Cant add dynamically created checkbox to jPanel

Question

I want to add checkboxes to a jpanel, which is on a jFrame. The UI was made on netbeans and i have copied the code to work on its functionality on eclipse. I cant get my checkboxes come over the Jpanel.

The code

    import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.util.List;

import javax.swing.BorderFactory;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JCheckBox;
import javax.swing.border.Border;

public class QueryBuilderUI extends javax.swing.JFrame {

QueryBuilderMethods objQBM = new QueryBuilderMethods();

DefaultComboBoxModel<String> repoModel = new DefaultComboBoxModel<String>();
public QueryBuilderUI() {
    getRepositoryListing();
    initComponents();
}
private void getRepositoryListing()
{
    repoModel = new QueryBuilderMethods().getAllRepositoryName();
}
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jLabel1 = new javax.swing.JLabel();
    jComboBox1 = new javax.swing.JComboBox();
    jLabel2 = new javax.swing.JLabel();
    jComboBox2 = new javax.swing.JComboBox();
    jLabel3 = new javax.swing.JLabel();
    jPanel1 = new javax.swing.JPanel();
    jTextField1 = new javax.swing.JTextField();
    jLabel4 = new javax.swing.JLabel();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jLabel1.setText("Choose Repository");

    jComboBox1.setModel(repoModel);
    jComboBox1.addItemListener(new java.awt.event.ItemListener() {
        public void itemStateChanged(java.awt.event.ItemEvent evt) {
            jComboBox1ItemStateChanged(evt);
        }
    });

    jLabel2.setText("Choose Table");

    //jComboBox2.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));

    jComboBox2.addItemListener(new java.awt.event.ItemListener() {
        public void itemStateChanged(java.awt.event.ItemEvent evt) {
            jComboBox2ItemStateChanged(evt);
        }
    });


    jLabel3.setText("Choose Columns");

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    Border border = BorderFactory.createTitledBorder("Select Columns");
    jPanel1.setBorder(border);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 459, Short.MAX_VALUE)
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 124, Short.MAX_VALUE)
    );

    jTextField1.setText("jTextField1");

    jLabel4.setText("Generated Query");

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jLabel1)
                        .addComponent(jLabel2))
                    .addGap(57, 57, 57)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 106, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, 106, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addComponent(jLabel3)
                .addComponent(jLabel4)
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 412, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap(65, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addGap(18, 18, 18)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel1)
                .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(18, 18, 18)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel2)
                .addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(18, 18, 18)
            .addComponent(jLabel3)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(44, 44, 44)
            .addComponent(jLabel4)
            .addGap(18, 18, 18)
            .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(92, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>                        

private void jComboBox1ItemStateChanged(java.awt.event.ItemEvent evt) {                                            
    // TODO add your handling code here:
    if(evt.getStateChange()== ItemEvent.SELECTED){
        Object item = evt.getItem();
        DefaultComboBoxModel<String> modelTable = objQBM.getAllTablesForRepo(item.toString());
        jComboBox2.setModel(modelTable);
    }
}    

private void jComboBox2ItemStateChanged(java.awt.event.ItemEvent evt) {                                            
    // TODO add your handling code here:
    if(evt.getStateChange()== ItemEvent.SELECTED){
        Object item = evt.getItem();
       String RepoName =  jComboBox1.getSelectedItem().toString();
       List<String> columnNames = objQBM.getAllColumnsForTable(item.toString());
        addCheckBox(columnNames);
    }
}    

   private void addCheckBox(List<String> columnNames)
  {
   int numberCheckBox = columnNames.size();
           JCheckBox[] checkBoxList = new JCheckBox[numberCheckBox];

           for(int i = 0; i < numberCheckBox; i++) {
               checkBoxList[i] = new JCheckBox("hi"+i);
               jPanel1.add(checkBoxList[i]);


           }

           jPanel1.revalidate();
   }



public static void main(String args[]) {



   // java.awt.EventQueue.invokeLater(new Runnable() {
   //     public void run() {
            new QueryBuilderUI().setVisible(true);


    //    }
   // });
    }

// Variables declaration - do not modify                     
private javax.swing.JComboBox jComboBox1;
private javax.swing.JComboBox jComboBox2;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JPanel jPanel1;
private javax.swing.JTextField jTextField1;
// End of variables declaration                   
}

the UI Looks like this

The checkboxes needs to be created dynamically according to what is selected on jComboBox2.

Answer 1

Your jPanel1 JPanel is being constrained by its layout, GroupLayout, which does not take kindly to the addition of new components without significant additions to code that are difficult to make, since GroupLayout was not built to be used for hand coding but rather for GUI-builder coding. I suggest that you build your GUI with much more coder-friendly layouts, or better still, combinations of nested JPanels each using a simpler layout, ones that are much more conducive to the addition of new components, and then your problems will be more easily solved.

You could even still use GroupLayout for the main of your GUI if you desire, but just not for jPanel1. I suggest that you consider using GridLayout or GridBagLayout to add a grid of JCheckBoxes. Or even FlowLayout. For example the following code uses the default JPanel's FlowLayout:

import java.awt.Dimension;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.util.ArrayList;
import java.util.List;

import javax.swing.BorderFactory;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JCheckBox;
import javax.swing.border.Border;

public class QueryBuilderUI extends javax.swing.JFrame {

   protected static final int PREF_W = 400;

   protected static final int PREF_H = 200;

   QueryBuilderMethods objQBM = new QueryBuilderMethods();

   DefaultComboBoxModel<String> repoModel = new DefaultComboBoxModel<String>();

   public QueryBuilderUI() {
      getRepositoryListing();
      initComponents();
   }

   private void getRepositoryListing() {
      repoModel = new QueryBuilderMethods().getAllRepositoryName();
   }

   @SuppressWarnings("unchecked")
   // <editor-fold defaultstate="collapsed" desc="Generated Code">
   private void initComponents() {

      jLabel1 = new javax.swing.JLabel();
      jComboBox1 = new javax.swing.JComboBox();
      jLabel2 = new javax.swing.JLabel();
      jComboBox2 = new javax.swing.JComboBox();
      jLabel3 = new javax.swing.JLabel();
      jPanel1 = new javax.swing.JPanel() {
         @Override 
         // !! so the JPanel has some size. This is a shameless kludge *****
         public Dimension getPreferredSize() {
            if (isPreferredSizeSet()) {
               return super.getPreferredSize();
            }
            return new Dimension(PREF_W, PREF_H);
         }
      };
      jTextField1 = new javax.swing.JTextField();
      jLabel4 = new javax.swing.JLabel();

      setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

      jLabel1.setText("Choose Repository");

      jComboBox1.setModel(repoModel);
      jComboBox1.addItemListener(new java.awt.event.ItemListener() {
         public void itemStateChanged(java.awt.event.ItemEvent evt) {
            jComboBox1ItemStateChanged(evt);
         }
      });

      jLabel2.setText("Choose Table");

      // jComboBox2.setModel(new javax.swing.DefaultComboBoxModel(new String[] {
      // "Item 1", "Item 2", "Item 3", "Item 4" }));

      jComboBox2.addItemListener(new java.awt.event.ItemListener() {
         public void itemStateChanged(java.awt.event.ItemEvent evt) {
            jComboBox2ItemStateChanged(evt);
         }
      });

      jLabel3.setText("Choose Columns");

      // *************** Note Changes Below ****************

      // !! javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(
      // !! jPanel1);
      // !! jPanel1.setLayout(jPanel1Layout);

      // !! jPanel1 now uses JPanel's default FlowLayout

      Border border = BorderFactory.createTitledBorder("Select Columns");
      jPanel1.setBorder(border);

      jTextField1.setText("jTextField1");

      jLabel4.setText("Generated Query");

      javax.swing.GroupLayout layout = new javax.swing.GroupLayout(
            getContentPane());
      getContentPane().setLayout(layout);
      layout.setHorizontalGroup(layout
            .createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(
                  layout.createSequentialGroup()
                        .addContainerGap()
                        .addGroup(
                              layout.createParallelGroup(
                                    javax.swing.GroupLayout.Alignment.LEADING)
                                    .addGroup(
                                          layout.createSequentialGroup()
                                                .addGroup(
                                                      layout.createParallelGroup(
                                                            javax.swing.GroupLayout.Alignment.LEADING)
                                                            .addComponent(
                                                                  jLabel1)
                                                            .addComponent(
                                                                  jLabel2))
                                                .addGap(57, 57, 57)
                                                .addGroup(
                                                      layout.createParallelGroup(
                                                            javax.swing.GroupLayout.Alignment.LEADING)
                                                            .addComponent(
                                                                  jComboBox1,
                                                                  javax.swing.GroupLayout.PREFERRED_SIZE,
                                                                  106,
                                                                  javax.swing.GroupLayout.PREFERRED_SIZE)
                                                            .addComponent(
                                                                  jComboBox2,
                                                                  javax.swing.GroupLayout.PREFERRED_SIZE,
                                                                  106,
                                                                  javax.swing.GroupLayout.PREFERRED_SIZE)))
                                    .addComponent(jLabel3)
                                    .addComponent(jLabel4)
                                    .addComponent(
                                          jPanel1,
                                          javax.swing.GroupLayout.PREFERRED_SIZE,
                                          javax.swing.GroupLayout.DEFAULT_SIZE,
                                          javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addComponent(
                                          jTextField1,
                                          javax.swing.GroupLayout.PREFERRED_SIZE,
                                          412,
                                          javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addContainerGap(65, Short.MAX_VALUE)));
      layout.setVerticalGroup(layout.createParallelGroup(
            javax.swing.GroupLayout.Alignment.LEADING).addGroup(
            layout.createSequentialGroup()
                  .addGap(18, 18, 18)
                  .addGroup(
                        layout.createParallelGroup(
                              javax.swing.GroupLayout.Alignment.BASELINE)
                              .addComponent(jLabel1)
                              .addComponent(jComboBox1,
                                    javax.swing.GroupLayout.PREFERRED_SIZE,
                                    javax.swing.GroupLayout.DEFAULT_SIZE,
                                    javax.swing.GroupLayout.PREFERRED_SIZE))
                  .addGap(18, 18, 18)
                  .addGroup(
                        layout.createParallelGroup(
                              javax.swing.GroupLayout.Alignment.BASELINE)
                              .addComponent(jLabel2)
                              .addComponent(jComboBox2,
                                    javax.swing.GroupLayout.PREFERRED_SIZE,
                                    javax.swing.GroupLayout.DEFAULT_SIZE,
                                    javax.swing.GroupLayout.PREFERRED_SIZE))
                  .addGap(18, 18, 18)
                  .addComponent(jLabel3)
                  .addPreferredGap(
                        javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                  .addComponent(jPanel1,
                        javax.swing.GroupLayout.PREFERRED_SIZE,
                        javax.swing.GroupLayout.DEFAULT_SIZE,
                        javax.swing.GroupLayout.PREFERRED_SIZE)
                  .addGap(44, 44, 44)
                  .addComponent(jLabel4)
                  .addGap(18, 18, 18)
                  .addComponent(jTextField1,
                        javax.swing.GroupLayout.PREFERRED_SIZE,
                        javax.swing.GroupLayout.DEFAULT_SIZE,
                        javax.swing.GroupLayout.PREFERRED_SIZE)
                  .addContainerGap(92, Short.MAX_VALUE)));

      pack();
   }// </editor-fold>

   private void jComboBox1ItemStateChanged(java.awt.event.ItemEvent evt) {
      // TODO add your handling code here:
      if (evt.getStateChange() == ItemEvent.SELECTED) {
         Object item = evt.getItem();
         DefaultComboBoxModel<String> modelTable = objQBM
               .getAllTablesForRepo(item.toString());
         jComboBox2.setModel(modelTable);
      }
   }

   private void jComboBox2ItemStateChanged(java.awt.event.ItemEvent evt) {
      // TODO add your handling code here:
      if (evt.getStateChange() == ItemEvent.SELECTED) {
         Object item = evt.getItem();
         String RepoName = jComboBox1.getSelectedItem().toString();
         List<String> columnNames = objQBM.getAllColumnsForTable(item
               .toString());
         addCheckBox(columnNames);
      }
   }

   private void addCheckBox(List<String> columnNames) {
      int numberCheckBox = columnNames.size();
      JCheckBox[] checkBoxList = new JCheckBox[numberCheckBox];

      System.out.println("numberCheckBox = " + numberCheckBox);
      for (int i = 0; i < numberCheckBox; i++) {
         checkBoxList[i] = new JCheckBox("hi" + i);
         jPanel1.add(checkBoxList[i]);

      }

      jPanel1.revalidate();
      jPanel1.repaint();
      System.out.println("check boxes added");
   }

   public static void main(String args[]) {

      // java.awt.EventQueue.invokeLater(new Runnable() {
      // public void run() {
      new QueryBuilderUI().setVisible(true);

      // }
      // });
   }

   // Variables declaration - do not modify
   private javax.swing.JComboBox jComboBox1;
   private javax.swing.JComboBox jComboBox2;
   private javax.swing.JLabel jLabel1;
   private javax.swing.JLabel jLabel2;
   private javax.swing.JLabel jLabel3;
   private javax.swing.JLabel jLabel4;
   private javax.swing.JPanel jPanel1;
   private javax.swing.JTextField jTextField1;
   // End of variables declaration
}

// mock code added so that the above code will compile and run
// because you didn't give us this code
class QueryBuilderMethods {

   public DefaultComboBoxModel<String> getAllRepositoryName() {
      DefaultComboBoxModel<String> cModel = new DefaultComboBoxModel<>();
      for (String item : new String[] { "one", "two", "three", "four", "five" }) {
         cModel.addElement(item);
      }
      return cModel;
   }

   public List<String> getAllColumnsForTable(String string) {
      List<String> columns = new ArrayList<>();
      for (String item : new String[] { "col 1", "col 2", "col 3", "col 4" }) {
         columns.add(item);
      }
      return columns;
   }

   public DefaultComboBoxModel<String> getAllTablesForRepo(String string) {
      DefaultComboBoxModel<String> cModel = new DefaultComboBoxModel<>();
      for (String item : new String[] { "repo one", "repo two", "repo three",
            "repo four", "repo five" }) {
         cModel.addElement(item);
      }
      return cModel;
   }

}