Java Swing

Content

 

Intro

MVC Pattern

Basic Components

Layoutmanager

 

Example: Basic Swing App

 

 

Intro

• AWT disadvantages
  • OS provides window and dialog elements
  • Difficult to achieve unified look and feel
  • Porting problems due to OS differences
  • Required lots of effort to unify behaviour
  • Small set of elements provided by AWT
• Swing characteristics
  • Components require minimum amount of platform specific GUI resources
  • Besides top-level window, dialogs and primitive operations, all GUI elements implemented in java
  • E.g. JButton not provided by Windows UI-Manager, entirely implemented in Java

Swing Characteristics

• Swing codebase is cleaner, since only minimal platform specific code
• Unified look and feel
• Independent of common platform components
  • May introduce new components
• Lightweight component
  • Paint method not defered to OS specific resources
  • Implemented via primitive graphic operations
  • AWT components are heavyweight
• Pluggable look and feel
  • May change during runtime

Model View Controller

• Divide codebase into three areas
  • Modell: holds the data
  • View: is concerned about the graphical presentation
  • Controller: connects modell with view
• Model-Delegate Pattern
  • Similar to MVC
  • View and Controller packed in a UI-Delegate
  • Easier to implement since view and controller no separate

Basic Swing App

Basic Swing App

public class BasicFrame extends JFrame implements ActionListener {

    // ...
    @Override
    public void actionPerformed(ActionEvent event) {
        // ...
    }
}

• Main class extends JFrame
• Implements ActionListener
• Overrides actionPerformed
• Adds known WindowClosingAdapter

JFrame

// JFrame class in JSE
public class JFrame extends Frame implements ... {
    // ...
}

// Content pane as container
JPanel namePanel = new JPanel();
namePanel.setBorder(BorderFactory.createEtchedBorder());
getContentPane().add(namePanel, BorderLayout.NORTH);

• Extends an AWT Frame
• Creates a Swing window (JDialog, JWindow, JApplet)
• Container is a content pane

JPanel

// JPanel class in JSE
public class JPanel extends JComponent implements ... {
    // ...
}

// Usage
JPanel buttonPanel = new JPanel();
buttonPanel.setBorder(BorderFactory.createEtchedBorder());
getContentPane().add(buttonPanel, BorderLayout.SOUTH);

• Extends JComponent
• Allows the usage of another layout manager
• Allows borders
• General purpose container

JLabel & JTextField

// JLabel class in JSE
public class JLabel extends JComponent implements ... {
    // ...
}

// JTextField class in JSE
public class JTextField extends JTextComponent implements ... {
    // ... 
}

// JLabel usage
JLabel nameLabel = new JLabel("Name: ", new ImageIcon("triblue.gif"), SwingConstants.LEFT);

// JTextField usage
JTextField tf = new JTextField(30);

• JLabel
  • Used to display immutable
  • May display an icon
• JTextField
  • Simple text input
  • Use JPasswordField for password inputs

Tooltip and Borders

// Tooltip on JButton
JButton btn1 = new JButton("Metal");
btn1.setToolTipText("Activate Metal-Look-and-Feel");

// Borders
JPanel buttonPanel = new JPanel();
buttonPanel.setBorder(BorderFactory.createEtchedBorder());

• Tooltip via setToolTipText(...)
• Borders
  • Feature of JComponent
  • Pass a Border instance
  • Created with BorderFactory

JList

String[] MONTHS = {
        "January", "February", "March", "April",
        "May", "June", "July", "August",
        "September", "October", "November", "December",
};

JList list = new JList(MONTHS);

• List of values, one or multiple entries selectable
• Pass list of values or
• Pass instance of ListModel to display complex and dynamic data structures

JScrollPane

JList list = new JList(MONTHS);
list.setToolTipText("Choose your birthdate");
getContentPane().add(new JScrollPane(list), BorderLayout.CENTER);

• Allows scrolling on bigger components
• Handles scrolling logic

Look and Feel

UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
SwingUtilities.updateComponentTreeUI(this);

• Use UIManager to set look and feel
• USe SwingUtilities to update component tree to refresh style

Layout Manager

• In some GUI systems absolute coords are used to position components
• AWT designers opted to use a layout manager
• Layout manager handles position of components
• Specify layout manager via setLayout method
• Components are passed to the add method, positions determined by layout manager

Layout Manager Overview

• FlowLayout
  • Position elements horizontally
  • Jump to next line if no horizontal space left
• GridLayout
  • Specify a rectangular grid
  • Number of colmuns and rows defined when initializing
• BorderLayout
  • Position on borders of container or middle
• CardLayout
  • Holds multiple containers, allows  to display one component at a time
• GridBagLayout
  • Extends functionalities of GridLayout

 

 

References

 

Handbuch der Java-Programmierung

(5. Auflage)

 

 

 

 

Thank you for your attention!