Lec26 Notes
2
ProgrammingII,FirstSemester2011 Lecture26Notes–MoreaboutInterfaces Lookatthesolutiontotheclassexercisefromthelastlecture.Inthisexercise,wehada Drawableinterface(shownbelow),andwecreatedtwoclasses,a RectangleandaTriangle, thatbothimplementthisinterface.Wehadanappletclass, Picture,thatcreatedanarrayof Drawables.Initsinit()method,the PictureappletcreatedtwoTriangleobjectsandone Rectangleobject,andputthemallinthearrayof Drawables.Thepaint()methodof Picture thensteppedthroughthearra ytodrawalltheitems.Se ethejavacodeforthesolutionstothe classexercisefordetailsoftheseclasses. Intoday’slesson,we extend theDrawableinterfacetocreateanewinterfacecalled ColoredDrawable.TheColoredDrawableinterfacespecifiesanewmethod,setColor(),that ismeanttospecifythecolorthattheobjectshouldbedrawnwith.ThesetColormethodtakes asanargument,anobjectoftype Color,whichisapredefinedclassinJava.Tousethisclass, weneedtoimportjava.awt.Color.Formoreinformationonthe Colorclass,see http://docs.oracle.com/javase/6/docs/api/java/awt/Color.html
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Transcript of Lec26 Notes
ProgrammingII,FirstSemester2011
Lecture26Notes–MoreaboutInterfaces
Lookatthesolutiontotheclassexercisefromthelastlecture.Inthisexercise,wehada
Drawableinterface(shownbelow),andwecreatedtwoclasses,aRectangleandaTriangle,
thatbothimplementthisinterface.Wehadanappletclass,Picture,thatcreatedanarrayof
Drawables.Initsinit()method,thePictureappletcreatedtwoTriangleobjectsandone
Rectangleobject,andputthemallinthearrayofDrawables.Thepaint()methodofPicture
thensteppedthroughthearraytodrawalltheitems.Seethejavacodeforthesolutionstothe
classexercisefordetailsoftheseclasses.
Intoday’slesson,weextend theDrawableinterfacetocreateanewinterfacecalled
ColoredDrawable.TheColoredDrawableinterfacespecifiesanewmethod,setColor(),that
ismeanttospecifythecolorthattheobjectshouldbedrawnwith.ThesetColormethodtakes
asanargument,anobjectoftypeColor,whichisapredefinedclassinJava.Tousethisclass,
weneedtoimportjava.awt.Color.FormoreinformationontheColorclass,see
http://docs.oracle.com/javase/6/docs/api/java/awt/Color.html
WechosetousetheColorclassastheargumenttooursetColor()methodinthe
ColoredDrawableinterfacebecausetheGraphicsclass(whichiswhattheappletusesto
paintitself)hasamethodcalledsetColorthatrequiresaColorobjectasanargument.Thus,if
wehaveaColorobject,wecanuseittodrawanitemwithaparticularcolor.
NotethatbecausetheColoredDrawableinterfaceextendstheDrawableinterface,anyclass
thatimplementstheColoredDrawableinterfacemustimplementthedrawWithText()and
drawWithGraphics()methodsoftheDrawableinterface,aswellasthesetColor()methodof
theColoredDrawableinterface.
WecreateaclasscalledColoredRectangle1thatimplementstheColoredDrawableinterface.
Thatis,itprovidesbodiesforthedrawWithText(),drawWithGraphics(),andsetColor()
methods.NotethattheconstructoroftheColoredRectangle1classcallsitssetColormethod
tosetitsdefaultcolortored.Itdoesthisusingthestatement:
setColor(Color.RED)
Color.REDisaconstantdeclaredintheColorclass.BelowisascreenshotfromtheJavaAPI
pagefortheclassColor:
Lastly,wemodifiedthePictureapplettocreateanarraythatholdsaRectangle,a
ColoredRectangle,andaTriangle.Thisistheresultwhentheappletisrun:
