How to switch tabs from a button placed in another class / package?

Question

I want to ask if there is a possible way to switch the tab panels from a click of a button in another class. I have 2 class and classA is in default package and the other one is in another package. My button is placed in classB and my tabbed panes are in classA.

How can I change tabs by clicking the button in my classB?

If passing variables are not going to work between the default package and another package its okay I'll just put classB in the same package so it'll be easier to access variables from classA.

** EDIT **

Okay I made a short ver of my code and this is the result:

Test.java

  package test;

  import java.awt.*;
  import java.awt.event.ActionEvent;
  import java.awt.event.ActionListener;
  import javax.swing.*;
  import btn.button;

public class Test {

JFrame frame = new JFrame();
JTabbedPane tabpane = new JTabbedPane();
JPanel panel1 = new JPanel();
GridBagConstraints c = new GridBagConstraints();
final static boolean shouldFill = true;
GridBagLayout grid = new GridBagLayout();

public Test() {
    // TODO code application logic here

   // public button switch;

    frame.setVisible(true);
    frame.setSize(821,421);


    final Toolkit toolkit = Toolkit.getDefaultToolkit();
    Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();      
int x=(int)((dimension.getWidth() - frame.getWidth())/2);
int y=(int)((dimension.getHeight() - frame.getHeight())/2);

    frame.setLocation(x, y);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

     JPanel container = new JPanel();
     container.setLayout(new BorderLayout());
     container.setBackground(new Color(0,128,0));

tabpane = new JTabbedPane(); //Tab Pane
tabpane.setBackground(new Color(0,128,0));
tabpane.setSize(801,351);       


JPanel jp1 = new JPanel(); // First Tab Panel
jp1.setBackground(new Color(0,128,0));
jp1.setLayout(grid);

    JButton popout = new JButton("MORE");
    popout.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
        button button = new button();     
        }
    });
    jp1.add(popout);

JPanel jp2 = new JPanel(); // Second Tab Panel
jp2.setBackground(new Color(0,128,0));
jp2.setLayout(grid);

    JPanel jp3 = new JPanel(); // Third Tab Panel
jp3.setBackground(new Color(0,128,0));
jp3.setLayout(grid);

    tabpane.addTab("Tab 1", jp1);
    //add selectedIndex here (1);
    tabpane.addTab("Tab 2", jp2);
    //add selectedIndex here (2);
    tabpane.addTab("Tab 3", jp3);
    //add selectedIndex here (3);

    frame.add(container);
    container.add(tabpane, BorderLayout.NORTH);

}

 public static void main(String[] args){
     //Use the event dispatch thread for Swing components
 EventQueue.invokeLater(new Runnable()
 {
    @Override
     public void run()
     {
         new Test();         
     }
 });

 }
}

button.java

 package btn;

import java.awt.Color;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class button {
 JFrame frame2 = new JFrame();
 GridBagLayout grid = new GridBagLayout();      

 public button(){

         frame2.setVisible(true);
         frame2.setSize(200,200);

         JPanel jp = new JPanel(); // First Tab Panel
         jp.setBackground(new Color(0,128,0));
         jp.setLayout(grid);

         JButton btn = new JButton("SWITCH TO PANEL 2");
         btn.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
        //what should i put here???
        }
    });

         jp.add(btn);

         frame2.add(jp);
 }
}

I know I'm missing the set selected index for each tab but I don't know how to replicate that because in my project those tabs are in a separate java file. So to shorten it I made it in one java file. So yeah. As you can see I have the more button and then the switch button for tab 2. My question is how can I switch to panel 2 by clicking the button in the pop out?

Answer 1

What you need to do is pass a reference of the object from the original class (here Test) into the class that needs to change the Test object's state, and by state I mean which JTabbedPane is showing, but the specific state doesn't matter. Again what matters is reference passing, and giving Test public methods that the second class can call to change the state. For example:

import java.awt.*;
import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

//!! import btn.button;

public class Test {

   private JFrame frame = new JFrame();
   private JTabbedPane tabpane = new JTabbedPane();
   private JPanel panel1 = new JPanel();
   private GridBagConstraints c = new GridBagConstraints();
   private final static boolean SHOULD_FILL = true;
   private GridBagLayout grid = new GridBagLayout();

   public Test() {

      frame.setVisible(true);
      frame.setSize(821, 421);

      final Toolkit toolkit = Toolkit.getDefaultToolkit();
      Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
      int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
      int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);

      frame.setLocation(x, y);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      JPanel container = new JPanel();
      container.setLayout(new BorderLayout());
      container.setBackground(new Color(0, 128, 0));

      tabpane = new JTabbedPane(); // Tab Pane
      tabpane.setBackground(new Color(0, 128, 0));
      tabpane.setSize(801, 351);

      JPanel jp1 = new JPanel(); // First Tab Panel
      jp1.setBackground(new Color(0, 128, 0));
      jp1.setLayout(grid);

      JButton popout = new JButton("MORE");
      popout.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            //!! HisTestButton button = new HisTestButton();

            new HisTestButton(Test.this); //!! passing in this
         }
      });
      jp1.add(popout);

      JPanel jp2 = new JPanel(); // Second Tab Panel
      jp2.setBackground(new Color(0, 128, 0));
      jp2.setLayout(grid);

      JPanel jp3 = new JPanel(); // Third Tab Panel
      jp3.setBackground(new Color(0, 128, 0));
      jp3.setLayout(grid);

      tabpane.addTab("Tab 1", jp1);
      // add selectedIndex here (1);
      tabpane.addTab("Tab 2", jp2);
      // add selectedIndex here (2);
      tabpane.addTab("Tab 3", jp3);
      // add selectedIndex here (3);

      frame.add(container);
      container.add(tabpane, BorderLayout.NORTH);

   }

   // !! public method that other classes can call to change tab
   public void openNextTab() {
      int selectedIndex = tabpane.getSelectedIndex();
      selectedIndex++;
      selectedIndex %= tabpane.getTabCount();
      tabpane.setSelectedIndex(selectedIndex);
   }

   //!! needed by JDialog
   public JFrame getFrame() {
      return frame;
   }

   public static void main(String[] args) {
      // Use the event dispatch thread for Swing components
      EventQueue.invokeLater(new Runnable() {
         @Override
         public void run() {
            new Test();
         }
      });

   }
}

class HisTestButton {
   protected static final int PREF_W = 200;
   protected static final int PREF_H = 200;
   JDialog dialog; // !! make this a JDialog
   GridBagLayout grid = new GridBagLayout();
   private Test test;  //!! add field

   //!! changed constructor parameter
   public HisTestButton(final Test test) {
      this.test = test; // !! set field

      // !! create our JDialog. Going to make it non-modal 
      dialog = new JDialog(test.getFrame(), "MyDialog", ModalityType.MODELESS);

      //!! frame2.setVisible(true);
      // !! frame2.setSize(200, 200); // never set visible til after components added

      JPanel jp = new JPanel() {
         @Override
         public Dimension getPreferredSize() {
            return new Dimension(PREF_W, PREF_H);
         }
      };
      jp.setBackground(new Color(0, 128, 0));
      jp.setLayout(grid);

      JButton btn = new JButton("SWITCH TO PANEL 2");
      btn.addActionListener(new ActionListener() {

         @Override
         public void actionPerformed(ActionEvent e) {
            //!! 
            test.openNextTab();
         }
      });

      jp.add(btn);

      dialog.add(jp);

      // !! added
      dialog.pack();
      dialog.setVisible(true);
   }
}

---

Key here is that I gave the second class a Test field and then changed the 2nd classes constructor to allow the Test class object to be passed into it:

class HisTestButton {
   protected static final int PREF_W = 200;
   protected static final int PREF_H = 200;
   JDialog dialog; // !! make this a JDialog
   GridBagLayout grid = new GridBagLayout();
   private Test test;  //!! add field   ****************

   //!! changed constructor parameter
   public HisTestButton(final Test test) { // *****
      this.test = test; // !! set field

I've given Test public methods that can be called:

// !! public method that other classes can call to change tab
public void openNextTab() {
  int selectedIndex = tabpane.getSelectedIndex();
  selectedIndex++;
  selectedIndex %= tabpane.getTabCount();
  tabpane.setSelectedIndex(selectedIndex);
}

//!! needed by JDialog constructor
public JFrame getFrame() {
  return frame;
}

And when creating the second class, I pass the current instance of Test, Test.this because it's in an inner class, into the second class's constructor:

     public void actionPerformed(ActionEvent e) {
        //!! HisTestButton button = new HisTestButton();

        new HisTestButton(Test.this); //!! passing in this
     }

Now the second class can call Test object methods:

     @Override
     public void actionPerformed(ActionEvent e) {
        //!! 
        test.openNextTab();
     }

---

Note that you can use a CardLayout in the very same way, again calling public methods of one class by another, as long as the 2nd class has a viable reference to the current displayed instance of the first class. Getting a handle on proper references as always is key.

---

Also note that all of your classes in the default package should be placed within packages, either existing packages or new packages, whichever makes more sense, and whichever combines like with like. The only classes that belong in the default package are toy classes that don't require interaction with other classes.