Getting string size in java (without having a Graphics object available)

Question

I\'m trying to write application which need to draw many strings using Graphics2D class in Java. I need to get sizes of each String object (to calculate exact p

Answer 1

Besides using FontMetrics, a JLabel can be used to determine the size of both unformatted and (basic HTML) rendered text. Here is an example.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;

import java.awt.image.BufferedImage;

import javax.swing.JOptionPane;
import javax.swing.JLabel;
import javax.swing.ImageIcon;

/** Sample code obtained from a thread on the Oracle forums that I cannot
locate at this instant.  My question was related to an unexpected rendering of
JLabel.  It was resolved by the 'added this' line courtesy of Darryl Burke. */
public class LabelRenderTest {

  String title = ""
          + "
Do U C Me?
"
          + "Here is a long string that will wrap.  "
          + "The effect we want is a multi-line label.";

  LabelRenderTest() {
    BufferedImage image = new BufferedImage(
            640,
            480,
            BufferedImage.TYPE_INT_RGB);
    Graphics2D imageGraphics = image.createGraphics();
    GradientPaint gp = new GradientPaint(
            20f, 20f, Color.blue,
            620f, 460f, Color.white);
    imageGraphics.setPaint(gp);
    imageGraphics.fillRect(0, 0, 800, 600);

    JLabel textLabel = new JLabel(title);
    textLabel.setSize(textLabel.getPreferredSize()); // <==== added this

    Dimension d = textLabel.getPreferredSize();
    BufferedImage bi = new BufferedImage(
            d.width,
            d.height,
            BufferedImage.TYPE_INT_ARGB);
    Graphics g = bi.createGraphics();
    g.setColor(new Color(255, 255, 255, 128));
    g.fillRoundRect(
            0,
            0,
            bi.getWidth(null),
            bi.getHeight(null),
            15,
            10);
    g.setColor(Color.black);
    textLabel.paint(g);
    Graphics g2 = image.getGraphics();
    g2.drawImage(bi, 20, 20, null);

    ImageIcon ii = new ImageIcon(image);
    JLabel imageLabel = new JLabel(ii);

    JOptionPane.showMessageDialog(null, imageLabel);
  }

  public static void main(String[] args) {
    LabelRenderTest ist = new LabelRenderTest();
  }
}

Edit 1: As to your "many strings" comment. Paint the strings to a BufferedImage that is only regenerated if needed. Use the buffered image each time paintComponent() is called.