我添加了以下代码，用于向文本字段显示滚动条。但它仍然没有出现。有人可以帮我解决这个问题。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，它正确编译而不会出错：
/*
* 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]);
}
}
任何想法??? 我是否需要设置任何可见性？ 感谢
答案 0 :(得分：3)
不，将textArea添加到ScrollPane，然后将ScrollPane添加到面板中。
作为旁注，我建议您更多地了解LayoutManagers。他们值得学习曲线。
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);
答案 1 :(得分：1)
您要将文本区域和包含它的滚动窗格都添加到内容窗格。 你也在textarea上设置尺寸，但不是滚动窗格。并且由于您的布局正在管理所有边界，因此滚动窗格可能是0,0
处的0x0setSize(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
为什么要摆脱布局，然后明确管理大小的一切？如果您使用像borderlayout和首选大小这样的东西并让那些东西为您管理边界，这会更简单。