java - 设置为不可编辑时如何在 JTextArea 中设置自动滚动？

Question

我用过this回答以获得在 JTextArea 上自动滚动的功能。但它似乎只有在同一 JTextArea 的 setEditable 属性设置为 TRUE 时才有效。当然，我使用的是 JScrollPane。

我正在开发一个聊天应用程序作为一个大学项目。显示消息的区域与 JTextArea 完全相同。我在上面链接的第一个答案中使用了第二组代码。但是当 setEditable 设置为 FALSE 时，我需要它来使其工作。

即使在 JTextArea 和 JScrollPane 的 setAutoScrolls 属性设置为 TRUE 后，它也不会工作。

请帮忙。谢谢。

Answer 1

I have used this answer to get the functionality of Autoscrolling on a JTextArea. But it seems that it works only when the setEditable property of the same JTextArea is set to TRUE. Of course, i use a JScrollPane

• 我没有发现 setEditable(false) 和/或 setEnabled(false) 及其可能的组合有任何问题

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• (在黑暗中疯狂拍摄)不包括 EventDispatchThread 的问题, 当 setText, append等未在 EDT 上完成，例如包装到 invokeLater()

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

public class CaretAndJTextArea {

    private JTextArea textArea = new JTextArea();
    private static final String string =
            "Trail: Creating a GUI with JFC/Swing\n"
            + "Lesson: Learning Swing by Example\n"
            + "This lesson explains the concepts you need to\n"
            + " use Swing components in building a user interface.\n"
            + " First we examine the simplest Swing application you can write.\n"
            + " Then we present several progressively complicated examples of creating\n"
            + " user interfaces using components in the javax.swing package.\n"
            + " We cover several Swing components, such as buttons, labels, and text areas.\n"
            + " The handling of events is also discussed,\n"
            + " as are layout management and accessibility.\n"
            + " This lesson ends with a set of questions and exercises\n"
            + " so you can test yourself on what you've learned.\n"
            + "http://docs.oracle.com/javase/tutorial/uiswing/learn/index.html\n";

    public CaretAndJTextArea() {
        DefaultCaret caret = (DefaultCaret) textArea.getCaret();
        caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);
        textArea.setEditable(false);
        textArea.setEnabled(false);
        textArea.getDocument().addDocumentListener(new DocumentListener() {
            @Override
            public void insertUpdate(DocumentEvent e) {
                setModelText();
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                setModelText();
            }

            @Override
            public void changedUpdate(DocumentEvent e) {
                setModelText();
            }

            private void setModelText() {
                SwingUtilities.invokeLater(new Runnable() {
                    @Override
                    public void run() {
                        //textArea.setText(textArea.getText());
                    }
                });
            }
        });
        JButton button2 = new JButton("Append String");
        button2.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textArea.append(string);
            }
        });
        JFrame frame = new JFrame();
        frame.add(new JScrollPane(textArea), BorderLayout.CENTER);
        frame.add(button2, BorderLayout.SOUTH);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 200);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new CaretAndJTextArea();
            }
        });
    }
}