GUI

Question 1

What is GUI

Answer 1

• Graphical User Interface, abbreviated GUI, is a type of
interface that takes advantage of a computer’s graphic ability to allow users to interact with electronic devices through graphical icons and visual indicators.

Question 2

What are the two packages that generate GUI components in Java

Answer 2

• java.awt

* javax.swing

Question 3

Compare and contrast AWT and SWING

Answer 3

AWT
• Heavyweight components
• Associated with native components called peers
• Same behaviour, but platform-dependent look
• Package java.awt

Swing
• Lightweight components, i.e., no peer components
• Same look and feel across platforms
• Support pluggable look and feel
• Package javax.swing

*See doc for pic

Question 4

Describe a container, a top level container and give examples

Answer 4

In Java, all GUI objects go into a Container.
• A top level container can stand alone in a web
browser or in an operating system. The two most common top-level containers are:
• JFrame
• JApplet
• Some containers may only be added to other containers.
• JPanel

Question 5

Describe layout managers and their role

Answer 5

• Associated with containers
• Automate the layout of elements
• When elements are added to the container
• When the window is resized
• automatically adjust the positions and sizes of the
elements.

Question 6

What is the hierarchy of layout managers?

Answer 6

Container- Layout Manager-

1. Border layout, Card Layout, FlowLayout, GridLayout
2. LayoutManager2-GridBagLayout

*See doc for pic

Question 7

Can you identify the design pattern used

here?(Border layout, Card Layout, FlowLayout, GridLayout)

Answer 7

*See doc for pic

Question 8

Describe events

Answer 8

• A way for GUI components to communicate with the rest of application
• Implemented as event classes (e.g., ActionEvent)

Question 9

Describe event sources

Answer 9

• Components generating events

* Examples: buttons, check boxes, combo boxes, etc.

Question 10

Describe event listeners/ handlers

Answer 10

• Objects that receives and processes events
• Must implement an appropriate listener
interface
• Must inform the source its interest in handling a
certain type of events (by registering)
• May listen to several sources and different
types of events

Question 11

Give an example to show how events, event sources and even handlers work together

Answer 11

[create a button]
JButton button = new JButton(“Increment”);

[register an action listener]
button.addActionListener(new ButtonActionListener());

[Action listener class]
class ButtonActionListener implements ActionListener {

public void actionPerformed(ActionEvent e) {
[ handle the event e …]
System.out.println(“Increment button pressed!”);
}
}

Question 12

Give examples of events and their respective listeners

Answer 12

ActionEvent - ActionListener
ComponentEvent -ComponentListener
,ComponentAdapter
FocusEvent-FocusListener ,FocusAdapter
KeyEvent-KeyListener ,KeyAdapter
MouseEvent- MouseListener ,MouseAdapter
MouseMotionListener-MouseMotionAdapter
WindowEvent-WindowListener ,WindowAdapter
ItemEvent- ItemListener
TextEvent- TextListener

Question 13

Explain what a JOptionPane is.

Answer 13

The JOptionPane class is used to provide standard dialog boxes such as message dialog box, confirm dialog box and input dialog box. These dialog boxes are used to display information or get input from the user. The JOptionPane class inherits JComponent class.

Question 14

What is the syntax of using a JOptionPane

Answer 14

import javax.swing.*;  
public class OptionPaneExample {  
JFrame f;  
OptionPaneExample(){  
    f=new JFrame();  
    JOptionPane.showMessageDialog(f,"Hello, Welcome to Javatpoint.");  
}  
public static void main(String[] args) {  
    new OptionPaneExample();  
}  
}  
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