Doing without layout manager

Question

Hi guys.
I have a very complex problem.
I've been writing a code that should be able to display a general tree. The tree has to look like an organigram, if you know what I mean. For example, the parent node is a the top and the child nodes are underneath it.
It's clear that there is no layout manager that can handle this correctly. At least I assume.
I used the Node Positioning of John Walker to compute the x- and y-coordinate of each node.
I can display the nodes so far, but I don't know how to force a scrollpane to react to the size of the JPanel containing the nodes.
In fact, the JPanel containing the nodes of the tree has a null layout manager. If it contains let say 10 nodes, it becomes big enough. However the scrollpane doesn't grow along with the panel.
What should I do to let the scroll pane grow so that all nodes can be seen.
Regards.
Edmond

Answer 1

It's clear that there is no layout manager that can handle this correctly. Correct. So you need to create a custom layout manager.
I used the Node Positioning of John Walker to compute the x- and y-coordinate of each node. This is the code that should be added to your custom layout manager.
but I don't know how to force a scrollpane to react to the size of the JPanel containing the nodes.This is the job of the layout manager. It will determine the preferred size of the panel based on the location/size of all the components added to the panel.
Here is a simple example to get you started. This layout displays the components diagonally:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.border.*;
public class NodeLayout implements LayoutManager, java.io.Serializable
     private int hgap = 20;
     private int vgap = 20;
     public NodeLayout()
      * Adds the specified component with the specified name to the layout.
      * @param name the name of the component
      * @param comp the component to be added
     @Override
     public void addLayoutComponent(String name, Component comp) {}
      * Removes the specified component from the layout.
      * @param comp the component to be removed
     @Override
     public void removeLayoutComponent(Component component)
      *     Determine the minimum size on the Container
      *  @param      target   the container in which to do the layout
      *  @return      the minimum dimensions needed to lay out the
      *                subcomponents of the specified container
     @Override
     public Dimension minimumLayoutSize(Container parent)
          synchronized (parent.getTreeLock())
               return preferredLayoutSize(parent);
      *     Determine the preferred size on the Container
      *  @param      parent   the container in which to do the layout
      *  @return  the preferred dimensions to lay out the
      *              subcomponents of the specified container
     @Override
     public Dimension preferredLayoutSize(Container parent)
          synchronized (parent.getTreeLock())
               return getLayoutSize(parent);
      *  The calculation for minimum/preferred size it the same. The only
      *  difference is the need to use the minimum or preferred size of the
      *  component in the calculation.
      *  @param      parent  the container in which to do the layout
     private Dimension getLayoutSize(Container parent)
          int components = parent.getComponentCount();
        int width = (components - 1) * hgap;
        int height = (components - 1) * vgap;
          Component last = parent.getComponent(components - 1);
          Dimension preferred = last.getPreferredSize();
          width += preferred.width;
          height += preferred.height;
          Insets parentInsets = parent.getInsets();
          width += parentInsets.top + parentInsets.right;
          height += parentInsets.top + parentInsets.bottom;
          Dimension d = new Dimension(width, height);
          return d;
      * Lays out the specified container using this layout.
      * @param       target   the container in which to do the layout
     @Override
     public void layoutContainer(Container parent)
     synchronized (parent.getTreeLock())
          Insets parentInsets = parent.getInsets();
          int x = parentInsets.left;
          int y = parentInsets.top;
          //  Set bounds of each component
          for (Component component: parent.getComponents())
               if (component.isVisible())
                    Dimension d = component.getPreferredSize();
                    component.setBounds(x, y, d.width, d.height);
                    x += hgap;
                    y += vgap;
      * Returns the string representation of this column layout's values.
      * @return      a string representation of this layout
     public String toString()
          return "["
               + getClass().getName()
               + "]";
     public static void main( String[] args )
          final JPanel panel = new JPanel( new NodeLayout() );
          panel.setBorder( new MatteBorder(10, 10, 10, 10, Color.YELLOW) );
          createLabel(panel);
          createLabel(panel);
          createLabel(panel);
          createLabel(panel);
          createLabel(panel);
          JButton button = new JButton("Add Another Component");
          button.addActionListener( new ActionListener()
               public void actionPerformed(ActionEvent e)
                    NodeLayout.createLabel( panel );
          JFrame frame = new JFrame();
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.add( new JScrollPane(panel) );
          frame.add(button, BorderLayout.SOUTH);
          frame.pack();
          frame.setLocationRelativeTo( null );
          frame.setVisible( true );
     public static void createLabel(JPanel panel)
          JLabel label = new JLabel( new Date().toString() );
          label.setOpaque(true);
          label.setBackground( Color.ORANGE );
          panel.add( label );
          panel.revalidate();
          panel.repaint();
}You would need to customize the getLayoutSize() and layoutContainer() methods to meet your Node Layout requirements.