Swing and Thread: cancel a lengthy operation
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class BalanceLookupCantCancel extends JPanel {
private JButton searchB = new JButton("Search");
private JButton cancelB = new JButton("Cancel Search");
private JLabel balanceL;
public BalanceLookupCantCancel() {
buildGUI();
hookupEvents();
}
private void buildGUI() {
cancelB.setEnabled(false);
JPanel innerButtonP = new JPanel();
innerButtonP.setLayout(new GridLayout(1, -1, 5, 5));
innerButtonP.add(searchB);
innerButtonP.add(cancelB);
JPanel buttonP = new JPanel();
buttonP.setLayout(new FlowLayout(FlowLayout.CENTER));
buttonP.add(innerButtonP);
JLabel balancePrefixL = new JLabel("Account Balance:");
balanceL = new JLabel("BALANCE UNKNOWN");
JPanel balanceP = new JPanel(new FlowLayout(FlowLayout.CENTER));
balanceP.add(balancePrefixL);
balanceP.add(balanceL);
JPanel northP = new JPanel();
northP.add(buttonP);
northP.add(balanceP);
setLayout(new BorderLayout());
add(northP, BorderLayout.NORTH);
}
private void hookupEvents() {
searchB.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
search();
}
});
cancelB.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
cancelSearch();
}
});
}
private void search() {
// better be called by event thread!
searchB.setEnabled(false);
cancelB.setEnabled(true);
balanceL.setText("SEARCHING ...");
String bal = lookupBalance();
setBalance(bal);
}
private String lookupBalance() {
try {
// Simulate a lengthy search that takes 5 seconds
// to communicate over the network.
Thread.sleep(5000);
// result "retrieved", return it
return "1,234.56";
} catch (InterruptedException x) {
return "SEARCH CANCELLED";
}
}
private void setBalance(String newBalance) {
// better be called by event thread!
balanceL.setText(newBalance);
cancelB.setEnabled(false);
searchB.setEnabled(true);
}
private void cancelSearch() {
System.out.println("in cancelSearch()");
// Here's where the code to cancel would go if this
// could ever be called!
}
public static void main(String[] args) {
BalanceLookupCantCancel bl = new BalanceLookupCantCancel();
JFrame f = new JFrame("Can't Cancel");
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
f.setContentPane(bl);
f.setSize(400, 150);
f.setVisible(true);
}
}
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