liang, oreilly, herbert schildt, joseph o’neil, steven holzner, ibm corp advanced java programming...

Liang, Oreilly, Herbert Schildt, Joseph O’Neil, Steven Holzner, IBM Corp

Advanced Java Programming

CSE 7345/5345/ NTU 531Session 7

Welcome Welcome Back!!!Back!!!


[email protected]@engr.smu.edu

Chantale Laurent-

Rice

Welcome Welcome Back!!!Back!!!

[email protected]@aol.com

Office Hours:by appt3:30pm-4:30pmSIC 353


Short reviewPackages

• In Java, each class is defined in a single file called ClassName.java.

• A package is a name for a set of related classes,• Java uses package names to locate classes at

compile-time and at runtime.• Packages can be seen as some kind of libraries in

which the classes are grouped.• The difference is that packages provide an

additional scope.• Each class file must belong to a package:• Example:• Package dpack;• Package java.awt.event;


Packages con’t• If no package is given, the class is placed

in a default package with no name.• A compilation unit (a file) declares one or

more classes. It is a file that may contain several class declarations. It is used as an input for the java Compiler (javac) which outputs a series of class files (bytecodes).

• There is a class file for each class in the compilation unit.

• At the most one class is declared public.Example:

Source code: ClassName.java hello.javaBytecode: className.class hello.class


Packages con’t

• To use the classes, one or more modules in a program can import the entire package with the declaration, such as

import graphics.*;• The asterisk indicates to the

compiler that it should import all classes in the graphics package.


Standard packages• Java.applet- provides the means to create applet• Java.awt- provides class-based GUI with windows• Java.awt.*- have subpackages such as java.awt,color,

java.awt.font, and java.awt.image• Java.beans- provides basic elements for JavaBeans• Java.io- provides I/O• Java.lang- wrapper classes such as: Char, int, Double,

String and StringBuffer• java.math- math programmers• Java.net- network, socket handler, internet utility classes• Java.rmi- Remote Method Invocation provide support for

distributed code controlled by remote interface

• Java.security- implements security, encryption keys, and certificates

• Java.sql- implements of Structured Query Language database fields types and methods

• Java.text- provide parsers and formatters• Java.util- Java Application and applet (Random class,

Collection, list, Set) packages container class.• Java.util.jar- subpackage w/I java.util.• Java.util.zip- subpackage for .zip file compression format.


Packages con’t• To import just one class:

import graphics.Rectangle;• It is not correct to import the package itself:

import graphics;• Some packages provide one or more

subpackages, such as java.util.jar, a subpackage of java.util.

• Importing a package does not import any subpackages.

• You must do that explicitly using statements like these:

• Import java.utils.*;• Import java.utils.jar.*;


Small Quiz

• What happen if you tried to compile and run the following code?

1. public class EqualsTest{2. public static void main(String[] args){3. Long L = new Long( 7 );

4. if( L.equals( 7L))5. System.out.println(“Equal”);

else System.out.println(“Not Equal”);

6. }7. }

a. The program would compile and print “Equal”b. The program would compile and print “Not Equal”.c. The compiler would object to line 4.d. A runtime cast error would occur at line 4.


Small Quiz

C. qualsTest.java:5: cannot resolve symbolsymbol : method equals (long)location: class java.lang.Long

if( L.equals( 7L)) ^1 error• The compiler knows that the equals method

takes an Object rather than a primitive as input. Because the compiler does not compile answer a, b, d are incorrect.


Small Quiz• What happen if you tried to compile and

run the following code?

1. public class EqualsTest{2. public static void main(String[] args){3. Object A = new Long ( 7 );4. Long L = new Long( 7 );

5. if( A.equals( L ))

System.out.println(“Equal”);6. else System.out.println(“Not

Equal”);7. }8. }

a. The program would compile and print “Equal”b. The program would compile and print “Not Equal”.c. The compiler would object to line 5.d. A runtime cast error would occur at line 5.


Small Quiz

a. • Because the Long object created in line 3

does not lose its identity when cast to Object A, so the equals method knows the class is correct and compares the values.

• Answer c, d, do not occur because this is the correct form for comparing objects with the equals method. Therefore, they are incorrect.


What compile-time error is generated for the following program?

class D3 implements B {public void display() {

System.out.println("D3");}

}

class InterfaceRefVar{public static void main(String[] args){

B b;b = new D1();b.display();b = new D2();b.display();b = new D3();b.display();

}}

interface B{void display();

}

class D1{}

class D2 implements B{public void display() {

System.out.println("D2");}

}

interface


interfaceThe line “b = new D1();” generates an

error because the types are incompatible for assignment. Class D1 does not implements interface B.

• C:\InterfaceRefVar.java:23: incompatible types

• found : D1• required: B• b = new D1();• ^• 1 error


Chapter 10 Getting Started with GUI Programming

• GUI Class Hierarchy• Frames

– Creating frames, centering frames, adding components to frames

• Layout Managers – FlowLayout, GridLayout, BorderLayout

• Drawing on Panels– The paintComponent method

• Using Colors, Fonts, and Font Metrics• Drawing Geometric Figures

– Lines, Rectangles, Ovals, Arcs, and Polygons

• Event-Driven Programming– Event Source, Listener, Listener Interface


AWT/JFC • AWT was a powerful toolkit when introduced

– it was the original driving force behind Java’s popularity

– is today’s standard , a limited implementation

– not designed to provide a serious, main UI for the needs of many programmers.

• Now Swing, which has about four times the number of user interface (UI) components as the AWT – Swing is part of the standard Java

distribution


AWT (Optional)AWTEvent

Font

FontMetrics

Component

Graphics

Object Color

Canvas

Button

TextComponent

Label

List

CheckBoxGroup

CheckBox

Choice

Container Panel Applet

Frame

Dialog FileDialog

Window

TextField

TextArea

MenuComponent MenuItem

MenuBar

Menu

Scrollbar

LayoutManager


Question?

• Is JFC and Swing the same?


JFC

• Many programmer that that JFC and Swing are the same thing, but that’s not so; the JFC contains Swing and quite a number of other items.


What’s in JFC?

Swing- The large UI packageCut and paste- Clipboard supportAccessibility features- Aimed at users with

disabilities.The desktop Colors features- First

introduced in Java 1.1

Java2D- Improved color, image, and text support

Printing- Originally enabled in Java 1.1


What’s in Swing?Class DescriptionAbstractButton Abstract superclass for Swing

buttonsButtonGroup Encapsulates a mutually exclusive

set of buttonsImageIcon Encapsulates an iconJApplet The Swing version of AppletJButton The Swing push button classJCheckBox The Swing check box classJComboBox Encapsulates a combo boxJLabel The Swing version of a labelJRadioButton The Swing version of a radio button JScrollPane Encapsulates a scrollable windowJTable Encapsulates a table-based controlJTextField The Swing version of a text fieldJTree Encapsulates a tree-based control


GUI Class Hierarchy (Swing)

Dimension

Font

FontMetrics

Component

Graphics

Object Color

Container

Panel Applet

Frame

Dialog

Window

JComponent

JApplet

JFrame

JDialog

Swing Components in the javax.swing package

Lightweight

Heavyweight

Classes in the java.awt package

1

LayoutManager

*


JComponent

.

JButton

JMenuItem

JCheckBoxMenuItem

AbstractButton

JComponent

JMenu

JRadioButtonMenuItem

JToggleButton JCheckBox

JRadioButton

JComboBox

JInternalFrame JLayeredPane

JList JMenuBar JOptionPane

JPopupMenu

JProgressBar

JPane

JFileChooser

JScrollBar JScrollPane

JSeparator

JSplitPane

JSlider

JTabbedPane

JTable

JTableHeader

JTextField JTextComponent

JEditorPane

JTextArea

JToolBar

JToolTip

JTree

JRootPane

JPanel

JPasswordField

JColorChooser

JLabel


JApplets

• Fundamental to Swing is the JApplet class, which extends Applet.

• Applets that use Swing must be subclasses of JApplet.

• JApplet is rich with functionality that is not found in Applet.

• For Example:• JApplet support various “panes”, such

as the content pane, the glass pane, and the root pane.


Frames

• Frame is a window that is not contained inside another window. Frame is the basis to contain other user interface components in Java GUI applications.

• The Frame class can be used to create windows.

• For Swing GUI programs, use JFrame class to create widows.


UI Components

Frame Pull-down Menus

User InterfaceComponents (UI)

Panel

Panel

Panel

UI

Panel

UI

Panel

UI

Applet

Panel

User InterfaceComponents

Panel


Panel


Panel


panel

Pull-down Menus


Creating Frames

RunRun

import javax.swing.*;public class MyFrame { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(400, 300); frame.setVisible(true); frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE); }

}

NOTE: You must have JDK 1.3 or higher to run the slides.


Centering Frames

By default, a frame is displayed in the upper-left corner of the screen. To display a frame at a specified location, you can use the setLocation(x, y) method in the JFrame class. This method places the upper-left corner of a frame at location (x, y).


Centering Frames, cont.

RunRun

screenHeight

screenWidth

getHeight()

getWidth()

(x, y)

Frame

Screen

(0, 0)


Adding Components into a Frame

// Add a button into the frame frame.getContentPane().add( new JButton("OK"));

RunRun


NOTE

The content pane is a subclass of Container.

The statement in the preceding slide can be

replaced by the following two lines:

Container container =

frame.getContentPane();

container.add(new JButton("OK"));

You may wonder how a Container object is

created. It is created when a JFrame object

is created. A JFrame object uses the content

pane to hold components in the frame.


Layout Managers

• Java’s layout managers provide a level of abstraction to automatically map your user interface on all window systems.

• The UI components are placed in containers. Each container has a layout manager to arrange the UI components within the container.


Kinds of Layout Managers• FlowLayout (Chapter 10)

• GridLayout (Chapter 10)

• BorderLayout (Chapter 10)

• CardLayout (Chapter 12)

• GridBagLayout (Chapter 12)


Example 10.1Testing the FlowLayout Manager

The components are arranged in the container from left to right in the order in which they were added. When one row becomes filled, a new row is started.

RunRun


FlowLayout Constructors• public FlowLayout(int align, int hGap, int vGap)

Constructs a new FlowLayout with a specified alignment, horizontal gap, and vertical gap. The gaps are the distances inpixel between components.

• public FlowLayout(int alignment)

Constructs a new FlowLayout with a specified alignment and a default gap of five pixels for both horizontal and vertical.

• public FlowLayout()

Constructs a new FlowLayout with a defaultcenter alignment and a default gap of five pixelsfor both horizontal and vertical.


Example 10.2Testing the GridLayout Manager

The GridLayout manager arranges componentsin a grid (matrix) formation with the number ofrows and columns defined by the constructor. The components are placed in the grid from left to right starting with the first row, then the second, and so on.

RunRun


GridLayout Constructors• public GridLayout(int rows,int columns)Constructs a new GridLayout with the specified number of rows and columns.

• public GridLayout(int rows, int columns, int hGap, int vGap)Constructs a new GridLayout with thespecified number of rows and columns,along with specified horizontal andvertical gaps between components.


Example 10.3Testing the BorderLayout Manager

The BorderLayout manager divides the container into five areas: East, South, West, North, and Center. Components are added to a BorderLayout by using the add method.

RunRun

add(Component, constraint), where constraint is BorderLayout.EAST, BorderLayout.SOUTH, BorderLayout.WEST, BorderLayout.NORTH, or BorderLayout.CENTER.


Example 10.3, cont.

RunRun


Using Panels as Containers

• Panels act as smaller containers for grouping user interface components.

• It is recommended that you place the user interface components in panels and place the panels in a frame. You can also place panels in a panel.


Example 10.4 Testing Panel This example uses panels to organize components. The program creates a user interface for a Microwave oven.

RunRun

A button

A textfield

12

buttons

frame

p2

p1


Drawing on Panels

JPanel can be used to draw graphics (including text) and enable user interaction.

To draw in a panel, you create a new class that extends JPanel and override the paintComponent method to tell the panel how to draw things. You can then display strings, draw geometric shapes, and view images on the panel.


Drawing on Panels, cont.public class DrawMessage extends JPanel { /** Main method */ public static void main(String[] args) { JFrame frame = new JFrame("DrawMessage"); frame.getContentPane().add(new DrawMessage()); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(300, 200); frame.setVisible(true); } /** Paint the message */ public void paintComponent(Graphics g) { super.paintComponent(g); g.drawString("Welcome to Java!", 40, 40); }}


Drawing on Panels, cont.


NOTEThe Graphics class is an abstract class for displaying figures and images on the screen on different platforms.

The Graphics class is implemented on the native platform in the JVM. When you use the paintComponent method to draw things on a graphics context g, this g is an instance of a concrete subclass of the abstract Graphics class for the specific platform.

The Graphics class encapsulates the platform details and enables you to draw things uniformly without concerning specific platforms.


NOTEWhenever a component is displayed, a Graphics object is created for the component. The Swing components use the paintComponent method to draw things. The paintComponent method is automatically invoked to paint the graphics context when the component is first displayed or whenever the component needs to be redisplayed. Invoking super.paintComponent(g) is necessary to ensure that the viewing area is cleared before a new drawing is displayed.


NOTE

To draw things, normally you create a subclass of JPanel and override its paintComponent method to tell the system how to draw.

In fact, you can draw things on any GUI component.


The Color ClassYou can set colors for GUI components by using the java.awt.Color class. Colors are made of red, green, and blue components, each of which is represented by a byte value that describes its intensity, ranging from 0 (darkest shade) to 255 (lightest shade). This is known as the RGB model. Color c = new Color(r, g, b);r, g, and b specify a color by its red, green, and blue components.

Example:Color c = new Color(228, 100, 255);


Setting ColorsYou can use the following methods to set the component’s background and foreground colors:

setBackground(Color c)

setForeground(Color c)

Example:

setBackground(Color.yellow); setForeground(Color.red);


The Font Class

Font myFont = Font(name, style, size);

Example:Font myFont = new Font("SansSerif ", Font.BOLD, 16);Font myFont = new Font("Serif", Font.BOLD+Font.ITALIC, 12);


Finding All Available Font Names

GraphicsEnvironment e =

GraphicsEnvironment.getLocalGraphicsEnvironment();

String[] fontnames = e.getAvailableFontFamilyNames();

for (int i = 0; i < fontnames.length; i++)

System.out.println(fontnames[i]);


Setting Fontspublic void paint(Graphics g) {

Font myFont = new Font("Times", Font.BOLD, 16);

g.setFont(myFont);

g.drawString("Welcome to Java", 20, 40);

//set a new font

g.setFont(new Font("Courier", Font.BOLD+Font.ITALIC, 12));

g.drawString("Welcome to Java", 20, 70);

}


The FontMetrics Class

public void paint(Graphics g) {

g.getFontMetrics(Font f); or g.getFontMetrics();}


Get FontMetrics • public int getAscent()

• public int getDescent()

• public int getLeading()

• public int getHeight()

• public int stringWidth(String str)


Example 10.5Using FontMetrics

• Objective: Display “Welcome to Java” in SansSerif 20-point bold, centered in the frame.

RunRun


Welcome to Java stringWidth

stringAscent getHeight()

getWidth()

messagePanel


Example 10.5, cont.

MessagePanel -xCoordinate: int -yCoordinate: int -centered: boolean -message: String +getMessage(): String +getXCoordinate(): int +getYCoordinate(): int +isCentered(): boolean +setMessage(message: String): void +setXCoordinate(x: int): void +setYCoordinate(y: int): void +setCentered(centered: boolean): void +paintComponent(g: Graphics): void +getPerferredSize(): Dimension +getMinimumSize(): Dimension

1 TestFontMetrics

JPanel -char token +getToken +setToken +paintComponet +mouseClicked

JFrame -char token +getToken +setToken +paintComponet +mouseClicked

1


Drawing Geometric Figures

• Drawing Lines

• Drawing Rectangles

• Drawing Ovals

• Drawing Arcs

• Drawing Polygons


Drawing Lines

drawLine(x1, y1, x2, y2);


Drawing Rectangles

• drawRect(x, y, w, h);

• fillRect(x, y, w, h);


Drawing Rounded Rectangles

• drawRoundRect(x, y, w, h, aw, ah);

• fillRoundRect(x, y, w, h, aw, ah);


Drawing Ovals

• drawOval(x, y, w, h);

• fillOval(x, y, w, h);


Drawing Arcs• drawArc(x, y, w, h, angle1, angle2);• fillArc(x, y, w, h, angle1, angle2);


Drawing Polygons

int[] x = {40, 70, 60, 45, 20};int[] y = {20, 40, 80, 45, 60};g.drawPolygon(x, y, x.length);g.fillPolygon(x, y, x.length);


Example 10.6Drawing a Clock

• Objective: Use drawing and trigonometric methods to draw a clock showing the specified hour, minute, and second in a frame.

RunRun


Drawing ClockxEnd = xCenter + handLength sin()

yEnd = yCenter - handLength cos()Since there are sixty seconds in one minute, the angle for the second hand is

second (2/60)


Drawing Clock, cont.xEnd = xCenter + handLength sin()

yEnd = yCenter - handLength cos()The position of the minute hand is

determined by the minute and second. The exact minute value comined with seconds is minute + second/60. For example, if the time is 3 minutes and 30 seconds. The total minutes are 3.5. Since there are sixty minutes in one hour, the angle for the minute hand is (minute + second/60) (2/60)


Drawing Clock, cont.xEnd = xCenter + handLength sin()

yEnd = yCenter - handLength cos()Since one circle is divided into twelve hours, the angle for the hour hand is (hour + minute/60 + second/(60 60))) (2/12)


Event-Driven Programming

• Procedural programming is executed in procedural order.

• In event-driven programming, code is executed upon activation of events.


Events• An event can be defined as a type of

signal to the program that something has happened.

• The event is generated by external user actions such as mouse movements, mouse button clicks, and keystrokes, or by the operating system, such as a timer.


Event Information• id: A number that identifies the event. • target: The source component upon which the event

occurred. • arg: Additional information about the source

components. • x, y coordinates: The mouse pointer location when a

mouse movement event occurred.• clickCount: The number of consecutive clicks for the

mouse events. For other events, it is zero.• when: The time stamp of the event.• key: The key that was pressed or released.


Event Classes


Selected User Actions

Source Event TypeUser Action Object Generated

Clicked on a button JButton ActionEvent

Changed text JTextComponent TextEvent

Double-clicked on a list item JList ActionEvent

Selected or deselected an item JList ItemEvent with a single click

Selected or deselected an item JComboBox ItemEvent


The Delegation Model


Selected Event Handlers Event Class Listener Interface Listener Methods (Handlers)ActionEvent ActionListener actionPerformed(ActionEvent)ItemEvent ItemListener itemStateChanged(ItemEvent)WindowEvent WindowListener windowClosing(WindowEvent)

windowOpened(WindowEvent)windowIconified(WindowEvent)windowDeiconified(WindowEvent)windowClosed(WindowEvent)windowActivated(WindowEvent)windowDeactivated(WindowEvent)

ContainerEvent ContainerListener componentAdded(ContainerEvent)

componentRemoved(ContainerEvent)


Example 10.7Handling Simple Action Events

• Objective: Display two buttons OK and Cancel in the window. A message is displayed on the console to indicate which button is clicked, when a button is clicked.

RunRun


Example 10.8Handling Window Events

RunRun

Objective: Demonstrate handling the window events. Any subclass of the Window class can generate the following window events: window opened, closing, closed, activated, deactivated, iconified, and deiconified. This program creates a frame, listens to the window events, and displays a message to indicate the occurring event.


Example 10.9 Multiple Listeners for a Single Source

RunRun

Objective: This example modifies Example 10.7 to add a new listener for each button. The two buttons OK and Cancel use the frame class as the listner. This example creates a new listener class as an additional listener for the action events on the buttons. When a button is clicked, both listeners respond to the action event.

liang, oreilly, herbert schildt, joseph o’neil, steven holzner, ibm corp advanced java programming...

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