getCursor() doesn't work in my actionListener

Question

So I am just putting the last details of my assignment in and I noticed the getCursor(); works when I run my program, but later in the program (in the two actionListeners) it doesn't teturn to the fahrenheitTB. I was wondering if I could get some input please. Thank you greatly. Here is my code:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;


public class Part3Question1 extends JPanel
{
private JTextField fahrenheitTB;
private JTextField celsiusResultTB;
private JButton tryAgain;

public Part3Question1()
{
    Color color=new Color(255,0,0);  

    JLabel fahrenheitLabel = new JLabel ("Enter Fahrenheit temperature:");
    add (fahrenheitLabel);

    fahrenheitTB = new JTextField (5);
    fahrenheitTB.setHorizontalAlignment(fahrenheitTB.CENTER);
    //Works here!
    fahrenheitTB.getCursor();
    add (fahrenheitTB);

    JLabel celsiusLabel = new JLabel ("Temperature in Celsius: ");
    add (celsiusLabel);

    celsiusResultTB = new JTextField (5);
    celsiusResultTB.setForeground(color);
    celsiusResultTB.setEditable(false);
    celsiusResultTB.setHorizontalAlignment(celsiusResultTB.CENTER);
    add (celsiusResultTB);

    JButton convertButton = new JButton("Convert!");
    add (convertButton);

    tryAgain = new JButton("Try Again!");
    tryAgain.setVisible(false);
    add (tryAgain);

    convertButton.addActionListener (new myFirstActionListener());
    tryAgain.addActionListener (new mysecondActionListener());
}
private class myFirstActionListener implements ActionListener
{
  public void actionPerformed (ActionEvent event)
  {
          int fahrenheitTemp, celsiusTemp;
          String text = fahrenheitTB.getText();
          try
          {
              fahrenheitTemp = Integer.parseInt (text);
              celsiusTemp = (fahrenheitTemp-32) * 5/9;
              celsiusResultTB.setText (Integer.toString (celsiusTemp));
              tryAgain.setVisible(true);

          }
          catch (NumberFormatException e)
          {
              String myException="Invalid entry. Please enter Integers Only";
              JOptionPane.showMessageDialog(null,myException);
              fahrenheitTB.setText("");
              //doesn't work here!
              fahrenheitTB.getCursor();
          }
      }
}
private class mysecondActionListener implements ActionListener
{
  public void actionPerformed (ActionEvent event)
  {
          fahrenheitTB.setText("");
          //doesn't work here!
          fahrenheitTB.getCursor();
          celsiusResultTB.setText("");
      }
}

public static void main (String[] args)
{
    JFrame myFrame = new JFrame ();
    myFrame.setTitle("Fahrenheit to Celsius Converter");
    myFrame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    myFrame.setPreferredSize(new Dimension(300,150));
    myFrame.setLocation(400,300);
    Part3Question1 panel = new Part3Question1();
    myFrame.getContentPane().add(panel);
    myFrame.pack();
    myFrame.setVisible(true);
}
}

Answer 1

A good point to start would be to read this tutorial: "How to Use the Focus Subsystem". For your situation, you can try calling requestFocusInWindow() on your component

Here's your updated code:

import java.awt.Color;
import java.awt.Dimension;
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.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class Part3Question1 extends JPanel {
    private JTextField fahrenheitTB;
    private JTextField celsiusResultTB;
    private JButton tryAgain;

    public Part3Question1() {
        Color color = new Color(255, 0, 0);

        JLabel fahrenheitLabel = new JLabel("Enter Fahrenheit temperature:");
        add(fahrenheitLabel);

        fahrenheitTB = new JTextField(5);
        fahrenheitTB.setHorizontalAlignment(fahrenheitTB.CENTER);
        // updated
        fahrenheitTB.requestFocusInWindow();
        add(fahrenheitTB);

        JLabel celsiusLabel = new JLabel("Temperature in Celsius: ");
        add(celsiusLabel);

        celsiusResultTB = new JTextField(5);
        celsiusResultTB.setForeground(color);
        celsiusResultTB.setEditable(false);
        celsiusResultTB.setHorizontalAlignment(celsiusResultTB.CENTER);
        add(celsiusResultTB);

        JButton convertButton = new JButton("Convert!");
        add(convertButton);

        tryAgain = new JButton("Try Again!");
        tryAgain.setVisible(false);
        add(tryAgain);

        convertButton.addActionListener(new myFirstActionListener());
        tryAgain.addActionListener(new mysecondActionListener());
    }

    private class myFirstActionListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            int fahrenheitTemp, celsiusTemp;
            String text = fahrenheitTB.getText();
            try {
                fahrenheitTemp = Integer.parseInt(text);
                celsiusTemp = (fahrenheitTemp - 32) * 5 / 9;
                celsiusResultTB.setText(Integer.toString(celsiusTemp));
                tryAgain.setVisible(true);

            } catch (NumberFormatException e) {
                String myException = "Invalid entry. Please enter Integers Only";
                JOptionPane.showMessageDialog(null, myException);
                fahrenheitTB.setText("");
            }finally{
                // updated
                fahrenheitTB.requestFocusInWindow();
                    }
        }
    }

    private class mysecondActionListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            fahrenheitTB.setText("");
            // updated
            fahrenheitTB.requestFocusInWindow();
            celsiusResultTB.setText("");
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame myFrame = new JFrame();
                myFrame.setTitle("Fahrenheit to Celsius Converter");
                myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                myFrame.setPreferredSize(new Dimension(300, 150));
                myFrame.setLocation(400, 300);
                Part3Question1 panel = new Part3Question1();
                myFrame.getContentPane().add(panel);
                myFrame.pack();
                myFrame.setVisible(true);

            }
        });
    }
}

Answer 2

The problem is in your myFirstActionListener, the request for focus is never begin called.

An exception block will only execute if there is an exception, otherwise it is ignored.

Instead of...

} catch (NumberFormatException e) {
    String myException = "Invalid entry. Please enter Integers Only";
    JOptionPane.showMessageDialog(null, myException);
    fahrenheitTB.setText("");
    //doesn't work here!
    fahrenheitTB.requestFocusInWindow();
}

You need to use

} catch (NumberFormatException e) {
    String myException = "Invalid entry. Please enter Integers Only";
    JOptionPane.showMessageDialog(null, myException);
    fahrenheitTB.setText("");
    //doesn't work here!
} finally {
    fahrenheitTB.requestFocusInWindow();
}

In my testing, the "Try Again" worked as expected

On a personal note, you may also want to call selectAll after you request focus fahrenheitTB.selectAll. It's a personal thing, but now the user doesn't need to manually clear the field to type in there next value... ;)