Java JTextPane JScrollPane 显示问题

下面的类实现了一个 chatGUI。当它运行正常时，屏幕如下所示：

精美 ChatGUI http://img21.imageshack.us/img21/7177/rightchat.jpg

当我输入大长度的文本时，问题经常出现。 50 - 100 个字符 GUI 会变得疯狂。聊天记录框缩小，如下所示

图片http://img99.imageshack.us/img99/6962/errorgui.jpg.

关于造成这种情况的原因有什么想法吗？

谢谢。

PS：下面的附件是完整的代码。你可以复制它并在你的计算机上编译以明白我的意思。

注意：一旦 GUI 变得疯狂，那么如果我点击“清除”按钮，历史记录窗口将被清除，并且 GUI 将再次正确显示。

package Sartre.Connect4;

import javax.swing.*;
import java.net.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.text.StyledDocument;
import javax.swing.text.Style;
import javax.swing.text.StyleConstants;
import javax.swing.text.BadLocationException;
import java.io.BufferedOutputStream;
import javax.swing.text.html.HTMLEditorKit;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.FileNotFoundException;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.JFileChooser;


/**
 * Chat form class
 * @author iAmjad
 */
public class ChatGUI extends JDialog implements ActionListener {

/**
 * Used to hold chat history data
 */
private JTextPane textPaneHistory = new JTextPane();

/**
 * provides scrolling to chat history pane
 */
private JScrollPane scrollPaneHistory = new JScrollPane(textPaneHistory);

/**
 * used to input local message to chat history
 */
private JTextPane textPaneHome = new JTextPane();

/**
 * Provides scrolling to local chat pane
 */
private JScrollPane scrollPaneHomeText = new JScrollPane(textPaneHome);

/**
 * JLabel acting as a statusbar
 */
private JLabel statusBar = new JLabel("Ready");

/**
 * Button to clear chat history pane
 */
private JButton JBClear = new JButton("Clear");

/**
 * Button to save chat history pane
 */
private JButton JBSave = new JButton("Save");

/**
 * Holds contentPane
 */
private Container containerPane;

/**
 * Layout GridBagLayout manager
 */
private GridBagLayout gridBagLayout = new GridBagLayout();

/**
 * GridBagConstraints
 */
private GridBagConstraints constraints = new GridBagConstraints();

/**
 * Constructor for ChatGUI
 */
public ChatGUI(){

    setTitle("Chat");

    // set up dialog icon
    URL url = getClass().getResource("Resources/SartreIcon.jpg");
    ImageIcon imageIcon = new ImageIcon(url);
    Image image = imageIcon.getImage();
    this.setIconImage(image);

    this.setAlwaysOnTop(true);

    setLocationRelativeTo(this.getParent());
    //////////////// End icon and placement /////////////////////////

    // Get pane and set layout manager
    containerPane = getContentPane();
    containerPane.setLayout(gridBagLayout);
    /////////////////////////////////////////////////////////////

    //////////////// Begin Chat History //////////////////////////////

    textPaneHistory.setToolTipText("Chat History Window");
    textPaneHistory.setEditable(false);
    textPaneHistory.setPreferredSize(new Dimension(350,250));

    scrollPaneHistory.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
    scrollPaneHistory.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

    // fill Chat History GridBagConstraints
    constraints.gridx = 0;
    constraints.gridy = 0;
    constraints.gridwidth = 10;
    constraints.gridheight = 10;
    constraints.weightx = 100;
    constraints.weighty = 100;
    constraints.fill = GridBagConstraints.BOTH;
    constraints.anchor = GridBagConstraints.CENTER;
    constraints.insets = new Insets(10,10,10,10);
    constraints.ipadx = 0;
    constraints.ipady = 0;

    gridBagLayout.setConstraints(scrollPaneHistory, constraints);

    // add to the pane
    containerPane.add(scrollPaneHistory);

    /////////////////////////////// End Chat History ///////////////////////

    ///////////////////////// Begin Home Chat //////////////////////////////

    textPaneHome.setToolTipText("Home Chat Message Window");
    textPaneHome.setPreferredSize(new Dimension(200,50));

    textPaneHome.addKeyListener(new MyKeyAdapter());

    scrollPaneHomeText.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
    scrollPaneHomeText.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

    // fill Chat History GridBagConstraints
    constraints.gridx = 0;
    constraints.gridy = 10;
    constraints.gridwidth = 6;
    constraints.gridheight = 1;
    constraints.weightx = 100;
    constraints.weighty = 100;
    constraints.fill = GridBagConstraints.BOTH;
    constraints.anchor = GridBagConstraints.CENTER;
    constraints.insets = new Insets(10,10,10,10);
    constraints.ipadx = 0;
    constraints.ipady = 0;

    gridBagLayout.setConstraints(scrollPaneHomeText, constraints);

    // add to the pane
    containerPane.add(scrollPaneHomeText);

    ////////////////////////// End Home Chat /////////////////////////

    ///////////////////////Begin Clear Chat History ////////////////////////

    JBClear.setToolTipText("Clear Chat History");

    // fill Chat History GridBagConstraints
    constraints.gridx = 6;
    constraints.gridy = 10;
    constraints.gridwidth = 2;
    constraints.gridheight = 1;
    constraints.weightx = 100;
    constraints.weighty = 100;
    constraints.fill = GridBagConstraints.BOTH;
    constraints.anchor = GridBagConstraints.CENTER;
    constraints.insets = new Insets(10,10,10,10);
    constraints.ipadx = 0;
    constraints.ipady = 0;

    gridBagLayout.setConstraints(JBClear, constraints);

    JBClear.addActionListener(this);

    // add to the pane
    containerPane.add(JBClear);

    ///////////////// End Clear Chat History ////////////////////////

    /////////////// Begin Save Chat History //////////////////////////

    JBSave.setToolTipText("Save Chat History");

    constraints.gridx = 8;
    constraints.gridy = 10;
    constraints.gridwidth = 2;
    constraints.gridheight = 1;
    constraints.weightx = 100;
    constraints.weighty = 100;
    constraints.fill = GridBagConstraints.BOTH;
    constraints.anchor = GridBagConstraints.CENTER;
    constraints.insets = new Insets(10,10,10,10);
    constraints.ipadx = 0;
    constraints.ipady = 0;

    gridBagLayout.setConstraints(JBSave, constraints);

    JBSave.addActionListener(this);

    // add to the pane
    containerPane.add(JBSave);

    ///////////////////// End Save Chat History /////////////////////

    /////////////////// Begin Status Bar /////////////////////////////
    constraints.gridx = 0;
    constraints.gridy = 11;
    constraints.gridwidth = 10;
    constraints.gridheight = 1;
    constraints.weightx = 100;
    constraints.weighty = 50;
    constraints.fill = GridBagConstraints.BOTH;
    constraints.anchor = GridBagConstraints.CENTER;
    constraints.insets = new Insets(0,10,5,0);
    constraints.ipadx = 0;
    constraints.ipady = 0;

    gridBagLayout.setConstraints(statusBar, constraints);

    // add to the pane
    containerPane.add(statusBar);

    ////////////// End Status Bar ////////////////////////////

    // set resizable to false
    this.setResizable(false);

    // pack the GUI
    pack();
}

/**
 * Deals with necessary menu click events
 * @param event
 */
public void actionPerformed(ActionEvent event) {

    Object source = event.getSource();

    // Process Clear button event
    if (source == JBClear){

        textPaneHistory.setText(null);
        statusBar.setText("Chat History Cleared");
    }

    // Process Save button event
    if (source == JBSave){

        // process only if there is data in history pane
        if (textPaneHistory.getText().length() > 0){

            // process location where to save the chat history file
            JFileChooser chooser = new JFileChooser();

            chooser.setMultiSelectionEnabled(false);

            chooser.setAcceptAllFileFilterUsed(false);

            FileNameExtensionFilter filter = new FileNameExtensionFilter("HTML Documents", "htm", "html");

            chooser.setFileFilter(filter);

            int option = chooser.showSaveDialog(ChatGUI.this);

            if (option == JFileChooser.APPROVE_OPTION) {

                // Set up document to be parsed as HTML
                StyledDocument doc = (StyledDocument)textPaneHistory.getDocument();

                HTMLEditorKit kit = new HTMLEditorKit();

                BufferedOutputStream out;

                try {

                    // add final file name and extension
                    String filePath = chooser.getSelectedFile().getAbsoluteFile() + ".html";

                    out = new BufferedOutputStream(new FileOutputStream(filePath));

                    // write out the HTML document
                    kit.write(out, doc, doc.getStartPosition().getOffset(), doc.getLength());

                } catch (FileNotFoundException e) {

                    JOptionPane.showMessageDialog(ChatGUI.this,
                    "Application will now close. \n A restart may cure the error!\n\n"
                    + e.getMessage(),
                    "Fatal Error",
                    JOptionPane.WARNING_MESSAGE, null);

                    System.exit(2);

                } catch (IOException e){

                    JOptionPane.showMessageDialog(ChatGUI.this,
                    "Application will now close. \n A restart may cure the error!\n\n"
                    + e.getMessage(),
                    "Fatal Error",
                    JOptionPane.WARNING_MESSAGE, null);

                    System.exit(3);

                } catch (BadLocationException e){

                    JOptionPane.showMessageDialog(ChatGUI.this,
                    "Application will now close. \n A restart may cure the error!\n\n"
                    + e.getMessage(),
                    "Fatal Error",
                    JOptionPane.WARNING_MESSAGE, null);

                    System.exit(4);
                }

                statusBar.setText("Chat History Saved");
            }
        }
    }
}

/**
 * Process return key for sending the message
 */
private class MyKeyAdapter extends KeyAdapter {

    @Override
    @SuppressWarnings("static-access")
    public void keyPressed(KeyEvent ke) {

        //DateTime dateTime = new DateTime();
        //String nowdateTime = dateTime.getDateTime();

        int kc = ke.getKeyCode();

        if (kc == ke.VK_ENTER) {

            try {
                // Process only if there is data
                if (textPaneHome.getText().length() > 0){

                    // Add message origin formatting
                    StyledDocument doc = (StyledDocument)textPaneHistory.getDocument();

                    Style style = doc.addStyle("HomeStyle", null);

                    StyleConstants.setBold(style, true);

                    String home = "Home [" + nowdateTime + "]: ";

                    doc.insertString(doc.getLength(), home, style);

                    StyleConstants.setBold(style, false);

                    doc.insertString(doc.getLength(), textPaneHome.getText() + "\n", style);

                    // update caret location
                    textPaneHistory.setCaretPosition(doc.getLength());

                    textPaneHome.setText(null);

                    statusBar.setText("Message Sent");
                }

            } catch (BadLocationException e) {

                JOptionPane.showMessageDialog(ChatGUI.this,
                        "Application will now close. \n A restart may cure the error!\n\n"
                        + e.getMessage(),
                        "Fatal Error",
                        JOptionPane.WARNING_MESSAGE, null);

                System.exit(1);
            }
            ke.consume();
        }
    }
}
}

首先有很多一般性评论：

a) 在发布代码时发布 SSCCE。如果您不知道 SSCCE 是什么，请搜索论坛或网络。我们看代码的时间有限，300 行就太多了。例如：

• 代码已设置，对话框图标与问题无关，并且不会运行，因为我们无权访问您的资源文件
• 执行保存的代码无关紧要，因为这不是您要解决的问题
• 如前所述，缺少 main() 方法

b) 使用正确的 Java 命名约定。变量名称以小写字符开头。 “JBSave”和“JBClear”不是标准名称，它会使您的代码难以阅读。

c) 我也同意 Gridbaglayout 很复杂，而其他布局管理器（如前面给出的 BorderLayout 方法）更容易使用。具体来说，您对 gridx 和 gridy 的理解是不正确的。它们应用于指示“连续”的行和列位置。在您的情况下，您应该使用 (0, 0)、(0, 1)、(1, 1)、(2, 1)。您将网格设置为 10。10 并不反映相对大小。所以你丢失了行，1,2,3,4,5,6,7...是的，它可能有效，但是在阅读代码时理解起来很混乱。

d) 不要使用 KeyListener 来处理文本窗格中的 Enter 键。 Swing 被设计为使用“按键绑定”。请阅读 Swing 教程中有关同一主题的部分以获取更多信息。

最后，对代码的修复很简单：

    textPaneHome.setToolTipText("Home Chat Message Window");
//    textPaneHome.setPreferredSize(new Dimension(200,50));
    textPaneHome.addKeyListener(new MyKeyAdapter());

    scrollPaneHomeText.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
    scrollPaneHomeText.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
    scrollPaneHomeText.setPreferredSize(new Dimension(200,50));

一般来说，您永远不应该设置添加到滚动窗格的组件的首选大小。 在这种情况下，当您将文本设置为 null 时，首选大小将重置为 0，并且所有组件的布局似乎都已重做。