Count number of lines in JTextArea given set width

Question

I'm trying to reliably count the number of lines (including those from line wraps and line breaks) in a JTextArea given a set width. I'm using this information to set the height of other components in my GUI (for example, for n lines, set n*height of a component).

I stumbled across this solution (reproduced below) but there is a problem with this. Sometimes it would miss a line if there isn't too much text on that line. For example, if a JTextArea of width 100 has 3 lines of text and on the 3rd line it only has say around width 15 of text, then it will only count 2 lines instead of 3.

public class MyTextArea extends JTextArea {

    //...

    public int countLines(int width) {

        AttributedString text = new AttributedString(this.getText());
        FontRenderContext frc = this.getFontMetrics(this.getFont()).getFontRenderContext();
        AttributedCharacterIterator charIt = text.getIterator();
        LineBreakMeasurer lineMeasurer = new LineBreakMeasurer(charIt, frc);
        lineMeasurer.setPosition(charIt.getBeginIndex());

        int noLines = 0;
        while (lineMeasurer.getPosition() < charIt.getEndIndex()) {
            lineMeasurer.nextLayout(width);
            noLines++;
        }

        System.out.print("there are " + noLines + "lines" + System.getProperty("line.separator"));
        return noLines;
    }
}

Any idea what might be causing this issue? Are there any alternatives to counting lines in a JTextArea? Thanks.

Answer 1

So I came up with a simple solution that uses FontMetrics to calculate the display width of the text, and by splitting the text into string tokens, I can count how many lines there will be.

public int countLines(int width) {

        FontMetrics fontMetrics = this.getFontMetrics(this.getFont());
        String text = this.getText();
        String[] tokens = text.split(" ");
        String currentLine = "";
        boolean beginningOfLine = true;
        int noLines = 1;

        for (int i = 0; i < tokens.length; i++) {
            if (beginningOfLine) {
                beginningOfLine = false;
                currentLine = currentLine + tokens[i];
            } else {
                currentLine = currentLine + " " + tokens[i];
            }

            if (fontMetrics.stringWidth(currentLine) > width) {
                currentLine = "";
                beginningOfLine = true;
                noLines++;
            }
        }

        System.out.print("there are " + noLines + "lines" + System.getProperty("line.separator"));
        return noLines;
}