Centre text in a "region"

Question

Howdy,
Forgive my ignorance, I'm jus' a simple compooder pwogrammer.
How do you paint some text centred in a jPanel (for instance).
What I can't figure out is how to get the font height, and the width of this string... paintComponent takes a Graphics object right... and that graphics has a current Font, right... so How do I get the height of the font (as user scale), and the width of a given string as it appears in that font (in user scale)?
I've been lost in the API doco for about for about an hour, and I think I'm gonna cry ;-)
It took me 15 minutes to work out the the Graphics passed in isa Graphics2D FFS!
Cheers, Keith.

Answer 1

Keith, if using a JTextPane suits your purpose, you can center-align the text via methods of the StyledDocument and StyleConstants classes. This is a (slightly modified) code I posted on another thread some time ago.import javax.swing.JFrame;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.Style;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyleContext;
import javax.swing.text.StyledDocument;
public class TestAlignment {
    JTextPane textPane;
    public void createEverything (){
        textPane=new JTextPane ();
        StyledDocument doc = textPane.getStyledDocument ();
        addStylesToDocument (doc);
        // Doesn't work if you comment the next line
        textPane.setLogicalStyle (doc.getStyle ("bold"));
        try{
            doc.insertString (doc.getLength (),
                    "Keith Corlett",
                    doc.getStyle ("bold"));
        } catch (BadLocationException ble) {
            ble.printStackTrace ();
        JFrame frame=new JFrame ();
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        frame.add (textPane);
        frame.setSize (400,300);
        frame.setVisible (true);
    protected void addStylesToDocument (StyledDocument doc) {
        Style def=new StyleContext ().getStyle (StyleContext.DEFAULT_STYLE);
        Style heading = doc.addStyle ("bold", null);
        StyleConstants.setFontFamily (heading, "SansSerif");
        StyleConstants.setBold (heading, true);
        StyleConstants.setFontSize (heading,30);
        StyleConstants.setAlignment (heading, StyleConstants.ALIGN_CENTER);
        StyleConstants.setSpaceAbove (heading, 10);
        StyleConstants.setSpaceBelow (heading, 10);
    public static void main (String args[]){
        TestAlignment pane=new TestAlignment ();
        pane.createEverything ();
}For painting text centered on any Component, with word wrap when the width does not permit displaying the text in one line, the TextLayout class is useful. Here's an example, resize the frame narrower than the text to see it in action:import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.font.FontRenderContext;
import java.awt.font.LineBreakMeasurer;
import java.awt.font.TextAttribute;
import java.awt.font.TextLayout;
import java.text.AttributedString;
import java.util.ArrayList;
import javax.swing.JComponent;
import javax.swing.JFrame;
public class LineBreak extends JComponent {
    Font font = new Font ("TimesRoman", Font.PLAIN, 14);
    String breakText;
    ArrayList<TextLayout> layouts = new ArrayList<TextLayout> ();
    public LineBreak (String inText) {
        breakText = inText;
    public void breakLines (FontMetrics metrics) {
        if (0 < breakText.length ()) {
            final AttributedString attStr = new AttributedString (breakText);
            attStr.addAttribute (TextAttribute.FONT, font);
            final LineBreakMeasurer measurer =
                    new LineBreakMeasurer (attStr.getIterator (),
                    new FontRenderContext (null, true, true));
            TextLayout layout;
            while (null != (layout = measurer.nextLayout (getWidth ()))) {
                layouts.add (layout);
    @Override
    public void paintComponent (Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
        FontMetrics metrics = g2.getFontMetrics (font);
        layouts.clear ();
        breakLines (metrics);
        int textHeight = metrics.getHeight ();
        int top = textHeight;
        for (TextLayout layout : layouts) {
            layout.draw (g2, (float) (getWidth() - layout.getBounds ().getWidth ()) / 2, top);
            top += textHeight;
    public static void main (String[] args) {
        String inText;
        if (args.length > 0) {
            inText = args [0];
        } else {
            inText = "Keith likes sweets.  Most of all, Keith likes icecream and chocolate.";
        JFrame frame = new JFrame ("Test Frame");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        frame.setSize (400, 200);
        frame.setLocationRelativeTo (null);
        frame.add (new LineBreak (inText));
        frame.setVisible (true);
}Yup... this one too is slightly modified from something I posted on another thread ;-)
cheers, db