JavaHTP6e_11.ppt

8/8/2019 JavaHTP6e_11.ppt

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© 2005 Pearson Education, Inc. All rights reserved.

11

11

GUI Components:

Part


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© 2005 Pearson Education Inc. All rights reserved.

Do you think I can listen all day to such stuff?

! Lewis Carroll

Even a minor event in the life of a child is an event

of that child’ s world and thus a world event.

! Gaston Bachelard

You pays your money and you takes your choice.

! Punch

Guess if you can, choose if you dare.! Pierre Corneille


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OBJECTIVES

In this chapter "ou #ill learn: $he design principles o% graphical user inter%aces

&GUIs'.

$o (uild GUIs and handle events generated ("user interactions #ith GUIs.

$o understand the pac)ages containing GUIcomponents, event*handling classes andinter%aces.

$o create and manipulate (uttons, la(els, lists,

te+t %ields and panels.

$o handle mouse events and )e"(oard events.

$o use la"out managers to arrange GUIcomponents


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11.1 Introduction

11.2 Simple GUI-Based Input/Output it! JOptionPane

11." O#er#ie o$ Sin% Components

11.& 'ispla(in% Te)t and Ima%es in a *indo

11.+ Te)t ,ields and an Introduction to E#ent andlin% it!ested Classes

11. Common GUI E#ent T(pes and 0istener Inter$aces

11. o E#ent andlin% *ors11.3 JButton

11.4 Buttons T!at 5aintain State

11.4.1 JCheckBox

11.4.2 JRadioButton

11.16 JComboBox and Usin% an 7non(mous Inner Class $or E#entandlin%


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11.11 JList

11.12 5ultiple-Selection 0ists

11.1" 5ouse E#ent andlin%11.1& 7dapter Classes

11.1+ JPanel Su8lcass $or 'rain% it! t!e 5ouse

11.1 9e(-E#ent andlin%

11.1 0a(out 5ana%ers11.1.1 FlowLayout

11.1.2 BorderLayout

11.1." GridLayout

11.13 Usin% :anels to 5ana%e 5ore Comple) 0a(outs

11.14 JTextrea

11.26 *rap-Up


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11.1 Introduction

• Graphical user interface (GUI) Presents a user-friendly mechanism for interacting with an

application

Often contains title ar! menu ar containing menus!

uttons and como o"es Built from GUI components


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0oo-and-,eel O8ser#ation 11.1

Consistent user interfaces enale a user to learnnew applications faster#


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,i%. 11.1 ; Internet E)plorer indo it! GUI components.

(utton menus title (ar menu (ar com(o (o+

scroll

(ars


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11.2 Simple GUI-Based Input/Output it!

JOptionPane

• $ialog o"es Used y applications to interact with the user

Pro%ided y &a%a's JOptionPane class

• Contains input dialogs and message dialogs


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© 2005 Pearson Education,Inc. All rights reserved.

-utline

ddition!"a#a

(1 of 2)

Show input dialog to receive first

integer

Show input dialog to receive

second integer

Show message dialog to output sum

to user


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ddition!"a#a

(2 of 2)

Input dialog displa"ed (" lines 0

Input dialog displa"ed (" lines 2

/essage dialog displa"ed (" lines 22 2

$e+t %ield in #hich

the user t"pes a

value

Prompt to the user

hen the user clic)s O9, show$nput%ialo&

returns to the program

the 166 t"ped (" theuser as a 'trin&. $heprogram must convert

the 'trin& to an int

title (ar

hen the user clic)s O9, the message dialog is dismissed

&removed %rom the

screen'


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he prompt in an input dialog typically usessentence-style capitaliation a style that

capitali*es only the first letter of the first wordin the te"t unless the word is a proper noun (fore"ample! $eitel)#


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0oo-and-,eel O8ser#ation 11."

he title ar of a window typically uses !ook-titlecapitaliation a style that capitali*es the firstletter of each significant word in the te"t anddoes not end with any punctuation (for e"ample!Capitali*ation in a Boo+ itle)#


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,i%. 11." ; JOptionPane static constants $or messa%e dialo%s.

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11." O#er#ie o$ Sin% Components

• ,wing GUI components $eclared in pac+age javax.swing

ost are pure &a%a components

Part of the &a%a .oundation Classes (&.C)

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,i%. 11.& ; Some 8asic GUI components.

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Sin% #s. 7*T

• /stract 0indow ool+it (/0) Precursor to ,wing

$eclared in pac+age java.awt

$oes not pro%ide consistent! cross-platform loo+-and-feel

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:orta8ilit( Tip 11.1

,wing components are implemented in &a%a! sothey are more portale and fle"ile than theoriginal &a%a GUI components from pac+age

"a#a!awt! which were ased on the GUIcomponents of the underlying platform# .or thisreason! ,wing GUI components are generallypreferred#

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0i%!tei%!t #s. ea#(ei%!t GUI

Components

• Lightweight components 1ot tied directly to GUI components supported y

underlying platform

• 2ea%yweight components

ied directly to the local platform

/0 components

,ome ,wing components

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0oo-and-,eel O8ser#ation 11.&

he loo+ and feel of a GUI defined withhea%yweight GUI components from pac+age"a#a!awt may %ary across platforms# Becausehea%yweight components are tied to the local-platform GUI! the loo+ and feel %aries fromplatform to platform#

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Superclasses o$ Sin%


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So$tare En%ineerin% O8ser#ation 11.1

,tudy the attriutes and eha%iors of the classesin the class hierarchy of .ig# 33#4# hese classesdeclare the features that are common to most

,wing components#

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,i%. 11.+ ; Common superclasses o$ man( o$ t!e Sin% components.

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Superclasses o$ Sin%


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11.& 'ispla(in% Te)t and Ima%es in a

*indo

• Class JFrame ost windows are an instance or suclass of this class

Pro%ides title ar

Pro%ides uttons to minimi*e! ma"imi*e and close the

application

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0a8elin% GUI Components

• Lael e"t instructions or information stating the purpose of

each component

Created with class JLabel

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0oo-and-,eel O8ser#ation 11.+

e"t in a JLabel normally uses sentence-stylecapitali*ation#

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Speci$(in% t!e 0a(out

• Laying out containers $etermines where components are placed in the container

$one in &a%a with layout managers

• One of which is class FlowLayout

,et with the setLayout method of class JFrame

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LabelFrame!"a#a

(1 of 2)

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LabelFrame!"a#a

(2 of 2)

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LabelTest!"a#a

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Creatin% and 7ttac!in% label1

• ethod setToolTipText of classJComponent

,pecifies the tool tip

• ethod add of class Container

/dds a component to a container

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Common :ro%rammin% Error 11.1

If you do not e"plicitly add a GUI componentto a container! the GUI component will not edisplayed when the container appears on the

screen#

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0oo-and-,eel O8ser#ation 11.

Use tool tips to add descripti%e te"t to your GUIcomponents# his te"t helps the user determinethe GUI component's purpose in the user

interface#

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Creatin% and 7ttac!in% label

• Interface !con Can e added to a JLabel with the set!con method

Implemented y class !mage!con

• Interface "wingConstants

$eclares a set of common integer constants such as those

used to set the alignment of components

Can e used with methods set#ori$ontal%lignment and set&ertical%lignment

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Creatin% and 7ttac!in% label'

• Other JLabel methods getText and setText

• .or setting and retrie%ing the te"t of a lael

get!con and set!con

• .or setting and retrie%ing the icon displayed in the lael

get#ori$ontalTextPosition andset#ori$ontalTextPosition

• .or setting and retrie%ing the hori*ontal position of the te"t

displayed in the lael

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,i%. 11.3 ; Some 8asic GUI components.

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C ti d 'i l i L b lF


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Creatin% and 'ispla(in% a LabelFrame *indo

• Other JFrame methods set(e)aultCloseOperation

• $ictates how the application reacts when the user clic+s the

close utton

set"i$e• ,pecifies the width and height of the window

set&isible

• $etermines whether the window is displayed (true) or not

()alse)

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11 + T t ,i ld d I t d ti t


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11.+ Te)t ,ields and an Introduction to

E#ent andlin% it! ested Classes

• GUIs are e%ent-dri%en / user interaction creates an e%ent

• Common e%ents are clic+ing a utton! typing in a te"t field!

selecting an item from a menu! closing and window and

mo%ing the mouse

he e%ent causes a call to a method called an e%ent handler

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11 + T t ,i ld d I t d ti t


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11.+ Te)t ,ields and an Introduction to

E#ent andlin% it! ested Classes

• Class JTextComponent ,uperclass of JTextField

• ,uperclass of JPasswordField

/dds echo character to hide te"t input in component

/llows user to enter te"t in the component whencomponent has the application's focus

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TextFieldFrame!"a#a

(1 of 3)

Create a new JTextField

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TextFieldFrame!"a#a

(2 of 3)

Create a new JTextField

Create a new uneditableJTextField

Create a new JPasswordField

Create event handler

Register event handler

Create event handler class by

implementing the

%ctionListener interface

eclare actionPer)ormed method

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!est if the source of the event is the


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TextFieldFrame!"a#a

(3 of 3)


first te"t field

#et te"t from te"t field



#et password from password field


second te"t field


third te"t field


password field

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TextFieldTest!"a#a

(1 of 2)

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TextFieldTest!"a#a

(2 of 2)

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Steps =e>uired to Set Up E#ent andlin%


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Steps =e>uired to Set Up E#ent andlin%

$or a GUI Component

• ,e%eral coding steps are re5uired for anapplication to respond to e%ents

Create a class for the e%ent handler

Implement an appropriate e%ent-listener interface

6egister the e%ent handler

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Usin% a ested Class to Implement an


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E#ent andler

• op-le%el classes 1ot declared within another class

• 1ested classes

$eclared within another class

1on-static nested classes are called inner classes

• .re5uently used for e%ent handling

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So$tare En%ineerin% O8ser#ation 11.2

/n inner class is allowed to directly access itstop-le%el class's %ariales and methods! e%en ifthey are pri#ate#

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E#ent andler

*JTextFields and JPasswordFields Pressing enter within either of these fields causes an

%ction+vent

• Processed y o7ects that implement the %ctionListener interface

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=e%isterin% t!e E#ent andler $or Eac!


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=e%isterin% t!e E#ent andler $or Eac!

Te)t ,ield

• 6egistering an e%ent handler Call method add%ctionListener to register an

%ctionListener o7ect

%ctionListener listens for e%ents on the o7ect

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So$tare En%ineerin% O8ser#ation 11."

he e%ent listener for an e%ent must implementthe appropriate e%ent-listener interface#

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Common :ro%rammin% Error 11.2

.orgetting to register an e%ent-handler o7ect fora particular GUI component's e%ent type causese%ents of that type to e ignored#

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'etails o$ Class TextField#andler


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'etails o$ Class TextField#andler sactionPer)ormed 5et!od

• 8%ent source Component from which e%ent originates

Can e determined using method get"ource

e"t from a JTextField can e ac5uired using

get%ctionCommand e"t from a JPasswordField can e ac5uired using

getPassword

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11 Common GUI E#ent T(pes and


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11. Common GUI E#ent T(pes and

0istener Inter$aces

• 8%ent types /ll are suclasses of %,T+vent

,ome declared in pac+age java.awt.event

hose specific to ,wing components declared in

javax.swing.event

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11 Common GUI E#ent T(pes and


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11. Common GUI E#ent T(pes and

0istener Inter$aces

• $elegation e%ent model 8%ent source is the component with which user interacts

8%ent o7ect is created and contains information aout the

e%ent that happened

8%ent listener is notified when an e%ent happens

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,i%. 11.11 ; Some e#ent classes o$ paca%e "a#a!awt!e#ent.

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,i%. 11.12 ; Some common e#ent-listener inter$aces o$ paca%e "a#a!awt!e#ent.

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11. o E#ent andlin% *ors

• 6emaining 5uestions 2ow did the e%ent handler get registered9

2ow does the GUI component +now to call

actionPer)ormed rather than some other e%ent-

handling method9

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= i t i E t


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=e%isterin% E#ents

• 8%ery JComponent has instance %arialelistenerList

O7ect of type +ventListenerList

aintains references to all its registered listeners

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,i%. 11.1" ; E#ent re%istration $or JTextField textField( .

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E t dl I ti


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E#ent-andler In#ocation

• 8%ents are dispatched to only the e%ent listenersthat match the e%ent type

8%ents ha%e a uni5ue e%ent I$ specifying the e%ent type

*-ouse+vents are handled y

-ouseListeners and-ouse-otionsListeners

*ey+vents are handled y eyListeners

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11 3 J/ tt


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11.3 J/utton

• Button Component user clic+s to trigger a specific action

Can e command utton! chec+ o"! toggle utton or radio

utton

Button types are suclasses of class %bstract/utton

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0oo-and-,eel O8ser#ation 11.

Buttons typically use oo+-title capitali*ation#

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11 3 J/ tt


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11.3 J/utton

• Command utton Generates an %ction+vent when it is clic+ed

Created with class J/utton

e"t on the face of the utton is called utton lael

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2a%ing more than one JButton with the samelael ma+es the JButtons amiguous to the user#Pro%ide a uni5ue lael for each utton#

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,i%. 11.1& ; Sin% 8utton !ierarc!(.

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©

2005 Pearson Education,Inc. All rights reserved.

ButtonFrame!"a#a

(1 of 2)

eclare two J/utton instancevariables

Create new J/utton

Create two !mage!cons

Create new J/utton

Set rollover icon for J/utton

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© 2005 Pearson Education,

Inc. All rights reserved.

ButtonFrame!"a#a

(2 of 2)

Create handler for buttons


$nner class implements

%ctionListener

%ccess outer class&s instance usingt0is reference

#et te"t of J/utton pressed

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ButtonTest!"a#a

(1 of 2)


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11 3 J/utton


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11.3 J/utton

*J/uttons can ha%e a rollo%er icon /ppears when mouse is positioned o%er a utton

/dded to a J/utton with method setollover!con

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Because class bstractButton supportsdisplaying te"t and images on a utton! allsuclasses of bstractButton also support

displaying te"t and images#

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Using rollo%er icons for JButtons pro%idesusers with %isual feedac+ indicating that whenthey clic+ the mouse while the cursor is

positioned o%er the utton! an action will occur#

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So$tare En%ineerin% O8ser#ation 11.&

0hen used in an inner class! +eyword this refers to the current inner-class o7ect eingmanipulated# /n inner-class method can use its

outer-class o7ect's this y preceding this with the outer-class name and a dot! as inButtonFrame!this#

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11 4 Buttons T!at 5aintain State


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11.4 Buttons T!at 5aintain State

• ,tate uttons ,wing contains three types of state uttons

JToggle/utton! JC0ec2/ox and Jadio/utton

JC0ec2/ox and Jadio/utton are suclasses of

JToggle/utton

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11 4 1 JC0ec2/ox


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11.4.1 JC0ec2/ox

*JC0ec2/ox Contains a chec+ o" lael that appears to right of chec+

o" y default

Generates an !tem+vent when it is clic+ed

* !tem+vents are handled y an !temListener• Passed to method item"tateC0anged

ethod is"elected returns whether chec+ o" isselected (true) or not ()alse)

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CheckBoxFrame!"a#a

(1 of 3)eclare two JC0ec2/ox instance

variables

Set font of te"t field

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CheckBoxFrame!"a#a

(2 of 3)

Create two JC0ec2/oxes

Create event handler

Register event handler with

JC0ec2/oxes

$nner class implements

!temListener

item"tateC0anged method iscalled when a JC0ec2/ox is

clic'ed

!est whether JC0ec2/ox isselected

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!est source of the event


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CheckBoxFrame!"a#a

(3 of 3)

!est source of the event

is"elected method returnswhether JC0ec2/ox is selected

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CheckBoxTest!"a#a

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11 4 2 Jadio/utton


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11.4.2 Jadio/utton

*Jadio/utton 2as two states : selected and unselected

1ormally appear in a group in which only one radio utton

can e selected at once

• Group maintained y a /utton3roup o7ect $eclares method add to add a Jadio/utton to

group

Usually represents mutually e"clusi%e options

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Common :ro%rammin% Error 11."

/dding a ButtonGroup o7ect (or an o7ect of anyother class that does not deri%e from Component)to a container results in a compilation error#

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RadioButtonFrame!"a#a

(1 of 3)

eclare four Jadio/uttonsand a /utton3roup to manage

them

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(2 of 3)

Create the four Jadio/uttons

Create the /utton3roup

%dd each Jadio/utton to the/utton3roup

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(3 of 3)

Register an event handler with each

Jadio/utton

vent handler inner class

implements !temListener

hen radio button is selected* the

te"t field&s font will be set to the

value passed to the constructor

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RadioButtonTest!"a#a

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11.16 JCombo/ox and Usin% an 7non(mousI Cl $ E t dli


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Inner Class $or E#ent andlin%

• Como o" /lso called a drop-down list

Implemented y class JCombo/ox

8ach item in the list has an inde"

set-aximumowCount sets the ma"imum numer ofrows shown at once

JCombo/ox pro%ides a scrollar and up and down arrowsto tra%erse list

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,et the ma"imum row count for a JComboBox to anumer of rows that pre%ents the list frome"panding outside the ounds of the window in

which it is used# his configuration will ensurethat the list displays correctly when it is e"pandedy the user#

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Usin% an 7non(mous Inner Class $or

E t dli


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E#ent andlin%

• /nonymous inner class ,pecial form of inner class

$eclared without a name

ypically appears inside a method call

2as limited access to local %ariales

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ComboBoxFrame!"a#a

(1 of 2)

eclare JCombo/ox instancevariable

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Create JCombo/ox and setma"imum row count


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ComboBoxrame!"a#a

(; of ;)

Create anonymous inner class as

the event handler

eclare methoditem"tateC0anged

+ethod get"elected!ndex locates selected item

!est state change of JCombo/ox

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ComboBoxTest!"a#a

1croll(ar to scroll through the

items in the list

scroll arro#s scroll (o+

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So$tare En%ineerin% O8ser#ation 11.+

/n anonymous inner class declared in a methodcan access the instance %ariales and methods ofthe top-le%el class o7ect that declared it! as well

as the method's )inal local %ariales! ut cannotaccess the method's non-)inal %ariales#

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So$tare En%ineerin% O8ser#ation 11.

Li+e any other class! when an anonymous innerclass implements an interface! the class mustimplement e%ery method in the interface#

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11.11 JList


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• List $isplays a series of items from which the user may select

one or more items

Implemented y class JList

/llows for single-selection lists or multiple-selection lists / List'election*#ent occurs when an item is selected

• 2andled y a List'electionListener and passed tomethod #alueChan&ed

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ListFrame!"a#a

(3 of ;)

eclare JList instance variable

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Create JList


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ListFrame!"a#a

(; of ;)

Set selection mode of JList

%dd JList to "crollPane andadd to application

#et inde" of selected item

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ListTest!"a#a

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11.12 5ultiple-Selection 0ists


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p

•ultiple-selection list 8nales users to select many items

,ingle inter%al selection allows only a continuous range of

items

ultiple inter%al selection allows any set of elements to eselected

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+ultiple'electionFrame!"a#a

(3 of


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(; of


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(< of


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+ultiple'electionTest!"a#a

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11.1" 5ouse E#ent andlin%


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•ouse e%ents Create a +ouse*#ent o7ect

2andled y +ouseListeners and+ouse+otionListeners

+ouse$nputListener comines the two interfaces Interface +ouse,heelListener declares method

mouse,heel+o#ed to handle +ouse,heel*#ents

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,i%. 11.2 ; +ouseListener and +ouse+otionListener inter$acemet!ods. ?:art 1 o$ 2.@

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,i%. 11.2 ; +ouseListener and +ouse+otionListener inter$acemet!ods. ?:art 2 o$ 2.@

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ethod calls to mouse%ra&&ed and mouseReleased are sent to the +ouse+otionListener for the

Component on which a mouse drag operationstarted# ,imilarly! the mouseReleased method callat the end of a drag operation is sent to the+ouseListener for the Component on which the

drag operation started#

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+ouseTrackerFrame!"a#a

(3 of =)

Create JPanel to capture mouseevents

Set bac'ground to white

Create JLabel and add toapplication

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Create event handler for mouse

events


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(; of =)


$mplement mouse listener interfaces

-ind location of mouse clic'

eclare mouseClic2ed method

eclare mousePressed method

eclare mouseeleased method

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eclare mouse+ntered method


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(< of =)

Set bac'ground of JPanel

eclare mouse+xited method

Set bac'ground of JPanel

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eclare mouse(ragged method


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(= of =)

eclare mouse-oved method

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(3 of ;)

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(; of ;)

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11.1& 7dapter Classes


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• /dapter class

Implements e%ent listener interface

Pro%ides default implementation for all e%ent-handling

methods

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So$tare En%ineerin% O8ser#ation 11


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So$tare En%ineerin% O8ser#ation 11.

0hen a class implements an interface! the classhas an >is a? relationship with that interface# /lldirect and indirect suclasses of that class inheritthis interface# hus! an o7ect of a class thate"tends an e%ent-adapter class is an o7ect of thecorresponding e%ent-listener type (e#g#! an o7ectof a suclass of +ousedapter is a +ouseListener)#

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E)tendin% +ousedapter


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*+ousedapter /dapter class for +ouseListener and

+ouse+otionListener interfaces

8"tending class allows you to o%erride only the methods

you wish to use

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C : i E 11 &


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Common :ro%rammin% Error 11.&

If you e"tend an adapter class and misspell thename of the method you are o%erriding! yourmethod simply ecomes another method in the

class# his is a logic error that is difficult to detect!since the program will call the empty %ersion ofthe method inherited from the adapter class#

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,i%. 11."6 ; E#ent-adapter classes and t!e inter$aces t!e( implement inpaca%e "a#a!awt!e#ent.

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+ouse%etailsFrame!"a#a

(3 of ;)


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+ouse%etailsFrame!"a#a

(; of ;)

#et number of times mouse button

was clic'ed

!est for right mouse button

!est for middle mouse button

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+ouse%etails!"a#a

(3 of ;)

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+ouse%etails!"a#a

(; of ;)

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11.1+ JPanel Su8class $or 'rain% it!t!e 5ouse


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• O%erriding class JPanel Pro%ides a dedicated drawing area

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,i%. 11."" ; $nput*#ent met!ods t!at !elp distin%uis! amon% le$t-Acenter- and ri%!t-mouse-8utton clics.

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5et!od paintComponent


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• ethod paintComponent $raws on a ,wing component

O%erriding method allows you to create custom drawings

ust call superclass method first when o%erridden

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0oo and ,eel O8ser#ation 11 1"


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0oo-and-,eel O8ser#ation 11.1"

ost ,wing GUI components can etransparent or opa5ue# If a ,wing GUIcomponent is opa5ue! its ac+ground will ecleared when its paintComponent method iscalled# Only opa5ue components can displaya customi*ed ac+ground color# JPanel o7ects are opa5ue y default#

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Error :re#ention Tip 11 1


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Error-:re#ention Tip 11.1

In a JComponent suclass's paintComponent method! the first statement should always e acall to the superclass's paintComponent method

to ensure that an o7ect of the suclass displayscorrectly#

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Common :ro%rammin% Error 11 +


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Common :ro%rammin% Error 11.+

If an o%erridden paintComponent method doesnot call the superclass's %ersion! the suclasscomponent may not display properly# If an

o%erridden paintComponent method calls thesuperclass's %ersion after other drawing isperformed! the drawing will e erased#

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'e$inin% t!e Custom 'rain% 7rea


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• Customi*ed suclass of JPanel Pro%ides custom drawing area

Class Graphics is used to draw on ,wing components

Class Point represents an " - y coordinate

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-utline


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PaintPanel!"a#a

(3 of ;)

Create array of Points

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-utline

%nonymous inner class for eventhandling

.verride mouse(ragged method


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PaintPanel!"a#a

(; of ;)

.verride mouse(ragged method

#et location of mouse cursor

Repaint the JFrame

#et the x and y/coordinates of the

Point

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0oo and ,eel O8ser#ation 11 1&


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0oo-and-,eel O8ser#ation 11.1&

Calling repaint for a ,wing GUI componentindicates that the component should erefreshed on the screen as soon as possile# he

ac+ground of the GUI component is clearedonly if the component is opa5ue# JComponentmethod setOpa-ue can e passed a boolean argument indicating whether the component is

opa5ue (true) or transparent ()alse)#

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0oo and ,eel O8ser#ation 11 1+


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0oo-and-,eel O8ser#ation 11.1+

$rawing on any GUI component is performedwith coordinates that are measured from theupper-left corner (@! @) of that GUI component!

not the upper-left corner of the screen#

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-utline


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Painter!"a#a

(3 of ;)

Create instance of custom drawing

panel

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-utline


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Painter!"a#a

(; of ;)

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11.1 9e(-E#ent andlin%


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*.eyListener interface .or handling .ey*#ents

$eclares methods keyPressed! keyReleased andkeyTyped

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-utline

. % F


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.ey%emoFrame!"a#a

(3 of


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.ey%emoFrame!"a#a

(; of


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.ey%emoFrame!"a#a

(< of


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.ey%emo!"a#a

(3 of ;)

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-utline

.ey%emo "a#a


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.ey%emo!"a#a

(3 of ;)

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11.1 0a(out 5ana%ers


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• Layout managers

Pro%ided to arrange GUI components in a container

Pro%ide asic layout capailities

Implement the interface Layout+ana&er

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0oo-and-,eel O8ser#ation 11 1


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0oo and ,eel O8ser#ation 11.1

ost &a%a programming en%ironmentspro%ide GUI design tools that help aprogrammer graphically design a GUIA thedesign tools then write the &a%a code to create

the GUI# ,uch tools often pro%ide greatercontrol o%er the si*e! position and alignmentof GUI components than do the uilt-in layoutmanagers#

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0oo-and-,eel O8ser#ation 11 1


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0oo and ,eel O8ser#ation 11.1

It is possile to set a Container's layout to null!which indicates that no layout manager shoulde used# In a Container without a layoutmanager! the programmer must position and

si*e the components in the gi%en container andta+e care that! on resi*e e%ents! all componentsare repositioned as necessary# / component'sresi*e e%ents can e processed y aComponentListener#

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11.1.1 FlowLayout


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*FlowLayout ,implest layout manager

Components are placed left to right in order they are

added

Components can e left aligned! centered or right aligned

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,i%. 11."3 ; 0a(out mana%ers.

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-utline

FlowLayoutFrame


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FlowLayoutFrame!"a#a

(3 of


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(; of


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(< of


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FlowLayout%emo!"a#a

(3 of ;)

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-utline

FlowLayout%emo


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FlowLayout%emo!"a#a

(; of ;)

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11.1.2 BorderLayout


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*BorderLayout /rranges components into fi%e regions : north! south! east!

west and center

Implements interface Layout+ana&er/

Pro%ides hori*ontal gap spacing and %ertical gap spacing

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oo a d ee O8se at o 3

8ach container can ha%e only one layout manager#,eparate containers in the same application canuse different layout managers#

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If no region is specified when adding a Component to a BorderLayout! the layout manager assumesthat the Component should e added to region

BorderLayout!C*0T*R#

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Common :ro%rammin% Error 11.


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% %

0hen more than one component is added to aregion in a BorderLayout! only the last componentadded to that region will e displayed# here is noerror that indicates this prolem#

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-utline

BorderLayout


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Frame!"a#a

(3 of ;)

eclare /orderLayout instancevariable

Create /orderLayout

Set layout


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-utline

BorderLayout


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Frame!"a#a

(; of ;)

%dd buttons to application using

layout manager constants

+a'e button invisible

+a'e button visible

,pdate layout

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-utline

BorderLayout


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%emo!"a#a

(3 of ;)

horiontal gap vertical gap

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-utline

BorderLayout


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%emo!"a#a

(; of ;)

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11.1." GridLayout


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*GridLayout $i%ides container into a grid

8%ery component has the same width and height

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-utline

GridLayout"


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Frame!"a#a

(3 of ;)

eclare two 3ridLayout instance variables

Create 3ridLayout

Set layout

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-utline

GridLayoutF "

%dd button to JFrame


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Frame!"a#a

(; of ;)

%dd button to JFrame

,se second layout

,se first layout

,pdate layout

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-utline

GridLayout%emo"


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!"a#a

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11.13 Usin% :anels to 5ana%e 5oreComple) 0a(outs


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• Comple" GUIs often re5uire multiple panels to

arrange their components properly

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-utline

PanelFrame!"a#a


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(3 of ;)

eclare a JPanel to hold buttons

Create JPanel

Set layout

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-utline

PanelFrame!"a#a

%dd button to panel


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(; of ;)

%dd panel to application

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-utline

Panel%emo!"a#a


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11.14 JTextrea


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*JTextrea Pro%ides an area for manipulating multiple lines of te"t

*Box container ,uclass of Container

Uses a BoxLayout layout manager

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o pro%ide line-wrapping functionality for aJTextrea! in%o+e JTextrea method setLine1,rap with a true argument#

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-utline

TextreaFrame"a#a


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!"a#a

(3 of ;)eclare JText%rea instance

variables

Create a /ox container

Create te"t area and add to bo"

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-utline

TextreaFrame"a#a

%dd button to bo"


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!"a#a

(; of ;)

Copy selected te"t from one te"t

area to the other

Create second te"t area and add it

to bo"

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-utline

Textrea%emo"a#a


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!"a#a

(3 of ;)

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-utline

Textrea%emo!"a#a


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!"a#a

(; of ;)

174

J"crollPane Scroll8ar :olicies

J" llP


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*J"crollPane has scrollar policies

2ori*ontal policies

• /lways (#O!4O5T%L6"COLL/%6%L,%7")

• /s needed (#O!4O5T%L6"COLL/%6%"65++(+()

• 1e%er (#O!4O5T%L6"COLL/%65+&+)

ertical policies

• /lways (&+T!C%L6"COLL/%6%L,%7")

• /s needed (&+T!C%L6"COLL/%6%"65++(+()

• 1e%er (&+T!C%L6"COLL/%65+&+)

Documents

JavaHTP6e_11.ppt