CODEWITHSUNDEEP
javawhitespacejtextpane
Vince
Vince

Reputation: 2646

Count number of spaces before text on a line in a JTextPane

I would like to know how to count the number of spaces on a given line before the text actually begins. For ex. if I have this in my JTextPane:

public static void main(String[] args) {
    int x = 1;

}

after I type 'x = 1;' and press enter, I would like to have the caret on the same indentation as the 'int x = 1;' starts, so I don't have to keep pressing tab or entering spaces manually. Any suggestions?

Upvotes: 3

Views: 517

Answers (3)

Sharcoux
Sharcoux

Reputation: 6075

If you want your new line to have the same indentation as the previous one, you can do that by simply checking the first characters of the previous line. Look at that :

public class Test {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame mainFrame = new JFrame("test");
                mainFrame.setSize(300, 100);
                mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                Container pane = mainFrame.getContentPane();
                pane.setLayout(new BorderLayout());

                JTextPane jtp = new JTP();
                pane.add(jtp);

                mainFrame.setVisible(true);
            }
        });
    }

    static class JTP extends JTextPane {
        JTP() {
            ((AbstractDocument)getDocument()).setDocumentFilter(new Filter());
        }
    }

    static class Filter extends DocumentFilter {
        @Override
        public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
            StringBuilder indentatedString = new StringBuilder(string);
            if(string.equals("\n")) {
                AbstractDocument doc = ((AbstractDocument)fb.getDocument());
                Element line = doc.getParagraphElement(offset);
                int lineStart = line.getStartOffset(), lineEnd = line.getEndOffset();
                String content = doc.getText(lineStart, lineEnd - lineStart);
                int start = 0;
                while(content.charAt(start)==' ') {
                    indentatedString.insert(0," ");
                    start++;
                }
            }
            fb.insertString(offset, indentatedString.toString(), attr);
        }
        @Override
        public void replace(FilterBypass fb, int offset, int length, String text,
                            AttributeSet attrs) throws BadLocationException {
            if(text.==0) {insertString(fb, offset, text, attrs);}
            else if(text.length()>0) {remove(fb, offset, length);insertString(fb, offset, text, attrs);}
            else {fb.replace(offset, length, text, attrs);}
        }
    }
}

The important part here is only the DocumentFilter that does the job.

Upvotes: 1

Shar1er80
Shar1er80

Reputation: 9041

Split the text of the JTextPane by '\n' and search each line until you find the String you're searching for.

If the line you're on doesn't have the String you're searching for then you add the length of that line + 1 (to include the '\n') to a sum.

If the line you're on does have the String, then starting from the beginning of the line count the number of spaces until you reach the 1st non-space character and add that number to the sum.

With the sum, you would just provide it to the JTextPane.setCaretPosition(). Something like:

int caretPosition = 0;
String[] lines = jTextPane1.getText().split("\n");
for (String line : lines) {
    if (line.contains(search)) {
        for (int i = 0; i < line.length(); i++) {
            if (line.charAt(i) != ' ') {
                break;
            }
            caretPosition++;
        }
        break;
    } else {
        // +1 to include the '\n' character
        caretPosition += line.length() + 1;
    }
}

jTextPane1.setCaretPosition(caretPosition);

Upvotes: 0

MC10
MC10

Reputation: 572

First, check this: Read JTextPane line by line

Then you can just get the line and count the number of spaces.

int spaces = s.length() - s.replaceAll("^\\s+", "").length();

Upvotes: 0

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