Terminate threads when closing JFrame

Question

How to call additional operations when the user closes the JFrame window? I have to stop existing threads.

As I understand it, setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); causes the frame to close and its flow stops. Should threads be closed after JFrame.EXIT_ON_CLOSE ?

Client:

 static boolean TERMINATE = false; public static void main(String[] args) { // some threads created while(true) { if(TERMINATE){ // do before frame closed break; } } } private static JPanel startGUI(){ JFrame f = new JFrame(); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel gui = new JPanel(); f.add( gui); f.setSize(500,500); f.setVisible(true); return gui; } 

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I need to close the sockets the thread is working with. What is the best practice?

Answer 1

Using JFrame.EXIT_ON_CLOSE actually terminates the JVM ( System.exit ). All running threads will be automatically stopped.

If you want to perform an action when a JFrame is close, use a WindowListener .

 JFrame frame = ... frame.addWindowListener(new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { // close sockets, etc } }); 

Answer 2

• You must add a WindowListener to the JFrame .

• Inside the windowClosing method windowClosing you can provide the required code.

For example:

 import javax.swing.*; import java.awt.*; import java.awt.event.*; public class ClosingFrame extends JFrame { private JMenuBar MenuBar = new JMenuBar(); private JFrame frame = new JFrame(); private static final long serialVersionUID = 1L; private JMenu File = new JMenu("File"); private JMenuItem Exit = new JMenuItem("Exit"); public ClosingFrame() { File.add(Exit); MenuBar.add(File); Exit.addActionListener(new ExitListener()); WindowListener exitListener = new WindowAdapter() { @Override public void windowClosing(WindowEvent e) { int confirm = JOptionPane.showOptionDialog(frame, "Are You Sure to Close this Application?", "Exit Confirmation", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, null, null); if (confirm == 0) { System.exit(1); } } }; frame.addWindowListener(exitListener); frame.setDefaultCloseOperation(EXIT_ON_CLOSE); frame.setJMenuBar(MenuBar); frame.setPreferredSize(new Dimension(400, 300)); frame.setLocation(100, 100); frame.pack(); frame.setVisible(true); } private class ExitListener implements ActionListener { @Override public void actionPerformed(ActionEvent e) { int confirm = JOptionPane.showOptionDialog(frame, "Are You Sure to Close this Application?", "Exit Confirmation", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE, null, null, null); if (confirm == 0) { System.exit(1); } } } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { ClosingFrame cf = new ClosingFrame(); } }); } } 

Answer 3

You can set the default close operation on a JFrame

 JFrame frame = new JFrame("My Frame"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);