component must be showing on the screen to determine its location when changing JCOMBOX

Question

I am receiving this error when i change items in the Jcombobox, nothing breaks it just shows this error, is there anyway to just throw it so it doesn't show up. everything still works fine, but if you wish to have a look at the code. i will post below.

Error message:

java.awt.IllegalComponentStateException: component must be showing on the screen to determine its location
at java.awt.Component.getLocationOnScreen_NoTreeLock(Component.java:2056)
at java.awt.Component.getLocationOnScreen(Component.java:2030)
at sun.lwawt.macosx.CAccessibility$23.call(CAccessibility.java:395)
at sun.lwawt.macosx.CAccessibility$23.call(CAccessibility.java:393)
at sun.lwawt.macosx.LWCToolkit$CallableWrapper.run(LWCToolkit.java:538)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:301)

And my code which i don't know which section to show so its all their.

import javax.swing.*;

import java.awt.Dialog.ModalityType;
import java.awt.event.*;
import java.awt.*;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Date;

public class TouchOn extends JDialog {
private JPanel mainPanel;


public ArrayList Reader(String Txtfile) {
    try {

    ArrayList<String> Trains = new ArrayList<String>();
    int count = 0;
    String testing = "";
    File file = new File(Txtfile);
    FileReader fileReader = new FileReader(file);
    BufferedReader bufferedReader = new BufferedReader(fileReader);
    StringBuffer stringBuffer = new StringBuffer();
    String line;
    while ((line = bufferedReader.readLine()) != null) 
    {
        stringBuffer.append(line);
        count += count;
        if(!line.contains("*")){
            Trains.add(line + "\n");
        }
        stringBuffer.append("\n");



    }
    fileReader.close();
    //Arrays.asList(Trains).stream().forEach(s -> System.out.println(s));
    return Trains;
} catch (IOException e) {
    e.printStackTrace();
}
//return toString();
return null;


}


public TouchOn()
{
    setPanels();

    setModalityType(ModalityType.APPLICATION_MODAL);
    setSize(400, 300);
    setVisible(true);
}
public void setPanels()
{
    mainPanel = new JPanel(new GridLayout(0, 2));
    JPanel containerPanel = new JPanel(new GridLayout(0, 1));
    JLabel startDay = new JLabel("Day:");
    JTextField sDay = new JTextField();

    JLabel startMonth = new JLabel("Month:");
    JTextField sMonth = new JTextField();

    JLabel startYear = new JLabel("Year:");
    JTextField sYear = new JTextField("2015");
    String trainline = "";

    JLabel touchOnTimehr = new JLabel("Time Hour: ");
    JLabel touchOnTimem = new JLabel("Time Minute:");
    JLabel station = new JLabel("Station: ");


    JTextField touchOnTimeFieldhour = new JTextField();
    JTextField touchOnTimeFieldminute = new JTextField();

    JPanel lowerPanel = new JPanel(new FlowLayout());
    ArrayList<String> stations = Reader("TrainLines.txt");
    JComboBox<String> cb = new JComboBox<>(stations.toArray(new String[stations.size()]));
    JRadioButton belgrave = new JRadioButton("Belgrave Line");
    belgrave.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){

            }
    });
    JRadioButton glenwaverly = new JRadioButton("Glen Waverly Line");
    glenwaverly.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){

        }
    });
    ButtonGroup bG = new ButtonGroup();
    JButton apply = new JButton("Touch on");
    JButton cancel = new JButton("Cancel");
    cancel.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e){
            dispose();
        }
    });
    apply.addActionListener(new ActionListener()
    {
        public void actionPerformed(ActionEvent e)
        {


String timestamp = new java.text.SimpleDateFormat("dd/MM/yyyy").format(new Date());
            String day = sDay.getText();
            String month = sMonth.getText();
            String year = sYear.getText();
            String hour = touchOnTimeFieldhour.getText();
            String minute = touchOnTimeFieldminute.getText();
            if(belgrave.isSelected()){
                String trainline = belgrave.getText();
            }
            if(glenwaverly.isSelected()){
                String trainline = glenwaverly.getText();
            }
            System.out.println(trainline);
        }
    });



    cb.setVisible(true);
    bG.add(belgrave);
    bG.add(glenwaverly);
    mainPanel.add(startDay);
    mainPanel.add(sDay);
    mainPanel.add(startMonth);
    mainPanel.add(sMonth);
    mainPanel.add(startYear);
    mainPanel.add(sYear);
    mainPanel.add(touchOnTimehr);
    mainPanel.add(touchOnTimeFieldhour);
    mainPanel.add(touchOnTimem);
    mainPanel.add(touchOnTimeFieldminute);
    mainPanel.add(belgrave);
    mainPanel.add(glenwaverly);
    mainPanel.add(station);
    mainPanel.add(new JLabel());
    mainPanel.add(cb);
    lowerPanel.add(apply);
    lowerPanel.add(cancel);
    touchOnTimeFieldhour.setSize(10,10);
    containerPanel.add(mainPanel);
    containerPanel.add(lowerPanel);

    add(containerPanel);
}

}

Answer 1

Don't create multiple JComboBoxes and then swap visibility. Instead use one JComboBox and create multiple combo box models, such as by using DefaultComboBoxModel<String>, and then swap out the model that it holds by using its setModel(...) method. Problem solved.

---

Note that using a variation on your code -- I'm not able to reproduce your problem:

import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Date;

import javax.swing.AbstractAction;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class TestFoo2 {

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

   public static void createAndDisplayGui() {
      final JFrame frame = new JFrame("Foo");
      frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
      JButton button = new JButton(new AbstractAction("Press Me") {

         @Override
         public void actionPerformed(ActionEvent evt) {
            TouchOn2 touchOn2 = new TouchOn2(frame);
            touchOn2.setVisible(true);
         }
      });

      JPanel panel = new JPanel();
      panel.add(button);
      frame.add(panel);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }
}

@SuppressWarnings("serial")
class TouchOn2 extends JDialog {
   private JPanel mainPanel;

   @SuppressWarnings({ "rawtypes", "unused" })
   public ArrayList Reader(String Txtfile) {
      ArrayList<String> list = new ArrayList<>();
      for (int i = 0; i < 100; i++) {
         list.add("Data String Number " + (i + 1));
      }

      // return toString();
      // !! return null;
      return list;
   }

   public TouchOn2(Window owner) {
      super(owner);
      setPanels();

      setModalityType(ModalityType.APPLICATION_MODAL);
      setSize(400, 300);
      setVisible(true);
   }

   @SuppressWarnings("unchecked")
   public void setPanels() {
      mainPanel = new JPanel(new GridLayout(0, 2));
      JPanel containerPanel = new JPanel(new GridLayout(0, 1));
      JLabel startDay = new JLabel("Day:");
      final JTextField sDay = new JTextField();

      JLabel startMonth = new JLabel("Month:");
      final JTextField sMonth = new JTextField();

      JLabel startYear = new JLabel("Year:");
      final JTextField sYear = new JTextField("2015");
      final String trainline = "";

      JLabel touchOnTimehr = new JLabel("Time Hour: ");
      JLabel touchOnTimem = new JLabel("Time Minute:");
      JLabel station = new JLabel("Station: ");

      final JTextField touchOnTimeFieldhour = new JTextField();
      final JTextField touchOnTimeFieldminute = new JTextField();

      JPanel lowerPanel = new JPanel(new FlowLayout());
      ArrayList<String> stations = Reader("TrainLines.txt");
      final JComboBox<String> cb = new JComboBox<>(
            stations.toArray(new String[stations.size()]));
      final JRadioButton belgrave = new JRadioButton("Belgrave Line");
      belgrave.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {

         }
      });
      final JRadioButton glenwaverly = new JRadioButton("Glen Waverly Line");
      glenwaverly.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {

         }
      });
      ButtonGroup bG = new ButtonGroup();
      JButton apply = new JButton("Touch on");
      JButton cancel = new JButton("Cancel");
      cancel.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            dispose();
         }
      });
      apply.addActionListener(new ActionListener() {
         @SuppressWarnings("unused")
         public void actionPerformed(ActionEvent e) {

            String timestamp = new java.text.SimpleDateFormat("dd/MM/yyyy")
                  .format(new Date());
            String day = sDay.getText();
            String month = sMonth.getText();
            String year = sYear.getText();
            String hour = touchOnTimeFieldhour.getText();
            String minute = touchOnTimeFieldminute.getText();
            if (belgrave.isSelected()) {
               // !! ***** note you're shadowing variables here!!!! ****
               String trainline = belgrave.getText();
            }
            if (glenwaverly.isSelected()) {
               // !! and here too
               String trainline = glenwaverly.getText();
            }
            System.out.println(trainline);
         }
      });

      cb.setVisible(true);
      bG.add(belgrave);
      bG.add(glenwaverly);
      mainPanel.add(startDay);
      mainPanel.add(sDay);
      mainPanel.add(startMonth);
      mainPanel.add(sMonth);
      mainPanel.add(startYear);
      mainPanel.add(sYear);
      mainPanel.add(touchOnTimehr);
      mainPanel.add(touchOnTimeFieldhour);
      mainPanel.add(touchOnTimem);
      mainPanel.add(touchOnTimeFieldminute);
      mainPanel.add(belgrave);
      mainPanel.add(glenwaverly);
      mainPanel.add(station);
      mainPanel.add(new JLabel());
      mainPanel.add(cb);
      lowerPanel.add(apply);
      lowerPanel.add(cancel);
      touchOnTimeFieldhour.setSize(10, 10);
      containerPanel.add(mainPanel);
      containerPanel.add(lowerPanel);

      add(containerPanel);
   }

}