JPanel Won't Focus After Switching in CardLayout

Question

I am creating a Tetris clone as a personal project. In order to switch between the menus, I am using a CardLayout, but I have come across a problem. When I switch from one menu to the other, the focus does not transfer to the other JPanel. How can I fix this?

Here is my JFrame:

package com.cgp.tetris;

import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.Toolkit;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class TetrisFrame extends JFrame {
    private static final long serialVersionUID = 1L;
    TetrisMenu tm = new TetrisMenu();
    static SinglePlayerMenu spm = new SinglePlayerMenu();
    public static CardLayout cl = new CardLayout();
    static JPanel parentComponent = new JPanel(cl);

    public static void main(String[] args) {
        new TetrisFrame();
    }

    public TetrisFrame() {
        setTitle("Tetris");
        setSize(new Dimension(646, 604));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
        setResizable(false);
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        setLocation((d.width / 2) - 323, (d.height / 2) - 302);
        parentComponent.add(tm, "tm");
        parentComponent.add(spm, "spm");
        cl.show(parentComponent, "tm");
        add(parentComponent);
    }

    public static void replace() {
        cl.show(parentComponent, "spm");
        spm.startClip();
    }
}

Here is my first JPanel/menu:

package com.cgp.tetris;

import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JPanel;
import javax.swing.KeyStroke;

public class TetrisMenu extends JPanel implements Runnable {
    private static final long serialVersionUID = 1L;
    private Thread thread;
    private BufferedImage titletop, titlebottom, selector;
    private boolean left = true, right = false;
    private AudioInputStream themestream;
    private Clip clip;

    public TetrisMenu() {
        super();
    }

    public void run() {
        requestFocus(true);
        loadImages();
        sound();
        bind();
        while (true) {
            repaint();
        }
    }

    private void sound() {
        File theme = new File("res/theme.wav");
        try {
            themestream = AudioSystem.getAudioInputStream(theme);
        } catch (UnsupportedAudioFileException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        DataLine.Info info = new DataLine.Info(Clip.class, themestream.getFormat());
        clip = null;
        try {
            clip = (Clip) AudioSystem.getLine(info);
        } catch (LineUnavailableException e) {
            e.printStackTrace();
        }
        try {
            clip.open(themestream);
        } catch (LineUnavailableException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        clip.start();
    }

    private void bind() {
        InputMap im = getInputMap();
        ActionMap am = getActionMap();

        im.put(KeyStroke.getKeyStroke("LEFT"), "left");
        am.put("left", new AbstractAction() {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent e) {
                left = true;
                right = false;
            }
        });

        im.put(KeyStroke.getKeyStroke("RIGHT"), "right");
        am.put("right", new AbstractAction() {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent e) {
                System.out.println("2");
                right = true;
                left = false;
            }
        });

        im.put(KeyStroke.getKeyStroke("SPACE"), "space");
        am.put("space", new AbstractAction() {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent e) {
                if (left) {
                    TetrisFrame.replace();
                    clip.stop();
                    thread.stop();a
                }
            }
        });
    }

    private void loadImages() {
        try {
            titletop = ImageIO.read(new File("res/tetrispic.png"));
            titlebottom = ImageIO.read(new File("res/titlebottom.png"));
            selector = ImageIO.read(new File("res/selector.png"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void addNotify() {
        super.addNotify();
        thread = new Thread(this);
        thread.start();
    }

    public void paint(Graphics g) {
        super.paint(g);

        g.drawImage(titletop, 0, 0, 640, 440, null);
        g.drawImage(titlebottom, 0, 440, 640, 136, null);
        if (left) {
            g.drawImage(selector, 36, 452, 16, 24, null);
        } else if (right) {
            g.drawImage(selector, 356, 452, 16, 24, null);
        }


    }
}

Here is my second JPanel/menu:

package com.cgp.tetris;

import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JPanel;
import javax.swing.KeyStroke;

public class SinglePlayerMenu extends JPanel implements Runnable {
    private static final long serialVersionUID = 1L;
    private Thread thread;
    private AudioInputStream themestream;
    private Clip clip;
    private BufferedImage base, bi1, bi2, bi3, bi4, bi1s, bi2s, bi3s, bi4s;
    private boolean typeselected = false, b1 = true, b2 = false, b3 = true, b4 = false, b5 = false, b6 = false;

    public SinglePlayerMenu() {
        super();
    }

    public void paint(Graphics g) {
        super.paint(g);

        g.drawImage(base, 0, 0, 640, 576, null);

        if (b1) {
            g.drawImage(bi1s, 80, 156, 240, 40, null);
        } else if (!b1) {
            g.drawImage(bi1, 80, 156, 240, 40, null);
        }
        if (b2) {
            g.drawImage(bi2s, 324, 156, 236, 40, null);
        } else if (!b2) {
            g.drawImage(bi2, 324, 156, 236, 40, null);
        }
    }

    public void run() {
        sound();
        loadImages();
        bind();
        while (true) {
            repaint();
        }
    }

    private void bind() {
        InputMap im = getInputMap();
        ActionMap am = getActionMap();

        im.put(KeyStroke.getKeyStroke("LEFT"), "left");
        am.put("left", new AbstractAction() {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent e) {
                if (!typeselected) {
                    b1 = true;
                    b2 = false;
                }
            }
        });

        im.put(KeyStroke.getKeyStroke("RIGHT"), "right");
        am.put("right", new AbstractAction() {
            private static final long serialVersionUID = 1L;

            public void actionPerformed(ActionEvent e) {
                if (!typeselected) {
                    b2 = true;
                    b1 = false;
                }
            }
        });
    }

    private void loadImages() {
        try {
            base = ImageIO.read(new File("res/base.png"));
            bi1 = ImageIO.read(new File("res/1.png"));
            bi2 = ImageIO.read(new File("res/2.png"));
            bi3 = ImageIO.read(new File("res/3.png"));
            bi4 = ImageIO.read(new File("res/4.png"));
            bi1s = ImageIO.read(new File("res/1s.png"));
            bi2s = ImageIO.read(new File("res/2s.png"));
            bi3s = ImageIO.read(new File("res/3s.png"));
            bi4s = ImageIO.read(new File("res/4s.png"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void sound() {
        File theme = new File("res/playtheme.wav");
        try {
            themestream = AudioSystem.getAudioInputStream(theme);
        } catch (UnsupportedAudioFileException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        DataLine.Info info = new DataLine.Info(Clip.class, themestream.getFormat());
        clip = null;
        try {
            clip = (Clip) AudioSystem.getLine(info);
        } catch (LineUnavailableException e) {
            e.printStackTrace();
        }
        try {
            clip.open(themestream);
        } catch (LineUnavailableException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void addNotify() {
        super.addNotify();
        thread = new Thread(this);
        thread.start();
    }

    public void startClip() {
        clip.loop(Clip.LOOP_CONTINUOUSLY);
    }
}

Thanks in advance!

For some reason, the files won't package correctly into the JAR. Just a minute. — Cg2916, Nov 27 '11 at 02:36
I'm trying to create a SSCCE, but for some reason, the images I'm using won't show up when I run the jar. — Cg2916, Nov 27 '11 at 03:01
What do you need images for? All you want is a small app that uses cardlayout and tries to get focus, ***that's it***. There's no need for images or any of that nonsense unrelated to the problem. — Hovercraft Full Of Eels, Nov 27 '11 at 03:08
That's my whole GUI. You can't tell if it's working or not without the images. — Cg2916, Nov 27 '11 at 03:09
*"You can't tell if it's working or not without the images."* I find that very hard to believe. Most focusable elements to which you can add an image also accept plain text. If it is the case that images are really required, generate some images in code as shown in the [Nested Layout Example](http://stackoverflow.com/questions/5621338/about-swing-and-jtable/5630271#5630271). The images do not even require a (nice) gradient like shown there - separate solid colors will be fine. — Andrew Thompson, Nov 27 '11 at 03:13
Oh wow. Eclipse is really giving me grief. I tried creating an SSCCE with just filled-in background colors (no images), and it STILL won't work. — Cg2916, Nov 27 '11 at 03:25

score 7 · Answer 1 · answered Nov 27 '11 at 02:57

Have you tried giving the component of interest a ComponentListener, and in its componentShown(...) request the focus via requestFocusInWindow()? Something like:

  myComponent.addComponentListener(new ComponentAdapter() {

     @Override
     public void componentShown(ComponentEvent cEvt) {
        Component src = (Component) cEvt.getSource();
        src.requestFocusInWindow();
     }

  });

Of course the component (a JPanel in your case) needs to have its focusable property set to true via

myComponent.setFocusable(true);

For example:

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

@SuppressWarnings("serial")
public class CardLayoutFocus extends JPanel {
   private static final int PREF_W = 300;
   private static final int PREF_H = 150;
   private static final int COUNT = 4;
   private CardLayout cardlayout = new CardLayout();
   private JPanel cardHolder = new JPanel(cardlayout );

   public CardLayoutFocus() {
      setLayout(new BorderLayout());
      add(cardHolder, BorderLayout.CENTER);
      for (int i = 0; i < COUNT; i++) {
         String labelString = "Card " + i;
         cardHolder.add(createCardLabel(labelString), labelString);
      }

      int timerDelay = 1000;
      new Timer(timerDelay , new ActionListener() {
         public void actionPerformed(ActionEvent arg0) {
            cardlayout.next(cardHolder);
         }
      }).start();
   }

   private JLabel createCardLabel(String labelString) {
      final JLabel label = new JLabel(labelString, SwingConstants.CENTER);
      label.setName(labelString);
      label.setOpaque(true);
      label.setFocusable(true);
      label.addFocusListener(new FocusListener() {

         @Override
         public void focusLost(FocusEvent arg0) {
            label.setBackground(null);
         }

         @Override
         public void focusGained(FocusEvent arg0) {
            label.setBackground(Color.pink);
         }
      });
      label.addComponentListener(new ComponentAdapter() {

         @Override
         public void componentShown(ComponentEvent cEvt) {
            Component src = (Component) cEvt.getSource();
            src.requestFocusInWindow();
         }

      });
      return label;
   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

   private static void createAndShowGui() {
      CardLayoutFocus mainPanel = new CardLayoutFocus();

      JFrame frame = new JFrame("Pink if has the focus");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

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

No, not like that. But again, no SSCCE, and we probably can't help you. — Hovercraft Full Of Eels, Nov 27 '11 at 03:08
*"Of course the component .. needs to have its focusable property set to true"* +1 — Andrew Thompson, Nov 27 '11 at 03:17

score 4 · Accepted Answer · edited Nov 27 '11 at 04:10

4

Add a ComponentListener so you can request the window to put it in focus. Replace your existing constructor with this:

public SinglePlayerMenu() {
    super();
    this.addComponentListener( new ComponentAdapter() {
        @Override
        public void componentShown( ComponentEvent e ) {
            SinglePlayerMenu.this.requestFocusInWindow();
        }
    });
}

edited Nov 27 '11 at 04:10

Hovercraft Full Of Eels

283,665
25
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answered Nov 27 '11 at 03:18

blackcompe

3,180
16
27

Hm that looks familiar. In fact it looks like my reply given 20 minutes ago. ;) – Hovercraft Full Of Eels Nov 27 '11 at 03:19
It worked! Thank you. Hovercraft, no clue why yours didn't work. – Cg2916 Nov 27 '11 at 03:27
1

-1, using a ComponentListener was suggested 20 minutes earlier. No need to clutter the forum with duplicate suggestions. – camickr Nov 27 '11 at 03:30
@cg2916, this was my suggestion; the only difference is that mine wasade 20 minutes earlier than his, and your code that you tried was not the same as what I posted. You shouldn't have accepted this. Not right. – Hovercraft Full Of Eels Nov 27 '11 at 03:37
@Hovercraft Sorry. I didn't mean that. I did borrow your suggestion. – blackcompe Nov 27 '11 at 03:58
@Cg2916 You should unselect my answer. – blackcompe Nov 27 '11 at 04:00
Yeah, but yours actually worked. No offence to Hovercraft, he tried the exact same thing. – Cg2916 Nov 27 '11 at 04:01
@blackcompe: Many thanks -- that's kind to say. I edited your question to enable me to remove down-vote and to give up-vote. – Hovercraft Full Of Eels Nov 27 '11 at 04:10

score 3 · Answer 3 · answered Nov 27 '11 at 02:34

3

This is usually achieved by calling requestFocusInWindow().

answered Nov 27 '11 at 02:34

Andrew Thompson

168,117
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score 3 · Answer 4 · answered Nov 27 '11 at 03:18

3

Card Layout Focus handles this by placing focus on the first component on the panel.

answered Nov 27 '11 at 03:18

camickr

321,443
19
166
288

JPanel Won't Focus After Switching in CardLayout

4 Answers4

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