AWT: Components disappear after minimizing the frame or after moving another window on top

Question

I'm using webcam-capture libraries and AWT to develop a simple interface for taking pictures from a webcam. The buttons and the combobox in my JFrame disappear after minimizing the window or after moving another window on top of it. Moving the pointer over the frame restores the components' visibility. I'm not skilled with Java UI, I can't figure out what's wrong with my code.

    @SuppressWarnings("serial")
public class ImageCaptureManager extends JFrame {

    private class SkipCapture extends AbstractAction {

        public SkipCapture() {
            super(“Skip”);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            /*SOME CODE HERE*/

        }
    }

    private class SnapMeAction extends AbstractAction {

        public SnapMeAction() {
            super(“Snap”);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            /*SOME CODE HERE*/

        }
    }

    private class captureCompleted extends AbstractAction {

        public captureCompleted() {
            super(“Completed”);
        }

        @Override
        public void actionPerformed(ActionEvent e) {

            /*SOME CODE HERE*/
        }
    }

    private class saveImage extends AbstractAction {

        public saveImage() {
            super(“Save”);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            /*SOME CODE HERE*/
        }
    }

    private class deleteImage extends AbstractAction {

        public deleteImage() {
            super(“Delete”);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            /*SOME CODE HERE*/
        }
    }


    private class StartAction extends AbstractAction implements Runnable {

        public StartAction() {
            super(“Start”);
        }

        @Override
        public void actionPerformed(ActionEvent e) {

            btStart.setEnabled(false);
            btSnapMe.setEnabled(true);

            executor.execute(this);
        }

        @Override
        public void run() {
            panel.start();
        }
    }

    private Executor executor = Executors.newSingleThreadExecutor();

    private Dimension captureSize = new Dimension(640, 480);

    private Dimension displaySize = new Dimension(640, 480);


    private Webcam webcam = Webcam.getDefault();

    private WebcamPanel panel;

    private JButton btSnapMe = new JButton(new SnapMeAction());
    private JButton btStart = new JButton(new StartAction());

    private JButton btComplete = new JButton(new captureCompleted());
    private JButton btSave = new JButton(new saveImage());
    private JButton btDelete = new JButton(new deleteImage());
    private JButton btSkip = new JButton(new SkipCapture());

    private JComboBox comboBox = new JComboBox();


    public ImageCaptureManager() {
        super(“Frame”);

        this.addWindowListener( new WindowAdapter()
        {

            @Override
            public void windowDeiconified(WindowEvent arg0) {

            }
                public void windowClosing(WindowEvent e)
                {

                }
        });


        List<Webcam> webcams =  Webcam.getWebcams();
        for (Webcam webcam : webcams) {
            System.out.println(webcam.getName());
            if (webcam.getName().startsWith("USB2.0 Camera 1")) {
                this.webcam = webcam;
                break;
            }
        }


        panel = new WebcamPanel(webcam, displaySize, false);
        webcam.setViewSize(captureSize);

        panel.setFPSDisplayed(true);
        panel.setFillArea(true);

        btSnapMe.setEnabled(false);
        btSave.setEnabled(false);
        btDelete.setEnabled(false);


        setLayout(new FlowLayout());

        Panel buttonPanel = new Panel();
        buttonPanel.setLayout(new GridLayout(10, 1));
        buttonPanel.add(Box.createHorizontalStrut(20));
        buttonPanel.add(btSnapMe);
        buttonPanel.add(Box.createHorizontalStrut(20));
        buttonPanel.add(btSave);
        buttonPanel.add(Box.createHorizontalStrut(20));
        buttonPanel.add(btDelete);
        buttonPanel.add(Box.createHorizontalStrut(20));
        buttonPanel.add(btComplete);
        buttonPanel.add(Box.createHorizontalStrut(20));
        buttonPanel.add(btSkip);

        JLabel label1 = new JLabel("Test");
        label1.setText(“Bla bla bla”);
        JLabel label2 = new JLabel("Test");
        label2.setText(" ");

        Panel captionAndWebcamPanel = new Panel();
        captionAndWebcamPanel.add(label1);
        captionAndWebcamPanel.add(label2);
        captionAndWebcamPanel.add(panel);
        captionAndWebcamPanel.add(label2);
        captionAndWebcamPanel.add(comboBox);
        captionAndWebcamPanel.setLayout(new BoxLayout(captionAndWebcamPanel, BoxLayout.Y_AXIS));


        add(captionAndWebcamPanel);

        add(buttonPanel);
        pack();
        setVisible(true);
        setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

        btStart.doClick();

        setSize(900,600);

    }

}

Answer 1

You are mixing AWT and Swing components.

"Historically, in the Java language, mixing heavyweight and lightweight components in the same container has been problematic." http://www.oracle.com/technetwork/articles/java/mixing-components-433992.html

I suggest you try using JPanels instead of Panels for captionAndWebcamPanel and buttonPanel, I'd also set layout to captionAndWebcamPanel before adding components.