翻译文献-图形，字体和颜色

外文原文GRAPHICS,FONTS,ANDCOLORTHEGRAPHICSCLASSWITHJAVASGRAPHICSCAPABILITIES,YOUCANDRAWLINES,SHAPES,CHARACTERS,ANDIMAGESTOTHESCREENINSIDEYOURAPPLETMOSTOFTHEGRAPHICSOPERATIONSINJAVAAREMETHODSDEFINEDINTHEGRAPHICSCLASSYOUDONTHAVETOCREATEANINSTANCEOFGRAPHICSINORDERTODRAWSOMETHINGINYOURAPPLETINYOURAPPLETSPAINTMETHODWHICHYOULEARNEDABOUTYESTERDAY,YOUAREGIVENAGRAPHICSOBJECTBYDRAWINGONTHATOBJECT,YOUDRAWONTOYOURAPPLETANDTHERESULTSAPPEARONSCREENTHEGRAPHICSCLASSISPARTOFTHEJAVAAWTPACKAGE,SOIFYOURAPPLETDOESANYPAINTINGASITUSUALLYWILL,MAKESUREYOUIMPORTTHATCLASSATTHEBEGINNINGOFYOURJAVAFILEIMPORTJAVAAWTGRAPHICSPUBLICCLASSMYCLASSEXTENDEDJAVAAPPLETAPPLETTHEGRAPHICSCOORDINATESYSTEMTODRAWANOBJECTONTHESCREEN,YOUCALLONEOFTHEDRAWINGMETHODSAVAILABLEINTHEGRAPHICSCLASSALLTHEDRAWINGMETHODSHAVEARGUMENTSREPRESENTINGENDPOINTS,CORNERS,ORSTARTINGLOCATIONSOFTHEOBJECTASVALUESINTHEAPPLETSCOORDINATESYSTEMFOREXAMPLE,ALINESTARTSATTHEPOINTS10,10ANDENDSATTHEPOINTS20,20JAVASCOORDINATESYSTEMHASTHEORIGIN0,0INTHETOPLEFTCORNERPOSITIVEXVALUESARETOTHERIGHT,ANDPOSITIVEYVALUESAREDOWNALLPIXELVALUESAREINTEGERSTHEREARENOPARTIALORFRACTIONALPIXELSFIGURE91SHOWSHOWYOUMIGHTDRAWASIMPLESQUAREBYUSINGTHISCOORDINATESYSTEMJAVASCOORDINATESYSTEMISDIFFERENTFROMMANYPAINTINGANDLAYOUTPROGRAMSTHATHAVETHEIRXANDYINTHEBOTTOMLEFTIFYOURENOTUSEDTOWORKINGWITHTHISUPSIDEDOWNGRAPHICSSYSTEM,ITMAYTAKESOMEPRACTICETOGETFAMILIARWITHITDRAWINGANDFILLINGTHEGRAPHICSCLASSPROVIDESASETOFSIMPLEBUILTINGRAPHICSPRIMITIVESFORDRAWING,INCLUDINGLINES,RECTANGLES,POLYGONS,OVALS,ANDARCSLINESTODRAWSTRAIGHTLINES,USETHEDRAWLINEMETHODDRAWLINETAKESFOURARGUMENTSTHEXANDYCOORDINATESOFTHESTARTINGPOINTANDTHEXANDYCOORDINATESOFTHEENDINGPOINTPUBLICVOIDPAINTGRAPHICSGGDRAWLINE25,25,75,75FIGURE92SHOWSTHERESULTOFTHISSNIPPETOFCODERECTANGLESTHEJAVAGRAPHICSPRIMITIVESPROVIDENOTJUSTONE,BUTTHREEKINDSOFRECTANGLESPLAINRECTANGLESROUNDEDRECTANGLES,WHICHARERECTANGLESWITHROUNDEDCORNERSTHREEDIMENSIONALRECTANGLES,WHICHAREDRAWNWITHASHADEDBORDERFOREACHOFTHESERECTANGLES,YOUHAVETWOMETHODSTOCHOOSEFROMONETHATDRAWSTHERECTANGLEINOUTLINEFORM,ANDONETHATDRAWSTHERECTANGLEFILLEDWITHCOLORTODRAWAPLAINRECTANGLE,USEEITHERTHEDRAWRECTORFILLRECTMETHODSBOTHTAKEFOURARGUMENTSTHEXANDYCOORDINATESOFTHETOPLEFTCORNEROFTHERECTANGLE,ANDTHEWIDTHANDHEIGHTOFTHERECTANGLETODRAWFOREXAMPLE,THEFOLLOWINGPAINTMETHODDRAWSTWOSQUARESTHELEFTONEISANOUTLINEANDTHERIGHTONEISFILLEDFIGURE93SHOWSTHERESULTPUBLICVOIDPAINTGRAPHICSGGDRAWRECT20,20,60,60GFILLRECT120,20,60,60ROUNDEDRECTANGLESARE,ASYOUMIGHTEXPECT,RECTANGLESWITHROUNDEDEDGESTHEDRAWROUNDRECTANDFILLROUNDRECTMETHODSTODRAWROUNDEDRECTANGLESARESIMILARTOREGULARRECTANGLESEXCEPTTHATROUNDEDRECTANGLESHAVETWOEXTRAARGUMENTSFORTHEWIDTHANDHEIGHTOFTHEANGLEOFTHECORNERSTHOSETWOARGUMENTSDETERMINEHOWFARALONGTHEEDGESOFTHERECTANGLETHEARCFORTHECORNERWILLSTARTTHEFIRSTFORTHEANGLEALONGTHEHORIZONTALPLANE,THESECONDFORTHEVERTICALLARGERVALUESFORTHEANGLEWIDTHANDHEIGHTMAKETHEOVERALLRECTANGLEMOREROUNDEDVALUESEQUALTOTHEWIDTHANDHEIGHTOFTHERECTANGLEITSELFPRODUCEACIRCLEFIGURE94SHOWSSOMEEXAMPLESOFROUNDEDCORNERSHERESAPAINTMETHODTHATDRAWSTWOROUNDEDRECTANGLESONEASANOUTLINEWITHAROUNDEDCORNER10PIXELSSQUARETHEOTHER,FILLED,WITHAROUNDEDCORNER20PIXELSSQUAREFIGURE95SHOWSTHERESULTINGSQUARESPUBLICVOIDPAINTGRAPHICSGGDRAWROUNDRECT20,20,60,60,10,10GFILLROUNDRECT120,20,60,60,20,20FINALLY,THEREARETHREEDIMENSIONALRECTANGLESTHESERECTANGLESARENTREALLY3DINSTEAD,THEYHAVEASHADOWEFFECTTHATMAKESTHEMAPPEAREITHERRAISEDORINDENTEDFROMTHESURFACEOFTHEAPPLETTHREEDIMENSIONALRECTANGLESHAVEFOURARGUMENTSFORTHEXANDYOFTHESTARTPOSITIONANDTHEWIDTHANDHEIGHTOFTHERECTANGLETHEFIFTHARGUMENTISABOOLEANINDICATINGWHETHERTHE3DEFFECTISTORAISETHERECTANGLETRUEORINDENTITFALSEASWITHTHEOTHERRECTANGLES,THEREAREALSODIFFERENTMETHODSFORDRAWINGANDFILLINGDRAW3DRECTANDFILL3DRECTHERESCODETOPRODUCETWOOFTHEMTHELEFTONEINDENTED,THERIGHTONERAISEDFIGURE96SHOWSTHERESULTPUBLICVOIDPAINTGRAPHICSGGDRAW3DRECT20,20,60,60,TRUEGDRAW3DRECT120,20,60,60,FALSEPOLYGONSPOLYGONSARESHAPESWITHANUNLIMITEDNUMBEROFSIDESTODRAWAPOLYGON,YOUNEEDASETOFXANDYCOORDINATES,ANDTHEDRAWINGMETHODTHENSTARTSATONE,DRAWSALINETOTHESECOND,THENALINETOTHETHIRD,ANDSOONASWITHRECTANGLES,YOUCANDRAWANOUTLINEORAFILLEDPOLYGONTHEDRAWPOLYGONANDFILLPOLYGONMETHODS,RESPECTIVELYYOUALSOHAVEACHOICEOFHOWYOUWANTTOINDICATETHELISTOFCOORDINATESEITHERASARRAYSOFXANDYCOORDINATESORASANINSTANCEOFTHEPOLYGONCLASSUSINGTHEFIRSTMETHOD,THEDRAWPOLYGONANDFILLPOLYGONMETHODSTAKETHREEARGUMENTSANARRAYOFINTEGERSREPRESENTINGXCOORDINATESANARRAYOFINTEGERSREPRESENTINGYCOORDINATESANINTEGERFORTHETOTALNUMBEROFPOINTSTHEXANDYARRAYSSHOULD,OFCOURSE,HAVETHESAMENUMBEROFELEMENTSHERESANEXAMPLEOFDRAWINGAPOLYGONSOUTLINEBYUSINGTHISMETHODFIGURE97SHOWSTHERESULTPUBLICVOIDPAINTGRAPHICSGINTEXES39,94,97,142,53,58,26INTWHYS33,74,36,70,108,80,106INTPTSEXESLENGTHGDRAWPOLYGONEXES,WHYS,PTSTHESECONDWAYOFCALLINGDRAWPOLYGONANDFILLPOLYGONISTOUSEAPOLYGONOBJECTTHEPOLYGONCLASSISUSEFULIFYOUINTENDTOADDPOINTSTOTHEPOLYGONORIFYOUREBUILDINGTHEPOLYGONONTHEFLYTHEPOLYGONCLASSENABLESYOUTOTREATTHEPOLYGONASANOBJECTRATHERTHANHAVINGTODEALWITHINDIVIDUALARRAYSTOCREATEAPOLYGONOBJECTYOUCANEITHERCREATEANEMPTYPOLYGONPOLYGONPOLYNEWPOLYGONORCREATEAPOLYGONFROMASETOFPOINTSUSINGINTEGERARRAYS,ASINTHEPREVIOUSEXAMPLEINTEXES39,94,97,142,53,58,26INTWHYS33,74,36,70,108,80,106INTPTSEXESLENGTHPOLYGONPOLYNEWPOLYGONEXES,WHYS,PTSONCEYOUHAVEAPOLYGONOBJECT,YOUCANAPPENDPOINTSTOTHEPOLYGONASYOUNEEDTOPOLYADDPOINT20,35THEN,TODRAWTHEPOLYGON,JUSTUSETHEPOLYGONOBJECTASANARGUMENTTODRAWPOLYGONORFILLPOLYGONHERESTHATPREVIOUSEXAMPLE,REWRITTENTHISTIMEWITHAPOLYGONOBJECTYOULLALSOFILLTHISPOLYGONRATHERTHANJUSTDRAWINGITSOUTLINEFIGURE98SHOWSTHEOUTPUTPUBLICVOIDPAINTGRAPHICSGINTEXES39,94,97,142,53,58,26INTWHYS33,74,36,70,108,80,106INTPTSEXESLENGTHPOLYGONPOLYNEWPOLYGONEXES,WHYS,PTSGFILLPOLYGONPOLYCOPYINGANDCLEARINGONCEYOUVEDRAWNAFEWTHINGSONTHESCREEN,YOUMAYWANTTOMOVETHEMAROUNDORCLEARTHEENTIREAPPLETTHEGRAPHICSCLASSPROVIDESMETHODSFORDOINGBOTHTHESETHINGSTHECOPYAREAMETHODCOPIESARECTANGULARAREAOFTHESCREENTOANOTHERAREAOFTHESCREENCOPYAREATAKESSIXARGUMENTSTHEXANDYOFTHETOPCORNEROFTHERECTANGLETOCOPY,THEWIDTHANDTHEHEIGHTOFTHATRECTANGLE,ANDTHEDISTANCEINTHEXANDYDIRECTIONSTOWHICHTOCOPYITFOREXAMPLE,THISLINECOPIESASQUAREAREA100PIXELSONASIDE100PIXELSDIRECTLYTOITSRIGHTGCOPYAREA0,0,100,100,100,0TOCLEARARECTANGULARAREA,USETHECLEARRECTMETHODCLEARRECT,WHICHTAKESTHESAMEFOURARGUMENTSASTHEDRAWRECTANDFILLRECTMETHODS,FILLSTHEGIVENRECTANGLEWITHTHECURRENTBACKGROUNDCOLOROFTHEAPPLETYOULLLEARNHOWTOSETTHECURRENTBACKGROUNDCOLORLATERONTODAYTOCLEARTHEENTIREAPPLET,YOUCANUSETHESIZEMETHOD,WHICHRETURNSADIMENSIONOBJECTREPRESENTINGTHEWIDTHANDHEIGHTOFTHEAPPLETYOUCANTHENGETTOTHEACTUALVALUESFORWIDTHANDHEIGHTBYUSINGTHEWIDTHANDHEIGHTINSTANCEVARIABLESGCLEARRECT0,0,THISSIZEWIDTH,THISHEIGHTTEXTANDFONTSTHEGRAPHICSCLASSALSOENABLESYOUTOPRINTTEXTONTHESCREEN,INCONJUNCTIONWITHTHEFONTCLASS,AND,SOMETIMES,THEFONTMETRICSCLASSTHEFONTCLASSREPRESENTSAGIVENFONTITSNAME,STYLE,ANDPOINTSIZEANDFONTMETRICSGIVESYOUINFORMATIONABOUTTHATFONTFOREXAMPLE,THEACTUALHEIGHTORWIDTHOFAGIVENCHARACTERSOTHATYOUCANPRECISELYLAYOUTTEXTINYOURAPPLETNOTETHATTHETEXTHEREISSTATICTEXT,DRAWNTOTHESCREENONCEANDINTENDEDTOSTAYTHEREYOULLLEARNABOUTENTERINGTEXTFROMTHEKEYBOARDLATERONTHISWEEKCREATINGFONTOBJECTSTODRAWTEXTTOTHESCREEN,FIRSTYOUNEEDTOCREATEANINSTANCEOFTHEFONTCLASSFONTOBJECTSREPRESENTANINDIVIDUALFONTTHATIS,ITSNAME,STYLEBOLD,ITALIC,ANDPOINTSIZEFONTNAMESARESTRINGSREPRESENTINGTHEFAMILYOFTHEFONT,FOREXAMPLE,“TIMESROMAN”,“COURIER”,OR“HELVETICA”FONTSTYLESARECONSTANTSDEFINEDBYTHEFONTCLASSYOUCANGETTOTHEMUSINGCLASSVARIABLESFOREXAMPLE,FONTPLAIN,FONTBOLD,ORFONTITALICFINALLY,THEPOINTSIZEISTHESIZEOFTHEFONT,ASDEFINEDBYTHEFONTITSELFTHEPOINTSIZEMAYORMAYNOTBETHEHEIGHTOFTHECHARACTERSTOCREATEANINDIVIDUALFONTOBJECT,USETHESETHREEARGUMENTSTOTHEFONTCLASSSNEWCONSTRUCTORFONTFNEWFONT“TIMESROMAN”,FONTBOLD,24THISEXAMPLECREATESAFONTOBJECTFORTHETIMESROMANBOLDFONT,IN24POINTSNOTETHATLIKEMOSTJAVACLASSES,YOUHAVETOIMPORTTHISCLASSBEFOREYOUCANUSEITFONTSTYLESAREACTUALLYINTEGERCONSTANTSTHATCANBEADDEDTOCREATECOMBINEDSTYLESFOREXAMPLE,FONTBOLDFONTITALICPRODUCESAFONTTHATISBOTHBOLDANDITALICTHEFONTSYOUHAVEAVAILABLETOYOUINYOURAPPLETDEPENDONTHESYSTEMONWHICHTHEAPPLETISRUNNINGCURRENTLY,ALTHOUGHTHEREISAMECHANISMINJAVATOGETALISTOFFONTSSEETHEGETFONTLISTMETHOD,DEFINEDINTHEJAVAAWTTOOLKITCLASS,ITAPPEARSNOTTOBEWORKINGCURRENTLYINTHEBETAVERSIONOFTHEJDKONCETHESECAPABILITIESWORK,ITISPOSSIBLETOGETALISTOFFONTSONTHESYSTEMANDTOBEABLETOMAKECHOICESBASEDONTHATLISTFORNOW,TOMAKESUREYOURAPPLETISCOMPLETELYCOMPATIBLEACROSSSYSTEMS,ITSAVERYGOODIDEATOLIMITTHEFONTSYOUUSEINYOURAPPLETSTO“TIMESROMAN”,“HELVETICA”,AND“COURIER”IFJAVACANTFINDAFONTYOUWANTTOUSE,ITWILLSUBSTITUTESOMEDEFAULTFONT,USUALLYCOURIERDRAWINGCHARACTERSANDSTRINGSWITHAFONTOBJECTINHAND,YOUCANDRAWTEXTONTHESCREENUSINGTHEMETHODSDRAWCHARSANDDRAWSTRINGFIRST,THOUGH,YOUNEEDTOSETTHECURRENTFONTTOYOURFONTOBJECTUSINGTHESETFONTMETHODTHECURRENTFONTISPARTOFTHEGRAPHICSSTATETHATISKEPTTRACKOFBYTHEGRAPHICSOBJECTONWHICHYOUREDRAWINGEACHTIMEYOUDRAWACHARACTERORASTRINGTOTHESCREEN,THATTEXTISDRAWNBYUSINGTHECURRENTFONTTOCHANGETHEFONTOFTHETEXT,FIRSTCHANGETHECURRENTFONTHERESAPAINTMETHODTHATCREATESANEWFONT,SETSTHECURRENTFONTTOTHATFONT,ANDDRAWSTHESTRING“THISISABIGFONT”,STARTINGFROMTHEPOINT10,100PUBLICVOIDPAINTGRAPHICSGFONTFNEWFONT“TIMESROMAN”,FONTPLAIN,72GSETFONTFGDRAWSTRING“THISISABIGFONT”,10,100THISSHOULDALLLOOKFAMILIARTOYOUTHISISHOWTHEHELLOAPPLETSTHROUGHOUTTHISBOOKWEREPRODUCEDTHELATTERTWOARGUMENTSTODRAWSTRINGDETERMINETHEPOINTWHERETHESTRINGWILLSTARTTHEXVALUEISTHESTARTOFTHELEFTMOSTEDGEOFTHETEXTYISTHEBASELINEFORTHEENTIRESTRINGSIMILARTODRAWSTRINGISTHEDRAWCHARSMETHODTHAT,INSTEADOFTAKINGASTRINGASANARGUMENT,TAKESANARRAYOFCHARACTERSDRAWCHARSHASFIVEARGUMENTSTHEARRAYOFCHARACTERS,ANNINTEGERREPRESENTINGTHEFIRSTCHARACTERINTHEARRAYTODRAW,ANOTHERINTEGERFORTHELASTCHARACTERINTHEARRAYTODRAWALLCHARACTERSBETWEENTHEFIRSTANDLASTAREDRAWN,ANDTHEXANDYFORTHESTARTINGPOINTMOSTOFTHETIME,DRAWSTRINGISMOREUSEFULTHANDRAWCHARSLISTING92SHOWSANAPPLETTHATDRAWSSEVERALLINESOFTEXTINDIFFERENTFONTSFIGURE920SHOWSTHERESULTFINDINGOUTINFORMATIONABOUTAFONTSOMETIMES,YOUMAYWANTTOMAKEDECISIONSINYOURJAVAPROGRAMBASEDONTHEQUALITIESOFTHECURRENTFONTFOREXAMPLE,ITSPOINTSIZE,ORTHETOTALHEIGHTOFITSCHARACTERSYOUCANFINDOUTSOMEBASICINFORMATIONABOUTFONTSANDFONTOBJECTSBYUSINGSIMPLEMETHODSONGRAPHICSANDONTHEFONTOBJECTSTABLE91SHOWSSOMEOFTHESEMETHODSFORMOREDETAILEDINFORMATIONABOUTTHEQUALITIESOFTHECURRENTFONTFOREXAMPLE,THELENGTHORHEIGHTOFGIVENCHARACTERS,YOUNEEDTOWORKWITHFONTMETRICSTHEFONTMETRICSCLASSDESCRIBESINFORMATIONSPECIFICTOAGIVENFONTTHELEADINGBETWEENLINES,THEHEIGHTANDWIDTHOFEACHCHARACTER,ANDSOONTOWORKWITHTHESESORTSOFVALUES,YOUCREATEAFONTMETRICSOBJECTBASEDONTHECURRENTFONTBYUSINGTHEAPPLETMETHODGETFONTMETRICSFONTFNEWFONT“TIMESROMAN”,FONTBOLD,36FONTMETRICSFMETRICSGETFONTMETRICSFGSETFONTFTABLE92SHOWSSOMEOFTHETHINGSYOUCANFINDOUTUSINGFONTMETRICSALLTHESEMETHODSSHOULDBECALLEDONAFONTMETRICSOBJECTCOLORDRAWINGBLACKLINESANDTESTSONAGRAYBACKGROUNDISALLVERYNICE,BUTBEINGABLETOUSEDIFFERENTCOLORSISMUCHNICERJAVAPROVIDESMETHODSANDBEHAVIORSFORDEALINGWITHCOLORINGENERALTHROUGHTHECOLORCLASS,ANDALSOPROVIDESMETHODSFORSETTINGTHECURRENTFOREGROUNDANDBACKGROUNDCOLORSSOTHATYOUCANDRAWWITHTHECOLORSYOUCREATEDJAVASABSTRACTCOLORMODELUSES24BITCOLOR,WHEREINACOLORISREPRESENTEDASACOMBINATIONOFRED,GREEN,ANDBLUEVALUESEACHCOMPONENTOFTHECOLORCANHAVEANUMBERBETWEEN0AND2550,0,0ISBLACK,255,255,255ISWHITE,ANDJAVACANREPRESENTMILLIONSOFCOLORSBETWEENASWELLJAVASABSTRACTCOLORMODELMAPSONTOTHECOLORMODELOFTHEPLATFORMJAVAISRUNNINGON,WHICHUSUALLYHASONLY256COLORSORFEWERFROMWHICHTOCHOOSEIFAREQUESTEDCOLORINACOLOROBJECTISNOTAVAILABLEFORDISPLAY,THERESULTINGCOLORMAYBEMAPPEDTOANOTHERORDITHERED,DEPENDINGONHOWTHEBROWSERVIEWINGTHECOLORIMPLEMENTEDIT,ANDDEPENDINGONTHEPLATFORMONWHICHYOURERUNNINGINOTHERWORDS,ALTHOUGHJAVAGIVESTHECAPABILITYOFMANAGINGMILLIONSOFCOLORS,VERYFEWMAYACTUALLYBEAVAILABLETOYOUINREALLIFEUSINGCOLOROBJECTSTODRAWANOBJECTINAPARTICULARCOLOR,YOUMUSTCREATEANINSTANCEOFTHECOLORCLASSTOREPRESENTTHATCOLORTHECOLORCLASSDEFINESASETOFSTANDARDCOLOROBJECTS,STOREDINCLASSVARIABLES,THATENABLEYOUQUICKLYTOGETACOLOROBJECTFORSOMEOFTHEMOREPOPULARCOLORSFOREXAMPLE,COLORREDGIVESYOUACOLOROBJECTREPRESENTINGREDRGBVALUESOF255,0,AND0,COLORWHITEGIVESYOUAWHITECOLORRGBVALUESOF255,255,AND255,ANDSOONTABLE93SHOWSTHESTANDARDCOLORSDEFINEDBYVARIABLESINTHECOLORCLASSIFTHECOLORYOUWANTTODRAWINISNOTONEOFTHESTANDARDCOLOROBJECTS,FEARNOTYOUCANCREATEACOLOROBJECTFORANYCOMBINATIONOFRED,GREEN,ANDBLUE,ASLONGASYOUHAVETHEVALUESOFTHECOLORYOUWANTJUSTCREATEANEWCOLOROBJECTCOLORCNEWCOLOR140,140,140THISLINEOFJAVACODECREATESACOLOROBJECTREPRESENTINGADARKGREYYOUCANUSEANYCOMBINATIONOFRED,GREEN,ANDBLUEVALUESTOCONSTRUCTACOLOROBJECTALTERNATIVELY,YOUCANALSOCREATEACOLOROBJECTUSINGTHREEFLOATSFROM00TO10COLORCNEWCOLOR034,10,025TESTINGANDSETTINGTHECURRENTCOLORSTODRAWANOBJECTORTEXTUSINGACOLOROBJECT,YOUHAVETOSETTHECURRENTCOLORTOBETHATCOLOROBJECT,JUSTASYOUHAVETOSETTHECURRENTFONTTOTHEFONTINWHICHYOUWANTTODRAWUSETHESETCOLORMETHODAMETHODFORGRAPHICSOBJECTSTODOTHISGSETCOLORCOLORGREENAFTERSETTINGTHECURRENTCOLOR,ALLDRAWINGOPERATIONSWILLOCCURINTHATCOLORINADDITIONTOSETTINGTHECURRENTCOLORFORTHEGRAPHICSCONTEXT,YOUCANALSOSETTHEBACKGROUNDANDFOREGROUNDCOLORSFORTHEAPPLETITSELFBYUSINGTHESETBACKGROUNDANDSETFOREGROUNDMETHODSBOTHOFTHESEMETHODSAREDEFINEDINTHEJAVAAWTCOMPONENTCLASS,WHICHAPPLETANDTHEREFOREYOURCLASSESAUTOMATICALLYINHERITSTHESETBACKGROUNDMETHODSETSTHEBACKGROUNDCOLOROFTHEAPPLET,WHICHISUSUALLYADARKGREYITTAKESASINGLEARGUMENT,ACOLOROBJECTSETBACKGROUNDCOLORWHITETHESETFOREGROUNDMETHODALSOTAKESASINGLECOLORASANARGUMENT,ANDAFFECTSEVERYTHINGTHATHASBEENDRAWNONTHEAPPLET,REGARDLESSOFTHECOLORINWHICHITHASBEENDRAWNYOUCANUSESETFOREGROUNDTOCHANGETHECOLOROFEVERYTHINGINTHEAPPLETATONCE,RATHERTHANHAVINGTOREDRAWEVERYTHINGSETFOREGROUNDCOLORBLACKINADDITIONTOTHESETCOLOR,SETFOREGROUND,ANDSETBACKGROUNDMETHODS,THEREARECORRESPONDING“GET”METHODSTHATENABLEYOUTORETRIEVETHECURRENTGRAPHICSCOLOR,BACKGROUND,ORFOREGROUNDTHOSEMETHODSAREGETCOLORDEFINEDINGRAPHICSOBJECTS,GETFOREGROUNDDEFINEDINAPPLET,ANDGETBACKGROUNDALSOINAPPLETYOUCANUSETHESEMETHODSTOCHOOSECOLORSBASEDONEXISTINGCOLORSINTHEAPPLETSETFOREGROUNDGGETCOLORASINGLECOLOREXAMPLELISTING94SHOWSTHECODEFORANAPPLETTHATFILLSTHEAPPLETSDRAWINGAREAWITHSQUAREBOXES,EACHOFWHICHHASARANDOMLYCHOSENCOLORINITITSWRITTENSOTHATITCANHANDLEANYSIZEOFAPPLETANDAUTOMATICALLYFILLTHEAREAWITHTHERIGHTNUMBEROFBOXESTHETWOFORLOOPSARETHEHEARTOFTHISEXAMPLETHEFIRSTONEDRAWSTHEROWS,ANDTHESECONDDRAWSTHEINDIVIDUALBOXESWITHINTHEROWWHENABOXISDRAWN,THERANDOMCOLORISCALCULATEDFIRST,ANDTHENTHEBOXISDRAWNABLACKOUTLINEISDRAWNAROUNDEACHBOX,BECAUSESOMEOFTHEMTENDTOBLENDINTOTHEBACKGROUNDOFTHEAPPLETBECAUSETHISPAINTMETHODGENERATESNEWCOLORSEACHTIMETHEAPPLETISPAINTED,YOUCANREGENERATETHECOLORSBYMOVINGTHEWINDOWAROUNDORBYCOVERINGTHEAPPLETSWINDOWWITHANOTHERONEFIGURE922SHOWSTHEFINALAPPLETALTHOUGHGIVENTHATTHISPICTUREISBLACKANDWHITE,YOUCANTGETTHEFULLEFFECTOFTHEMULTICOLOREDSQUARES中文翻译图形，字体和颜色GRAPHICS类在JAVA的图形处理能力帮助下，我们可以绘制线条，形状，字符及图像画面在你的APPLET小程序中。在JAVA中大部分的图形操作，是将方法定义到图形类中在中。你不需要为了在你的APPLET小程序中绘制某些东西而去创建一个GRAPHICSAPPLET小程序的PAINT（）方法的参数之一就是GRAPHICS对象。借助该对象，可以描绘你的APPLET小程序并把结果显示在屏幕上。GRAPHICS类是JAVAAWT包的一部分，因此APPLET小程序要进行绘图的话必须在你的JAVA文件的开始使用如下的IMPORT语句IMPORTJAVAAWTGRAPHICSPUBLICCLASSMYCLASSEXTENDEDJAVAAPPLETAPPLET图形坐标系统在屏幕上绘制一个对象，你可以通过调用GRAPHICS类中的一个绘图方法来完成。在APPLET小程序的坐标系统中，所有绘图方法都需要传入参数，它指出了所绘图像的起始点和终点的X，Y坐标。类如，一条线的起始点坐标为（10,10）和终点坐标为（20,20）。在JAVA坐标系统中，原点0,0位于APPLET小程序窗口的左上角。X值的正方向是0,0的右边，而Y坐标将沿着向下的方向增加。所有像素的值都是整数不能使用小数来显示整数之间的某些东西。图91显示了在图形坐标系统上可以绘出的一个简单的正方形。JAVA的坐标系统和许多程序的绘画和布局不同，X和Y在左下方。如果你没有用这种倒置式图形系统来工作过，则可能需要一些练习来熟悉它。绘图和填充GRAPHICS类为原始绘图提供了一套简单的内置式图形，其中包括线，矩形，多边形，椭圆形，弧线等。线DRAWLINE（）方法用于绘制两点之间的直线。方法有4个参数起始点的X和Y坐标，以及终点的X和Y坐标，如下所示PUBLICVOIDPAINTGRAPHICSGGDRAWLINE25,25,75,75图92显示了这个代码片段的的结果矩形在JAVA图形中，提供的矩形有三种而不只是一种一般的矩形；有圆角的矩形；用阴影绘制出来的三维立体矩形。对于每个矩形，你都有两个方法可以选择以轮廓形式绘制或者用当前颜色填充。为了绘制普通的矩形，使用用于轮廓的DRAWRECT（）方法和用于填充形状的FILLRECT（）方法。这些方法都有4个参数矩形的左上角的X和Y坐标；矩形的宽度；矩形的高度。例如下面是用PAINT（）方法绘制的两个矩形左边的是轮廓的类型的，右边的是被填充类型的。图93显示了结果带有圆角的矩形需要使用DRAWROUNDRECT（）和FILLROUNDRECT（）方法来绘制，他们的前4个参数和一般的矩形相似，但在末尾加入了两个参数，这两个参数定义了修正圆角区域的宽度和高度。第一个参数表示角的水平宽度，第二个参数表示角的垂直高度，当角的宽度和高度越大时，区域越大，则圆角越圆。若让这些参数值足够大，甚至可以让矩形看起来类似一个圆或椭圆。图94显示了一些圆角矩形的例子下面是用PAINT（）方法绘制出的两个圆角矩形一个是用10像素绘制的轮廓的类型的圆角矩形，另一个是用20像素绘制的被填充类型的圆角矩形。图95显示了矩形的结果PUBLICVOIDPAINTGRAPHICSGGDRAWROUNDRECT20,20,60,60,10,10GFILLROUNDRECT120,20,60,60,20,20最后，是第三种类型的立体矩形，这种矩形并不是真正的三维图形。相反的，它们由于阴影的影响，使得从表面上看来APPLET小程序上的矩形凸起或凹陷。三维立体矩形有前4个参数是X和Y的开始位置，矩形的宽度，矩形的高度。第五个参数是一个布尔类型的值来表明是否为三维效果，当为TRUE时图像凸起，当为FALSE时图像凹陷。对于其他的矩形，也有不同的方法来描绘或填充，比如DRAW3DRECT（）方法和FILL3DRECT（）方法。下面的代码产生了两个立体矩形的效果，左边的那个是凸起的，右边的是凹陷的。PUBLICVOIDPAINTGRAPHICSGGDRAW3DRECT20,20,60,60,TRUEGDRAW3DRECT120,20,60,60,FALSE图96显示出结果多边形多边形是一种由任意多个边连接组成的形状。要绘制一个多边形，你需要整一套的X、Y坐标和绘制方法，首先，画第一条线，然后画第二条线连接第一条线，再画第三条线连接第二条，像这样的一直画下去。作为一个矩形，你可以使用DRAWPOLYGON（）方法和FILLPOLYGON（）方法来绘制轮廓的类型的或是被填充类型的多边形。你也可以选择你想要两种方法去指定这些坐标把X、Y坐标作为整数数组对或者是作为POLYGON类的一个实例。用DRAWPOLYGON（）和FILLPOLYGON（）方法使用第一种方式需要传入三个参数一个保存X坐标的整数组，一个保存Y坐标的整数组和坐标点的总数。当然，数组中有着相同数量的X和Y。下面的例子就是用这种方法来绘制的一个轮廓型的多边形。（图97显示了结果）PUBLICVOIDPAINTGRAPHICSGINTEXES39,94,97,142,53,58,26INTWHYS33,74,36,70,108,80,106INTPTSEXESLENGTHGDRAWPOLYGONEXES,WHYS,PTS第二种方式是作为一个POLYGON对象去使用DRAWPOLYGON（）和FILLPOLYGON（）方法。如果你打算增加多边形的点或是正在构建一个不确定的多边形，那么POLYGON类将会是非常有用处的。POLYGON类能够让你将多边形视为一个对象，而不用处理个别的数组。创建一个多边形对象，您可以创建一个空的多边形POLYGONPOLYNEWPOLYGON或者像前面所说的，也可以用一组整数数组的点来创建一个多边形INTEXES39,94,97,142,53,58,26INTWHYS33,74,36,70,108,80,106INTPTSEXESLENGTHPOLYGONPOLYNEWPOLYGONEXES,WHYS,PTS一旦有了一个POLYGON对象，你就可以按照需要去把点添加进去POLYADDPOINT20,35那么，绘制多边形，只要使用POLYGON对象作为一个参数传入到DRAWPOLYGON（）或FILLPOLYGON（）方法中即可。这里有一个以往的例子，采用了这种方法被改写而且，多边形不是轮廓类型的而是被填充绘制的（图98显示了输出）PUBLICVOIDPAINTGRAPHICSGINTEXES39,94,97,142,53,58,26INTWHYS33,74,36,70,108,80,106INTPTSEXESLENGTHPOLYGONPOLYNEWPOLYGONEXES,WHYS,PTSGFILLPOLYGONPOLY复制和清除当你绘制出一些东西后，你可能想移动它们或是完全的清除APPLET小程序。GRAPHICS类提供一些方法可以完成这些事情。COPYAREA（）方法用来将窗口的矩形区域复制到窗口的另一个区域。COPYAREA（）方法有6个参数要复制的矩形区域的X，Y坐标；那个区域的宽度和高度；以像素为单位，在显示它的副本之前要从区域移开的水平和垂直距离。下面语句将一个100100的像素区域复制向右移动GCOPYAREA0,0,100,100,100,0CLEARRECT（）方法有和DRAWRECT（）和FILLRECT（）方法相同的4个参数，而且它用窗口的当前背景颜色填充矩形区域。如果希望清除整个窗口，可以通过SIZE（）方法来确定窗口大小，这将返回