Problem(s) with GridBagLayout - more confused

[Gary Fletcher]

I am trying to use the GridBagLayout in order to develop a windowed application.

Currently I am at a VERY early stage, just trying to add 3 components to a content pane. They should simply be displayed next to each other, in the top left of the frame, but they are being displayed in the centre of the window and I do not know why. Can anyone point me in the right direction.

Code is:

Main

public class GridBagTest
{

	public static void main(String[] args)
	{
		EventQueue.invokeLater(new Runnable()
		{
			public void run()
			{
				try
				{
					GridBagFrame frame = new GridBagFrame();
				}
				catch (Exception e)
				{
					e.printStackTrace();
				}
			}
		});

	}

}

Frame Class

public class GridBagFrame extends JFrame
{
	public GridBagFrame() throws ClassNotFoundException,
                InstantiationException, IllegalAccessException,
                UnsupportedLookAndFeelException
	{
		super("Grid Bag Test");
		
		initialiseFrame();
		GridBagPanel gbp = new GridBagPanel(getContentPane());
		pack();
		setVisible(true);
	}
	
	private void initialiseFrame() throws ClassNotFoundException,
               InstantiationException, IllegalAccessException,
               UnsupportedLookAndFeelException
	{
		int height = Toolkit.getDefaultToolkit().getScreenSize().height;
		int width = Toolkit.getDefaultToolkit().getScreenSize().width;
		
		UIManager.setLookAndFeel(
               "com.sun.java.swing.plaf.windows.WindowsLookAndFeel");  
        SwingUtilities.updateComponentTreeUI(this); 
        setSize(width-100,height-100);
        setExtendedState(JFrame.MAXIMIZED_BOTH);
		setLocationByPlatform(true);
		setIconImage(new ImageIcon("images\\icon.gif").getImage());
	}
}

Content Pane Class

public class GridBagPanel
{
	private Container contentPane;
	
	public GridBagPanel(Container contentPane)
	{
		this.contentPane = contentPane;
		initialise();
		addComponents();
	}
	
	private void initialise()
	{
		int height = Toolkit.getDefaultToolkit().getScreenSize().height;
		int width = Toolkit.getDefaultToolkit().getScreenSize().width;
		
		contentPane.setLayout(new GridBagLayout());
		contentPane.setPreferredSize(new Dimension(width-200,height-200));
	}
	
	private void addComponents()
	{
		JLabel file1 = new JLabel("File 1:");
		//file1.setPreferredSize(new Dimension(100,20));

		JTextField fileName1 = new JTextField("Filename 1");
		fileName1.setPreferredSize(new Dimension(200,25));
		
		JButton chooser1 = new JButton(new ImageIcon("images\\file-open-icon.png"));
		chooser1.setPreferredSize(new Dimension(25,25));
		
		GridBagConstraints gbConstraints = new GridBagConstraints();
		
		gbConstraints.weightx = 0;
		gbConstraints.weighty = 0;
		gbConstraints.gridx = 0;
		gbConstraints.gridy = 0;
		gbConstraints.gridwidth = 1;
		gbConstraints.gridheight = 1;
		contentPane.add(file1, gbConstraints);

		gbConstraints.weightx = 0;
		gbConstraints.weighty = 0;
		gbConstraints.gridx = 1;
		gbConstraints.gridy = 0;
		gbConstraints.gridwidth = 1;
		gbConstraints.gridheight = 1;
		contentPane.add(fileName1, gbConstraints);
		
		gbConstraints.weightx = 0;
		gbConstraints.weighty = 0;
		gbConstraints.gridx = 2;
		gbConstraints.gridy = 0;
		gbConstraints.gridwidth = 1;
		gbConstraints.gridheight = 1;
		contentPane.add(chooser1, gbConstraints);

	}
}

[Gary Fletcher]

Also, is it possible to add a filler, or spaces, between components, or would I need to create a space JLabel and add that in the appropriate place?

[Rob Camick]

They should simply be displayed next to each other, in the top left of the frame, but they are being displayed in the centre of the window and I do not know why.

Check out the section from the Swing tutorial on How to Use Grid Bag Layout. The section on weightx / weighty will explain the problem and the solution.

The GridBagLayout is one of the most complicated layout managers to use. A simpler layout manager would be the FlowLayout. The tutorial also has examples of how to use this layout manager.

[Gary Fletcher]

Thanks Rob.

Unfortuntely the FlowLayout will not be flexible enogh for the end application which requires multiple Components of various sizes, hence the dive into GridBagLayout.

I have read the tutorial and it has lead to more confusion.

The book I am reading states that values of GridBagLayout.weightx/y are between 0-100, the tutorial says between 0-1, although both could be considered a percentage weighting which is correct? Or are they both correct?

[Gary Fletcher]

Stil having issues even when making the weightx/y non zero.

As the finished app will have mutilple components that need diffreent requirements I have decided to split the Componets into individual JPanels, but the initial test STILL puts the panel in the centre of the content pane, please help as I think I am going a bit mad.

Main Class

public class GridBagTest
{

	public static void main(String[] args)
	{
		EventQueue.invokeLater(new Runnable()
		{
			public void run()
			{
				try
				{
					GridBagFrame frame = new GridBagFrame();
				}
				catch (Exception e)
				{
					e.printStackTrace();
				}
			}
		});

	}

}

Main Frame Class

public class GridBagFrame extends JFrame
{
	public GridBagFrame() throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException
	{
		super("Grid Bag Test");
		
		initialiseFrame();
		ContentPane gbp = new ContentPane(getContentPane());
		pack();
		setVisible(true);
	}
	
	private void initialiseFrame() throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException
	{
		int height = Toolkit.getDefaultToolkit().getScreenSize().height;
		int width = Toolkit.getDefaultToolkit().getScreenSize().width;
		
		UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");  
        SwingUtilities.updateComponentTreeUI(this); 
        setSize(width-100,height-100);
        setExtendedState(JFrame.MAXIMIZED_BOTH);
		setLocationByPlatform(true);
		setIconImage(new ImageIcon("images\\icon.gif").getImage());
	}
}

Content Pane Class

public class ContentPane
{
	private Container contentPane;
	
	public ContentPane(Container contentPane)
	{
		this.contentPane = contentPane;
		initialise();
		addComponents();
	}
	
	private void initialise()
	{
		int height = Toolkit.getDefaultToolkit().getScreenSize().height;
		int width = Toolkit.getDefaultToolkit().getScreenSize().width;
		
		contentPane.setLayout(new GridBagLayout());
		contentPane.setPreferredSize(new Dimension(width-200,height-200));
	}
	
	private void addComponents()
	{
		GridBagConstraints gbConstraints = new GridBagConstraints();
		
		gbConstraints.weightx = 1;
		gbConstraints.weighty = 1;
		gbConstraints.gridx = 0;
		gbConstraints.gridy = 0;
		gbConstraints.gridwidth = 1;
		gbConstraints.gridheight = 1;
		contentPane.add(new ActionPanel(), gbConstraints);
	}
}

Component Class

public class ActionPanel extends JPanel
{
	public ActionPanel()
	{
		super();
		initialise();
		addComponents();
	}
	
	private void initialise()
	{
		setLayout(new FlowLayout());
	}
	
	private void addComponents()
	{
		JLabel spaces = new JLabel("            ");
		spaces.setEnabled(false);
		
		JLabel file1 = new JLabel("File 1:");
		JLabel file2 = new JLabel("File 2:");
		
		JTextField fileName1 = new JTextField("Filename 1");
		fileName1.setPreferredSize(new Dimension(200,25));
		
		JTextField fileName2 = new JTextField("Filename 2");
		fileName2.setPreferredSize(new Dimension(200,25));
		
		JButton chooser1 = new JButton(new ImageIcon("images\\file-open-icon.png"));
		chooser1.setPreferredSize(new Dimension(25,25));
		
		JButton chooser2 = new JButton(new ImageIcon("images\\file-open-icon.png"));
		chooser2.setPreferredSize(new Dimension(25,25));
		
		add(file1);
		add(fileName1);
		add(chooser1);
		add(spaces);
		add(file2);
		add(fileName2);
		add(chooser2);
	}
}