Swing - ensure visible line in text component

I have some text component (particularly it JEditorPane), and need as response to certain event to make some line in the text component visible - i.e. scroll to开发者_如何转开发 it if that necessary. How to do this with Swing?

I find setCaretPosition but it not always good. If caret was already at position set for it new, it not make it visible again.

from tutorials How to Use Editor Panes and Text Panes and How to Use Scroll Panes you can get JViewPort that's determine visible Rectangle

example:

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

public class IsRectVisible {

    private static void createAndShowUI() {
        JFrame frame = new JFrame("IsRectVisible");
        frame.getContentPane().add(new IsRectVisibleGui());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {

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

    private IsRectVisible() {
    }
}

class IsRectVisibleGui extends JPanel {

    public static final Rectangle RECT = new Rectangle(450, 400, 100, 100);
    public static final Dimension INNER_PANEL_SIZE = new Dimension(600, 800);
    private static final Dimension SCROLLPANE_SIZE = new Dimension(250, 300);
    private static final String NOT_VISIBLE = "Not Visible";
    private static final String VISIBLE = "Visible";
    private static final long serialVersionUID = 1L;
    private InnerPanel innerPanel = new InnerPanel();
    private JViewport viewport = new JViewport();
    private JLabel statusLabel = new JLabel(NOT_VISIBLE);

    IsRectVisibleGui() {
        JScrollPane scrollpane = new JScrollPane();
        scrollpane.setViewport(viewport);
        viewport.add(innerPanel);
        scrollpane.setPreferredSize(SCROLLPANE_SIZE);
        viewport.addChangeListener(new ChangeListener() {

            @Override
            public void stateChanged(ChangeEvent e) {
                Rectangle viewRect = viewport.getViewRect();
                if (viewRect.intersects(RECT)) {
                    statusLabel.setText(VISIBLE);
                } else {
                    statusLabel.setText(NOT_VISIBLE);
                }
            }
        });

        setLayout(new BorderLayout());
        add(scrollpane, BorderLayout.CENTER);
        add(statusLabel, BorderLayout.SOUTH);
    }

    class InnerPanel extends JPanel {

        private static final long serialVersionUID = 1L;

        InnerPanel() {
            setPreferredSize(INNER_PANEL_SIZE);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.setColor(Color.red);
            g2.setStroke(new BasicStroke(4));
            g2.draw(RECT);
        }
    }
}

and you can move with that by using JScrollPane#scrollRectToVisible(Rectangle aRect)

Use modelToView() method passing the offset and getting the Rectangles. Then use scrollRectToVisible

StanislavL is totaly right, as usual :). You have to save somewhere the position you want to go to. Than you get the ractengle you need with

Rectangle ractYouNeed = thePane.getUI().modelToView(thePane, position);

After that you could easyly scroll to that rectangle or whatever.