java - JScrollBar 显示问题

Question

我添加了以下代码，用于在文本字段中显示滚动条。但它仍然没有出现。有人可以帮我解决这个问题吗？我无法弄清楚错误发生在哪里:

public JTextArea talkArea = new JTextArea();

public JScrollPane talkAreaScrollPane = new JScrollPane(talkArea);

this.getContentPane(talkArea,null);

this.getContentPane(talkAreaScrollPane,null);

整个文件的代码如下，编译正确，没有报错:

/*
 * 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]);
  }

}

有什么想法吗？？？我需要设置任何类型的可见性吗？谢谢

Answer 1

不，将 textArea 添加到 ScrollPane，然后将 ScrollPane 放入面板中。

作为旁注，我建议了解有关 LayoutManager 的更多信息。它们值得学习。

示例:

//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);

取自:How to use scroll panes