Graphics_Objects[1].ppt

Chapter15 BasicFiguresColorsFontsandOtherTextDetails GraphicsObjects Earlierchaptersexplainhowtomakegraphicaluserinterfaces GUIs ThischapterexplainsadifferentwayofusinggraphicsinJava drawingpictures Wewilllearnhowtobasicfiguressuchaslines ovals andrectangles Basicfigurescanbecombinedtocreateelaboratepictures Anoptionalsectionexplainshowtodrawpolygons BasicFigures ScreenCoordinateSystem 0 0 origin Y coordinateispositiveandincreasinginthedownwarddirection X coordinateispositiveandincreasingtotheright Allcoordinatesarenormallypositive ScreenCoordinateSystem 100 75 0 0 origin X coordinate 100pixelsfromleftedgeofscreen Y coordinate 75pixelsfromtopedgeofscreen Locationofarectangleisspecifiedbycoordinatesofupperleftcorner ScreenCoordinateSystem 100 75 0 0 origin Locationofanovalisspecifiedbyatightlyfittingrectangle ThepaintMethod MostSwingandSwingrelatedcomponentshaveamethodnamedpaint Thepaintmethoddrawsthecomponentonthescreen Todrawbasicfiguressuchasovalsandrectangles youneedtoredefinethepaintmethod Thepaintmethodiscalledautomaticallyandshouldnotbeinvokedintheprogrammer scode publicvoidpaint Graphicsg super paint g g drawOval X FACE Y FACE FACE DIAMETER FACE DIAMETER DrawNose g fillOval X NOSE Y NOSE NOSE DIAMETER NOSE DIAMETER DrawEyes g fillOval X LEFT EYE Y LEFT EYE EYE WIDTH EYE HEIGHT g fillOval X RIGHT EYE Y RIGHT EYE EYE WIDTH EYE HEIGHT Draweyebrows g drawLine X1 LEFT BROW Y1 LEFT BROW X2 LEFT BROW Y2 LEFT BROW g drawLine X1 RIGHT BROW Y1 RIGHT BROW X2 RIGHT BROW Y2 RIGHT BROW DrawMouth g drawArc X MOUTH Y MOUTH MOUTH WIDTH MOUTH HEIGHT MOUTH START ANGLE MOUTH ARC SWEEP ThecompletepaintmethodfromMadeleine java Theprogramdrawsthispicture publicvoidpaint Graphicsg super paint g g drawOval X FACE Y FACE FACE DIAMETER FACE DIAMETER DrawNose g fillOval X NOSE Y NOSE NOSE DIAMETER NOSE DIAMETER DrawEyes g fillOval X LEFT EYE Y LEFT EYE EYE WIDTH EYE HEIGHT g fillOval X RIGHT EYE Y RIGHT EYE EYE WIDTH EYE HEIGHT Draweyebrows g drawLine X1 LEFT BROW Y1 LEFT BROW X2 LEFT BROW Y2 LEFT BROW g drawLine X1 RIGHT BROW Y1 RIGHT BROW X2 RIGHT BROW Y2 RIGHT BROW DrawMouth g drawArc X MOUTH Y MOUTH MOUTH WIDTH MOUTH HEIGHT MOUTH START ANGLE MOUTH ARC SWEEP Theface nose andeyesareovals Theeyebrowsarelines andthemouthisanarc Themethodfordrawingeachshapehasnumericparameterstellingwheretodrawtheshapeandhowbigtomakeit publicvoidpaint Graphicsg super paint g g drawOval X FACE Y FACE FACE DIAMETER FACE DIAMETER DrawNose g fillOval X NOSE Y NOSE NOSE DIAMETER NOSE DIAMETER DrawEyes g fillOval X LEFT EYE Y LEFT EYE EYE WIDTH EYE HEIGHT g fillOval X RIGHT EYE Y RIGHT EYE EYE WIDTH EYE HEIGHT Draweyebrows g drawLine X1 LEFT BROW Y1 LEFT BROW X2 LEFT BROW Y2 LEFT BROW g drawLine X1 RIGHT BROW Y1 RIGHT BROW X2 RIGHT BROW Y2 RIGHT BROW DrawMouth g drawArc X MOUTH Y MOUTH MOUTH WIDTH MOUTH HEIGHT MOUTH START ANGLE MOUTH ARC SWEEP Thepaintmethodreceivesoneparameter whichisanobjectoftheGraphicsclass TheGraphicsparameteristhecallingobjectforallofthemethodsthatdrawlinesandshapes Callingthepaintmethodoftheparentclassisagoodprogrammingpractice TheGraphicsclass ContainsmethodsusedtodrawbasicshapesandlinesIspartoftheAWTpackage orlibrary sotheAWTmustbeimported importjava awt Mostmethodsforpaintingshapeshavetwoversions AdrawversionwhichonlydrawstheoutlineoftheshapedrawOvalAfillversionwhichfillsintheshapefillOval DrawingRectanglesandOvals 100 120 0 0 g fillOval 100 120 40 20 100 50 width height 40 20 Graphicsobject 20 40 g fillRect 100 50 40 20 XandYcoordinatesofupperleftcorner DrawingArcs Anarcisspecifiedbygivinganovalandthenspecifyingwhatportionoftheovalwillbeusedforthearc Totellwhichpartoftheovalwillbeused specifythebeginningangleandthedegreesofthesweep positivedirection 0degrees width height x y gdrawArc x y width height 0 360 ArcExamples positivedirection 0degrees negativedirection 0degrees 180degrees gdrawArc x y width height 0 90 gdrawArc x y width height 0 360 gdrawArc x y width height 0 90 gdrawArc x y width height 180 90 plus90degrees RoundRectangles Roundrectangleisarectanglewherecornershavebeenreplacedwitharcs Specifybygivingrectangleinformationandthenheightandwidthofcornerarcs arcWidth width height x y gdrawRoundRect x y width height arcWidth arcHeight arcHeight Polygons drawPolygonallowsaprogramtodrawshapeswithanynumberofsides publicvoiddrawPolygon int x int y intpoint Eachpointinthepolygonwillhaveanxcoordinatefromthefirstparameterandaycoordinatefromthecorrespondingelementofthesecondparameter Thethirdparametertellshowmanypointsthepolygonwillhave Alwaysdrawsaclosedpolygon Iffirstandlastpointsarenotequal drawsalinefromlasttofirst drawPolylineissimilarbutcandrawanopenfigure fillPolygonissimilarbutfillswithcolorinsteadofdrawingoutline ActionDrawingsandrepaint TheSadMadeleineprogramdemonstrateshowaprogramcanchangeapicture Intheoriginalpicture thefacehasafrown Whentheuserclicksonthebutton thepicturechangestoasmilingfaceandmovesuponthescreen ActionDrawingsandrepaint TheactionPerformedmethodchangesthesmilevariablethatthepaintmethoduses Whenthesmilevariableischangedtotrue thepaintmethodknowstodrawasmileinsteadofafrown publicvoidactionPerformed ActionEvente if e getActionCommand equals ClickforaSmile smile true elseSystem out println Errorinbuttoninterface repaint ActionDrawingsandrepaint Unlesstherepaintmethodiscalled thechangewillnotbeshownonscreen Therepaintmethodcallspainttoupdatethepicture Thepaintmethdshouldnotbecalleddirectly publicvoidactionPerformed ActionEvente if e getActionCommand equals ClickforaSmile smile true elseSystem out println Errorinbuttoninterface repaint Colors DrawandfillmethodslikefillOvalwillusethecurrentcolor YoucanusethesetColormethodofaGraphicsobjecttochangethecurrentcolor TodrawaredmouthyoucouldchangethepaintmethodoftheMadeleineprogramtoincludetheselines DrawMouth g setColor Color red g drawArc X MOUTH Y MOUTH MOUTH WIDTH MOUTH HEIGHT MOUTH START ANGLE MOUTH ARC SWEEP DefiningColors TheColorclassmixesamountsofred green andbluetoproduceanewcolor Sincecolorsaremadebycombingdifferentamountsofred green andblue thisiscalledtheRGBcolorsystem TheparameterstotheColorconstructormustbetypeintorfloat WhenintegersareusedasparameterstotheColorconstructortheyshouldbeintherange0to255 WhenfloatsareusedasparameterstotheColorconstructortheyshouldbeintherange0 0to1 0 FontsandOtherTextDetails Afontisastyleoftext Ap