java语言程序设计-基础篇--原书第八版--课件-PPT(第十二章).ppt

1 Chapter12GUIBasics 2 Motivations ThedesignoftheAPIforJavaGUIprogrammingisanexcellentexampleofhowtheobject orientedprincipleisapplied Inthechaptersthatfollow youwilllearntheframeworkofJavaGUIAPIandusetheGUIcomponentstodevelopuser friendlyinterfacesforapplicationsandapplets 3 Objectives TodistinguishbetweenSwingandAWT 12 2 TodescribetheJavaGUIAPIhierarchy 12 3 Tocreateuserinterfacesusingframes panels andsimpleGUIcomponents 12 4 Tounderstandtheroleoflayoutmanagers 12 5 TousetheFlowLayout GridLayout andBorderLayoutmanagerstolayoutcomponentsinacontainer 12 5 TouseJPanelassubcontainers 12 7 TospecifycolorsandfontsusingtheColorandFontclasses 12 7 12 8 Toapplycommonfeaturessuchasborders tooltips fonts andcolorsonSwingcomponents 12 9 Touseborderstovisuallygroupuser interfacecomponents 12 9 TocreateimageiconsusingtheImageIconclass 12 10 4 CreatingGUIObjects CreateabuttonwithtextOKJButtonjbtOK newJButton OK Createalabelwithtext Enteryourname JLabeljlblName newJLabel Enteryourname Createatextfieldwithtext TypeNameHere JTextFieldjtfName newJTextField TypeNameHere CreateacheckboxwithtextboldJCheckBoxjchkBold newJCheckBox Bold CreatearadiobuttonwithtextredJRadioButtonjrbRed newJRadioButton Red Createacomboboxwithchoicesred green andblueJComboBoxjcboColor newJComboBox newString Red Green Blue Button Label Textfield CheckBox RadioButton ComboBox 5 Swingvs AWT SowhydotheGUIcomponentclasseshaveaprefixJ InsteadofJButton whynotnameitsimplyButton Infact thereisaclassalreadynamedButtoninthejava awtpackage WhenJavawasintroduced theGUIclasseswerebundledinalibraryknownastheAbstractWindowsToolkit AWT ForeveryplatformonwhichJavaruns theAWTcomponentsareautomaticallymappedtotheplatform specificcomponentsthroughtheirrespectiveagents knownaspeers AWTisfinefordevelopingsimplegraphicaluserinterfaces butnotfordevelopingcomprehensiveGUIprojects Besides AWTispronetoplatform specificbugsbecauseitspeer basedapproachreliesheavilyontheunderlyingplatform WiththereleaseofJava2 theAWTuser interfacecomponentswerereplacedbyamorerobust versatile andflexiblelibraryknownasSwingcomponents SwingcomponentsarepainteddirectlyoncanvasesusingJavacode exceptforcomponentsthataresubclassesofjava awt Windoworjava awt Panel whichmustbedrawnusingnativeGUIonaspecificplatform SwingcomponentsarelessdependentonthetargetplatformanduselessofthenativeGUIresource Forthisreason Swingcomponentsthatdon trelyonnativeGUIarereferredtoaslightweightcomponents andAWTcomponentsarereferredtoasheavyweightcomponents 6 GUIClassHierarchy Swing 7 ContainerClasses ContainerclassescancontainotherGUIcomponents 8 ThehelperclassesarenotsubclassesofComponent TheyareusedtodescribethepropertiesofGUIcomponentssuchasgraphicscontext colors fonts anddimension GUIHelperClasses 9 SwingGUIComponents 10 ComponentsCoveredintheBriefVersion 11 ComponentsCoveredintheComprehensiveVersion 12 AWT Optional 13 Frames Frameisawindowthatisnotcontainedinsideanotherwindow FrameisthebasistocontainotheruserinterfacecomponentsinJavaGUIapplications TheJFrameclasscanbeusedtocreatewindows ForSwingGUIprograms useJFrameclasstocreatewidows 14 CreatingFrames Run importjavax swing publicclassMyFrame publicstaticvoidmain String args JFrameframe newJFrame TestFrame frame setSize 400 300 frame setVisible true frame setDefaultCloseOperation JFrame EXIT ON CLOSE MyFrame 15 AddingComponentsintoaFrame Addabuttonintotheframeframe getContentPane add newJButton OK Run MyFrameWithComponents Titlebar Contentpane 16 ContentPaneDelegationinJDK1 5 Addabuttonintotheframeframe getContentPane add newJButton OK Titlebar Contentpane Addabuttonintotheframeframe add newJButton OK 17 JFrameClass 18 LayoutManagers Java slayoutmanagersprovidealevelofabstractiontoautomaticallymapyouruserinterfaceonallwindowsystems TheUIcomponentsareplacedincontainers EachcontainerhasalayoutmanagertoarrangetheUIcomponentswithinthecontainer LayoutmanagersaresetincontainersusingthesetLayout LayoutManager methodinacontainer 19 KindsofLayoutManagers FlowLayout Chapter13 GridLayout Chapter13 BorderLayout Chapter13 SeveralotherlayoutmanagerswillbeintroducedinChapter33 Containers LayoutManagers andBorders 20 FlowLayoutExample WriteaprogramthataddsthreelabelsandtextfieldsintothecontentpaneofaframewithaFlowLayoutmanager ShowFlowLayout Run 21 TheFlowLayoutClass 22 GridLayoutExample RewritetheprogramintheprecedingexampleusingaGridLayoutmanagerinsteadofaFlowLayoutmanagertodisplaythelabelsandtextfields ShowGridLayout Run 23 TheGridLayoutClass 24 TheBorderLayoutManager TheBorderLayoutmanagerdividesthecontainerintofiveareas East South West North andCenter ComponentsareaddedtoaBorderLayoutbyusingtheaddmethod add Component constraint whereconstraintisBorderLayout EAST BorderLayout SOUTH BorderLayout WEST BorderLayout NORTH orBorderLayout CENTER 25 BorderLayoutExample ShowBorderLayout Run 26 TheBorderLayoutClass 27 TheColorClass YoucansetcolorsforGUIcomponentsbyusingthejava awt Colorclass Colorsaremadeofred green andbluecomponents eachofwhichisrepresentedbyabytevaluethatdescribesitsintensity rangingfrom0 darkestshade to255 lightestshade ThisisknownastheRGBmodel Colorc newColor r g b r g andbspecifyacolorbyitsred green andbluecomponents Example Colorc newColor 228 100 255 28 StandardColors Thirteenstandardcolors black blue cyan darkGray gray green lightGray magenta orange pink red white yellow aredefinedasconstantsinjava awt Color Thestandardcolornamesareconstants buttheyarenamedasvariableswithlowercaseforthefirstwordanduppercaseforthefirstlettersofsubsequentwords ThusthecolornamesviolatetheJavanamingconvention SinceJDK1 4 youcanalsousethenewconstants BLACK BLUE CYAN DARK GRAY GRAY GREEN LIGHT GRAY MAGENTA ORANGE PINK RED WHITE andYELLOW 29 SettingColors Youcanusethefollowingmethodstosetthecomponent sbackgroundandforegroundcolors setBackground Colorc setForeground Colorc Example jbt setBackground Color yellow jbt setForeground Color red 30 TheFontClass FontmyFont newFont name style size Example FontmyFont newFont SansSerif Font BOLD 16 FontmyFont newFont Serif Font BOLD Font ITALIC 12 JButtonjbtOK newJButton OK jbtOK setFont myFont FontNamesStandardfontnamesthataresupportedinallplatformsare SansSerif Serif Monospaced Dialog orDialogInput FontStyleFont PLAIN 0 Font BOLD 1 Font ITALIC 2 andFont BOLD Font ITALIC 3 31 FindingAllAvailableFontNames GraphicsEnvironmente GraphicsEnvironment getLocalGraphicsEnvironment String fontnames e getAvailableFontFamilyNames for inti 0 i fontnames length i System out println fontnames i 32 UsingPanelsasSub Containers Panelsactassub containersforgroupinguserinterfacecomponents Itisrecommendedthatyouplacetheuserinterfacecomponentsinpanelsandplacethepanelsinaframe Youcanalsoplacepanelsinapanel ToaddacomponenttoJFrame youactuallyaddittothecontentpaneofJFrame Toaddacomponenttoapanel youadditdirectlytothepanelusingtheaddmethod 33 CreatingaJPanel YoucanusenewJPanel tocreateapanelwithadefaultFlowLayoutmanagerornewJPanel LayoutManager tocreateapanelwiththespecifiedlayoutmanager Usetheadd Component methodtoaddacomponenttothepanel Forexample JPanelp newJPanel p add newJButton OK 34 TestingPanelsExample Thisexampleusespanelstoorganizecomponents TheprogramcreatesauserinterfaceforaMicrowaveoven TestPanels Run 35 CommonFeaturesofSwingComponents 36 Borders YoucansetaborderonanyobjectoftheJComponentclass Swinghasseveraltypesofborders Tocreateatitledborder usenewTitledBorder Stringtitle Tocreatealineborder usenewLineBorder Colorcolor intwidth wherewidthspecifiesthethicknessoftheline Forexample thefollowingcodedisplaysatitledborderonapanel JPanelpanel newJPanel panel setBorder newTitleBorder MyPanel 37 TestSwingCommonFeatures ComponentProp