Question

Hi i have MainFrame class:

public class MainFrame extends JFrame{

    private JLabel originalLabel;
    private JLabel filteredImage;

    public MainFrame(){
        setExtendedState(JFrame.MAXIMIZED_BOTH);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());
        initComponents();
        setVisible(true);
    }

    private void initComponents(){
        ImageFilterMenuBar menuBar = new ImageFilterMenuBar();

        originalLabel = new JLabel("Test1");
        filteredImage = new JLabel("Test2");

        Component verticalStrut = Box.createVerticalStrut(10);

        JPanel central = new JPanel();
        central.add(originalLabel);
        central.add(verticalStrut);
        central.add(filteredImage);


        add(new RadioButtonsPanel(), BorderLayout.SOUTH);
        add(central, BorderLayout.CENTER);

        setJMenuBar(menuBar);
    }

}

and MenuBar class:

public class ImageFilterMenuBar extends JMenuBar{

    private JMenu fileMenu;
    private JMenuItem openImage;
    private JMenuItem exit;


    public ImageFilterMenuBar(){
        initCompoments();
    }

    private void initCompoments() {
        fileMenu = new JMenu("File");
        setMenuItems();
        add(fileMenu);
    }

    private void setMenuItems(){
        openImage = new JMenuItem("Open Image");
        exit = new JMenuItem("Exit");

        openImage.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O,
                InputEvent.CTRL_MASK));

        exit.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_CANCEL,InputEvent.SHIFT_MASK));

        openImage.addActionListener(new OpenListener());
        exit.addActionListener(new ExiteListener());

        fileMenu.add(openImage);
        fileMenu.add(exit);
    }

}

in MenuBar class you can sea OpenButton. it’s open JFileChooser and returns me url of file which I chose.
So now I don’t know how to send this url into my MainFrame class where I want to display this file..
Any ideas??

Answer 1

The easiest solution is to pass a reference to MainFrame to the ImageFilterMenuBar:

ImageFilterMenuBar menuBar = new ImageFilterMenuBar(this);

Then, add a method like below in the MainFrame:

public void setImageFile(File file) {
  // do whatever here
}

In the ImageFilterMenuBar you would keep a reference to the MainFrame in a member variable and use it to call setImageFile() once the JFileChooser returns a File.

A more difficult to implement solution would be to implement the observer pattern. This is the way the listeners work in Swing.
You would register the main frame as a listener and the other class would be the one to notify about file selection changes.

To open a file chooser and get the selected file:

JFileChooser chooser = new JFileChooser(path);
int result = chooser.showOpenDialog(mainFrame);
File file = chooser.getSelectedFile();
if (result == JFileChooser.APPROVE_OPTION && file != null && file.exists()) {
  mainFrame.setImageFile(file);
}