How to calculate the number of rows (and columns in each row) a text takes in a JTextArea?

After getting interested in the problem presented in the question I tried to approach it few times and failed, and I do not like that :)

I think if the problem was split into sub issues it might help to solve it.

For simplicity lets assume the JTextArea will not change its size, so we d开发者_如何学JAVAo not need to worry about re-evaluation etc. I think the important issues are:

1.How to calculate the number of rows a certain text takes in a JTextArea?

2.What is the relation between the number of columns in a JTextArea and a number of characters it can fit in a row? So we can calculate row length.

Please find included below the sample code presenting the text area to process:

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class TextAreaLines
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                JPanel p = new JPanel();
                JFrame f = new JFrame();
                JTextArea ta = new JTextArea("dadsad sasdasdasdasdasd");
                ta.setWrapStyleWord(true);
                ta.setLineWrap(true);
                ta.setRows(5);
                ta.setColumns(5);
                p.add(ta);
                f.setContentPane(p);
                f.setSize(400, 300);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);             
                //BTW the code below prints 1
                System.out.println("ta.getLineCount()="+ta.getLineCount());
            }
        });
    }
}

EDIT1: So I have come up with the following code but the problem is that the output is not what you see, i.e

//for input
//JTextArea ta = new JTextArea("alfred abcdefghijklmnoprstuwvxyz abcdefg");

//we have output    
//s=alfred abcdefghijk
//s=lmnoprstuwvxyz a
//s=bcdefg



        FontMetrics fm = ta.getFontMetrics(ta.getFont());
        String text = ta.getText();
        List<String> texts = new ArrayList<String>();               
        String line = "";
        //no word wrap
        for(int i = 0;i < text.length(); i++)  
        {       
            char c = text.charAt(i);
            if(fm.stringWidth(line +c)  <= ta.getPreferredSize().width)
            {                       
                //System.out.println("in; line+c ="+(line + c));
                line += c;
            }
            else
            {
                texts.add(line);//store the text
                line = ""+c;//empty the line, add the last char
            }
        }
        texts.add(line);                
        for(String s: texts)
            System.out.println("s="+s);

What am I doing wrong, what am I forgetting about? There is no word wrap on the text area.

EDIT2: @trashgod This is the output I am getting. Apparent from this is that we have different default fonts. And the problem in fact might be either font or even system dependent. (PS: I am on Win7).

line: Twas brillig and the slithy tovesD
line: id gyre and gimble in the wabe;
line count: 2
preferred: java.awt.Dimension[width=179,height=48]
bounds1: java.awt.geom.Rectangle2D$Float[x=0.0,y=-12.064453,w=170.0,h=15.09375]
layout1: java.awt.geom.Rectangle2D$Float[x=0.28125,y=-8.59375,w=168.25,h=11.125]
bounds2: java.awt.geom.Rectangle2D$Float[x=0.0,y=-12.064453,w=179.0,h=15.09375]
layout2: java.awt.geom.Rectangle2D$Float[x=0.921875,y=-8.59375,w=177.34375,h=11.125]

Compiling in my head what all of you guys are saying I think that the possibly reliable solution might be to hack the way in which the text area sets its text, and take a full control over it. By running the algorithm (above one, please notice, as suggested by @trashgod the '<' was changed to '<=') in the setText of the area.

What got me to think like this... for example in the sample I have provided if you change text of the textarea to JTextArea ta = new JTextArea("alfred abcdefghijkl\nmnoprstuwvxyz ab\ncdefg"); as it is calculated in my case then it will fit perfectly into the textarea.

EDIT3: This is a kind of solution I quickly hacked, at least now the shown characters and calculated are exactly the same. Can someone else please check it out and let me know, possibly how it works on other machine then Win7? The example below is ready to use you should be able to resize the window and get the printout of lines the same as you see.

import java.awt.BorderLayout;
import java.awt.FontMetrics;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class TextAreaLines
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                JPanel p = new JPanel(new BorderLayout());
                JFrame f = new JFrame();
                final JTextArea ta = new JTextArea("alfred abcdefghijklmnoprstuwvxyz abcdefg");
                ta.addComponentListener(new ComponentAdapter()
                {
                    @Override
                    public void componentResized(ComponentEvent e)
                    {
                        super.componentResized(e);
                        System.out.println("ta componentResized");
                        reformatTextAreaText(ta);
                    }
                });
                //ta.setWrapStyleWord(true);
                ta.setLineWrap(true);
                p.add(ta);
                f.setContentPane(p);
                f.setSize(200, 100);
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);
            }

            private void reformatTextAreaText(JTextArea ta)
            {
                String text = ta.getText();
                //remove all new line characters since we want to control line braking
                text = text.replaceAll("\n", "");
                FontMetrics fm = ta.getFontMetrics(ta.getFont());
                List<String> texts = new ArrayList<String>();
                String line = "";
                //no word wrap
                for(int i = 0; i < text.length(); i++)
                {
                    char c = text.charAt(i);
                    if(fm.stringWidth(line + c) <= ta.getPreferredSize().width)
                    {
                        //System.out.println("in; line+c ="+(line + c));
                        line += c;
                    }
                    else
                    {
                        texts.add(line);//store the text
                        line = "" + c;//empty the line, add the last char
                    }
                }
                texts.add(line);
                //print out of the lines
                for(String s : texts)
                    System.out.println("s=" + s);
                //build newText for the
                String newText = "";
                for(String s : texts)
                    newText += s + "\n";
                ta.setText(newText);
            }
        });
    }
}

Thanks in advance.

---

What am I doing wrong, what am I forgetting about?

Nothing, really. I modified your example to use "<=" on the width and to highlight a few features:

1. FontMetrics notes, "the advance of a String is not necessarily the sum of the advances of its characters measured in isolation…"

2. The preferred size of the text component matches the metric bounds pretty well for the widest line. This varies by font due to proportional spacing.

3. TextLayout shows even tighter bounds, but note the "baseline-relative coordinates."

4. The getLineCount() method counts line.separator delimited lines, not wrapped lines.

line: Twas brillig and the slithy toves
line: Did gyre and gimble in the wabe;
line count: 2
preferred: java.awt.Dimension[width=207,height=48]
bounds1: java.awt.geom.Rectangle2D$Float[x=0.0,y=-12.568359,w=205.0,h=15.310547]
layout1: java.awt.geom.Rectangle2D$Float[x=0.0,y=-10.0,w=200.0,h=13.0]
bounds2: java.awt.geom.Rectangle2D$Float[x=0.0,y=-12.568359,w=207.0,h=15.310547]
layout2: java.awt.geom.Rectangle2D$Float[x=1.0,y=-10.0,w=205.0,h=13.0]

import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.font.FontRenderContext;
import java.awt.font.TextLayout;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

/** #see http://stackoverflow.com/questions/5979795 */
public class TextAreaLine {

    private static final String text1 =
        "Twas brillig and the slithy toves\n";
    private static final String text2 =
        "Did gyre and gimble in the wabe;";
    private static final JTextArea ta = new JTextArea(text1 + text2);

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                display();
            }
        });
    }

    static void display() {
        JFrame f = new JFrame();
        ta.setWrapStyleWord(false);
        ta.setLineWrap(false);
        ta.setRows(3);
        f.add(ta);
        f.pack();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
        FontMetrics fm = ta.getFontMetrics(ta.getFont());
        List<String> texts = new ArrayList<String>();
        Dimension d = ta.getPreferredSize();
        String text = ta.getText();
        String line = "";
        for (int i = 0; i < text.length(); i++) {
            char c = text.charAt(i);
            if (c != '\n') {
                if (fm.stringWidth(line + c) <= d.width) {
                    line += c;
                } else {
                    texts.add(line);
                    line = "" + c;
                }
            }
        }
        texts.add(line);
        for (String s : texts) {
            System.out.println("line: " + s);
        }
        System.out.println("line count: " + ta.getLineCount());
        System.out.println("preferred: " + d);
        System.out.println("bounds1: " + fm.getStringBounds(text1, null));
        FontRenderContext frc = new FontRenderContext(null, false, false);
        TextLayout layout = new TextLayout(text1, ta.getFont(), frc);
        System.out.println("layout1: " + layout.getBounds());
        System.out.println("bounds2: " + fm.getStringBounds(text2, null));
        layout = new TextLayout(text2, ta.getFont(), frc);
        System.out.println("layout2: " + layout.getBounds());
    }
}

---

One thing you can do is use FontMetrics. I wrote some code for splitting JTextAreas up at certain line numbers. The setup code looked like:

Graphics2D g = (Graphics2D) g2;
FontMetrics m = g.getFontMetrics();
int lineHeight = m.getHeight();

This will tell you how tall a line of text is.

Unfortunately, letters have different widths in most fonts. But, you can use the following code to determine the width of a String.

int width = m.getStringBounds("Some String", g).getWidth();

I know this doesn't fully answer your question, but I hope it helps.

If you aren't using word wrap, here is the general algorithm you could use: (in the paint component method)

String text[] = getText().split("\n");
String newText = "";
for (String line: text) {
    newText = line + "| " + line.length() + "\n";
}
setText(newText);

That's the general idea. Not sure how well it would work out. Let me know if you try it.

---

Not sure if this helps but you need to set the width of the text area so that the view knows when to wrap the text. Once you set the size you can determine the preferred height. When you know the preferred height you can use the font metrice line height to determine the total number of lines including the wrapped lines if any.

import java.awt.*;
import javax.swing.*;

public class TextAreaPreferredHeight extends JFrame
{

    public TextAreaPreferredHeight()
    {
        JTextArea textArea = new JTextArea();
        textArea.setText("one two three four five six seven eight nine ten");
        textArea.setLineWrap( true );
        textArea.setWrapStyleWord( true );

        FontMetrics fm = textArea.getFontMetrics( textArea.getFont() );
        int height = fm.getHeight();

        System.out.println("000: " + textArea.getPreferredSize());
        textArea.setSize(100, 1);
        System.out.println("100: " + textArea.getPreferredSize());
        System.out.println("lines : " + textArea.getPreferredSize().height / height);

        textArea.setSize(200, 1);
        System.out.println("200: " + textArea.getPreferredSize());
        System.out.println("lines : " + textArea.getPreferredSize().height / height);

        textArea.setSize(300, 1);
        System.out.println("300: " + textArea.getPreferredSize());
        System.out.println("lines : " + textArea.getPreferredSize().height / height);
        add(textArea);
        pack();
        setVisible(true);
}

    public static void main(String[] args)
    {
        new TextAreaPreferredHeight();
    }
}

---

I've seen people using TextLayout for something like this.

---

Okay, I had written a program that you could load in an image, and it would convert it to ascii art. I wanted it to automatically make the text area the right aspect ration based on the image that was input.

However, I could never get it to work quite right. I gave up and remarked out my attempts, here is the snippet of what I tried. What I ended up doing was just having a textarea that sometimes didn't fill all the way.

                //Graphics fontG = this.textBox4.CreateGraphics();
                //fontG.PageUnit = GraphicsUnit.Point;
                //SizeF fontSize = fontG.MeasureString(RowData, this.textBox4.Font,(SizeF) this.textBox4.ClientSize);
                sb.AppendLine();
                RowData = "";
                //fontH +=  fontSize.Height + 1.2F;
                //fontW = (int) fontSize.Width;

---

There was a similar question for android yesterday. The way I see it need to be solved is by an iterative approach:

• Get JTextArea width
• Use the FontMetrics to get the width of a string, as jjnguy suggested
• split your string in words.
• Start measuring the witdh of a string adding one word at a time until you reach the area width. Save that number.
• Once you reached it, start a new iteration, adding one word at a time (beginning with the number saved).
• The numbers of lines will be the number of iterations.

Unfortunately, row length will depend on the font and the particular string (not every character as the same width). You can count the number of characters in the words in each iteration, and return an array of lengths or a length average.

This is the related android question: How to find android TextView number of characters per line?

---

I found that counting the number of lines by text analysis only led to nothing. Instead my solution was calculating it from the preferred size of the text area ...

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;

public class LineNumbering extends JFrame {

    private static final long serialVersionUID = 1L;
    private static final Font fixedFont = new Font("Monospaced", Font.PLAIN, 12);
    private static JTextArea jta;
    private static JTextArea lines;
    private static String lineSeparator = "\n";
    private static int numRows = 10;
    private static int numCols = 30;

    public LineNumbering() {
        super("Line Numbering Example");
    }

    public static void createAndShowGUI() {
        JFrame frame = new LineNumbering();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JScrollPane jsp = new JScrollPane();
        jta = new JTextArea(numRows, numCols);
        jta.setFont(fixedFont);
        jta.setLineWrap(true);
        jta.setWrapStyleWord(true);

        lines = new JTextArea(numRows, 3);
        lines.setEditable(false);
        lines.setFocusable(false);
        lines.setEnabled(false);
        lines.setFont(fixedFont);
        lines.setBackground(Color.LIGHT_GRAY);
        lines.setDisabledTextColor(Color.BLACK);
        // do initial line numbering
        for (int i = 1; i <= lines.getRows(); i++) {
            lines.append(i + System.getProperty("line.separator"));
        }

        final class DebugCaretListener implements CaretListener {

            int rowHeight = jta.getFontMetrics(jta.getFont()).getHeight();

            /**
             * @return total of lines showed in the text area
             */
            private int getTotalLinesInView() {
                int insetsTotalHeight = jta.getInsets().top + jta.getInsets().bottom;
                return (jta.getPreferredSize().height - insetsTotalHeight) / rowHeight;
            }

            /**
             * @return text with line numbers
             */
            public String getText() {
                StringBuffer text = new StringBuffer();
                int totalLines = getTotalLinesInView();
                System.out.println("totalLines : " + totalLines);
                for (int i = 1; i <= totalLines; i++) {
                    text.append(i);
                    if (i < totalLines) {
                        text.append(lineSeparator);
                    }
                }
                return text.toString();
            }

            /**
             * <p>
             * Reset line numbers on caret event. Since the total number of
             * lines is calculated from preferred size of text area, we do this
             * on an event that occurred after repainting of the text area.
             * </p>
             * (non-Javadoc)
             * 
             * @see javax.swing.event.CaretListener#caretUpdate(javax.swing.event.CaretEvent)
             */
            @Override
            public void caretUpdate(CaretEvent e) {
                int totalLines = getTotalLinesInView();
                System.out.println("totalLines : " + totalLines);
                if (totalLines >= numRows) {
                    lines.setText(getText());
                }
            }

        }

        jta.addCaretListener(new DebugCaretListener());
        jsp.getViewport().add(jta);
        jsp.setRowHeaderView(lines);
        jsp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);
        jsp.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);

        JPanel textPanel = new JPanel();
        textPanel.add(jsp);
        JPanel contentPanel = new JPanel();
        contentPanel.add(textPanel);
        frame.setContentPane(contentPanel);
        contentPanel.setOpaque(true);
        frame.pack();
        frame.setPreferredSize(new Dimension(500, 500));
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

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