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GUIProgramming

CMSC202

WhyJavaGUIDevelopment?

• A>erallCMSC202isisaboutObjectOrientedProgramming,notGUIs • GUIsareagoodexampleofOOP• GUIsareanotherexampleofcontainers

JavaandGUIs

• Therearetwoprimarybuilt-inpackagesthatprovideGUIcomponentsinJava - java.awt.*- java.swing.* • TheAbstractWindowToolkit(AWT) - Java'soriginalGUItoolkit- LeveragesnaSvetoolkitstodrawwidgets • Swing - Offersamorecompletesetofwidgets- SystemorJavalookandfeel- LeveragesAWTthroughoutAPIs

Containers

• InJava,allGUIcomponentsgointoaContainer-whichissimplyawidgetthatcancontainotherwidgets • Atop-levelcontainercanstandaloneina windowenvironment - e.g.JFrame • Somecontainersmayonlybeaddedtoother containers - e.g.JPanel

Components

• AcomponentissimplyanobjectthathasagraphicalrepresentaSonthatcanbedisplayedonscreen • Acomponentactsasabaseclassforallswing components,excepttoplevelcontainers • Examplesofcomponentsinclude: - JBuYon,JComboBox,JLabel,JList,JMenuBar,

JPanel,JSlider,JSpinner,JTable,etc...

JFrame

• AJFrameiso>enthehighest-levelwidgetinyourapplicaSoninwhichallotherwidgetswillgetpacked • JFramesareusuallyconstructedusingthe followingconstructor: public JFrame(String title);

CommonJFrameMethods

• add(Componentc) - addsobjectstotheframe • setVisible(booleanb) - makestheframevisible • setLocaSon(intx,inty) - alignstople>cornerofframewithcoordinatesonscreen • setSize(intwidth,intheight) - setssizeofframeinpixels • setDefaultCloseOperaSon(intoperaSon) - defineswhatshouldhappenwhenthewindowisclosed,

JFrameExample

import javax.swing.JFrame;!import javax.swing.WindowConstants;!!public class UpperCaseConverter extends JFrame {!!"public UpperCaseConverter() {!""super("Upper Case Converter");!""setLocation(100, 100);!""setSize(480, 320);!""setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);!"}!!"public static void main(String[] args) {!""UpperCaseConverter ucc = new UpperCaseConverter();!""ucc.setVisible(true);!"}!!}

JFrameExample

LayoutManagers

• EverycontainerhasanunderlyingdefaultLayoutManager • TheLayoutManagerdetermines: - Thesizeoftheobjectsinthecontainerand- Howtheobjectswillbelaidout • ThedefaultLayoutManagerforaJFrameisa

BorderLayout

BorderLayout

• TheBorderLayoutmanagerdividescontainerintofiveregions - BorderLayout.NORTH- BorderLayout.SOUTH- BorderLayout.CENTER- BorderLayout.EAST- BorderLayout.WEST

• Onecomponentperregion• Componenttakessizeofregion• Centerregionisgreedy• Componentsareaddedtocenterbydefault

JBuYon

• AJBuYonprovidesabasicbuYonthatausercaninteractwith • AJBuYonmayconsistofacombinaSonoflabel - JBuYon(Iconicon) • CreatesabuYonwithanicon - JBuYon(Stringtext) • CreatesabuYonwithtext - JBuYon(Stringtext,Iconicon) • CreatesabuYonwithiniSaltextandanicon

BorderLayoutExample

import java.awt.BorderLayout;!!import javax.swing.JButton;!import javax.swing.JFrame;!!public class BorderLayoutExample extends JFrame {!"! public BorderLayoutExample(String name) {! super(name);! setSize(300, 300);! add(new JButton("North"), BorderLayout.NORTH);! add(new JButton("South"), BorderLayout.SOUTH);! add(new JButton("East"), BorderLayout.EAST);! add(new JButton("West"), BorderLayout.WEST);! add(new JButton("Center"), BorderLayout.CENTER);! }! public static void main(String args[]) {! BorderLayoutExample b = new BorderLayoutExample("BorderLayoutExample");! b.setVisible(true);! }!}

BorderLayoutExample

JPanel

• SaywewanttoputseveralbuYonsintheNorthregionoftheGUI,butBorderLayoutonlyallowsonecomponentperregion...

• AddasecondlevelcontainerlikeaJPanel• JPanelshaveaFlowLayoutmanagerbydefault

FlowLayout

• LayscomponentsinafluiddirecSonasdeterminedbyitsorientaSon • Bydefault,orientaSonisL→R,T→B• PossibletosetthehorizontalandverScal widthbetweencomponents • Componentstakepreferredsize - ForbuYons,preferredsizeisthesizeofthetext withinthem

FlowLayout

// ...!"!public UpperCaseConverter() {!! // code from previous slides ...!"!"JPanel topPanel = new JPanel();!"JButton upperButton = new JButton("To Upper");!"JButton clearButton = new JButton("Clear");!"topPanel.add(upperButton);!"topPanel.add(clearButton);!"add(topPanel, BorderLayout.NORTH);!}!!// ...

FlowLayout

JLabel

• TheJLabelrepresentsastaSclabel • LikebuYons,theycanconsistoftextand/orimagesandare - JLabel() • CreatesaJLabelinstancewithnoimageandwithanemptystringfor theStle. - JLabel(Iconimage) • CreatesaJLabelinstancewiththespecifiedimage. - JLabel(Stringtext) • CreatesaJLabelinstancewiththespecifiedtext. - JLabel(Stringtext,Iconicon,inthorizontalAlignment) • CreatesaJLabelinstancewiththespecifiedtext,image,and horizontalalignment

JTextField

• AJTextFieldprovidesanentryforasinglelineoftext • AJTextFieldmaybeconstructedwithasetwidthorwith - JTextField() • ConstructsanewTextField - JTextField(intcolumns) • ConstructsanewemptyTextFieldwiththespecifiednumberof columns - JTextField(Stringtext) • ConstructsanewTextFieldiniSalizedwiththespecifiedtext - JTextField(Stringtext,intcolumns) • ConstructsanewTextFieldiniSalizedwiththespecifiedtextand columns

OverridingaPanel'sLayoutManager

• Youcanalsoover-ridethelayoutmanagerformostcontainers • Forexample,wecanchangeaJPanel'slayout

OverridingaPanel'sLayoutManager

// ...!"!public UpperCaseConverter() {!!"// code from previous slides ...!!"JPanel bottomPanel = new JPanel();!"bottomPanel.setLayout(new BorderLayout());!"JLabel enterTextLabel = new JLabel("Enter text: ");!"JTextField textField = new JTextField(20);!"bottomPanel.add(enterTextLabel, BorderLayout.WEST);!"bottomPanel.add(textField, BorderLayout.CENTER);!"add(bottomPanel, BorderLayout.SOUTH);!}!!// ...!

OverridingaPanel'sLayoutManager

JTextArea

• AJTextAreaissimilartoaJTextField,exceptthatitiscapableofdisplayingmulSplelinesoftext • AJTextAreacanbeconstructedwithagivensizeand/or - JTextArea() • ConstructsanewTextArea. - JTextArea(introws,intcolumns) • ConstructsanewemptyTextAreawiththespecifiednumberofrows andcolumns. - JTextArea(Stringtext) • ConstructsanewTextAreawiththespecifiedtextdisplayed. - JTextArea(Stringtext,introws,intcolumns) • ConstructsanewTextAreawiththespecifiedtextandnumberof rowsandcolumns.

JTextArea

// ...!"!public UpperCaseConverter() {!!"// code from previous slides ...!!"JTextArea textArea = new JTextArea();!"textArea.setEditable(false);!"add(textArea, BorderLayout.CENTER);!}!!// ...!

JTextArea

RespondingtoAcSons

• CurrentlyourbuYondoesn'tdoanythingwhenpressed,torespondtothisacSonweneedtoaddanAcSonListener • AnAcSonListenercanbeaddedtoabuYonusing thefollowingmethod: - publicvoidaddAcSonListener(AcSonListenerl); • TheAcSonListenerinterfaceisquitesimple,in - voidacSonPerformed(AcSonEvente)

LejngourclassimplementAcSonListener

• OneapproachtoimplemenSnganAcSonListeneristohave"this"classimplementit button.addActionListener(this); • AnotherapproachistoactuallydefineaninlineanonymousclasstohandletheacSons • Theclassisconsideredinlineasitisdeclared inthecontextofanotherclass • Itisalsoconsideredanonymous,asthenew classisnotgivenaname

SimpleAcSonListeners

// ...!"!public UpperCaseConverter() {!!"// code from previous slides ...!"upperButton.addActionListener(new ActionListener() {!""public void actionPerformed(ActionEvent e) {!"""System.out.println("button pressed");!""}!"});"!"clearButton.addActionListener(new ActionListener() {!""public void actionPerformed(ActionEvent e) {!"""System.out.println("button pressed");!""}!"});!}!!// ...!

ManipulaSngWidgets

• RatherthansimplyprinSng"buYonpressed"let'smodifyourAcSonListenertoreadthevalueoftheJTextFieldandwritetotheJTextArea

• Assuchwe'regoingtoneedtoreferencesto thosewidgets - wehave2opSons - Storethewidgetsasmembersoftheclass- Markthewidgetreferencesasfinal

MoreInteresSngAcSonListeners

// ...!"!public UpperCaseConverter() {!!"// code from previous slides...!"// with upperButton and clearButton declared final!!"upperButton.addActionListener(new ActionListener() {!""public void actionPerformed(ActionEvent e) {!"""textArea.setText(textField.getText().toUpperCase());!""}!"});!"!"clearButton.addActionListener(new ActionListener() {!""public void actionPerformed(ActionEvent e) {!"""textArea.setText("");!"""textField.setText("");!"""textField.requestFocus();!""}!"});!}!// ...!

MoreInteresSngAcSonListeners

LookandFeel

• Bydefault,JavausesitsownLookandFeel • Ifyou'dliketousethenaSvelookandfeelfor

try {!"UIManager.setLookAndFeel(!""UIManager.getSystemLookAndFeelClassName()!");!} catch (Exception e) {!"// handle or ignore!}

ScratchingtheSurface

• Whatwe'velookedathereisreallyjusttheSpoftheiceberg,therealottoswing • Someselectedreferences...

- AVisualGuidetoLayoutManagers- SwingFeatures- AVisualGuidetoSwingComponents- Trail:CreaSngaGUIWithJFC/Swing

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