• Clicking the close‐window button on a JFrame fires a window event

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Chapter 18

Swing II

Window Listeners Window Listeners

Cli ki th l i d b tt JF fi

• Clicking the close‐window button on a JFrame fires a window event

– Window events are objects of the class Window events are objects of the class WindowEvent WindowEvent

• The setWindowListener method can register a window listener for a window event

– A window listener can be programmed to respond to this type of event

A window listener is any class that satisfies the – A window listener is any class that satisfies the

WindowListener interface

Window Listeners Window Listeners

• A class that implements the

WindowListener interface must have definitions for all seven method headers in this interface

this interface

• Should a method not be needed, it is defined

h b

with an empty body

public void windowDeiconified(WindowEvent e) { }

Methods in the WindowListener Interface

(Part 1 of 2)

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Methods in the WindowListener Interface (Part 2 of 2)

A Window Listener Inner Class A Window Listener Inner Class

A i l ft i d li t f

• An inner class often serves as a window listener for a JFrame

– The following example uses a window listener inner class The following example uses a window listener inner class named CheckOnExit

addWindowListener(new CheckOnExit());

• When the close‐window button of the main window is clicked, it fires a window event

This is received by the anonymous window listener object – This is received by the anonymous window listener object

• This causes the windowClosing method to be invoked

invoked

A Window Listener Inner Class A Window Listener Inner Class

Th th d i d Cl i t d di l

• The method windowClosing creates and displays a ConfirmWindow class object

– It contains the message "Are you sure you want to t co ta s t e essage e you su e you a t to exit?" as well as "Yes" and "No" buttons

• If the user clicks "Yes," the action event fired is received by the actionPerformed method

the actionPerformed method

– It ends the program with a call to System.exit

• If the user clicks If the user clicks "No," No, the actionPerformed the actionPerformed method method invokes the dispose method

– This makes the calling object go away (i.e., the small window of the

A Window Listener (Part 1 of 8)

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A Window Listener (Part 2 of 8) A Window Listener (Part 2 of 8)

A Window Listener (Part 3 of 8) A Window Listener (Part 3 of 8)

A Window Listener (Part 4 of 8)

A Window Listener (Part 4 of 8) A Window Listener (Part 5 of 8) A Window Listener (Part 5 of 8)

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A Window Listener (Part 6 of 8) A Window Listener (Part 6 of 8)

A Window Listener (Part 7 of 8) A Window Listener (Part 7 of 8)

A Window Listener (Part 8 of 8)

A Window Listener (Part 8 of 8) The dispose Method The dispose Method

Th di th d f th JF l i d

• The dispose method of the JFrame class is used to eliminate the invoking JFrame without ending the program

the program

– The resources consumed by this JFrame and its components are returned for reuse

U l ll h l li i d (i i

– Unless all the elements are eliminated (i.e., in a one window program), this does not end the program

• dispose dispose is often used in a program with multiple is often used in a program with multiple

windows to eliminate one window without ending

the program

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Pitfall: Forgetting to Invoke setDefaultCloseOperation

Th b h i b h

• The behavior set by the

setDefaultCloseOperation takes place even if there is a window listener registered to the

if there is a window listener registered to the JFrame

– Whether or not a window listener is registered to respond – Whether or not a window listener is registered to respond

to window events, a setDefaultCloseOperation invocation should be included

– This invocation is usually made in the JFrame constructor

Pitfall: Forgetting to Invoke setDefaultCloseOperation

• If the window listener takes care of all of the window behavior, then the JFrame constructor should contain the following:

should contain the following:

setDefaultCloseOperation(

JFrame.DO NOTHING ON CLOSE) _ _ _ )

• If it is not included, the following default action will take place instead, regardless of whether or

i d li i d k

not a window listener is supposed to take care of it:

setDefaultCloseOperation(

JFrame.HIDE_ON_CLOSE);

– This will hide the JFrame , but not end the program

The WindowAdapter Class The WindowAdapter Class

Wh l d i i l i f

• When a class does not give true implementations to most of the method headings in the WindowListener interface, it may be better to make it a derived class of the y

WindowAdapter class

– Only the method headings used need be defined

Th th th d h di i h it t i i l i l t ti f – The other method headings inherit trivial implementation from

WindowAdapter , so there is no need for empty method bodies

• This can only be done when the JFrame does not need to be derived from any other class

Using WindowAdapter

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Icons Icons

JL b l JB tt d JM It h

• JLabels, JButtons, and JMenuItems can have icons

– An icon is just a small picture (usually) An icon is just a small picture (usually) – It is not required to be small

• An icon is an object of the j ImageIcon g class

– It is based on a digital picture file such as .gif, .jpg, or .tiff

L b l b tt d it di l

• Labels, buttons, and menu items may display a string, an icon, a string and an icon, or nothing

Icons Icons

• The class ImageIcon is used to convert a picture file to a Swing icon

ImageIcon dukeIcon = new

ImageIcon("duke_waving.gif");

– The picture file must be in the same directory as the class in which this code appears, unless a complete or relative path name is given

path name is given

– Note that the name of the picture file is given as a string

Icons Icons

A i b dd d l b l i h

• An icon can be added to a label using the setIcon method as follows:

JLabel dukeLabel = new JLabel("Mood check");

dukeLabel.setIcon(dukeIcon);

• Instead, an icon can be given as an argument to the Instead, an icon can be given as an argument to the JLabel constructor:

JLabel dukeLabel = new JLabel(dukeIcon);

• Text can be added to the label as well using the setText method:

Icons Icons

d b dd d

• Icons and text may be added to JButtons and JMenuItems in the same way as they are added to a JLabel

JButton happyButton = new

JButton("Happy");

ImageIcon happyIcon = new

ImageIcon("smiley.gif");

happyButton.setIcon(happyIcon);

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Icons Icons

B i b d i h j i b

• Button or menu items can be created with just an icon by giving the ImageIcon object as an argument to the JButton or JMenuItem constructor

ImageIcon happyIcon = new

ImageIcon("smiley.gif");

JB tt il B tt JB tt (h I )

JButton smileButton = new JButton(happyIcon);

JMenuItem happyChoice = new

JMenuItem(happyIcon); ppy – A button or menu item created without text should use the

setActionCommand method to explicitly set the action command, since there is no stringg

Using Icons (Part 1 of 5) Using Icons (Part 1 of 5)

Using Icons (Part 2 of 5)

Using Icons (Part 2 of 5) Using Icons (Part 3 of 5) Using Icons (Part 3 of 5)

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Using Icons (Part 4 of 5) Using Icons (Part 4 of 5)

Using Icons (Part 5 of 5) g ( )

Some Methods in the Classes JButton, JM It d JL b l (P t 1 f 4) JMenuItem , and JLabel (Part 1 of 4)

Some Methods in the Classes JButton,

JM It d JL b l (P t 2 f 4)

JMenuItem , and JLabel (Part 2 of 4)

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Some Methods in the Classes JButton, JM It d JL b l (P t 3 f 4) JMenuItem , and JLabel (Part 3 of 4)

Some Methods in the Classes JButton, JM It d JL b l (P t 4 f 4) JMenuItem , and JLabel (Part 4 of 4)

The Insets Class The Insets Class

Obj f h l d

• Objects of the class Insets are used to specify the size of the margin in a button or menu item

– The arguments given when an Insets class object is created are in pixels

– The Insets class is in the package java.awt

public Insets(int top, int left, int bottom, int right)

Scroll Bars Scroll Bars

Wh i d h b f li h

• When a text area is created, the number of lines that are visible and the number of characters per line are specified as follows:

specified as follows:

JTextArea memoDisplay = new

JTextArea(15 30);

JTextArea(15, 30);

• However, it would often be better not to have to set a firm limit on the number of lines or the number of a firm limit on the number of lines or the number of characters per line

– This can be done by using scroll bars with the text area This can be done by using scroll bars with the text area

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Scroll Bars Scroll Bars

• When using scroll bars, the text is viewed through a view port that shows only part of the text at a time

text at a time

– A different part of the text may be viewed by using the scroll bars placed along the side and bottom of

h i

the view port

• Scroll bars can be added to text areas using the JScrollPane class

JScrollPane class

– The JScrollPane class is in the javax.swing package

– An object of the class JScrollPane is like a view port with scroll bars

View Port for a Text Area

Scroll Bars Scroll Bars

• When a JScrollPane is created, the text area to be viewed is given as an argument

JScrollPane scrolledText = new

JScrollPane(memoDisplay);

• The JScrollPane can then be added to a container, such as a JPanel or JFrame

textPanel.add(scrolledText);

Scroll Bars Scroll Bars

Th ll b li i b f ll

• The scroll bar policies can be set as follows:

scrolledText.setHorizontalScrollBarPolicy(

JScrollPane.HORIZONTAL SCROLLBAR ALWAYS);

JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

scrolledText.setVerticalScrollBarPolicy(

JscrollPane.VERTICAL_SCROLLBAR_ALWAYS);

• If invocations of these methods are omitted, then the scroll bars will be visible only when needed

– If all the text fits in the view port then no scroll bars will be visible If all the text fits in the view port, then no scroll bars will be visible

– If enough text is added, the scroll bars will appear automatically

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Some Methods in the Class JScrollPane (P 1 f 2)

(Part 1 of 2)

Some Methods in the Class JScrollPane (P 2 f 2)

(Part 2 of 2)

A Text Area with Scroll Bars (Part 1 of 8)

A Text Area with Scroll Bars (Part 1 of 8) A Text Area with Scroll Bars (Part 2 of 8) A Text Area with Scroll Bars (Part 2 of 8)

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A Text Area with Scroll Bars (Part 3 of 8) A Text Area with Scroll Bars (Part 3 of 8)

A Text Area with Scroll Bars (Part 4 of 8) A Text Area with Scroll Bars (Part 4 of 8)

A Text Area with Scroll Bars (Part 5 of 8)

A Text Area with Scroll Bars (Part 5 of 8) A Text Area with Scroll Bars (Part 6 of 8) A Text Area with Scroll Bars (Part 6 of 8)

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A Text Area with Scroll Bars (Part 7 of 8) A Text Area with Scroll Bars (Part 7 of 8)

A Text Area with Scroll Bars (Part 8 of 8) A Text Area with Scroll Bars (Part 8 of 8)

Components with Changing Visibility Components with Changing Visibility

A GUI h t th t h f i ibl t

• A GUI can have components that change from visible to invisible and back again

• In the following example, the label with the character Duke g p not waving is shown first

– When the "Wave" button is clicked, the label with Duke not waving disappears and the label with Duke waving appears

– When the " Stop " button is clicked, the label with Duke waving disappears, and the label with Duke not waving returns

– Duke is Sun Microsystem's mascot for the Java Language

• A component can be made invisible without making the entire GUI invisible

Labels with Changing Visibility (Part 1 of 6)

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Labels with Changing Visibility (Part 2 of 6) Labels with Changing Visibility (Part 2 of 6)

Labels with Changing Visibility (Part 3 of 6) Labels with Changing Visibility (Part 3 of 6)

Labels with Changing Visibility (Part 4 of 6)

Labels with Changing Visibility (Part 4 of 6) Labels with Changing Visibility (Part 5 of 6) Labels with Changing Visibility (Part 5 of 6)

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Labels with Changing Visibility (Part 6 of 6)

Coordinate System for Graphics Objects Coordinate System for Graphics Objects

Wh d i bj h J di

• When drawing objects on the screen, Java uses a coordinate system where the origin point (0,0) is at the upper‐left corner of the screen area used for drawingg

– The x‐coordinate (horizontal) is positive and increasing to the right – The y‐ coordinate(vertical) is positive and increasing down

All di t ll iti

– All coordinates are normally positive – Units and sizes are in pixels

– The area used for drawing is typically a JFrame or JPanel

Coordinate System for Graphics Objects Coordinate System for Graphics Objects

Th i t ( ) i l t d i l i f th l ft

• The point (x,y) is located x pixels in from the left edge of the screen, and down y pixels from the top of the screen

of the screen

• When placing a rectangle on the screen, the location of its upper‐left corner is specified

• When placing a figure other than a rectangle on the screen, Java encloses the figure in an imaginary

t l ll d b di b d iti th

rectangle, called a bounding box, and positions the upper‐left corner of this rectangle

Screen Coordinate System

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The Method paint and the Class Graphics The Method paint and the Class Graphics

Al t ll S i d S i l t d t d

• Almost all Swing and Swing‐related components and containers have a method called paint

• The method paint draws the component or

• The method paint draws the component or container on the screen

– It is already defined, and is called automatically when the y , y figure is displayed on the screen

– However, it must be redefined in order to draw geometric figures like circles and boxes

figures like circles and boxes

– When redefined, always include the following:

super.paint(g);

The Method paint and the Class Graphics The Method paint and the Class Graphics

E t i d t th t b d

• Every container and component that can be drawn on the screen has an associated Graphics object

– The The Graphics Graphics class is an abstract class found in the class is an abstract class found in the java.awt package

• This object has data specifying what area of the h

screen the component or container covers

– The Graphics object for a JFrame specifies that drawing takes place inside the borders of the JFrame drawing takes place inside the borders of the JFrame object

The Method paint and the Class Graphics The Method paint and the Class Graphics

• The object g of the class Graphics can be used as the calling object for a drawing method

The drawing will then take place inside the area of – The drawing will then take place inside the area of

the screen specified by g

• The method paint p has a parameter p g g of type yp Graphics

– When the paint method is invoked, g is replaced by the Graphics object associated with the by the Graphics object associated with the JFrame

– Therefore, the figures are drawn inside the JFrame

Drawing a Very Simple Face (part 1 of 5)

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Drawing a Very Simple Face (part 2 of 5) Drawing a Very Simple Face (part 2 of 5)

Drawing a Very Simple Face (part 3 of 5) Drawing a Very Simple Face (part 3 of 5)

Drawing a Very Simple Face (part 4 of 5)

Drawing a Very Simple Face (part 4 of 5) Drawing a Very Simple Face (part 5 of 5) Drawing a Very Simple Face (part 5 of 5)

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Some Methods in the Class Graphics (part 1 of 4)

Some Methods in the Class Graphics (part 2 of 4)

Some Methods in the Class Graphics (part 3 of 4)

Some Methods in the Class Graphics (part 4

of 4)

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Drawing Ovals Drawing Ovals

A l i d b h h d d l

• An oval is drawn by the method drawOval

– The arguments specify the location, width, and height of the smallest rectangle that can enclose the oval

the smallest rectangle that can enclose the oval g.drawOval(100, 50, 300, 200);

• A circle is a special case of an oval in which the width

• A circle is a special case of an oval in which the width and height of the rectangle are equal

g drawOval(X FACE Y FACE g.drawOval(X_FACE, Y_FACE,

FACE_DIAMETER, FACE_DIAMETER);

Drawing a Happy Face (Part 1 of 5)

Drawing a Happy Face (Part 2 of 5) Drawing a Happy Face (Part 3 of 5)

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Drawing a Happy Face (Part 4 of 5)

Drawing a Happy Face (Part 5 of 5)

Drawing Arcs Drawing Arcs

• Arcs are described by giving an oval, and then specifying a portion of it to be used for the arc

The following statement draws the smile on the happy – The following statement draws the smile on the happy

face:

g.drawArc(X_MOUTH, Y_MOUTH, MOUTH_WIDTH, MOUTH_HEIGHT, MOUTH_START_ANGLE,

MOUTH_ARC_SWEEP);

– The arguments MOUTH WIDTH and MOUTH HEIGHT g _ _ determine the size of the bounding box, while the arguments X_MOUTH and Y_MOUTH determine its

Specifying an Arc (Part 1 of 2) p y g ( )

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Specifying an Arc (Part 2 of 2) p y g ( )

Rounded Rectangles Rounded Rectangles

A d d t l i t l h h b

• A rounded rectangle is a rectangle whose corners have been replaced by arcs so that the corners are rounded

g.drawRoundRect(x, y, width, height, arcWidth, arcHeight) – The arguments x , y , width , and height determine a regular

rectangle in the usual way g y

– The last two arguments arcWidth , and arcHeight , specify the arcs that will be used for the corners

– Each corner is replaced with an quarter of an oval that is Each corner is replaced with an quarter of an oval that is

arcWidth pixels wide and arcHeight pixels high

– When arcWidth and arcHeight are equal, the corners will be arcs of circles

be arcs of circles

A Rounded Rectangle

A Rounded Rectangle paintComponent paintComponent for Panels for Panels

A JP l i JC t b t JF i

• A JPanel is a JComponent , but a JFrame is a Component, not a JComponent

– Therefore they use different methods to paint the screen Therefore, they use different methods to paint the screen

• Figures can be drawn on a JPanel , and the JPanel can be placed in a p JFrame

– When defining a JPanel class in this way, the

paintComponent method is used instead of the paint method

method

– Otherwise the details are the same as those for a JFrame

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paintComponent Demonstration (Part 1 of 4) paintComponent Demonstration (Part 1 of 4)

paintComponent Demonstration (Part 2 of 4) paintComponent Demonstration (Part 2 of 4)

paintComponent Demonstration (Part 3 of 4) paintComponent Demonstration (Part 3 of 4)

0

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Action Drawings and repaint Action Drawings and repaint

Th i h d h ld b i k d h h

• The repaint method should be invoked when the graphics content of a window is changed

Th i t th d t k f h d d

– The repaint method takes care of some overhead, and then invokes the method paint, which redraws the screen

– Although the repaint method must be explicitly invoked, it is already defined

– The paint method, in contrast, must often be defined, but is not explicitly invoked

An Action Drawing (Part 1 of 7) An Action Drawing (Part 1 of 7)

An Action Drawing (Part 2 of 7)

An Action Drawing (Part 2 of 7) An Action Drawing (Part 3 of 7) An Action Drawing (Part 3 of 7)

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An Action Drawing (Part 4 of 7) An Action Drawing (Part 4 of 7)

An Action Drawing (Part 5 of 7) An Action Drawing (Part 5 of 7)

An Action Drawing (Part 6 of 7)

An Action Drawing (Part 6 of 7) An Action Drawing (Part 7 of 7) An Action Drawing (Part 7 of 7)

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Some More Details on Updating a GUI Some More Details on Updating a GUI

Wi h S i h GUI d d i ll

• With Swing, most changes to a GUI are updated automatically to become visible on the screen

– This is done by the repaint manager object This is done by the repaint manager object

• Although the repaint manager works automatically, there are a few updates that it does not perform

– For example, the ones taken care of by validate or repaint

• One other updating method is pack

pack resizes the window to something known as the preferred size – pack resizes the window to something known as the preferred size

The validate Method The validate Method

A i ti f lid t t i t l t it

• An invocation of validate causes a container to lay out its components again

– It is a kind of "update" method that makes changes in the components It is a kind of update method that makes changes in the components shown on the screen

– Every container class has the validate method, which has no arguments

arguments

• Many simple changes made to a Swing GUI happen automatically, while others require an invocation of validate or some other "update" method

– When in doubt, it will do no harm to invoke validate

Specifying a Drawing Color Specifying a Drawing Color

• Using the method drawLine inside the paint method is similar to drawing with a pen that can change colors

– The method setColor will change the color of the pen – The color specified can be changed later on with another

invocation of setColor so that a single drawing can have lti l l

multiple colors

g.setColor(Color.BLUE)

Adding Color

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Defining Colors Defining Colors

• Standard colors in the class Color are already defined in Chapter 17

• The Color class can also be used to define additional colors

– It uses the RGB color system in which different amounts of red, green, and blue light are used to produce any color

The Color Constants

Defining Colors Defining Colors

I t fl t b d h if i th

• Integers or floats may be used when specifying the amount of red, green, and/or blue in a color

– Integers must be in the range 0‐255 inclusive Integers must be in the range 0 255 inclusive

Color brown = new Color(200, 150, 0);

– float values must be in the range 0.0‐1.0 inclusive

Color brown = new Color(

(float)(200.0/255),(float)(150.0/255), (float)0.0);

Pitfall: Using doubles to Define a Color Pitfall: Using doubles to Define a Color

C t t f th l C l l t

• Constructors for the class Color only accept arguments of type int or float

– Without a cast numbers like 200 0/255 0 5 and 0 0 are Without a cast, numbers like 200.0/255, 0.5, and 0.0 are considered to be of type double, not of type float

• Don't forget to use a type cast when intending to use b

float numbers

– Note that these numbers should be replaced by defined constants in any final code produced

constants in any final code produced

public static final float RED_VALUE =

(float)0.5;

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Some Methods in the Class Color (Part 1 of 2) Some Methods in the Class Color (Part 1 of 2)

Some Methods in the Class Color (Part 2 of 2) Some Methods in the Class Color (Part 2 of 2)

The JColorChooser Dialog Window The JColorChooser Dialog Window

Th l l h b d ll

• The class JColorChooser can be used to allow a user to choose a color

Th h i l h d f C l Ch

• The showDialog method of JColorChooser produces a color‐choosing window

Th h l b l ti RGB l

– The user can choose a color by selecting RGB values or from a set of color samples

sample Color = p

JColorChooser.showDialog(this,

"JColorChooser", sampleColor);

JColorChooser Dialog (Part 1 of 5)

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JColorChooser Dialog (Part 2 of 5) JColorChooser Dialog (Part 2 of 5)

JColorChooser Dialog (Part 3 of 5) JColorChooser Dialog (Part 3 of 5)

JColorChooser Dialog (Part 4 of 5)

JColorChooser Dialog (Part 4 of 5) JColorChooser Dialog (Part 5 of 5)

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The drawString Method The drawString Method

• The method drawString is similar to the drawing methods in the Graphics p class

– However, it displays text instead of a drawing If no font is specified a default font is used – If no font is specified, a default font is used

g.drawString(theText, X_START, Y_Start);

Using drawString (Part 1 of 7) Using drawString (Part 1 of 7)

Using drawString (Part 2 of 7)

Using drawString (Part 2 of 7) Using drawString (Part 3 of 7) Using drawString (Part 3 of 7)

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Using drawString (Part 4 of 7) Using drawString (Part 4 of 7)

Using drawString (Part 5 of 7) Using drawString (Part 5 of 7)

Using drawString (Part 6 of 7)

Using drawString (Part 6 of 7) Using drawString (Part 7 of 7) Using drawString (Part 7 of 7)

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Fonts Fonts

A f t i bj t f th F t l

• A font is an object of the Font class

– The Font class is found in the java.awt package

• The constructor for the Font class creates a font in a

• The constructor for the Font class creates a font in a given style and size

Font fontObject = new Font("SansSerif", Font.PLAIN, POINT_SIZE);

• A program can set the font for the drawString method within the paint method

method within the paint method

g.setFont(fontObject);

Font Types Font Types

A f t tl il bl t b d i J

• Any font currently available on a system can be used in Java

– However, Java guarantees that at least three fonts will be available:

"Monospaced" , "SansSerif" , and "Serif"

f f ff f

• Serifs are small lines that finish off the ends of the lines in letters

– This This S S has serifs, but this has serifs, but this S S does not does not – A "Serif" font will always have serifs

– Sans means without, so the "SansSerif" font will not have serifs

"Monospaced" means that all the characters have equal width – Monospaced means that all the characters have equal width

Font Styles Font Styles

• Fonts can be given style modifiers, such as bold or italic

– Multiple styles can be specified by connecting them with the | symbol (called the bitwise OR symbol)

( if

new Font("Serif",

Font.BOLD|Font.ITALIC, POINT_SIZE);

• The size of a font is called its point size

– Character sizes are specified in units known as points – One point is 1/72 of an inch p /