LECTURE 11: GUI APPLICATION
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GUI Application: Understanding Swing Components and Event Handling, Schemes and Mind Maps of Java Programming
An introduction to Graphical User Interfaces (GUI) and Swing components in Java. It covers the differences between lightweight and heavyweight components, the use of JOptionPane for input and output, and creating a JFrame. The document also explains event handling and the delegation-based event model in Java.
Typology: Schemes and Mind Maps
Pre 2010
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LECTURE 11: GUI APPLICATION
o GUI
o GUI Components
o Event Handler
PLAN
o Built from GUI components.
- Sometimes called controls or widgets—short for window gadgets.
o User interacts via the mouse, the keyboard or another form of input,
such as voice recognition.
o IDEs
- Provide GUI design tools to specify a component’s exact size and
location in a visual manner by using the mouse.
- Generates the GUI code for you.
- Greatly simplifies creating GUIs, but each IDE has different
capabilities and generates different code.
Introduction (cont.)
GUI Example
o Most Swing components are not tied to actual GUI components of
the underlying platform.
- Known as lightweight components.
o AWT components are tied to the local platform and are called
heavyweight components, because they rely on the local
platform’s windowing system to determine their functionality and
their look-and-feel.
o Several Swing components are heavyweight components.
Overview of Swing Components
Using JOptionPane for Output
import javax.swing.*;
...
JOptionPane.showMessageDialog( null, “I Love Java” );
JOptionPane for Input
import javax.swing.*;
...
String inputstr =
JOptionPane.showInputDialog( null, “What is your name?” );
JOptionPane static constants
o To create a customized frame window, we define a subclass of the
JFrame class.
o The JFrame class contains rudimentary functionalities to support
features found in any frame window.
Subclassing JFrame
Creating a Plain JFrame
import javax.swing.*;
class DefaultJFrame {
public static void main( String[] args ) { JFrame defaultJFrame; defaultJFrame = new JFrame(); defaultJFrame.setVisible(true); }
}
o The content pane is where we put GUI objects such as buttons,
labels, scroll bars, and others.
o We access the content pane by calling the frame’s
getContentPane method.
The Content Pane of a Frame
This gray area is the content pane of this frame.
o Here's how we can change the background color of a content
pane to blue:
Changing the Background Color
Container contentPane = getContentPane(); contentPane.setBackground(Color.BLUE);
o A JButton object a GUI component that represents a pushbutton.
o Here's an example of how we place a button with FlowLayout.
Placing a Button
contentPane.setLayout( new FlowLayout()); okButton = new JButton("OK"); cancelButton = new JButton("CANCEL"); contentPane.add(okButton); contentPane.add(cancelButton);