




已阅读5页,还剩27页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
外文原文JAVAEVENTSAREPARTOFTHEJAVAAWTABSTRACTWINDOWINGTOOLKITPACKAGEANEVENTISTHEWAYTHATTHEAWTCOMMUNICATESTOYOU,ASTHEPROGRAMMER,ANDTOOTHERJAVAAWTCOMPONENTSTHATSOMETHINGHASHAPPENEDTHATSOMETHINGCANBEINPUTFROMTHEUSERMOUSEMOVEMENTSORCLICKS,KEYPRESSES,CHANGESINTHESYSTEMENVIRONMENTAWINDOWOPENINGORCLOSING,THEWINDOWBEINGSCROLLEDUPORDOWN,ORAHOSTOFOTHERTHINGSTHATMIGHT,INSOMEWAY,BEINTERESTINGTOTHEOPERATIONOFTHEPROGRAMNOTEJAVASABSTRACTWINDOWINGTOOLKITISAPACKAGEOFCLASSESTHATIMPLEMENTSMOSTCOMMONUICOMPONENTS,SUCHASWINDOWS,BUTTONS,MENUS,ANDSOONITISALSOSPECIFICALLYTHEAWT,ANDNOTJAVA,THATGENERATESANDMANAGESEVENTSINOTHERWORDS,WHENEVERJUSTABOUTANYTHINGHAPPENSTOAJAVAAWTCOMPONENT,INCLUDINGANAPPLET,ANEVENTISGENERATEDSOMEEVENTSAREHANDLEDBYTHEAWTORBYTHEBROWSERWITHOUTYOURNEEDINGTODOANYTHINGPAINTMETHODS,FOREXAMPLE,AREGENERATEDANDHANDLEDBYTHEBROWSERALLYOUHAVETODOISTELLTHEAWTWHATYOUWANTPAINTEDWHENITGETSTOYOURPARTOFTHEWINDOWSOMEEVENTS,HOWEVERFOREXAMPLE,AMOUSECLICKINSIDETHEBOUNDARIESOFYOURAPPLETYOUMAYNEEDTOKNOWABOUTWRITINGYOURJAVAPROGRAMSTOHANDLETHESEKINDSOFEVENTSENABLESYOUTOGETINPUTFROMTHEUSERANDHAVEYOURAPPLETCHANGEITSBEHAVIORBASEDONTHATINPUTTODAY,YOULLLEARNABOUTMANAGINGSIMPLEEVENTS,INCLUDINGTHEFOLLOWINGBASICSNNMOUSECLICKSNNMOUSEMOVEMENTS,INCLUDINGMOUSEDRAGGINGNNKEYBOARDACTIONSYOULLALSOLEARNABOUTTHEHANDLEEVENTMETHOD,WHICHISTHEBASISFORCOLLECTING,HANDLING,ANDPASSINGONEVENTSOFALLKINDSFROMYOURAPPLETTOOTHERUICOMPONENTSINTHEWINDOWORINYOURAPPLETITSELFTOMORROW,YOULLLEARNHOWTOCOMBINEEVENTSWITHTHEAWTTOCREATEACOMPLETEINTERFACEFORYOURAPPLETMOUSECLICKSLETSSTARTWITHTHEMOSTCOMMONEVENTYOUMIGHTBEINTERESTEDINMOUSECLICKSMOUSECLICKEVENTSOCCURWHENYOURUSERCLICKSTHEMOUSESOMEWHEREINTHEBODYOFYOURAPPLETYOUCANINTERCEPTMOUSECLICKSTODOVERYSIMPLETHINGSFOREXAMPLE,TOTOGGLETHESOUNDONANDOFFINYOURAPPLET,TOMOVETOTHENEXTSLIDEINAPRESENTATION,ORTOCLEARTHESCREENANDSTARTOVERORYOUCANUSEMOUSECLICKSINCONJUNCTIONWITHMOUSEMOVEMENTSTOPERFORMMORECOMPLEXMOTIONSINSIDEYOURAPPLETMOUSEDOWNANDMOUSEUPWHENYOUCLICKTHEMOUSEONCE,THEAWTGENERATESTWOEVENTSAMOUSEDOWNEVENTWHENTHEMOUSEBUTTONISPRESSED,ANDAMOUSEUPEVENTWHENTHEBUTTONISRELEASEDWHYTWOINDIVIDUALEVENTSFORASINGLEMOUSEACTIONBECAUSEYOUMAYWANTTODODIFFERENTTHINGSFORTHE“DOWN”ANDTHE“UP”FOREXAMPLE,LOOKATAPULLDOWNMENUTHEMOUSEDOWNEXTENDSTHEMENU,ANDTHEMOUSEUPSELECTSANITEMWITHMOUSEDRAGSBETWEENBUTYOULLLEARNABOUTTHATONELATERIFYOUHAVEONLYONEEVENTFORBOTHACTIONSMOUSEUPANDMOUSEDOWN,YOUCANNOTIMPLEMENTTHATSORTOFUSERINTERACTIONHANDLINGMOUSEEVENTSINYOURAPPLETISEASYALLYOUHAVETODOISOVERRIDETHERIGHTMETHODDEFINITIONINYOURAPPLETTHATMETHODWILLBECALLEDWHENTHATPARTICULAREVENTOCCURSHERESANEXAMPLEOFTHEMETHODSIGNATUREFORAMOUSEDOWNEVENTPUBLICBOOLEANMOUSEDOWNEVENTEVT,INTX,INTYTHEMOUSEDOWNMETHODANDTHEMOUSEUPMETHODASWELLTAKESTHREEPARAMETERSTHEEVENTITSELFANDTHEXANDYCOORDINATESWHERETHEMOUSEDOWNORMOUSEUPEVENTOCCURREDTHEEVENTARGUMENTISANINSTANCEOFTHECLASSEVENTALLSYSTEMEVENTSGENERATEANINSTANCEOFTHEEVENTCLASS,WHICHCONTAINSINFORMATIONABOUTWHEREANDWHENTHEEVENTTOOKPLACE,THEKINDOFEVENTITIS,ANDOTHERINFORMATIONTHATYOUMIGHTWANTTOKNOWABOUTTHISEVENTSOMETIMESHAVINGAHANDLETOTHATEVENTOBJECTISUSEFUL,ASYOULLDISCOVERLATERONINTHISSECTIONTHEXANDTHEYCOORDINATESOFTHEEVENT,ASPASSEDINTHROUGHTHEXANDYARGUMENTS,AREPARTICULARLYNICETOKNOWBECAUSEYOUCANUSETHEMTODETERMINEPRECISELYWHERETHEMOUSECLICKTOOKPLACEFOREXAMPLE,HERESASIMPLEMETHODTHATPRINTSOUTINFORMATIONABOUTAMOUSEDOWNWHENITOCCURSPUBLICBOOLEANMOUSEDOWNEVENTEVT,INTX,INTYSYSTEMOUTPRINTLN“MOUSEDOWNAT“X“,”YRETURNTRUEBYINCLUDINGTHISMETHODINYOURAPPLET,EVERYTIMEYOURUSERCLICKSTHEMOUSEINSIDEYOURAPPLET,THISMESSAGEWILLGETPRINTEDNOTETHATTHISMETHOD,UNLIKETHEOTHERSYSTEMMETHODSYOUVESTUDIEDTHISFAR,RETURNSABOOLEANVALUEINSTEADOFNOTRETURNINGANYTHINGVOIDTHISWILLBECOMEIMPORTANTTOMORROWWHENYOUCREATEUSERINTERFACESANDTHENMANAGEINPUTTOTHESEINTERFACESHAVINGANEVENTHANDLERRETURNTRUEORFALSEDETERMINESWHETHERAGIVENUICOMPONENTCANINTERCEPTANEVENTORWHETHERITNEEDSTOPASSITONTOTHEENCLOSINGCOMPONENTTHEGENERALRULEISTHATIFYOURMETHODDEALSWITHTHEEVENT,ITSHOULDRETURNTRUE,WHICHFORTHEFOCUSOFTODAYSLESSONISALMOSTALWAYSTHECASETHESECONDHALFOFTHEMOUSECLICKISTHEMOUSEUPMETHOD,WHICHISCALLEDWHENTHEMOUSEBUTTONISRELEASEDTOHANDLEAMOUSEUPEVENT,ADDTHEMOUSEUPMETHODTOYOURAPPLETMOUSEUPLOOKSJUSTLIKEMOUSEDOWNPUBLICBOOLEANMOUSEUPEVENTEVT,INTX,INTYANEXAMPLESPOTSINTHISSECTION,YOULLCREATEANEXAMPLEOFANAPPLETTHATUSESMOUSEEVENTSMOUSEDOWNEVENTSINPARTICULARTHESPOTSAPPLETSTARTSWITHABLANKSCREENANDTHENSITSANDWAITSWHENYOUCLICKTHEMOUSEONTHATSCREEN,ABLUEDOTISDRAWNYOUCANPLACEUPTOTENDOTSONTHESCREENFIGURE121SHOWSTHESPOTSAPPLETLETSSTARTFROMTHEBEGINNINGANDBUILDTHISAPPLET,STARTINGFROMTHEINITIALCLASSDEFINITIONIMPORTJAVAAWTGRAPHICSIMPORTJAVAAWTCOLORIMPORTJAVAAWTEVENTPUBLICCLASSSPOTSEXTENDSJAVAAPPLETAPPLETFINALINTMAXSPOTS10INTXSPOTSNEWINTMAXSPOTSINTYSPOTSNEWINTMAXSPOTSINTCURRSPOTS0THISCLASSUSESTHREEOTHERAWTCLASSESGRAPHICS,COLOR,ANDEVENTTHATLASTCLASS,EVENT,NEEDSTOBEIMPORTEDINANYAPPLETSTHATUSEEVENTSTHECLASSHASFOURINSTANCEVARIABLESACONSTANTTODETERMINETHEMAXIMUMNUMBEROFSPOTSTHATCANBEDRAWN,TWOARRAYSTOSTORETHEXANDYCOORDINATESOFTHESPOTSTHATHAVEALREADYBEENDRAWN,ANDANINTEGERTOKEEPTRACKOFTHENUMBEROFTHECURRENTSPOTNOTETHISCLASSDOESNTINCLUDETHEIMPLEMENTSRUNNABLEWORDSINITSDEFINITIONASYOULLSEELATERONASYOUBUILDTHISAPPLET,ITALSODOESNTHAVEARUNMETHODWHYNOTBECAUSEITDOESNTACTUALLYDOANYTHINGONITSOWNALLITDOESISWAITFORINPUTANDTHENDOSTUFFWHENINPUTHAPPENSTHERESNONEEDFORTHREADSIFYOURAPPLETISNTACTIVELYDOINGSOMETHINGALLTHETIMELETSSTARTWITHTHEINITMETHOD,WHICHHASONELINE,TOSETTHEBACKGROUNDTOWHITEPUBLICVOIDINITSETBACKGROUNDCOLORWHITESETTHEBACKGROUNDHERE,INSTEADOFINPAINT,BECAUSEPAINTISCALLEDREPEATEDLYEACHTIMEANEWSPOTISADDEDBECAUSEYOUREALLYNEEDTOSETTHEBACKGROUNDONLYONCE,PUTTINGITINTHEPAINTMETHODUNNECESSARILYSLOWSDOWNTHATMETHODPUTTINGITHEREISAMUCHBETTERIDEATHEMAINACTIONOFTHISAPPLETOCCURSONTHEMOUSEDOWNMETHOD,SOLETSADDTHATONENOWPUBLICBOOLEANMOUSEDOWNEVENTEVT,INTX,INTYIFCURRSPOTSMAXSPOTSADDSPOTX,YELSESYSTEMOUTPRINTLN“TOOMANYSPOTS”RETURNTRUEWHENTHEMOUSECLICKOCCURS,THEMOUSEDOWNMETHODTESTSTOSEEWHETHERTHEREARELESSTHANTENSPOTSIFSO,ITCALLSTHEADDSPOTMETHODWHICHYOULLWRITESOONIFNOT,ITJUSTPRINTSANERRORMESSAGEFINALLY,ITRETURNSTRUE,BECAUSEALLTHEEVENTMETHODSHAVETORETURNABOOLEANVALUEUSUALLYTRUEWHATDOESADDSPOTDOITADDSTHECOORDINATESOFTHESPOTTOTHEARRAYSTHATSTORETHECOORDINATES,INCREMENTSTHECURRSPOTSVARIABLE,ANDTHENCALLSREPAINTVOIDADDSPOTINTX,INTYXSPOTSCURRSPOTSXYSPOTSCURRSPOTSYCURRSPOTSREPAINT()YOUMAYBEWONDERINGWHYYOUHAVETOKEEPTRACKOFALLTHEPASTSPOTSINADDITIONTOTHECURRENTSPOTTHEREASONISBECAUSEOFREPAINTEACHTIMEYOUPAINTTHESCREEN,YOUHAVETOPAINTALLTHEOLDSPOTSINADDITIONTOTHENEWESTSPOTOTHERWISE,EACHTIMEYOUPAINTEDANEWSPOT,THEOLDERSPOTSWOULDGETERASEDNOW,ONTOTHEPAINTMETHODPUBLICVOIDPAINTGRAPHICSGGSETCOLORCOLORBLUEFORINTI0ICURRSPOTSIGFILLOVALXSPOTSI10,YSPOTSI10,20,20INSIDEPAINT,YOUJUSTLOOPTHROUGHTHESPOTSYOUVESTOREDINTHEXSPOTSANDYSPOTSARRAYS,PAINTINGEACHONEACTUALLY,PAINTINGTHEMALITTLETOTHERIGHTANDUPWARDSOTHATTHESPOTISPAINTEDAROUNDTHEMOUSEPOINTERRATHERTHANBELOWANDTOTHERIGHTTHATSITTHATSALLYOUNEEDTOCREATEANAPPLETTHATHANDLESMOUSECLICKSEVERYTHINGELSEISHANDLEDFORYOUYOUHAVETOADDTHEAPPROPRIATEBEHAVIORTOMOUSEDOWNORMOUSEUPTOINTERCEPTANDHANDLETHATEVENTLISTING121SHOWSTHEFULLTEXTFORTHESPOTSAPPLETTYPELISTING121THESPOTSAPPLET1IMPORTJAVAAWTGRAPHICS2IMPORTJAVAAWTCOLOR3IMPORTJAVAAWTEVENT45PUBLICCLASSSPOTSEXTENDSJAVAAPPLETAPPLET67FINALINTMAXSPOTS108INTXSPOTSNEWINTMAXSPOTS9INTYSPOTSNEWINTMAXSPOTS10INTCURRSPOTS01112PUBLICVOIDINIT13SETBACKGROUNDCOLORWHITE141516PUBLICBOOLEANMOUSEDOWNEVENTEVT,INTX,INTY17IFCURRSPOTSMAXSPOTS18ADDSPOTX,Y19ELSESYSTEMOUTPRINTLN“TOOMANYSPOTS”20RETURNTRUE212223VOIDADDSPOTINTX,INTY24XSPOTSCURRSPOTSX25YSPOTSCURRSPOTSY26CURRSPOTS27REPAINT282930PUBLICVOIDPAINTGRAPHICSG31GSETCOLORCOLORBLUE32FORINTI0ICURRSPOTSI33GFILLOVALXSPOTSI10,YSPOTSI10,20,20343536MOUSEMOVEMENTSEVERYTIMETHEMOUSEISMOVEDASINGLEPIXELINANYDIRECTION,AMOUSEMOVEEVENTISGENERATEDTHEREARETWOMOUSEMOVEMENTEVENTSMOUSEDRAGS,WHERETHEMOVEMENTOCCURSWITHTHEMOUSEBUTTONPRESSEDDOWN,ANDPLAINMOUSEMOVEMENTS,WHERETHEMOUSEBUTTONISNTPRESSEDTOMANAGEMOUSEMOVEMENTEVENTS,USETHEMOUSEDRAGANDMOUSEMOVEMETHODSMOUSEDRAGANDMOUSEMOVETHEMOUSEDRAGANDMOUSEMOVEMETHODS,WHENINCLUDEDINYOURAPPLETCODE,INTERCEPTANDHANDLEMOUSEMOVEMENTEVENTSTHEMOUSEMOVEMETHOD,FORPLAINMOUSEPOINTERMOVEMENTSWITHOUTTHEMOUSEBUTTONPRESSED,LOOKSMUCHLIKETHEMOUSECLICKMETHODSPUBLICBOOLEANMOUSEMOVEEVENTEVT,INTX,INTYTHEMOUSEDRAGMETHODHANDLESMOUSEMOVEMENTSMADEWITHTHEMOUSEBUTTONPRESSEDDOWNACOMPLETEDRAGGINGMOVEMENTCONSISTSOFAMOUSEDOWNEVENT,ASERIESOFMOUSEDRAGEVENTSFOREACHPIXELTHEMOUSEISMOVED,ANDAMOUSEUPEVENWHENTHEBUTTONISRELEASEDTHEMOUSEDRAGMETHODLOOKSLIKETHISPUBLICBOOLEANMOUSEDRAGEVENTEVT,INTX,INTYMOUSEENTERANDMOUSEEXITFINALLY,THEREARETHEMOUSEENTERANDMOUSEEXITMETHODSTHESETWOMETHODSARECALLEDWHENTHEMOUSEPOINTERENTERSTHEAPPLETORWHENITEXITSTHEAPPLETINCASEYOUREWONDERINGWHYYOUMIGHTNEEDTOKNOWTHIS,ITSMOREUSEFULONCOMPONENTSOFUSERINTERFACESTHATYOUMIGHTPUTINSIDEANAPPLETYOULLLEARNMOREABOUTUITOMORROWBOTHMOUSEENTERANDMOUSEEXITHAVESIMILARSIGNATURESTHREEARGUMENTSTHEEVENTOBJECTANDTHEXANDYCOORDINATESOFTHEPOINTWHERETHEMOUSEENTEREDOREXITEDTHEAPPLETPUBLICBOOLEANMOUSEENTEREVENTEVT,INTX,INTYPUBLICBOOLEANMOUSEEXITEVENTEVT,INTX,INTYANEXAMPLEDRAWINGLINESEXAMPLESALWAYSHELPTOMAKECONCEPTSMORECONCRETEINTHISSECTIONYOULLCREATEANAPPLETTHATENABLESYOUTODRAWSTRAIGHTLINESONTHESCREENBYDRAGGINGFROMTHESTARTPOINTTOTHEENDPOINTFIGURE122SHOWSTHEAPPLETATWORKASWITHTHESPOTSAPPLETONWHICHTHISAPPLETISBASED,LETSSTARTWITHTHEBASICDEFINITIONANDWORKOURWAYTHROUGHITLISTING122SHOWSTHETOPOFTHELINESAPPLETTYPELISTING122THETOPOFTHELINESAPPLET1IMPORTJAVAAWTGRAPHICS2IMPORTJAVAAWTCOLOR3IMPORTJAVAAWTEVENT4IMPORTJAVAAWTPOINT56PUBLICCLASSLINESEXTENDSJAVAAPPLETAPPLET78FINALINTMAXLINES109POINTSTARTSNEWPOINTMAXLINES/STARTINGPOINTS10POINTENDSNEWPOINT10/ENDINGPOINTS11POINTANCHOR/STARTOFCURRENTLINE12POINTCURRENTPOINT/CURRENTENDOFLINE13INTCURRLINE0/NUMBEROFLINES1415PUBLICVOIDINIT16SETBACKGROUNDCOLORWHITE1718COMPAREDTOSPOTS,THISAPPLETADDEDAFEWEXTRATHINGSUNLIKESPOTS,WHICHKEEPSTRACKOFINDIVIDUALINTEGERCOORDINATES,THISONEKEEPSTRACKOFPOINTOBJECTSPOINTSREPRESENTANXANDAYCOORDINATE,ENCAPSULATEDINASINGLEOBJECTTODEALWITHPOINTS,YOUIMPORTTHEPOINTCLASSLINE4ANDSETUPABUNCHOFINSTANCEVARIABLESTHATHOLDPOINTSTHESTARTSARRAYHOLDSPOINTSREPRESENTINGTHESTARTSOFLINESALREADYDRAWNTHEENDSARRAYHOLDSTHEENDPOINTSOFTHOSESAMELINESANCHORHOLDSTHESTARTINGPOINTOFTHELINECURRENTLYBEINGDRAWNCURRENTPOINTHOLDSTHECURRENTENDPOINTOFTHELINECURRENTLYBEINGDRAWNCURRLINEHOLDSTHECURRENTNUMBEROFLINESTOMAKESUREYOUDONTGOOVERMAXLINESFINALLY,THEINITMETHODLINES15THROUGH17,ASINTHESPOTSAPPLET,SETSTHEBACKGROUNDOFTHEAPPLETTOWHITETHETHREEMAINEVENTSTHISAPPLETDEALSWITHAREMOUSEDOWN,TOSETTHEANCHORPOINTFORTHECURRENTLINE,MOUSEDRAG,TOANIMATETHECURRENTLINEASITSBEINGDRAWN,ANDMOUSEUP,TOSETTHEENDINGPOINTFORTHENEWLINEGIVENTHATYOUHAVEINSTANCEVARIABLESTOHOLDEACHOFTHESEVALUES,ITSMERELYAMATTEROFPLUGGINGTHERIGHTVARIABLESINTOTHERIGHTMETHODSHERESMOUSEDOWN,WHICHSETSTHEANCHORPOINTWHILETHEMOUSEISBEINGDRAGGEDTODRAWTHELINE,THEAPPLETANIMATESTHELINEBEINGDRAWNASYOUDRAWTHEMOUSEAROUND,THENEWLINEMOVESWITHITFROMTHEANCHORPOINTTOTHETIPOFTHEMOUSETHEMOUSEDRAGEVENTCONTAINSTHECURRENTPOINTEACHTIMETHEMOUSEMOVES,SOUSETHATMETHODTOKEEPTRACKOFTHECURRENTPOINTANDTOREPAINTFOREACHMOVEMENTSOTHELINE“ANIMATES”THENEWLINEDOESNTGETADDEDTOTHEARRAYSOFOLDLINESUNTILTHEMOUSEBUTTONISRELEASEDHERESMOUSEUP,WHICHTESTSTOMAKESUREYOUHAVENTEXCEEDEDTHEMAXIMUMNUMBEROFLINESBEFORECALLINGTHEADDLINEMETHODDESCRIBEDNEXTPUBLICBOOLEANMOUSEUPEVENTEVT,INTX,INTYIFCURRLINEMAXLINESADDLINEX,YELSESYSTEMOUTPRINTLN“TOOMANYLINES”RETURNTRUETHEADDLINEMETHODISWHERETHEARRAYSOFLINESGETUPDATEDANDWHERETHEAPPLETISREPAINTEDTOTAKETHENEWLINEINTOEFFECTVOIDADDLINEINTX,INTYSTARTSCURRLINEANCHORENDSCURRLINENEWPOINTX,YCURRLINECURRENTPOINTNULLREPAINTNOTETHATINTHISLINEYOUALSOSETCURRENTPOINTTONULLWHYBECAUSETHECURRENTLINEINPROCESSISOVERBYSETTINGCURRENTPOINTTONULL,YOUCANTESTFORTHATVALUEINTHEPAINTMETHODPAINTINGTHEAPPLETMEANSDRAWINGALLTHEOLDLINESSTOREDINTHESTARTSANDENDSARRAYS,ASWELLASDRAWINGTHECURRENTLINEINPROCESSWHOSEENDPOINTSAREINANCHORANDCURRENTPOINT,RESPECTIVELYTOSHOWTHEANIMATIONOFTHECURRENTLINE,DRAWITINBLUEHERESTHEPAINTMETHODFORTHELINESAPPLETPUBLICVOIDPAINTGRAPHICSG/DRAWEXISTINGLINESFORINTI0ICURRLINEIGDRAWLINESTARTSIX,STARTSIY,ENDSIX,ENDSIY/DRAWCURRENTLINEGSETCOLORCOLORBLUEIFCURRENTPOINTNULLGDRAWLINEANCHORX,ANCHORY,CURRENTPOINTX,CURRENTPOINTYINPAINT,WHENYOUREDRAWINGTHECURRENTLINE,YOUTESTFIRSTTOSEEWHETHERCURRENTPOINTISNULLIFITIS,THEAPPLETISNTINTHEMIDDLEOFDRAWINGALINE,SOTHERESNOREASONTOTRYDRAWINGALINETHATDOESNTEXISTBYTESTINGFORCURRENTPOINTANDBYSETTINGCURRENTPOINTTONULLINTHEADDLINEMETHOD,YOUCANPAINTONLYWHATYOUNEEDTHATSITJUST60LINESOFCODEANDAFEWBASICMETHODS,ANDYOUHAVEAVERYBASICDRAWINGAPPLICATIONINYOURWEBBROWSERLISTING123SHOWSTHEFULLTEXTOFTHELINESAPPLETSOTHATYOUCANPUTTHEPIECESTOGETHERTYPELISTING123THELINESAPPLET1IMPORTJAVAAWTGRAPHICS2IMPORTJAVAAWTCOLOR3IMPORTJAVAAWTEVENT4IMPORTJAVAAWTPOINT56PUBLICCLASSLINESEXTENDSJAVAAPPLETAPPLET78FINALINTMAXLINES9POINTSTARTSNEWPOINTMAXLINES/STARTINGPOINTS10POINTENDSNEWPOINT10/ENDINGPOINTS11POINTANCHOR/STARTOFCURRENTLINE12POINTCURRENTPOINT/CURRENTENDOFLINE13INTCURRLINE0/NUMBEROFLINES1415PUBLICVOIDINIT16SETBACKGROUNDCOLORWHITE171819PUBLICBOOLEANMOUSEDOWNEVENTEVT,INTX,INTY20ANCHORNEWPOINTX,Y21RETURNTRUE222324PUBLICBOOLEANMOUSEUPEVENTEVT,INTX,INTY25IFCURRLINEMAXSPOTS26ADDLINEX,Y27ELSESYSTEMOUTPRINTLN“TOOMANYLINES”28RETURNTRUE293031PUBLICBOOLEANMOUSEDRAGEVENTEVT,INTX,INTY32CURRENTPOINTNEWPOINTX,Y33REPAINT34RETURNTRUE353637VOIDADDLINEINTX,INTY38STARTSCURRLINEANCHOR39ENDSCURRLINENEWPOINTX,Y40CURRLINE41CURRENTPOINTNULL42REPAINT434445PUBLICVOIDPAINTGRAPHICSG4647/DRAWEXISTINGLINES48FORINTI0ICURRLINEI49GDRAWLINESTARTSIX,STARTSIY,50ENDSIX,ENDSIY515253/DRAWCURRENTLINE54GSETCOLORCOLORBLUE55IFCURRENTPOINTNULL56GDRAWLINEANCHORX,ANCHORY,57CURRENTPOINTX,CURRENTPOINTY5859KEYBOARDEVENTSKEYBOARDWVWNTSAREGENERATEDWHENEVERUSERSPRESSAKEYONTHEKEYBOARDBYUSINGKEYEVENTS,YOUCANGETHOLDOFTHEVALUESOFTHEKEYSTHEYPRESSEDTOPERFORMANACTIONORMERELYTOGETCHARACTERINPUTFROMTHEUSERSOFYOURAPPLETTHEKEYDOWNMETHODTOCAPTUREAKEYBOARDEVENT,USETHEKEYDOWNMETHODPUBLICBOOLEANKEYDOWNEVENTEVT,INTKEYTHEKEYSGENERATEDBYKEYDOWNEVENTSANDPASSEDINTOKEYDOWNASTHEKEYARGUMENTAREINTEGERSREPRESENTINGASCIICHARACTERVALUES,WHICHINCLUDEALPHANUMERICCHARACTERS,FUNCTIONKEYS,TABS,RETURNS,ANDSOONTOUSETHEMASCHARACTERSFOREXAMPLE,TOPRINTTHEM,YOUNEEDTOCASTTHEMTOCHARACTERSCURRENTCHARCHARKEYHERESASIMPLEEXAMPLEOFAKEYDOWNMETHODTHATDOESNOTHINGBUTPRINTTHEKEYYOUJUSTTYPEDINBOTHITSASCIIANDCHARACTERREPRESENTATIONPUBLICBOOLEANKEYDOWNEVENTEVT,INTKEYSYSTEMOUTPRINTLN“ASCIIVALUE”KEYSYSTEMOUTPRINTLN“CHARACTER”CHARKEYRETURNTRUEDEFAULTKEYSTHEEVENTCLASSPROVIDESASETOFCLASSVARIABLESTHATREFERTOSEVERALSTANDARDNONALPHANUMERICKEYS,SUCHASTHEARROWKEYSIFYOURINTERFACEUSERTHESEKEYS,YOUCANPROVIDEMOREREADABLECODEBYTESTINGFORTHESENAMESINYOURKEYDOWNMETHODRATHERTHANTESTINGFORTHEIRNUMERICVALUESFOREXAMPLE,TOTESTWHETHERTHEUPARROWWASPRESSED,YOUMIGHTUSETHEFOLLOWINGSNIPPETOFCODEIFKEYEVENTUPBECAUSETHEVALUESTHESECLASSVARIABLESHOLDAREINTEGERS,YOUALSOCANUSETHESWITCHSTATEMENTTOTESTFORTHEMTABLE121SHOWSTHESTANDARDEVENTCLASSVARIABLESFORVARIOUSKEYSANDTHEACTURLKEYSTHEYREPRESENTTABLE121STANDARDKEYSDEFINEDBYTHEEVENTCLASSCLASSVARIABLEREPRESENEDKEYEVENTHOMETHEHOMEKEYEVENTENDTHEENDKEYEVENTPGUPTHEPAGEUPKEYEVENTPGDNTHEPAGEDOWNKEYEVENTUPTHEUPARROWEVENTDOWNTHEDOWNARROWEVENTLEFTTHELEFTARROWEVENTRIGHTTHERIGHTARROWANEXAMPLEENTERING,DISPLAYING,ANDMOVINGCHARACTERSLETSLOOKATANAPPLETTHATDEMONSTRATESKEYBOARDEVENTSTHISONEENABLESYOUTOTYPEACHARACTER,ANDITDISPLAYSTHATCHARACTERINTHECENTEROFTHEAPPLETWINDOWYOUTHENCANMOVETHATCHARACTERAROUNDONTHESCREENBYTHESCREENBYUSINGTHEARROWKEYSTYPINGANOTHERCHARACTERATANYTIMECHANGESTHECHARACTERAITSCURRENTLYDISPLAYEDFIGURE123SHOWSANEXAMPLEFIGURE123THEKESAPPLETTHISAPPLETISACTUALLYLESSCOMPLICATEDTHANTHEPREVIOUSAPPLETSYOUVEUSEDTHISONEHASONLYTHREEMETHODSINIT,KEYDOWN,ANDPAINTTHEINSTANCEVARIABLESAREALSOSIMPLER,BECAUSETHEONLYTHINGSYOUNEEDTOKEEPTRACKOFARETHEXANDYPOSITIONSOFTHECURRENTCHARACTERANDTHEVALUESOFTHATCHARACTERITSELFHERESTHETOPOFTHISCLASSDEFINITIONIMPORTJAVAAWTGRAPHICSIMPORTJAVAAWTEVENTIMPORTJAVAAWTFONTPUBLICCLASSKEYSEXTENDSJAVAAPPLETAPPLETCHARCURRKEYINTCURRXINTCURRYTHEINITMETHODISRESPONSIBLEFORTHREETHINGSSETTINGTHEBACKGROUNDCOLOR,SETTINGTHEAPPLETSFONTHERE,36POINTHELVETICABOLD,ANDSETTINGTHEBEGINNINGPOSITIONFORTHECHARACTERTHEMIDDLEOFTHESCREEN,MINUSAFEWPOINTSTONUDGEITUPANDTOTHERIGHTPUBLICVOIDINITCURRXTHISSIZEWIDTH/28/DEFAULTCURRYTHIDSIZEHEIGHT/216SETBACKGROUNDCOLORWHITESETFONTNEWFONT“HELVETICA”,FONTBOLD,36BECAUSETHISAPPLETSBEHAVIORISBASEDONKEYBOARDINPUT,THEKEYDOWNMETHODISWHEREMOSTOFTHEWORKOFTHEAPPLETTAKESPLACEPUBLICBOOLEANKEYDOWNEVENTEVT,INTKEYSWITCHKEYCASEEVENTDOWNCURRY5BREAKCASEEVENTUPCURRY5BREAKCASEEVENTLEFTCURRY5BREAKCASEEVENTRIGHTCURRY5BREAKDEFAULTCURRKEYCHARKEYREPAINTRETURNTRUEINTHECENTEROFTHEKEYDOWNAPPLETISASWITCHSTATEMENTTHATTESTSFORDIFFERENTKEYEVENTSIFTHEEVENTISANARROWKEY,THEAPPROPRIATECHANGEISMADECHARACTERSPOSITIONIFTHEEVENTISANYOTHERKEY,THECHARACTERITSELFISCHANGEDTHEMETHODFINISHESUPWITHAREPAINTANDRETURNSTRUETHEPAINTMETHODHEREISALMOSTTRIVIALJUSTDISPLAYTHECURRENTATTHECURRENTPOSITIONHOWEVER,NOTETHATWHENTHEAPPLETSTARTSUP,THERESNOINITIALCHARACTERANDNOTHINGTODRAW,SOYOUHAVETOTAKETHATINTOACCOUNTTHECURRKEYVARIABLEISINITIALIZEDTO0,SOYOUPAINTTHEAPPLETONLYIFCURRKEYHASANACTUALVALUEPUBLICVOIDPAINTGRAPHICSGIFCURRKEY0GDRAWSTRINGSTRINGVALUEOFCURRKEY,CURRX,CURRYLISTING124SHOWSTHECOMPLETESOURCEFORTHEKEYSAPPLETTYPELISTING124THEKEYSAPPLET1IMPORTJAVAAWTGRAPHICS2IMPORTJAVAAWTEVENT3IMPORTJAVAAWTFONT45PUBLICCLASSKEYSEXTENDSJAVAAPPLETAPPLET67CHARCURRKEY8INTCURRX9INTCURRY1011PUBLICVOIDINIT12CURRXTHISSIZEWIDTH/28/DEFAULT13CURRYTHISSIZEHEIGHT/2161415SETBACKGROUNDCOLORWHITE16SETFONTNEWFONT“HELVETICA”,FONTBOLD,36171819PUBLICBOOLEANKEYDOWNEVENTEVT,INTKEY20SWITCHKEY21CASEEVENTDOWN22CURRY523BREAK24CASEEVENTUP25CURRY526BREAK27CASEEVENTLEFT28CURRX529BREAK30CASEEVENTRIGHT31CURRX532BREAK33DEFAULT34CURRKEYCHARKEY353637REPAINT38RETURNTRUE394041PUBLICVOIDPAINTGRAPHICSG42IFCU
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2025版企业员工特殊技能培训借款协议
- 2025年度客运服务人员劳动合同样本
- 2025版旅游产品居间服务合同范本
- 二零二五年度海外房产购置咨询合同
- 2025年度户外拓展训练赛事策划与服务合同
- 2025年度房地产抵押合同:文化旅游地产贷款范本
- 2025版动物养殖废弃物资源化利用与购销合同
- 2025返聘合同:返聘法律顾问企业法律事务合同范本
- 2025版旅游度假村开发甲方投资合同条款
- 二零二五年度绿色生态环保项目环境行政合同
- 2025年R1快开门式压力容器操作考试100题及答案
- 2025年中国离心式冷水中央空调行业市场深度分析及发展前景预测报告
- 滴灌通收入分成协议合同
- 园区建设保障房管理办法
- 2025入党培训考试题库及答案
- 2025至2030机场运营行业市场深度调研及前景趋势与投资报告
- 遂宁市射洪市招聘社区专职工作者考试真题2024
- 智慧工会平台管理办法
- 合作共建园区管理办法
- 2025年广东省中考英语试卷真题及答案详解(精校打印版)
- 2025年通 用技术集团招聘笔试备考题库(带答案详解)
评论
0/150
提交评论