Java : Swing : Hide frame after button pressed

Question

I have a button in a java frame that when pressed it reads a value from a text field and uses that string as a port name attempting to connect to a serial device.

If this connection is successful the method returns true if not it returns false. If it returns true I want the frame to disappear. A series of other frames specifed in other classes will then appear with options to control the serial device.

My problem is: the button is connected to an action listener, when pressed this method is invoked. If I try to use the frame.setVisible(true); method java throws a abstract button error because I'm effectively telling it to disappear the frame containing the button before the button press method has exited. Removing the frame.setVisible(true); allow the program to run correctly however I am left with a lingering connection frame that is no longer any use.

How to I get the frame to disappear upon pressing a the button?

package newimplementation1;

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


/**
 *
 * @author Zac
 */

public class ConnectionFrame extends JPanel implements ActionListener {


private JTextField textField;
private JFrame frame;
private JButton connectButton;
private final static String newline = "\n";

public ConnectionFrame(){

    super(new GridBagLayout());

    textField = new JTextField(14);
    textField.addActionListener(this);
    textField.setText("/dev/ttyUSB0");

    connectButton = new JButton("Connect");

    //Add Components to this panel.
    GridBagConstraints c = new GridBagConstraints();
    c.gridwidth = GridBagConstraints.REMAINDER;

    c.fill = GridBagConstraints.HORIZONTAL;
    add(textField, c);

    c.fill = GridBagConstraints.BOTH;
    c.weightx = 1.0;
    c.weighty = 1.0;
    add(connectButton, c);



    connectButton.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent e)
        {

            boolean success = Main.mySerialTest.initialize(textField.getText());

            if (success == false) {System.out.println("Could not connect"); return;}

            frame.setVisible(false);  // THIS DOES NOT WORK!!

            JTextInputArea myInputArea = new JTextInputArea();
            myInputArea.createAndShowGUI();

            System.out.println("Connected");


        }
    });

}

    public void actionPerformed(ActionEvent evt) {

            // Unimplemented required for JPanel

    }

    public void createAndShowGUI() {

    //Create and set up the window.
    frame = new JFrame("Serial Port Query");
    frame.setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);


    //Add contents to the window.
    frame.add(new ConnectionFrame());
    frame.setLocation(300, 0);


    //Display the window.
    frame.pack();
    frame.setVisible(true);

            frame.addComponentListener(new ComponentAdapter() {
        @Override
        public void componentHidden(ComponentEvent e) {
            System.out.println("Exiting Gracefully");
            Main.mySerialTest.close();
            ((JFrame)(e.getComponent())).dispose();
            System.exit(0);
        }
    });


}

}

Answer 1

Running your snippet (after removing/tweaking around the custom classes), throws an NPE. Reason is that the frame you'r accessing is null. And that's because it's never set. Better not rely on any field, let the button find its toplevel ancestor and hide that, like in

        public void actionPerformed(final ActionEvent e) {

            boolean success = true;
            if (success == false) {
                System.out.println("Could not connect");
                return;
            }

            Window frame = SwingUtilities.windowForComponent((Component) e
                    .getSource());
            frame.setVisible(false); //no problem :-)

        }

Answer 2

Your problem is with this line:

  frame.add(new ConnectionFrame());

You're creating a new ConnectionFrame object, and so the frame that your button tries to close on is not the same as the one being displayed, and this is the source of your problem.

If you change it to,

  //!! frame.add(new ConnectionFrame());
  frame.add(this);

so that the two JFrames are one and the same, things may work more smoothly.

But having said that, your whole design smells bad and I'd rethink it in a more OOP and less static fashion. Also, use dialogs where dialogs are needed, not frames, and rather than dialogs consider swapping views (JPanels) via CardLayout as a better option still.

Myself, I'd create a "dumb" GUI for this, one that creates a JPanel (here in my example it extends a JPanel for simplicity, but I'd avoid extending if not necessary), and I'd let whoever is calling this code decide what to do with the information via some control. For e.g.,

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

@SuppressWarnings("serial")
public class ConnectionPanel extends JPanel {

   private JTextField textField;
   private JButton connectButton;
   private ConnectionPanelControl control;

   public ConnectionPanel(final ConnectionPanelControl control) {
      super(new GridBagLayout());
      this.control = control;

      ActionListener listener = new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            if (control != null) {
               control.connectButtonAction();
            }
         }
      };

      textField = new JTextField(14);
      textField.addActionListener(listener);
      textField.setText("/dev/ttyUSB0");

      connectButton = new JButton("Connect");

      GridBagConstraints c = new GridBagConstraints();
      c.gridwidth = GridBagConstraints.REMAINDER;

      c.fill = GridBagConstraints.HORIZONTAL;
      add(textField, c);

      c.fill = GridBagConstraints.BOTH;
      c.weightx = 1.0;
      c.weighty = 1.0;
      add(connectButton, c);

      connectButton.addActionListener(listener);
   }

   public String getFieldText() {
      return textField.getText();
   }

}

Again, something outside of the simple GUI would make decisions on what to do with the text that the textfield contains and what to do with the GUI that is displaying this JPanel:

public interface ConnectionPanelControl {

   void connectButtonAction();

}

Also, you will likely do any connecting in a background thread so as to not freeze your GUI, probably a SwingWorker. Perhaps something like this:

import java.awt.event.ActionEvent;
import java.util.concurrent.ExecutionException;

import javax.swing.*;

@SuppressWarnings("serial")
public class MyMain extends JPanel {
   public MyMain() {
      add(new JButton(new ConnectionAction("Connect", this)));
   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("My Main");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new MyMain());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

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

@SuppressWarnings("serial")
class ConnectionAction extends AbstractAction {
   private MyMain myMain;
   private ConnectionPanel cPanel = null;
   private JDialog dialog = null;

   public ConnectionAction(String title, MyMain myMain) {
      super(title);
      this.myMain = myMain;
   }

   @Override
   public void actionPerformed(ActionEvent e) {
      if (dialog == null) {
         dialog = new JDialog(SwingUtilities.getWindowAncestor(myMain));
         dialog.setTitle("Connect");
         dialog.setModal(true);
         cPanel = new ConnectionPanel(new ConnectionPanelControl() {

            @Override
            public void connectButtonAction() {
               final String connectStr = cPanel.getFieldText();
               new MySwingWorker(connectStr).execute();
            }
         });
         dialog.getContentPane().add(cPanel);
         dialog.pack();
         dialog.setLocationRelativeTo(null);
      }
      dialog.setVisible(true);
   }

   private class MySwingWorker extends SwingWorker<Boolean, Void> {
      private String connectStr = "";

      public MySwingWorker(String connectStr) {
         this.connectStr = connectStr;
      }

      @Override
      protected Boolean doInBackground() throws Exception {
         // TODO: make connection and then return a result
         // right now making true if any text in the field
         if (!connectStr.isEmpty()) {
            return true;
         }
         return false;
      }

      @Override
      protected void done() {
         try {
            boolean result = get();
            if (result) {
               System.out.println("connection successful");
               dialog.dispose();
            } else {
               System.out.println("connection not successful");
            }
         } catch (InterruptedException e) {
            e.printStackTrace();
         } catch (ExecutionException e) {
            e.printStackTrace();
         }
      }
   }
}