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Swing
Swing is a framework or API that is used to create GUI (or) window-based applications.It is an advanced version of AWT (Abstract Window Toolkit) API and entirely written in java.
Unlike AWT, Java Swing provides platform-independent and lightweight components.
The javax.swing package provides classes for java swing API such as JButton, JTextField, JTextArea, JRadioButton, JCheckbox, JMenu, JColorChooser etc.
Difference between AWT and Swing
There are many differences between java awt and swing that are given below.
No. AWT Swing
AWT components are platform-dependent. Swing components are platform-independent.
AWT components are heavyweight. Swing components are lightweight.
AWT provides less components than Swing. Swing provides more powerful components such as tables, lists, scrollpanes, colorchooser and` etc.
AWT doesn't follows MVC (Model View Controller) where model represents data, view represents presentation and controller acts as an interface between model and view.
Swing follows MVC.
Commonly used Methods of Component class
Method Description
add(Component c) inserts a component on this component.
setSize(int width,int height) sets the size (width and height) of the component.
setLayout(LayoutManager m) defines the layout manager for the component.
setVisible(boolean status) changes the visibility of the component, by default false.
setTitle(String text) Sets the title for component
Swing Hierarchy
To create simple swing example, you need a frame. In swing, we use JFrame class to create a frame.
There are two ways to create a frame in swing.
- By extending JFrame class (inheritance) Ex: class Example extends JFrame { …….. }
- By creating the object of JFrame class (association) Ex: class Example { JFrame obj=new JFrame(); …….. }
Components of Swing:
JButton: The JButton class is used to create a labeled button that has platform independent implementation. The application result in some action when the button is pushed. Syntax: JButton b= new JButton(“Text"); (Or) JButton b1,b2; b1=new JButton(“Text”); b.setBounds(50,100,80,30); JLabel: The JLabel class is a component for placing text in a container. It is used to display a single line of read only text. The text can be changed by an application but a user cannot edit it directly. Syntax: JLabel l1=new JLabel(“Text”); (or) JLabel l1,l2; l1=new JLabel(“Text”); JTextField: The JTextField class is a text component that allows the editing of a single line text. Syntax: JTextField t1=new JTextField(“Text”); (or) JTextField t1,t2; t1=new JTextField(“Text”); JTextArea : The JTextArea class is a multi line region that displays text. It allows the editing of multiple line text. Syntax: JTextArea t1=new JTextArea(“Text”); (or) JTextArea t1,t2; t1=new JTextArea(“Text”);
JCheckBox : The JCheckBox class is used to create a checkbox. It is used to turn an option on (true) or off (false). Clicking on a Checkbox changes its state from "on" to "off" or from "off" to "on". Syntax: JCheckBox c1=new JCheckBox(“Text”); (or) JCheckBox c1,c2; c1=new JCheckBox(“Text”); JList The object of JList class represents a list of text items. The list of text items can be set up so that the user can choose one or more items from list of items. Syntax: DefaultListModel l1 = new DefaultListModel<>(); l1.addElement("Item1"); l1.addElement("Item2"); l1.addElement("Item3"); l1.addElement("Item4"); JList list = new JList<>(l1); JPasswordField: The JPasswordField class is a text component specialized for password entry. It allows the editing of a single line of text. Syntax: JPasswordField pwd = new JPasswordField(); pwd.setBounds(100,50,80,30);
JRadioButton The JRadioButton class is used to create a radio button. It is used to choose one option from multiple options. It is widely used in exam systems or quiz.
- It should be added in ButtonGroup to select one radio button only. Syntax: ButtonGroup bg= new ButtonGroup(); JRadioButton r1= new JRadioButton("Male"); JRadioButton r2= new JRadioButton("Female"); bg.add(r1);bg.add(r2);
Example: An example for JButton Component in swing. JButtonExample.java import javax.swing.*; public class JButtonExample { public static void main(String[] args) { JFrame f=new JFrame("Button Example"); JButton b=new JButton("Click Here"); b.setBounds(50,100,95,30); f.add(b); f.setSize(400,400); f.setLayout(null); f.setVisible(true); } } Execution: D:/>javac JButtonExample.java
D:/>java JButtonExample
Example: An example for Login page which includes JLabel,JTextField,JPasswordField, JCheckBox and JButton Components. LoginExample.java import javax.swing.*; class LoginExample extends JFrame { public static void main(String args[]) { JLabel l1,l2; JTextField t1; JPasswordField p1; JCheckBox cb; JButton b; JFrame f=new JFrame(“Login Page”); l1=new JLabel("User Name :"); l1.setBounds(50,60,100,30); t1=new JTextField(""); t1.setBounds(150,60, 200,30); l2=new JLabel("Password :"); l2.setBounds(50,120,100,30); p1=new JPasswordField(""); p1.setBounds(150,120, 200,30); cb=new JCheckBox("Save Password"); cb.setBounds(50,150,200,30); b=new JButton("Login"); b.setBounds(150,180,100,30); f.add(l1);f.add(l2); f.add(t1);f.add(p1); f.add(cb);f.add(b); f.setSize(400,400); f.setLayout(null); f.setVisible(true); } } Execution: D:/>javac LoginExample.java D:/>java LoginExample
Example: An example for JRadioButton Class component of swing JRadioButtonExample.java import javax.swing.*; public class JRadioButtonExample { public static void main(String[] args) { JFrame f=new JFrame(); JRadioButton r1=new JRadioButton(" Male"); JRadioButton r2=new JRadioButton(" Female"); r1.setBounds(75,50,100,30); r2.setBounds(75,100,100,30); ButtonGroup bg=new ButtonGroup(); bg.add(r1);bg.add(r2); f.add(r1);f.add(r2); f.setSize(300,300); f.setLayout(null); f.setVisible(true); f.setTitle(“RadioButtonExample”); } } Output: Javac JRadioButtonExample.java Java JRadioButtonExample
Example: An example for JList Class component of swing JListExample.java import javax.swing.*; public class JListExample { public static void main(String args[]) { JFrame f= new JFrame(); DefaultListModel l1 = new DefaultListModel<>(); l1.addElement("Item1"); l1.addElement("Item2"); l1.addElement("Item3"); l1.addElement("Item4"); JList list = new JList<>(l1); list.setBounds(100,100, 75,75); f.add(list); f.setSize(400,400); f.setLayout(null); f.setVisible(true); f.setTitle(“JList Example”); } } Output: Javac JListExample.java Java JListExample
Example: An example for JOptionPane Class component of swing JOptionPaneExample.java import javax.swing.*; public class JOptionPaneExample { public static void main(String[] args) { JFrame f=new JFrame(); JOptionPane.showMessageDialog(f,"Hello, Welcome to Swing."); } } Output: Javac JOptionPaneExample.java Java JOptionPaneExample
Example: An example for JTextArea Class component of swing JTextAreaExample.java import javax.swing.*; class JTextAreaExample { public static void main(String args[]) { JFrame f= new JFrame("JTextArea Example"); JTextArea area=new JTextArea("Welcome"); area.setBounds(10,30, 200,200); f.add(area); f.setSize(300,300); f.setLayout(null); f.setVisible(true); } } Output: Javac JTextAreaExample.java Java JTextAreaExample
Example: An example for JProgressBar Class component of swing JProgressBarExample.java import javax.swing.*; public class JProgressBarExample extends JFrame { JProgressBar jb; int i=0,num=0; JProgressBarExample() { jb=new JProgressBar(0,2000); jb.setBounds(40,40,160,30); jb.setValue(0); jb.setStringPainted(true); add(jb); setSize(250,150); setLayout(null); setTitle(“JProgressBar”); } public void iterate() { while(i<=2000) { jb.setValue(i); i=i+20; try{Thread.sleep(150);}catch(Exception e){} } } public static void main(String[] args) { JProgressBarExample m=new JProgressBarExample(); m.setVisible(true); m.iterate(); } } Output: Javac JProgressBarExample.java Java JProgressBarExample
Lifecycle of Applet: There are 5 lifecycle methods of Applet, Those are
public void init(): is used to initialized the Applet. It is invoked only once. public void start(): is invoked after the init() method or browser is maximized. It is used to start the Applet. public void paint(Graphics g): is invoked immediately after the start() method, and this method helps to create Applet’s GUI such as a colored background, drawing and writing. public void stop(): is used to stop the Applet. It is invoked when Applet is stop or browser is minimized. public void destroy(): is used to destroy the Applet. It is invoked only once.
Remember: java.applet.Applet class provides 4 methods ( init,start,stop & destroy ) and java.awt.Graphics class provides 1 method ( paint ) to create Applet.
Simple example of Applet: To execute an Applet, First Create an applet and compile it just like a simple java program. First.java import java.applet.Applet; import java.awt.Graphics; public class First extends Applet { public void paint(Graphics g){ g.drawString(“Welcome to Applet",50,150); } } Compile: D:> javac First.java After successful compilation, we get First.class file. After that create an html file and place the applet code in html file. First.html
**
** **Execute:** D:\> appletviewer First.html
GraphicsDemo.html
Execution: D:> javac GraphicsDemo.java D:> appletviewer GraphicsDemo.html
Components of Applet: The components of AWT are the components of Applet ,i.e we can use AWT components (Button,TextField,Checkbox, TextArea,Choice & etc.…) in applet.
As we perform event handling in AWT or Swing, we can perform it in applet also.
Let's see the simple example of components and event handling in applet that prints a message by click on the button. Example: AppletComponents.java import java.applet.; import java.awt.; import java.awt.event.*; public class AppletComponents extends Applet implements ActionListener{ Button b; TextField tf; public void init(){ tf=new TextField(); tf.setBounds(80,40,150,20); b=new Button("Click"); b.setBounds(80,120,80,30); add(b);add(tf); b.addActionListener(this); setLayout(null); } public void actionPerformed(ActionEvent e) { tf.setText("Welcome"); } } AppletComponents.html
Execution: D:>javac AppletComponents.java D:>appletviewer AppletComponents.html
