如何使JTextPane仅在滚动条位于底部且滚动锁定关闭时才自动滚动？

我认为我下面的程序完全符合您的要求，但有一个可能的警告：您不得在文本区域中键入内容。因此，这对于日志查看器来说是件好事，但对于交互式控制台来说却不是。代码运行得有点长，因为我已经把它变成了一个随时可以运行的方法演示。我建议按原样运行程序并检查行为。如果行为对您有效，那么请花一点时间研究代码。我在代码中包含了注释，以突出显示一些更重要的部分。

2013-07-17更新：您可能还想在页面下方的单独答案中查看随机伙计的解决方案。他的方法比我更优雅。

另请参阅 Swing：滚动到 JScrollPane 的底部，条件是当前视口位置，以获取不干扰脱字符号位置的潜在解决方案。

SCCE 源代码如下：

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.Timer;

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

public class ScrollingJTextAreaExample extends JFrame {
    // Worker thread to help periodically append example messages to JTextArea
    Timer timer = new Timer();
    // Merely informative counter, will be displayed with the example messages
    int messageCounter = 0;
    // GUI components
    JScrollPane jScrollPane;
    JTextArea jTextArea;

    public ScrollingJTextAreaExample() {
        initComponents(); // Boiler plate GUI construction and layout

        // Configure JTextArea to not update the cursor position after
        // inserting or appending text to the JTextArea. This disables the
        // JTextArea's usual behavior of scrolling automatically whenever
        // inserting or appending text into the JTextArea: we want scrolling
        // to only occur at our discretion, not blindly. NOTE that this
        // breaks normal typing into the JTextArea. This approach assumes
        // that all updates to the ScrollingJTextArea are programmatic.
        DefaultCaret caret = (DefaultCaret) jTextArea.getCaret();
        caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE);

        // Schedule a task to periodically append example messages to jTextArea
        timer.schedule(new TextGeneratorTask(), 250, 250);

        // This DocumentListener takes care of re-scrolling when appropriate
        Document document = jTextArea.getDocument();
        document.addDocumentListener(new ScrollingDocumentListener());
    }

    // Boring, vanilla GUI construction and layout code
    private void initComponents() {
        jScrollPane = new javax.swing.JScrollPane();
        jTextArea = new javax.swing.JTextArea();
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        jScrollPane.setViewportView(jTextArea);
        getContentPane().add(jScrollPane, java.awt.BorderLayout.CENTER);
        setSize(320, 240);
        setLocationRelativeTo(null);
    }

    // ScrollingDocumentListener takes care of re-scrolling when appropriate
    class ScrollingDocumentListener implements DocumentListener {
        public void changedUpdate(DocumentEvent e) {
            maybeScrollToBottom();
        }

        public void insertUpdate(DocumentEvent e) {
            maybeScrollToBottom();
        }

        public void removeUpdate(DocumentEvent e) {
            maybeScrollToBottom();
        }

        private void maybeScrollToBottom() {
            JScrollBar scrollBar = jScrollPane.getVerticalScrollBar();
            boolean scrollBarAtBottom = isScrollBarFullyExtended(scrollBar);
            boolean scrollLock = Toolkit.getDefaultToolkit()
                    .getLockingKeyState(KeyEvent.VK_SCROLL_LOCK);
            if (scrollBarAtBottom && !scrollLock) {
                // Push the call to "scrollToBottom" back TWO PLACES on the
                // AWT-EDT queue so that it runs *after* Swing has had an
                // opportunity to "react" to the appending of new text:
                // this ensures that we "scrollToBottom" only after a new
                // bottom has been recalculated during the natural
                // revalidation of the GUI that occurs after having
                // appending new text to the JTextArea.
                EventQueue.invokeLater(new Runnable() {
                    public void run() {
                        EventQueue.invokeLater(new Runnable() {
                            public void run() {
                                scrollToBottom(jTextArea);
                            }
                        });
                    }
                });
            }
        }
    }

    class TextGeneratorTask extends TimerTask {
        public void run() {
            EventQueue.invokeLater(new Runnable() {
                public void run() {
                    String message = (++messageCounter)
                            + " Lorem ipsum dolor sit amet, consectetur"
                            + " adipisicing elit, sed do eiusmod tempor"
                            + " incididunt ut labore et dolore magna aliqua.\n";
                    jTextArea.append(message);
                }
            });
        }
    }

    public static boolean isScrollBarFullyExtended(JScrollBar vScrollBar) {
        BoundedRangeModel model = vScrollBar.getModel();
        return (model.getExtent() + model.getValue()) == model.getMaximum();
    }

    public static void scrollToBottom(JComponent component) {
        Rectangle visibleRect = component.getVisibleRect();
        visibleRect.y = component.getHeight() - visibleRect.height;
        component.scrollRectToVisible(visibleRect);
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new ScrollingJTextAreaExample().setVisible(true);
            }
        });
    }
}

这个问题有点晚了，但我提出了这个解决方案。

  conversationPane = new JTextPane();
  final JScrollPane conversationScrollPane = new JScrollPane(conversationPane);
  conversationScrollPane.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() {

     BoundedRangeModel brm = conversationScrollPane.getVerticalScrollBar().getModel();
     boolean wasAtBottom = true;

     public void adjustmentValueChanged(AdjustmentEvent e) {
        if (!brm.getValueIsAdjusting()) {
           if (wasAtBottom)
              brm.setValue(brm.getMaximum());
        } else
           wasAtBottom = ((brm.getValue() + brm.getExtent()) == brm.getMaximum());

     }
  });   

似乎完全满足我的需求。小解释：基本上，如果滚动条没有被人移动，并且该条最后位于最大值/底部，则将其重置为最大值。如果正在手动调整，请检查它是否被调整为位于底部。