Introduction to Drag and Drop - Apple Inc_.pdf

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1、NextIntroductiontoDragandDropCocoagivesyoutheabilitytoimplementsophisticateddrag-and-dropcapabilitiesbothwithinyourapplicationandbetweenapplications.Thisprogrammingtopicdescribeshowyoucanimplementdrag-and-dropwithjustafewmethods.OrganizationofThisDocumentInthetexthereandinthedraggingprotocold

2、escriptions,thetermdraggingsessionistheentireprocessduringwhichanimageisselected,dragged,released,andabsorbedorrejectedbythedestination.Adraggingoperationistheactionthatthedestinationtakesinabsorbingtheimagewhenitisreleased.Thedraggingsourceistheobjectthat“owns”theimagethatisbeingdragged;itis

3、specifiedasanargumenttothemethodthatinstigatesthedraggingsession.Draggingisavisualphenomenon.Tobethesourceordestinationofadraggingoperation,anobjectmustrepresentaportionofscreenrealestate;thus,onlywindowandviewobjectscanbethesourcesanddestinationsofdrags.(Notethatthesourceviewisnotnecessarilyt

4、hesameobjectsasthedraggingsourcedefinedabove.)NSWindowandNSViewprovidemethodsthathandletheuserinterfacefordragginganobject.YouonlyneedtoimplementafewmethodsfromeithertheNSDraggingSourceorNSDraggingDestinationprotocol,dependingonwhetheryourwindoworviewsubclassisthesourceordestination.Thedraggin

5、gprotocolsaredescribedinthesearticles:•“DraggingSources”•“DraggingDestinations”Howtoreceiveadragisdescribedinthesearticles:•“ReceivingDragOperations”•“DraggingFiles”Draggingsupportintableviewsisdescribedinthisarticle:•UsingDragandDropinTablesCommonly-askedquestionsaboutdrag-and-dropareaddress

6、edinthisarticle:•“FrequentlyAskedQuestions”Next©2012AppleInc.AllRightsReserved.(Lastupdated:2012-01-09)Didthisdocumenthelpyou?YesIt'sgood,but...Nothelpful...NextPreviousDraggingSourcesAdraggingsessionisinitiatedbytheuserclickingthemouseinsideawindoworviewandmovingthemouse.NSViewandNSWindowimp

7、lementthemethoddragImage:at:offset:event:pasteboard:source:slideBack:tohandlethedraggingsession.YouinvokethismethodinthemouseDown:ormouseDragged:methodofyoursubclassofNSVieworNSWindow.Youprovideanimagetodisplayduringthedrag,apasteboardholding