"relative" positioning of buttons in a JFrame

Question

I want to draw an image as a background on a JFrame and then position several buttons in the frame such that when the frame is resized, the background is resized and the buttons remain "over" the same thing in the background image. I've tried to "do the right thing" and use a layout manager to position the buttons, but they just don't seem to behave like I need them to.
Is there an easy way to get a button to appear at e.g. 70% horizontally across the frame and 40% down the frame? And then when I resize, have the button still be 70% across and 40% down (based on the new size of the frame). Or should I just give up on the layout managers, and calculate my own absolute positions for everything?
Thanks

Answer 1

Check this out:
import javax.swing.*;
import java.awt.*;
public class CompassButtons extends JFrame {
  JButton nb = new JButton("North");
  JButton sb = new JButton("South");
  JButton eb = new JButton("East");
  JButton wb = new JButton("West");
  JViewport viewport = new JViewport();
  public CompassButtons() {
    super("SpringLayout Compass Demo");
    setSize(500,300);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    SpringLayout sl = new SpringLayout();
    Container c = getContentPane();
    c.setLayout(sl);
    int offset = 50;  // gap between buttons and outside edge
    int w      = 80;  // width of buttons
    int h      = 26;  // height of buttons
    int border =  3;  // border around viewport
    Spring offsetS     = Spring.constant(offset);
    Spring borderS     = Spring.constant(border);
    Spring widthS      = Spring.constant(w);
    Spring halfWidthS  = FractionSpring.half(widthS);
    Spring heightS     = Spring.constant(h);
    Spring halfHeightS = FractionSpring.half(heightS);
    Spring leftEdgeS   = sl.getConstraint(SpringLayout.WEST, c);
    Spring topEdgeS    = sl.getConstraint(SpringLayout.NORTH, c);
    Spring rightEdgeS  = sl.getConstraint(SpringLayout.EAST, c);
    Spring bottomEdgeS = sl.getConstraint(SpringLayout.SOUTH, c);
    Spring xCenterS    = FractionSpring.half(rightEdgeS);
    Spring yCenterS    = FractionSpring.half(bottomEdgeS);
    Spring leftBorder  = Spring.sum(leftEdgeS, borderS);
    Spring topBorder   = Spring.sum(topEdgeS, borderS);
    Spring northX = Spring.sum(xCenterS, Spring.minus(halfWidthS));
    Spring southY = Spring.sum(bottomEdgeS, Spring.minus(Spring.sum(heightS,
                                                                    offsetS)));
    Spring eastX = Spring.sum(rightEdgeS, Spring.minus(Spring.sum(widthS,
                                                                  offsetS)));
    Spring eastY = Spring.sum(yCenterS, Spring.minus(halfHeightS));
    c.add(nb, new SpringLayout.Constraints(northX, offsetS, widthS, heightS));
    c.add(sb, new SpringLayout.Constraints(northX, southY, widthS, heightS));
    c.add(wb);
    sl.getConstraints(wb).setX(offsetS);
    sl.getConstraints(wb).setY(eastY);
    sl.getConstraints(wb).setWidth(widthS);
    sl.getConstraints(wb).setHeight(heightS);
    c.add(eb);
    sl.getConstraints(eb).setX(eastX);
    sl.getConstraints(eb).setY(eastY);
    sl.getConstraints(eb).setWidth(widthS);
    sl.getConstraints(eb).setHeight(heightS);
    c.add(viewport); // this sets a bounds of (0,0,pref_width,pref_height)
    // The order here is important...need to have a valid width and height
    // in place before binding the (x,y) location
    sl.putConstraint(SpringLayout.SOUTH, viewport, Spring.minus(borderS),
                     SpringLayout.SOUTH, c);
    sl.putConstraint(SpringLayout.EAST, viewport, Spring.minus(borderS),
                     SpringLayout.EAST, c);
    sl.putConstraint(SpringLayout.NORTH, viewport, topBorder,
                     SpringLayout.NORTH, c);
    sl.putConstraint(SpringLayout.WEST, viewport, leftBorder,
                     SpringLayout.WEST, c);
    ImageIcon icon = new ImageIcon("images/terrain.jpg");
    viewport.setView(new JLabel(icon));
    // Hook up the buttons.  See the CompassScroller class (on-line) for details
    // on controlling the viewport.
    nb.setActionCommand(CompassScroller.NORTH);
    sb.setActionCommand(CompassScroller.SOUTH);
    wb.setActionCommand(CompassScroller.WEST);
    eb.setActionCommand(CompassScroller.EAST);
    CompassScroller scroller = new CompassScroller(viewport);
    nb.addActionListener(scroller);
    sb.addActionListener(scroller);
    eb.addActionListener(scroller);
    wb.addActionListener(scroller);
    setVisible(true);
  public static void main(String args[]) {
    new CompassButtons();
}Copyright 2003, O'Reilly & Associates
Provided as example.
Cheer
DB