Question

I am trying to get a JInternalFrame to be maximized when it is launched. I have done web searches on this and have tried various code suggestions, but they do not seem to work properly on my machine, which is running Java 6 on Windows 7.

I have simplified the code below so that it will be easier to isolate the solution.

Can anyone show me how to change the code below so that the internal frame is maximized automatically when it is created?

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;

import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JLayeredPane;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.KeyStroke;

public class MaximizeInternalFrame extends JFrame implements ActionListener{
private static final long serialVersionUID = 1L;
JLayeredPane desktop;
JInternalFrame internalFrame;

public MaximizeInternalFrame() {
    super("Test To Maximize Internal Frame");
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Make the big window be indented 50 pixels from each edge of the screen.
    int inset = 50;
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension screenMinus50 = new Dimension(screenSize.width - inset*2, screenSize.height - inset*2); 

    this.setPreferredSize(screenMinus50);
    desktop = new JDesktopPane();
    setJMenuBar(createMenuBar());
    this.add(desktop, BorderLayout.CENTER);
    this.pack();
    this.setSize(screenMinus50);
    this.setLocationRelativeTo(null);
}
protected JMenuBar createMenuBar() {
    JMenuBar menuBar = new JMenuBar();
    //Set up the File menu.
    JMenu FileMenu = new JMenu("File");
    FileMenu.setMnemonic(KeyEvent.VK_F);
    menuBar.add(FileMenu);
    //Set up the first menu item.
    JMenuItem menuItem = new JMenuItem("New");
    menuItem.setMnemonic(KeyEvent.VK_N);
    menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N, ActionEvent.ALT_MASK));
    menuItem.setActionCommand("new");
    menuItem.addActionListener(new OpenListener());
    FileMenu.add(menuItem);
    //Set up the second menu item.
    menuItem = new JMenuItem("Quit");
    menuItem.setMnemonic(KeyEvent.VK_Q);
    menuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_Q, ActionEvent.ALT_MASK));
    menuItem.setActionCommand("quit");
    menuItem.addActionListener(this);
    FileMenu.add(menuItem);

    return menuBar;
    }
class OpenListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        // create internal frame
        internalFrame = new JInternalFrame("this internal frame needs to be maximized", true, true, true, true);
        desktop.add(internalFrame);
        internalFrame.setSize(internalFrame.getMaximumSize());
        internalFrame.pack();
        internalFrame.setVisible(true);
    }
}
public static void main(String args[]) {
    MaximizeInternalFrame myParentFrame = new MaximizeInternalFrame();
    myParentFrame.setVisible(true);
}
public void actionPerformed(ActionEvent e) {if ("quit".equals(e.getActionCommand())){System.exit(0);}}
}

Answer 1

Add the following after internalFrame.setVisible(true):

try {
  internalFrame.setMaximum(true);
} catch (PropertyVetoException e) {
  // Vetoed by internalFrame
  // ... possibly add some handling for this case
}

You can also remove internalFrame.setSize(internalFrame.getMaximumSize());