.

ThecontentsofchildelementscanbeconvertedtoplaintextwithtoPlainText（）;toXHTMLusingtoInnerXml（）.Toincludetheelement'stagintheoutput,usetoOuterXml（）.

ItispossibletoreplacethecontentsofchildelementsusingsetPlainText（）andsetInnerXml（）.Toreplacetheelementitselfanditscontents,usesetOuterXml（）.

2.QtWebKit

Overview

Thetechnology

TheQtWebKitbridgeisamechanismthatextendsWebKit'sJavaScriptenvironmenttoaccessnativeobjectsthatarerepresentedasQObjects.IttakesadvantageoftheQObjectintrospection,apartoftheObjectModel,whichmakesiteasytointegratewiththedynamicJavaScriptenvironment,forexampleQObjectpropertiesmapdirectlytoJavaScriptproperties.

Forexample,bothJavaScriptandQObjectshaveproperties:

aconstructthatrepresentagetter/setterpairunderonename.

UseCases

TherearetwomainusecasesfortheQtWebKitbridge.Webcontentinanativeapplication,andThinClients.

WebContentinaNativeApplication

ThisisacommonusecaseinclassicQtapplication,andadesignpatternusedbyseveralmodernapplications.Forexample,anapplicationthatcontainsamedia-player,playlistmanager,andmusicstore.Theplaylistmanagerisusuallybestauthoredasaclassicdesktopapplication,withthenative-lookingrobustQWidgetshelpingwithproducingthatapplication.Themedia-playercontrol,whichusuallylookscustom,canbewrittenusingtheGraphicsViewframeworkorwithinadeclarativewaywithQtDeclarative.Themusicstore,whichshowsdynamiccontentfromtheinternetandgetsmodifiedrapidly,isbestauthoredinHTMLandmaintainedontheserver.

WiththeQtWebKitbridge,thatmusicstorecomponentcaninteractwithnativepartsoftheapplication,forexample,ifafileneedstobesavedtoaspecificlocation.

ThinClient

AnotherusecaseisusingQtasanativebackendtoafullwebapplication,referredtohereasathinclient.Inthisuse-case,theentireUIisdrivenbyHTML,JavaScriptandCSS,andnativeQt-basedcomponentsareusedtoallowthatapplicationaccesstonativefeaturesnotusuallyexposedtotheweb,ortoenablehelpercomponentsthatarebestwrittenwithC++.

AnexampleforsuchaclientisaUIforavideo-on-demandserviceonaTV.TheentirecontentandUIcanbekeptontheserver,serveddynamicallythroughHTTPandrenderedwithWebKit,withadditionalnativecomponentsforaccessinghardware-specificfeatureslikeextractingthelistofimagesoutofthevideo.

DifferencefromOtherBridgeTechnologies

OfcourseQtWebKitisnottheonlybridgetechnologyoutthere.NPAPI,forexample,isalong-timestandardorweb-nativebridging.DuetoQt'smeta-objectsystem,fullapplicationsbuiltpartiallywithweb-technologiesaremucheasiertodevelop.NPAPI,however,ismoregearedtowardscross-browserplugins,duetoitbeinganacceptedstandard.

Whendevelopingapluginforabrowser,NPAPIisrecommended.WhendevelopingafullapplicationthatutilizesHTML-rendering,theQtWebKitbridgeisrecommended.

AccessingQObjects

CreatingthelinkviaQWebFrame

Bydefault,noQObjectsareaccessiblethroughthewebenvironment,forsecurityreasons.ToenablewebcontentaccessforanativeQObject,theapplicationmustexplicitlygrantitaccess,usingthefollowingcall:

//...

QWebFrame*frame=myWebPage->mainFrame（）;

frame->addToJavaScriptWindowObject（"someNameForMyObject",myObject）;

//...

SeeQWebFrame:

:

addToJavaScriptWindowObject（）formoreinformation.

UsingSignalsandSlots

TheQtWebKitbridgeadaptsQt'scentralSignalsandSlotsfeatureforscripting.TherearethreeprincipalwaystousesignalsandslotswiththeQtWebKitbridge:

HybridC++/script:

C++applicationcodeconnectsasignaltoascriptfunction.Forexample,thescriptfunctioncanbeafunctionthattheuserhastypedin,oronethatyouhavereadfromafile.ThisapproachisusefulifyouhaveaQObjectbutdon'twanttoexposetheobjectitselftothescriptingenvironment;youjustwantascripttobeabletodefinehowasignalshouldbereactedto,andleaveituptotheC++sideofyourapplicationtoestablishtheconnection.

Hybridscript/C++:

Ascriptcanconnectsignalsandslotstoestablishconnectionsbetweenpre-definedobjectsthattheapplicationexposestothescriptingenvironment.Inthisscenario,theslotsthemselvesarestillwritteninC++,butthedefinitionoftheconnectionsisfullydynamic（script-defined）.

Purelyscript-defined:

Ascriptcanbothdefinesignalhandlerfunctions（effectively"slotswritteninJavaScript"）,andsetuptheconnectionsthatutilizethosehandlers.Forexample,ascriptcandefineafunctionthatwillhandletheQLineEdit:

:

returnPressed（）signal,andthenconnectthatsignaltothescriptfunction.

NotethatQtScriptfunctionssuchasqScriptConnectareunavilableinthewebenvironment.

SignaltoFunctionConnections

connect（function）;

Inthisformofconnection,theargumenttoconnect（）isthefunctiontoconnecttothesignal.

functionmyInterestingScriptFunction（）{...}

...

myQObject.somethingChanged.connect（myInterestingScriptFunction）;

TheargumentcanbeaJavaScriptfunction,asintheaboveexample,oritcanbeaQObjectslot,asinthefollowingexample:

myQObject.somethingChanged.connect（myOtherQObject.doSomething）;

WhentheargumentisaQObjectslot,theargumenttypesofthesignalandslotdonotnecessarilyhavetobecompatible;Ifnecessary,theQtWebKitbridgewill,performconversionofthesignalargumentstomatchtheargumenttypesoftheslot.

Todisconnectfromasignal,youinvokethesignal'sdisconnect（）function,passingthefunctiontodisconnectasargument:

myQObject.somethingChanged.disconnect（myInterestingFunction）;

myQObject.somethingChanged.disconnect（myOtherQObject.doSomething）;

Whenascriptfunctionisinvokedinresponsetoasignal,thethisobjectwillbetheGlobalObject.

SignaltoMemberFunctionConnections

connect（thisObject,function）

Inthisformoftheconnect（）function,thefirstargumentistheobjectthatwillbeboundtothevariable,this,whenthefunctionspecifiedusingthesecondargumentisinvoked.

Ifyouhaveapushbuttoninaform,youtypicallywanttodosomethinginvolvingtheforminresponsetothebutton'sclickedsignal;passingtheformasthethisobjectmakessenseinsuchacase.

varobj={x:

123};

varfun=function（）{print（this.x）;};

myQObject.somethingChanged.connect（obj,fun）;

Todisconnectfromthesignal,passthesameargumentstodisconnect（）:

myQObject.somethingChanged.disconnect（obj,fun）;

SignaltoNamedMemberFunctionConnections

connect（thisObject,functionName）

Thisformoftheconnect（）functionrequiresthatthefirstargumentistheobjectthatwillbeboundtothevariablethiswhenafunctionisinvokedinresponsetothesignal.Thesecondargumentspecifiesthenameofafunctionthatisconnectedtothesignal,andthisreferstoamemberfunctionoftheobject