SwingWorker Cancel Action - multithreading

Question

i've looking for How to cancel my thread, found some answers but it didn't help me.
My app needs to go from 0-X and by pressing Cancel button the thread is canceled and update Atual Label value with the last counting number.
Again: I've found some examples and explications and didn't help me, so please, do not post another post example.
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
public class SwingWorker extends JFrame {
Thread worker=new Thread();
boolean parar=false;
int em;
public int quantos;
public int sleep;
private JLabel contador = new JLabel("0");
private JLabel statusLabel = new JLabel("N\u00E3o completado");
private JButton startButton = new JButton("Iniciar");
private JLabel atual = new JLabel("0");
JButton btnNewButton = new JButton("Cancelar");
JLabel lblltimoNmero = new JLabel("\u00DAltimo n\u00FAmero");
public SwingWorker(String title) {
super(title);
setTitle("Contador do n\u00FAmero!");
getContentPane().setLayout(null);
contador.setBounds(106, 97, 48, 37);
contador.setFont(new Font("serif", Font.BOLD, 28));
getContentPane().add(contador);
statusLabel.setBounds(76, 155, 139, 14);
getContentPane().add(statusLabel);
startButton.setBounds(35, 210, 79, 23);
getContentPane().add(startButton);
//Button cancelar
btnNewButton.setBounds(118, 210, 100, 23);
getContentPane().add(btnNewButton);
btnNewButton.setEnabled(false);
btnNewButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
parar=true;
atual.setText(""+(em-1));
//----------------------------------------
// Worker cancel action
//worker.cancel();
//-------------------------
}
});
lblltimoNmero.setBounds(10, 288, 110, 14);
getContentPane().add(lblltimoNmero);
atual.setFont(new Font("Serif", Font.BOLD, 28));
atual.setBounds(106, 269, 59, 37);
getContentPane().add(atual);
JButton btnQuantosNmeros = new JButton("Ir at\u00E9");
btnQuantosNmeros.setBounds(35, 244, 79, 23);
getContentPane().add(btnQuantosNmeros);
JButton btnSleepPor = new JButton("Sleep por");
btnSleepPor.setBounds(118, 244, 89, 23);
getContentPane().add(btnSleepPor);
btnSleepPor.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
sleep =Integer.parseInt(JOptionPane.showInputDialog("Thread dormir por(ms): "));
startButton.setEnabled(true);
}
});
btnQuantosNmeros.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
quantos =Integer.parseInt(JOptionPane.showInputDialog("Ir até o número :"));
}
});
startButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
btnNewButton.setEnabled(true);
start();
startButton.setEnabled(false);
}
});
setSize(244, 400);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
JOptionPane.showMessageDialog(null, "Clique em -Ir até- e em -Sleep por-");
}
private void start() {
worker = new Thread() {
public void run() {
if(quantos!=0){
for(int i=0; i<=quantos; i++) {
final int count = i;
em++;
SwingUtilities.invokeLater(new Runnable() {
public void run() {
contador.setText(Integer.toString(count));
}
});
try {
Thread.sleep(sleep);
} catch (InterruptedException e) {
}
}}
SwingUtilities.invokeLater(new Runnable() {
public void run() {
statusLabel.setText("Completo");
startButton.setEnabled(true);
atual.setText(Integer.toString( em-1 ));
em=0;
parar=false;
}
});
}
};
worker.start();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new SwingWorker("SwingWorker");
}
});
}
}

Answer 1

The correct way to use SwingWorker is to make a subclass of it and override its doInBackground method. See the tutorial for an example: https://docs.oracle.com/javase/tutorial/uiswing/concurrency/simple.html, as well as the tutorial on canceling a SwingWorker: https://docs.oracle.com/javase/tutorial/uiswing/concurrency/cancel.html.
You've created a subclass of JFrame and just named it SwingWorker, so I don't quite understand what you're trying to do. You should possibly find some tutorials on how inheritance works in Java, such as http://docs.oracle.com/javase/tutorial/java/IandI/index.html.