1. Advanced Programming in Java
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Fall 2015

2. Agenda Graphical User Interface (GUI) GUI Components Event Handlers
Inner Classes
Anonymous Inner Classes
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3. Graphical User Interface (GUI)
GUI presents a mechanism for interacting with application.
a user-friendly mechanism
What are other mechanisms?
Console Applications
File
Web Applications …
GUI is pronounced “GOO-ee”
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4. GUI Components GUIs are built from GUI components GUI component:
sometimes called controls or widgets
widget: short for window gadgets
GUI component:
an object with which the user interacts
via the mouse or the keyboard
Example?
Button, Textbox, Menu, …
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6. Swing An AWT component’s behavior may be different between platforms.
AWT was the early way for GUI in java
Abstract Window Toolkit
Java.awt package
An AWT component’s behavior may be different between platforms.
Swing is a newer approach
In this presentation we review Swing GUI components
javax.swing package
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7. JOptionPane JOptionPane.showInputDialog JOptionPane.showMessageDialog
JOptionPane class has simple static methods
for input and output
Using Dialog boxes
JOptionPane.showInputDialog
Returns a String
JOptionPane.showMessageDialog
Shows a dialog box
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8. JOptionPane Sample
String name = JOptionPane.showInputDialog("Enter your name:"); JOptionPane.showMessageDialog(null, "Salam "+name +"!");
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9. Modal Dialog JOptionPane dialogs are called modal dialogs
While the dialog is on the screen…
the user cannot interact with the rest of the application
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10. JFrame We create a window containing Swing GUI components
This window object is usually instance of JFrame or a subclass of JFrame
JFrame provides the basic attributes and behaviors of a window
a title bar at the top
minimize and maximize buttons
close button
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11. JFrame Example
JFrame frame = new JFrame(); frame.setSize(300, 150); frame.setVisible(true); frame.setLayout(new FlowLayout()); frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE);
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12. Swing GUI Components JButton JLabel JTextField JComboBox JRadioButton
JMenu …
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13. JLabel and JButton JLabel label = new JLabel("Salam");
label.setToolTipText("Tooltip1");
frame.add(label);
JButton button = new JButton("Click!");
button.setToolTipText("salam :-)");
frame.add(button);
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14. Other GUI Components
JTextField textbox = new JTextField(10); frame.add(textbox); JComboBox combo = new JComboBox( new String[]{"Red", "Blue", "Green"}); frame.add(combo);
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15. Layout Management You must attach each GUI component to a container
such as a JFrame.
You typically must decide where to position each GUI component
known as specifying the layout
Java provides several layout managers
They help you position components
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16. FlowLayout In FlowLayout layout manager:
components are placed on a container
from left to right in the order in which they’re added
When no more components can fit on the current line
continue on the next line
Other layouts:
GridLayout, BoxLayout, …
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17. Layouts Three ways to arrange components in a GUI Layout managers
Simple and Fast
Absolute positioning
provides the greatest level of control GUI’s appearance.
Visual programming in an IDE
They generate codes
They may use layout managers
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18. Absolute Positioning Set Container’s layout to null
Specify the absolute position of each GUI component
with respect to the upper-left corner of the Container
by using Component methods
setSize and setLocation or setBounds
absolute positioning can be tedious
unless you have a support by an IDE
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19. IDE Support Many IDEs provide GUI design tools
You can specify a component’s exact size and location
in a visual manner by using the mouse
simplifies creating GUIs
each IDE generates this code differently
You should know the underlying codes
Eclipse Plugin
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20. Extending JFrame You can also extend JFrame to create new frames…
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21. public class MyFrame extends JFrame{ JLabel label; JButton button; JTextField textbox; JComboBox combo; public MyFrame(){ super("Frame Title"); label = new JLabel("Salam"); label.setToolTipText("Label Tooltip"); add(label); button = new JButton("Click!"); button.setToolTipText("salam :-)"); add(button); textbox = new JTextField(10); add(textbox); combo = new JComboBox( new String[]{"Red", "Blue", "Green"}); add(combo); }
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22. Event Handling GUIs are event driven User interaction => events
An Event drives the program to perform a task
Some events:
clicking a button
typing in a text field
selecting an item from a menu
closing a window
moving the mouse
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23. Event Handling (2) event handler :
The code that performs a task in response to an event
event handling :
The overall process of responding to events
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26. Event Handlers
button = new JButton("Click!"); ActionListener al = new ClickListener(); button.addActionListener(al); public class ClickListener implements ActionListener { public void actionPerformed(ActionEvent e) { JOptionPane.showMessageDialog(null, “Salam!!!”); }
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27. Better Event Handlers I want to show a message-box
According to the value of a component
For example a text-field or a combo-box
How can I do that?
Inner Classes
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28. public class MyFrame extends JFrame{ public class ClickListener implements ActionListener { public void actionPerformed(ActionEvent e) { JOptionPane.showMessageDialog(null, textbox.getText()); } JButton button; JTextField textbox; public MyFrame(){ button = new JButton("Click!"); button.addActionListener(new ClickListener()); add(button); textbox = new JTextField(10); add(textbox);
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29. Inner Classes

30. Class Types
class FriendlyClass{ } public class OuterClass { private int value; public class Inner{ public void f(){ …
Friendly Class
Public class
Inner Class
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31. Inner Classes Declared in another class
Instantiated using a reference object of outer class
Has access to this object
The inner class can be static
No reference object of outer class is needed
No access to outer class is provided
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32. OuterClass.this is implicitly saved in inner object
public class OuterClass {
private int value = 2;
class Inner{
public void innerMethod(){
OuterClass.this.value = 5; }
public void outerMethod(){
Inner inner = new Inner();
inner.innerMethod();
public static void main(String[] args) {
OuterClass outer = new OuterClass();
System.out.println(outer.value);
outer.outerMethod();
OuterClass.this is implicitly saved in inner object
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33. Why we need outer reference?
public class OuterClass {
private int value = 2;
class Inner{
public void f(){
OuterClass.this.value = 5; }
public static void main(String[] args) {
OuterClass outer = new OuterClass();
OuterClass.Inner inner = outer.new Inner();
System.out.println(outer.value);
inner.f();
Why we need outer reference?
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34. OuterClass.Inner in = new OuterClass.Inner();
class OuterClass {
static class Inner{
public void f(){
System.out.println("f() invoked"); }
public class MainClass {
public static void main(String[] args) {
OuterClass.Inner in = new OuterClass.Inner();
in.f();
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35. Inner Class Specifiers
static
final
Access Specifiers
public
private
Friendly (no specifier)
protected
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36. Anonymous Inner Class An inner class With no name Created once
Used once
No access to this class from any other place
Once created and used
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37. Inner inner = new Inner() { public void innerMethod() {
interface Inner{ void innerMethod();}
public class OuterClass {
private int value = 2;
public void outerMethod(){
Inner inner = new Inner() {
public void innerMethod() {
OuterClass.this.value = 5; } };
inner.innerMethod();
public static void main(String[] args) {
OuterClass outer = new OuterClass();
System.out.println(outer.value);
outer.outerMethod();
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38. Anonymous Inner Class Usually implements an interface
Or extends another class
And Overrides some special method
Main Application : Event Handlers
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39. public class MyFrame extends JFrame{ JButton button; JTextField textbox; public MyFrame(){ button = new JButton("Click!"); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { JOptionPane.showMessageDialog(null, textbox.getText()); } }); add(button); textbox = new JTextField(10); add(textbox);
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40. Further Reading javaw Java Web Applications SWT Java Look and Feels
Web Interface
SWT
Java Look and Feels
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