Re: Multiple Lines with a FlowLayout within a SOUTH region in a BorderLayout

Thank you all.

markspace, your "LayoutInspector" saves the day. It realy works.
Actually I was looking for a "straight forward" solution, because I
teach "swing" in a 4-day-course. Your answers made clear, what I
expected.

thanks again.

here again the full code from markspace (minor changes):

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import java.awt.FlowLayout;
import java.util.logging.Logger;
import java.awt.*;
import java.util.logging.ConsoleHandler;
import java.util.logging.Level; //import java.util.logging.Logger;
import javax.swing.*;

/**
 * TODO Document Class or Interface
 *
 * @author Philipp Gressly (phi AT gressly DOT ch) + "markspace"
from the java gui mailing list.
 */
public class TestLayout {

    public static void main(String[] args) {
        new TestLayout().buildAndShowGui();
    }

    private void buildAndShowGui() {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                top();
            }
        });
    }

    void top() {
        JFrame jf = new JFrame("Multiple Lines in the South");
        jf.add(new JLabel("center"));
        // JPanel mainPanel = makeMainPanel();
        // jf.add(mainPanel);
        jf.add(makeSouthPanel(), BorderLayout.SOUTH);
        jf.setSize(300, 300);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setVisible(true);
    }

    JPanel makeMainPanel() {
        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new BorderLayout());
        populateMainPanel(mainPanel);
        return mainPanel;
    }

    void populateMainPanel(JPanel mainPanel) {
        JLabel centerLabel = new JLabel("center");
        mainPanel.add(centerLabel, BorderLayout.CENTER);
        JPanel southPanel = makeSouthPanel();
        mainPanel.add(southPanel, BorderLayout.SOUTH);
    }

    JPanel makeSouthPanel() {
        JPanel southPanel = new JPanel();
        southPanel.setLayout(new LayoutInspector());
        // southPanel.setLayout(null); // which to use here?
        populateMultiLinePanel(southPanel);
        southPanel.setBackground(Color.GREEN);
        return southPanel;
    }

    JPanel makeMultiLinePanel() {
        JPanel mzp = new JPanel();
        mzp.setLayout(new LayoutInspector());
        populateMultiLinePanel(mzp);
        return mzp;
    }

    void populateMultiLinePanel(Container mzp) {
        mzp.add(new JButton("Hello"));
        mzp.add(new JButton("World"));
        mzp.add(new JButton("OK"));
        mzp.add(new JButton("Cancel"));
    }

} // end of class TestLayout

class LayoutInspector extends FlowLayout {

    private static Logger log = Logger.getAnonymousLogger();

    static {
        ConsoleHandler ch = new ConsoleHandler();
        ch.setLevel(Level.ALL);
        log.addHandler(ch);
        log.setLevel(Level.ALL);
        log.setUseParentHandlers(false);
    }

    public void addLayoutComponent(String name, Component comp) {
        log.entering("FlowLayout", "addLayoutComponent", new
Object[] { name,
                comp });
        // throw new UnsupportedOperationException( "Not supported
yet." );
        super.addLayoutComponent(name, comp);
        log.exiting("FlowLayout", "addLayoutComponent");
    }

    public void removeLayoutComponent(Component comp) {
        log.entering("FlowLayout", "removeLayoutComponent",
                new Object[] { comp });
        // throw new UnsupportedOperationException( "Not supported
yet." );
        super.removeLayoutComponent(comp);
        log.exiting("FlowLayout", "removeLayoutComponent");
        throw new UnsupportedOperationException("Not supported yet.");
    }

    public Dimension preferredLayoutSize(Container parent) {
        log.entering("FlowLayout", "preferredLayoutSize",
                new Object[] { parent });
        // throw new UnsupportedOperationException( "Not supported
yet." );
        // Dimension rt =
        // super.preferredLayoutSize( parent );
        // log.finest( "Dimenions="+rt);

        Insets insets = parent.getInsets();
        int maxwidth = parent.getWidth()
                - (insets.left + insets.right + super.getHgap() * 2);
        int ourMaxwidth = 0;
        int nmembers = parent.getComponentCount();
        int x = 0, y = insets.top + super.getVgap();
        int rowh = 0, start = 0;

        boolean ltr = parent.getComponentOrientation().isLeftToRight();

        boolean useBaseline = getAlignOnBaseline();
        int[] ascent = null;
        int[] descent = null;

        if (useBaseline) {
            ascent = new int[nmembers];
            descent = new int[nmembers];
        }

        for (int i = 0; i < nmembers; i++) {
            Component m = parent.getComponent(i);
            if (m.isVisible()) {
                Dimension d = m.getPreferredSize();
                m.setSize(d.width, d.height);

                if (useBaseline) {
                    int baseline = m.getBaseline(d.width, d.height);
                    if (baseline >= 0) {
                        ascent[i] = baseline;
                        descent[i] = d.height - baseline;
                    } else {
                        ascent[i] = -1;
                    }
                }
                if ((x == 0) || ((x + d.width) <= maxwidth)) {
                    if (x > 0) {
                        x += super.getHgap();
                    }
                    x += d.width;
                    rowh = Math.max(rowh, d.height);
                } else {
                    // rowh = moveComponents( parent, insets.left +
hgap, y,
                    // maxwidth - x, rowh, start, i, ltr,
                    // useBaseline, ascent, descent );
                    ourMaxwidth = Math.max(ourMaxwidth, x);
                    x = d.width;
                    y += super.getVgap() + rowh;
                    rowh = d.height;
                    start = i;
                }
            }
        }
        // moveComponents( parent, insets.left + hgap, y, maxwidth -
x, //rowh,
        // start, nmembers, ltr, useBaseline, ascent, descent );

        ourMaxwidth = Math.max(ourMaxwidth, x);
        Dimension rt = new Dimension(ourMaxwidth, y + rowh);
        log.finest("Dimenions=" + rt);
        log.exiting("FlowLayout", "preferredLayoutSize");
        return rt;
    }

    public Dimension minimumLayoutSize(Container parent) {
        log
                .entering("FlowLayout", "minimumLayoutSize",
                        new Object[] { parent });
        // throw new UnsupportedOperationException( "Not supported
yet." );
        Dimension rt = super.minimumLayoutSize(parent);
        log.finest("Dimenions=" + rt);
        log.exiting("FlowLayout", "minimumLayoutSize");
        return rt;
    }

    public void layoutContainer(Container parent) {
        log.entering("FlowLayout", "layoutContainer", new Object[] {
parent });
        // throw new UnsupportedOperationException( "Not supported
yet." );
        super.layoutContainer(parent);
        log.exiting("FlowLayout", "layoutContainer");
    }
}