Java AWT | WindowStateListener

WindowStateListener is a part of java.awt.event package. It is an interface to handle window state events. This interface returns an event when the frame or window associated with it is iconified or maximized.

Abstract function of the class:

windowStateChanged(WindowEvent e) : invoked when a state of the window is changed.

Below programs illustrate the WindowStateListener:

Java Program to handle window events

// Java Program to handle window events 
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 
class listener1 extends JFrame implements WindowStateListener { 
    listener1() 
    { 
        super("main frame"); 
        setSize(500, 500); 
  
        // create a sub frame 
        JFrame f = new JFrame("sub"); 
  
        // add window state listener 
        f.addWindowStateListener(this); 
  
        // set size of window 
        f.setSize(200, 200); 
  
        show(); 
        f.show(); 
    } 
  
    // if state of window is changed 
    public void windowStateChanged(WindowEvent e) 
    { 
        JOptionPane.showMessageDialog(this, "window state changed"); 
    } 
    // main class 
    public static void main(String args[]) 
    { 
        listener1 l = new listener1(); 
    } 
} 

Output:

Java Program to handle window events and identify them:

// Java Program to handle window events and identify them 
import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 
class listener extends JFrame implements WindowStateListener { 
    // label 
    JLabel l; 
    JLabel l1; 
  
    listener() 
    { 
        super("main frame"); 
        setSize(500, 500); 
  
        // create a sub frame 
        JFrame f = new JFrame("sub"); 
  
        // add window state listener 
        f.addWindowStateListener(this); 
  
        // set size of window 
        f.setSize(200, 200); 
  
        // create a label 
        JLabel lo = new JLabel("old state : "); 
        JLabel lo1 = new JLabel("new state : "); 
  
        l = new JLabel(""); 
        l1 = new JLabel(""); 
  
        // create a panel 
        JPanel p = new JPanel(); 
  
        p.add(lo); 
        p.add(l); 
        p.add(lo1); 
        p.add(l1); 
        add(p); 
  
        show(); 
        f.show(); 
    } 
  
    // if state of window is changed 
    public void windowStateChanged(WindowEvent e) 
    { 
        int s = e.getOldState(), s1 = e.getNewState(); 
  
        // for old state 
        if (s == Frame.ICONIFIED) 
            l.setText("window iconified"); 
  
        if (s == Frame.MAXIMIZED_BOTH) 
            l.setText("window maximized horizontally and vertically"); 
  
        if (s == Frame.MAXIMIZED_HORIZ) 
            l.setText("window maximized horizontally"); 
  
        if (s == Frame.MAXIMIZED_VERT) 
            l.setText("window maximized verically"); 
  
        if (s == Frame.NORMAL) 
            l.setText("window normal"); 
  
        // for new state 
  
        if (s1 == Frame.ICONIFIED) 
            l1.setText("window iconified"); 
  
        if (s1 == Frame.MAXIMIZED_BOTH) 
            l1.setText("window maximized horizontally and vertically"); 
  
        if (s1 == Frame.MAXIMIZED_HORIZ) 
            l1.setText("window maximized horizontally"); 
  
        if (s1 == Frame.MAXIMIZED_VERT) 
            l1.setText("window maximized verically"); 
  
        if (s1 == Frame.NORMAL) 
            l1.setText("window normal"); 
    } 
  
    // main class 
    public static void main(String args[]) 
    { 
        listener l = new listener(); 
    } 
} 