JScrollBar Display的問題

Question

我添加了下面的代碼來顯示滾動條到我的文本框。但它仍然沒有出現。有人可以幫助我解決這個問題。我無法找出其中的錯誤是發生：

public JTextArea talkArea = new JTextArea(); 

public JScrollPane talkAreaScrollPane = new JScrollPane(talkArea); 

this.getContentPane(talkArea,null); 

this.getContentPane(talkAreaScrollPane,null); 

整個文件的代碼如下所示，正確編譯沒有給錯誤：

/* 
* Client.java 
* 
*/ 

package ChatClientRMI; 

import javax.naming.*; 
import java.rmi.RemoteException; 
import javax.rmi.PortableRemoteObject; 
import java.rmi.RMISecurityManager; 

import ChatServerRMI.*; 

import java.io.*; 
import javax.swing.*; 
import javax.swing.event.*; 
import java.awt.*; 
import java.awt.event.*; 
import java.awt.image.*; 
import java.util.*; 

public class Client extends JFrame implements Runnable, ActionListener { 

    private static final String connectStr = "Connect"; 
    private static final String disconnectStr = "Disonnect"; 

    private String _nickname; 
    private Thread _thread; 
    private Context _initialContext; 
    private JTextField inputField = new JTextField(); 
    public JTextArea talkArea = new JTextArea; 

    JScrollPane talkAreaScrollPane = new JScrollPane(talkArea); 

    private JButton _connectButton; 
    private JButton _disconnectButton; 

    private Vector serverVector = new Vector(); 
    private JList serverList = new JList(serverVector); 

    ChatRoom chatroom = null; 
    String chatroomName; 

    Client myFrame = this; 
    MyActionListener myActionListener = new MyActionListener(); 

    boolean loaded = false; 

    static int REFRESH_TIME = 200; 

    // a timer for refresh graphic area 
    javax.swing.Timer frameTimer = 
    new javax.swing.Timer(REFRESH_TIME, myActionListener); 

    // client area info 
    public static int CLIENT_WIDTH = 800; 
    public static int CLIENT_HEIGHT = 600; 

    // left panel info 
    public static int LEFT_PANEL_WIDTH = 120; 
    public static int LEFT_PANEL_HEIGHT = 420; 
    public static int LEFT_PANEL_LEFT = 20; 
    public static int LEFT_PANEL_TOP = 20; 

    // graphic area info 
    public static int GRAPHIC_TOP = 30; 
    public static int GRAPHIC_LEFT = 30; 
    public static int GRAPHIC_WIDTH = 400; 
    public static int GRAPHIC_HEIGHT = 300; 

    // talk area info 
    public static int TALK_TOP = GRAPHIC_TOP + GRAPHIC_HEIGHT + 5; 
    public static int TALK_LEFT = GRAPHIC_LEFT; 
    public static int TALK_WIDTH = GRAPHIC_WIDTH; 
    public static int TALK_HEIGHT = 175; 

    // input field info 
    public static int INPUT_TOP = TALK_TOP + TALK_HEIGHT + 25; 
    public static int INPUT_LEFT = GRAPHIC_LEFT; 
    public static int INPUT_WIDTH = GRAPHIC_WIDTH; 
    public static int INPUT_HEIGHT = 20; 

    // server list info 
    public static int SERVER_LIST_TOP = GRAPHIC_TOP; 
    public static int SERVER_LIST_LEFT = GRAPHIC_LEFT + GRAPHIC_WIDTH + 160; 
    public static int SERVER_LIST_WIDTH = 120; 
    public static int SERVER_LIST_HEIGHT = GRAPHIC_HEIGHT; // 420; 

    // user list info 
    public static int USER_LIST_TOP = 20; 
    public static int USER_LIST_LEFT = GRAPHIC_LEFT + GRAPHIC_WIDTH + 10; 
    public static int USER_LIST_WIDTH = 120; 
    public static int USER_LIST_HEIGHT = 420; 

    public static int SHADOW_WIDTH = 5; 

    // background color 
    static Color backColor = new Color(130, 60, 170); 

    // command label 
    static final String CMD_LABEL[] = 
    { "change icon", "query friend", "change location", "open room", 
     "query hero", "help", "temp leave", "leave" }; 

    // icon info 
    public static final int MAX_ICONS = 100; 
    public static final String ICON_FILENAME = "icons.gif"; 
    public static int ICON_WIDTH = 32; 
    public static int ICON_HEIGHT = 32; 
    Image icons[] = new Image[MAX_ICONS]; 
    int totalIcons = 16; 

    static String BACKIMG_FILENAME[] = 
    { "back0.jpg", "back1.jpg", "back2.jpg", "back3.jpg" }; 

    Image backImg = null; 
    Image leftPanelImg = null; 
    Image graphicImg = null; 
    Image userListImg = null; 
    Image serverListImg = null; 

    // user info 
    static int MAX_USERS = 100; 
    UserInfo userInfo[] = new UserInfo[MAX_USERS]; 
    int totalUsers = 0; 
    int myIdx = 0; 
    Hashtable users = new Hashtable(); 

    // say delay 
    static int SAY_TIME = 15; 

    // say rectangle's width 
    static int SAY_WIDTH = 100; 

    // move step 
    static int ONE_STEP = 10; 

    boolean endChat = true; 
    boolean moveEnd = true; 
    boolean sayEnd = true; 

    int enterListIndex = -1; 
    int exitListIndex = -1; 

    /** Creates new ChatClient */ 
    public Client(String name) { 
    super(name); 
    _nickname = name; 
    try { 
     _initialContext = new InitialContext(); 
    } catch (Exception e) { 
     System.out.println(e); 
    } 

    // Create and install a security manager 
    if (System.getSecurityManager() == null) { 
     System.setSecurityManager(new RMISecurityManager()); 
    } 

    setSize(new Dimension(CLIENT_WIDTH, CLIENT_HEIGHT)); 
    this.getContentPane().setLayout(null); 
    this.getContentPane().setBackground(backColor); 

    talkArea.setEditable(false); 
    talkArea.setBackground(Color.white); 
    talkArea.setBounds(new Rectangle(TALK_LEFT, TALK_TOP, TALK_WIDTH, 
     TALK_HEIGHT)); 
    this.getContentPane().add(talkArea, null); 

    // set input area 
    inputField.setBackground(Color.white); 
    inputField.setBounds(new Rectangle(INPUT_LEFT, INPUT_TOP, INPUT_WIDTH, 
     INPUT_HEIGHT)); 

    inputField.addActionListener(this); 
    this.getContentPane().add(inputField, null); 
    this.getContentPane().add(talkAreaScrollPane, null); 

    // connect button 
    _connectButton = new JButton(connectStr); 
    _connectButton.setBounds(new Rectangle(600, 400, 100, 30)); 
    _connectButton.addActionListener(this); 
    this.getContentPane().add(_connectButton); 

    // disconnect button 
    _disconnectButton = new JButton(disconnectStr); 
    _disconnectButton.setBounds(new Rectangle(600, 450, 100, 30)); 
    _disconnectButton.setEnabled(false); 
    // _disconnectButton.addActionListener(this); 
    this.getContentPane().add(_disconnectButton); 

    // testButton = new JButton("test"); 
    // testButton.setBounds(new Rectangle(600,500,100,30)); 
    // testButton.addActionListener(this); 
    // this.getContentPane().add(testButton); 

    for (int i = 0; i < 5; i++) { 
     serverVector.add("ChatRoom" + i); 
    } 

    serverList.setBackground(new Color(190, 180, 255)); 
    serverList.setBounds(new Rectangle(SERVER_LIST_LEFT + 2, 
     SERVER_LIST_TOP + 40, SERVER_LIST_WIDTH - SHADOW_WIDTH - 10, 
     SERVER_LIST_HEIGHT - 40 - 50)); 
    serverList.setSelectedIndex(0); 
    serverList.setCellRenderer(new CustomCellRenderer()); 
    this.getContentPane().add(serverList); 

    // add mouse listener for serverList 
    serverList.addMouseListener(new java.awt.event.MouseAdapter() { 
     public void mouseEntered(MouseEvent e) { 
     int index = serverList.locationToIndex(e.getPoint()); 
     enterListIndex = index; 
     // setForeground(new Color(0,0,255)); 
     System.out.println("you entered index " + index); 
     } 

     public void mouseExited(MouseEvent e) { 
     int index = serverList.locationToIndex(e.getPoint()); 
     exitListIndex = index; 
     // setForeground(new Color(0,255,255)); 
     System.out.println("you exited index " + index); 
     } 
    }); 

    // add mouse listener 
    this.addMouseListener(new java.awt.event.MouseAdapter() { 
     public void mousePressed(java.awt.event.MouseEvent event) { 
     mouseClick_performed(event); 
     } 
    }); 

    // Always need this to enable closing the frame 
    this.addWindowListener(new java.awt.event.WindowAdapter() { 
     public void windowClosing(java.awt.event.WindowEvent e) { 
     if (endChat) { 
      System.exit(0); 
      return; 
     } 
     boolean success = false; 
     try { 
      success = chatroom.disconnect(_nickname); 
     } catch (java.rmi.RemoteException err) { 
      System.out.println(err); 
     } 
     if (success) 
      System.out.println("Disonnected..."); 
     else 
      System.out.println("Not disconnected."); 

     System.exit(0); 
     } 
    }); 

    // Wait for incoming requests 
    this.startThread(); 

    // Enable GUI 
    this.setVisible(true); 

    // create offscreen images 
    leftPanelImg = createImage(LEFT_PANEL_WIDTH, LEFT_PANEL_HEIGHT); 
    graphicImg = createImage(GRAPHIC_WIDTH, GRAPHIC_HEIGHT); 
    userListImg = createImage(USER_LIST_WIDTH, USER_LIST_HEIGHT); 
    serverListImg = createImage(SERVER_LIST_WIDTH, SERVER_LIST_HEIGHT); 

    drawServerList(); 
    serverList.repaint(); 

    (new LoadImageThread()).load(); 

    try { 
     _initialContext.rebind(_nickname, new ChatUserImpl(this)); 
    } catch (Exception e) { 
     System.out.println(e); 
    } 

    } 

    public void actionPerformed(java.awt.event.ActionEvent evt) { 
    Object source = evt.getSource(); 
    if (source == _connectButton) { 
     if (serverList.getSelectedIndex() == -1) { 
     JOptionPane.showMessageDialog(this, "please select a chatroom", 
      "Error Dialog", JOptionPane.ERROR_MESSAGE); 
     return; 
     } 
     _connectButton.removeActionListener(this); 
     _connectButton.setEnabled(false); 
     _disconnectButton.addActionListener(this); 
     _disconnectButton.setEnabled(true); 
     inputField.addActionListener(this); 

     chatroomName = (String) serverList.getSelectedValue(); 
     int code = (new Random()).nextInt(totalIcons - 1); 
     boolean success = false; 
     try { 

     System.out.println("chat room name: " + chatroomName); 
     chatroom = 
      (ChatRoom) PortableRemoteObject.narrow(_initialContext 
      .lookup(chatroomName), ChatRoom.class); 
     success = chatroom.connect(_nickname, code); 
     } catch (Exception e) { 
     System.out.println("ChatUserClient exception: " + e.getMessage()); 
     e.printStackTrace(); 
     } 

     if (success) { 
     System.out.println("Connected..."); 
     endChat = false; 
     frameTimer.start(); 
     } else { 
     System.out 
      .println("Not connected: the selected nickname is in use. Please choose another nickname."); 
     } 
    } else if (source == _disconnectButton) { 

     _connectButton.addActionListener(this); 
     _connectButton.setEnabled(true); 
     _disconnectButton.removeActionListener(this); 
     _disconnectButton.setEnabled(false); 
     inputField.removeActionListener(this); 

     // clear everything 
     talkArea.setText(""); 
     inputField.setText(""); 

     if (backImg == null) { 
     Graphics g = graphicImg.getGraphics(); 
     g.setColor(Color.blue); 
     g.fillRect(0, 0, GRAPHIC_WIDTH, GRAPHIC_HEIGHT); 
     getGraphics().drawImage(graphicImg, GRAPHIC_LEFT, GRAPHIC_TOP, this); 
     } else { 
     getGraphics().drawImage(backImg, GRAPHIC_LEFT, GRAPHIC_TOP, this); 
     } 

     users.clear(); 

     if (endChat) { 
     return; 
     } 

     boolean success = false; 
     try { 
     success = chatroom.disconnect(_nickname); 
     } catch (java.rmi.RemoteException e) { 
     System.out.println(e); 
     } 
     if (success) { 
     endChat = true; 
     System.out.println("Disonnected..."); 
     } else { 
     System.out.println("Not disconnected."); 
     } 

    } else if (source == inputField) { 
     String message = inputField.getText(); 
     try { 
     chatroom.sendMessage(message, _nickname); 
     } catch (java.rmi.RemoteException e) { 
     System.out.println(e); 
     } 
    } 
    } // end actionperformed 

    public void startThread() { 
    _thread = new Thread(this); 
    _thread.start(); 
    } 

    public void run() { 

    } 

    public void update(Graphics g) { 
    paint(g); 
    } 

    public void paint(Graphics g) { 
    super.paint(g); 
    if (loaded) { 
     g.drawImage(graphicImg, GRAPHIC_LEFT, GRAPHIC_TOP, this); 
     g.drawImage(serverListImg, SERVER_LIST_LEFT, SERVER_LIST_TOP, this); 
     serverList.repaint(); 
    } 
    } 

    // sgn func 
    public int sgn(int x) { 
    if (x > 0) 
     return 1; 
    if (x < 0) 
     return -1; 
    return 0; 
    } 

    // everyone move one step 
    public void moveOneStep() { 
    int count = 0; 
    int direction; 

    for (Enumeration e = users.elements(); e.hasMoreElements();) { 
     UserInfo p = (UserInfo) e.nextElement(); 

     direction = sgn(p.dx - p.x); 
     if (direction == 0) 
     count++; 
     p.x += direction * ONE_STEP; 
     direction = sgn(p.dy - p.y); 
     if (direction == 0) 
     count++; 
     p.y += direction * ONE_STEP; 

     if (java.lang.Math.abs(p.x - p.dx) <= ONE_STEP) 
     p.x = p.dx; 
     if (java.lang.Math.abs(p.y - p.dy) <= ONE_STEP) 
     p.y = p.dy; 

     if (p.x <= ICON_WIDTH/2) { 
     p.x = ICON_WIDTH/2; 
     p.dx = p.x; 
     } 
     if (p.x >= GRAPHIC_WIDTH - ICON_WIDTH/2) { 
     p.x = GRAPHIC_WIDTH - ICON_WIDTH/2; 
     p.dx = p.x; 
     } 
     if (p.y <= ICON_HEIGHT/2) { 
     p.y = ICON_HEIGHT/2; 
     p.dy = p.y; 
     } 
     if (p.y >= GRAPHIC_HEIGHT - ICON_HEIGHT/2) { 
     p.y = GRAPHIC_HEIGHT - ICON_HEIGHT/2; 
     p.dy = p.y; 
     } 
    } 

    moveEnd = (count == users.size() * 2); 
    System.out.println("count = " + count); 
    System.out.println("size = " + users.size()); 
    System.out.println("messgeEnd = " + moveEnd); 
    } // end of moveOneStep 

    // timer action 
    public void timer_actionPerformed() { 
    if (endChat) 
     return; 
    if (!moveEnd) 
     moveOneStep(); 
    if (moveEnd && sayEnd) 
     return; 
    drawGraphicArea(); 
    getGraphics().drawImage(graphicImg, GRAPHIC_LEFT, GRAPHIC_TOP, this); 
    } 

    // mouse event 
    public void mouseClick_performed(java.awt.event.MouseEvent event) { 
    if (endChat) 
     return; 
    // if (endChat == true || myIdx == -1) return; 
    // if (userInfo[myIdx].x < 0) return; 
    if (event.getID() == event.MOUSE_PRESSED) { 
     int x = event.getX(); 
     int y = event.getY(); 
     if (x < GRAPHIC_LEFT || x >= GRAPHIC_LEFT + GRAPHIC_WIDTH 
     || y < GRAPHIC_TOP || y > GRAPHIC_TOP + GRAPHIC_HEIGHT) 
     return; 

     moveEnd = false; 
     UserInfo p = (UserInfo) users.get(_nickname); 
     p.dx = x - GRAPHIC_LEFT; 
     p.dy = y - GRAPHIC_TOP; 

     try { 
     chatroom.sendLocation(p.dx, p.dy, p.name); 
     } catch (java.rmi.RemoteException e) { 
     System.out.println(e); 
     } 
     // sendCmd(MsgType.MOVE, userInfo[myIdx].dx, userInfo[myIdx].dy); 
    } 
    } 

    public void printUserList() { 
    Enumeration usernames = users.keys(); 
    while (usernames.hasMoreElements()) { 
     System.out.println("user name: " + usernames.nextElement()); 
    } 
    } 

    // draw server list 
    public void drawServerList() { 
    Graphics g = serverListImg.getGraphics(); 

    g.setColor(backColor); 
    g.fillRect(0, 0, SERVER_LIST_WIDTH, SERVER_LIST_HEIGHT); 

    g.setColor(Color.black); 
    g.fillRoundRect(5, 5, SERVER_LIST_WIDTH - SHADOW_WIDTH, SERVER_LIST_HEIGHT 
     - SHADOW_WIDTH, 30, 30); 
    g.setColor(new Color(190, 180, 255)); 
    g.fillRoundRect(0, 0, SERVER_LIST_WIDTH - SHADOW_WIDTH, SERVER_LIST_HEIGHT 
     - SHADOW_WIDTH, 30, 30); 
    g.setColor(new Color(0, 0, 255)); 
    g.drawRoundRect(0, 0, SERVER_LIST_WIDTH - SHADOW_WIDTH, SERVER_LIST_HEIGHT 
     - SHADOW_WIDTH, 30, 30); 

    g.setFont(new Font(g.getFont().getName(), g.getFont().getStyle(), 20)); 
    g.setColor(Color.black); 

    FontMetrics fntM = g.getFontMetrics(); 
    String s = new String("Server List"); 
    int x = (SERVER_LIST_WIDTH - fntM.stringWidth(s))/2; 
    g.drawString(s, x, 30); 

    // update to screen 
    getGraphics().drawImage(serverListImg, SERVER_LIST_LEFT, SERVER_LIST_TOP, 
     this); 
    } 

    // draw graphic area 
    public synchronized void drawGraphicArea() { 
    Graphics g = graphicImg.getGraphics(); 
    FontMetrics fntM = g.getFontMetrics(); 

    if (backImg == null) { 
     g.setColor(Color.blue); 
     g.fillRect(0, 0, GRAPHIC_WIDTH, GRAPHIC_HEIGHT); 
    } else { 
     g.drawImage(backImg, 0, 0, this); 
    } 
    // if (myIdx == -1) return ; 

    UserInfo p; 
    g.setFont(new Font(g.getFont().getName(), g.getFont().getStyle(), 12)); 

    int count = 0; 

    for (Enumeration e = users.elements(); e.hasMoreElements();) { 
     // draw icon 
     p = (UserInfo) e.nextElement(); 
     g.drawImage(icons[p.code], p.x - ICON_WIDTH/2, p.y - ICON_HEIGHT/2, 
     this); 

     // draw name 
     if (p.name.equals(_nickname)) 
     g.setColor(Color.red); 
     else 
     g.setColor(Color.yellow); 
     int x = (p.x - fntM.stringWidth(p.name)/2); 
     int y = (p.y + ICON_HEIGHT/2); 
     g.fillRoundRect(x - 2, y, fntM.stringWidth(p.name) + 4, fntM.getHeight(), 
     10, 10); 
     g.setColor(Color.black); 
     g.drawRoundRect(x - 2, y, fntM.stringWidth(p.name) + 4, fntM.getHeight(), 
     10, 10); 
     g.drawString(p.name, x, y + fntM.getAscent()); 

     // draw say 
     if (p.sayTime <= 0) { 
     count++; 
     continue; 
     } 
     String saySplit[] = new String[100]; 
     int c = 0; 
     int st = 0, ed = 1; 
     while (ed <= p.say.length()) { 
     String s = p.say.substring(st, ed); 
     if (fntM.stringWidth(s) > SAY_WIDTH) { 
      saySplit[c] = p.say.substring(st, ed - 1); 
      c++; 
      st = ed - 1; 
     } 
     ed++; 
     } 
     saySplit[c] = p.say.substring(st, ed - 1); 
     c++; 
     x = p.x + ICON_WIDTH/2 + 5; 
     y = p.y - ICON_HEIGHT/2 + 5; 
     int w = ((c > 1) ? SAY_WIDTH : fntM.stringWidth(saySplit[0])) + 5; 
     int h = fntM.getHeight() * c + 5; 

     // draw say arrow 
     g.setColor(Color.green); 
     if (x + w >= GRAPHIC_WIDTH) { 
     x = p.x - ICON_WIDTH/2 - w - 5; 
     Polygon polygon = new Polygon(); 
     polygon.addPoint(p.x - ICON_WIDTH/2, p.y - 5); 
     polygon.addPoint(p.x - ICON_WIDTH/2 - 8, p.y - 10); 
     polygon.addPoint(p.x - ICON_WIDTH/2 - 8, p.y - 4); 
     // p.addPoint(x + ICON_WIDTH/2, y - 5); 
     g.fillPolygon(polygon); 
     } else { 
     Polygon polygon = new Polygon(); 
     polygon.addPoint(p.x + ICON_WIDTH/2, p.y - 5); 
     polygon.addPoint(p.x + ICON_WIDTH/2 + 8, p.y - 10); 
     polygon.addPoint(p.x + ICON_WIDTH/2 + 8, p.y - 4); 
     // p.addPoint(x + ICON_WIDTH/2, y - 5); 
     g.fillPolygon(polygon); 
     } 

     g.fillRoundRect(x, y, w, h, 10, 10); 
     g.setColor(Color.black); 
     // g.drawRoundRect(x, y, w, h, 10, 10); 
     for (int j = 0; j < c; j++) { 
     g.drawString(saySplit[j], x + 2, y + 2 + j * fntM.getHeight() 
      + fntM.getAscent()); 
     } 
     p.sayTime--; 
    } // end of for 
    sayEnd = (count == users.size()); 

    update(getGraphics()); 
    } // end of drawGraphicArea 

    class MyActionListener implements ActionListener { 
    public void actionPerformed(ActionEvent e) { 
     Object obj = e.getSource(); 
     if (obj == frameTimer) { 
     timer_actionPerformed(); 
     return; 
     } 

    } 
    } 

    // **************************************** 
    // a load image thread class in applet class 
    // **************************************** 
    class LoadImageThread extends Thread { 
    public void load() { 
     this.start(); 
    } 

    public void run() { 
     loadImages(); 
     loaded = true; 
     try { 
     sleep(1000); 
     } catch (java.lang.InterruptedException e) { 
     } 
     if (backImg == null) { 
     Graphics g = graphicImg.getGraphics(); 
     g.setColor(Color.blue); 
     g.fillRect(0, 0, GRAPHIC_WIDTH, GRAPHIC_HEIGHT); 
     (myFrame.getGraphics()).drawImage(graphicImg, GRAPHIC_LEFT, 
      GRAPHIC_TOP, myFrame); 
     } else { 
     myFrame.getGraphics().drawImage(backImg, GRAPHIC_LEFT, GRAPHIC_TOP, 
      myFrame); 
     } 
    } 

    // load all images 
    public void loadImages() { 

     Graphics g = graphicImg.getGraphics(); 
     g.setColor(Color.blue); 
     g.fillRect(0, 0, GRAPHIC_WIDTH, GRAPHIC_HEIGHT); 
     g.setColor(Color.yellow); 
     g.setFont(new Font(g.getFont().getName(), g.getFont().getStyle(), 30)); 
     g.drawString("loading, please wait ......", 30, 50); 
     (myFrame.getGraphics()).drawImage(graphicImg, GRAPHIC_LEFT, GRAPHIC_TOP, 
     myFrame); 

     MediaTracker m = new MediaTracker(myFrame); 
     for (int i = 0; i < totalIcons; i++) { 
     icons[i] = Toolkit.getDefaultToolkit().getImage(i + ".gif"); 
     m.addImage(icons[i], 0); 
     } 

     try { 
     m.waitForAll(); 
     } catch (InterruptedException e) { 
     System.out.println("can't read image from file"); 
     } 

    } 

    } // end of LoadImage class 

    class CustomCellRenderer extends JLabel implements ListCellRenderer { 
    public Component getListCellRendererComponent(JList list, Object value, 
     int index, boolean isSelected, boolean cellHasFocus) { 

     String s = value.toString(); 
     setText(s); 
     // setIcon((s.length() > 10) ? longIcon : shortIcon); 
     if (isSelected) { 
     // setBackground(list.getSelectionBackground()); 
     // setForeground(list.getSelectionForeground()); 
     setForeground(new Color(0, 0, 255)); 
     } else { 
     // setBackground(list.getBackground()); 
     // setForeground(list.getForeground()); 
     setForeground(new Color(0, 255, 255)); 
     } 
     /* 
     * if (index == enterListIndex){ System.out.println("****************"); 
     * setForeground(new Color(0,0,180)); } if (index == exitListIndex){ 
     * System.out.println("---------------"); setForeground(new 
     * Color(0,255,255)); } 
     */ 
     setEnabled(list.isEnabled()); 
     setFont(list.getFont()); 
     return this; 
    } 
    } 

    /** 
    * @param args the command line arguments 
    */ 
    public static void main(String args[]) { 
    // args[0] is user nickname 
    if (args.length != 1) { 
     System.out.println("Usage: ChatClient nickname"); 
     System.exit(0); 
    } 
    Client clientFrame = new Client(args[0]); 
    } 

} 

任何想法??? 我是否需要設置任何一種可見性？ 謝謝

Answer 1

你將兩個文本區域，它包含的內容窗格中的滾動窗格。 你也在textarea上設置尺寸，但不是滾動窗格。既然你的佈局管理所有的界限，滾動面板大概是爲0x0 0,0

setSize(new Dimension(CLIENT_WIDTH, CLIENT_HEIGHT)); 
this.getContentPane().setLayout(null); 
this.getContentPane().setBackground(backColor); 
talkArea.setEditable(false); 
talkArea.setBackground(Color.white); 
talkArea.setBounds(new Rectangle(TALK_LEFT, TALK_TOP, TALK_WIDTH,  TALK_HEIGHT)); 
this.getContentPane().add(talkArea, null); // <--- you want this inside the text area, not here! 
// set input area 
inputField.setBackground(Color.white); 
inputField.setBounds(new Rectangle(INPUT_LEFT, INPUT_TOP, INPUT_WIDTH,  INPUT_HEIGHT)); 
inputField.addActionListener(this); 
this.getContentPane().add(inputField, null); 
this.getContentPane().add(talkAreaScrollPane, null); // <--- you never set the size on here 

爲什麼你擺脫佈局，然後大小顯式管理的一切嗎？如果你使用了類似borderlayout和首選大小的東西，並且讓這些東西管理你的邊界，這將會簡單得多。

Answer 2

不，將textArea添加到ScrollPane，然後將ScrollPane放到面板中。

作爲一個便箋，我會建議學習更多關於LayoutManagers的知識。他們值得學習曲線。

例子：

//In a container that uses a BorderLayout: 
textArea = new JTextArea(5, 30); 
... 
JScrollPane scrollPane = new JScrollPane(textArea); 
... 
setPreferredSize(new Dimension(450, 110)); 
... 
add(scrollPane, BorderLayout.CENTER); 

來自How to use scroll panes