更改 JTextPane 中特定行的文本 alignment

Question

I am creating a program for screenplay writing and I have come up on a problem where I need to change the text alignment inside of a specific line JPanel based on what's typed inside of the line. I've been able to pull the actual text from the line and put it into a string, Just haven't been able to align a single line.

This is what I've tried so far, but it's giving me an illegal state exception.

StyledDocument doc = textPane1.getStyledDocument();
SimpleAttributeSet center = new SimpleAttributeSet();
StyleConstants.setAlignment(center, StyleConstants.ALIGN_CENTER);
textPane1.getDocument().addDocumentListener(new DocumentListener() {

    @Override
    public void removeUpdate(DocumentEvent e) {
    }

    @Override
    public void insertUpdate(DocumentEvent e) {
        if(ReadText.currentLine(textPane1).contains("INT.")){
            doc.setParagraphAttributes(0,1,center,false);
            System.out.println("Centered");
        }
    }

    @Override
    public void changedUpdate(DocumentEvent arg0) {
            
    }
});

What is the best method of doing this?

Answer 1

it's giving me an illegal state exception.

You can't update the Document in a Document listener.

You need to wrap the code in a SwingUtilities.invokeLater() so the code gets added to the end of the EDT and is executed after all the text has been added to the Document.

doc.setParagraphAttributes(0,1,center,false);

Not sure if that is what you want. That will always set the attribute of the first line of the Document since you are using an offset of 0.

Here is a basic example that allows you to have different alignment for each paragraph in the Document.

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

public class TextPaneAttributes extends JPanel
{

    public TextPaneAttributes()
    {
        setLayout( new BorderLayout() );

        JTextPane textPane = new JTextPane();
        textPane.setText( "one\ntwo\nthree\nfour\nfive\nsix\nseven\neight" );

//      DefaultHighlighter highlighter =  (DefaultHighlighter)textPane.getHighlighter();
//      highlighter.setDrawsLayeredHighlights(false);

        //  Define some character and paragraph attributes

        SimpleAttributeSet keyWord = new SimpleAttributeSet();
        StyleConstants.setBold(keyWord, true);

        SimpleAttributeSet green = new SimpleAttributeSet();
        StyleConstants.setForeground(green, Color.GREEN);
        System.out.println(green);
        System.out.println(textPane.getInputAttributes());

        SimpleAttributeSet center = new SimpleAttributeSet();
        StyleConstants.setAlignment(center, StyleConstants.ALIGN_CENTER);

        SimpleAttributeSet left = new SimpleAttributeSet();
        StyleConstants.setAlignment(left, StyleConstants.ALIGN_LEFT);

        //  Change attributes on some existing text

        StyledDocument doc = textPane.getStyledDocument();
        textPane.setCaretPosition(12);
        doc.setCharacterAttributes(0, 3, keyWord, false);
        doc.setCharacterAttributes(8, 5, green, false);
        doc.setParagraphAttributes(20, 1 , center, false);

        //  Add some text with attributes

        try
        {
            doc.insertString(doc.getLength(), "\nNormal text", null);
            doc.insertString(doc.getLength(), "\nGreen text centered", green);
//          int pos = doc.getLength();
//          doc.insertString(pos, "more green text", doc.getCharacterElement(pos-1).getAttributes());
            doc.setParagraphAttributes(doc.getLength(), 1 , center, false);
            doc.insertString(doc.getLength(), "\nKeyword text", keyWord);
            doc.setParagraphAttributes(doc.getLength(), 1 , left, false);

            //  Newly typed text at the end of the document will inherit the
            //  "keyword" attributes unless we remove the attributes

            textPane.setCaretPosition(doc.getLength());
            textPane.getInputAttributes().removeAttributes(keyWord);
        }
        catch(Exception e) {}

        //  Add text pane to frame

        JScrollPane scrollPane = new JScrollPane( textPane );
        scrollPane.setPreferredSize( new Dimension( 200, 250 ) );
        add( scrollPane );

        //  Create a Button panel

        JPanel buttons = new JPanel();
        add(buttons, BorderLayout.PAGE_END);

        //  Add a Bold button

        JButton bold = new JButton( new StyledEditorKit.BoldAction() );
        buttons.add( bold );

        //  Add Right Alignment button

        JButton right = new JButton( new StyledEditorKit.AlignmentAction("Align Right", StyleConstants.ALIGN_RIGHT) );
        buttons.add( right );
    }

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame("SSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new TextPaneAttributes());
        frame.pack();
        frame.setLocationByPlatform( true );
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater( () -> createAndShowGUI() );
/*
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowGUI();
            }
        });
*/
    }
}