*许多关于GUI的代码都是由NetBeans生成的。
我遇到的问题是在客户端，告诉我uploadBtn为空，nullPointException。我很确定这是因为它没有实例化，并且在构造函数中添加了actionListener。我通过NetBeans构建了GUI，但不确定如何去实现它。
我想要的是点击uploadBtn时，客户端和服务器端会发生什么。单击该按钮后，它会调用在客户端为我创建的actionPerformed() NetBeans，但不确定如何检查服务器端是否按下按钮，如果是，则调用方法服务器。任何帮助赞赏。我正在使用套接字/数据报。大学项目。
ClientGUI.java
public class ClientGUI extends javax.swing.JFrame {
String username;
/**
* Creates new form NewJFrame
*/
public ClientGUI() {
initComponents();
}
public ClientGUI(ActionListener listen)
{
uploadBtn.addActionListener(listen);
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jLabel1 = new javax.swing.JLabel();
usernameTxt = new javax.swing.JTextField();
passwordTxt = new javax.swing.JTextField();
loginBtn = new javax.swing.JButton();
jLabel2 = new javax.swing.JLabel();
jLabel3 = new javax.swing.JLabel();
uploadBtn = new javax.swing.JButton();
jLabel4 = new javax.swing.JLabel();
downloadBtn = new javax.swing.JButton();
logOffBtn = new javax.swing.JButton();
portTxt = new javax.swing.JTextField();
hostTxt = new javax.swing.JTextField();
createFile = new javax.swing.JButton();
fileNameTxt = new javax.swing.JTextField();
connectionLbl = new javax.swing.JLabel();
notifyLbl = new javax.swing.JLabel();
downloadFileNameTxt = new javax.swing.JTextField();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jPanel1.setBackground(new java.awt.Color(0, 0, 51));
jLabel1.setFont(new java.awt.Font("Tahoma", 0, 18)); // NOI18N
jLabel1.setForeground(new java.awt.Color(255, 255, 255));
jLabel1.setText("File Transfer System");
usernameTxt.setText("Username");
passwordTxt.setText("Password");
loginBtn.setText("Login");
loginBtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
loginBtnActionPerformed(evt);
}
});
jLabel2.setFont(new java.awt.Font("Tahoma", 0, 14)); // NOI18N
jLabel2.setForeground(new java.awt.Color(255, 255, 255));
jLabel2.setText("Login");
jLabel3.setFont(new java.awt.Font("Tahoma", 0, 14)); // NOI18N
jLabel3.setForeground(new java.awt.Color(255, 255, 255));
jLabel3.setText("Upload");
uploadBtn.setText("Upload");
uploadBtn.setName("Upload"); // NOI18N
uploadBtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
uploadBtnActionPerformed(evt);
}
});
jLabel4.setFont(new java.awt.Font("Tahoma", 0, 14)); // NOI18N
jLabel4.setForeground(new java.awt.Color(255, 255, 255));
jLabel4.setText("Download");
downloadBtn.setText("Download");
downloadBtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
downloadBtnActionPerformed(evt);
}
});
logOffBtn.setBackground(new java.awt.Color(153, 0, 0));
logOffBtn.setForeground(new java.awt.Color(255, 255, 255));
logOffBtn.setText("Log Off");
logOffBtn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
logOffBtnActionPerformed(evt);
}
});
portTxt.setText("7");
portTxt.setToolTipText("Port");
hostTxt.setText("localhost");
createFile.setText("Create File");
createFile.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
createFileActionPerformed(evt);
}
});
fileNameTxt.setText("File Name");
connectionLbl.setFont(new java.awt.Font("Tahoma", 0, 14)); // NOI18N
connectionLbl.setForeground(new java.awt.Color(255, 0, 0));
connectionLbl.setText("Not Connected");
notifyLbl.setFont(new java.awt.Font("Tahoma", 0, 12)); // NOI18N
notifyLbl.setForeground(java.awt.Color.green);
downloadFileNameTxt.setText("File Name");
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(21, 21, 21)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
.addComponent(portTxt, javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jLabel2, javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(usernameTxt, javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(passwordTxt, javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(loginBtn, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 82, Short.MAX_VALUE))
.addGap(101, 101, 101)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(notifyLbl)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
.addComponent(fileNameTxt, javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jLabel3, javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(createFile, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(uploadBtn, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addGap(115, 115, 115)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(downloadFileNameTxt, javax.swing.GroupLayout.PREFERRED_SIZE, 85, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jLabel4)
.addComponent(downloadBtn, javax.swing.GroupLayout.PREFERRED_SIZE, 85, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(logOffBtn)))))
.addComponent(connectionLbl)
.addComponent(hostTxt, javax.swing.GroupLayout.PREFERRED_SIZE, 82, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(152, 152, 152)
.addComponent(jLabel1)))
.addContainerGap(49, Short.MAX_VALUE))
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel1)
.addGap(26, 26, 26)
.addComponent(connectionLbl)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 53, Short.MAX_VALUE)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel2)
.addComponent(jLabel3)
.addComponent(jLabel4))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(usernameTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(createFile)
.addComponent(downloadFileNameTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(passwordTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(downloadBtn))
.addGap(30, 30, 30)
.addComponent(hostTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(10, 10, 10)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(portTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(fileNameTxt, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(loginBtn)
.addComponent(uploadBtn)
.addComponent(logOffBtn))
.addGap(42, 42, 42)
.addComponent(notifyLbl)
.addGap(36, 36, 36))
);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
pack();
}// </editor-fold>
private void loginBtnActionPerformed(java.awt.event.ActionEvent evt) {
try {
String hostname = hostTxt.getText();
String port = portTxt.getText();
username = usernameTxt.getText();
String password = passwordTxt.getText();
ClientGUI client = new ClientGUI();
Users usersClass = new Users();
if (hostname.length() == 0) // if user did not enter a name
{
hostname = "localhost"; // use the default host name
}
if (port.length() == 0) // if user did not enter a name
{
port = "7"; // use the default host name
}
Map<String, String> users;
users = usersClass.getSet();
if (users.containsKey(username) && users.containsValue(password)) {
JOptionPane.showMessageDialog(null, "Logged in Successfully. Welcome " + username);
connectionLbl.setText("Connected");
connectionLbl.setForeground(Color.green);
hostTxt.setEditable(false);
portTxt.setEditable(false);
usernameTxt.setEditable(false);
passwordTxt.setEditable(false);
loginBtn.setEnabled(false);
createUserFolder(username);
new File("C:\\ServerFolder\\" + username).mkdirs();
} else if (!users.containsKey(username) && !users.containsValue(password)) {
JOptionPane.showMessageDialog(null, "User does not exist. Try again.");
}
ClientHelper helper
= new ClientHelper(hostname, port, username, password);
boolean check = client.validateUsername(username);
while (check) {
String serverResponse = helper.sendMessageUsername(username);
System.out.println(serverResponse);
check = false;
}
} catch (SocketException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (UnknownHostException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
}
}
public File createUserFolder(String folderName) {
File directory = new File("C:\\" + folderName);
// if the directory does not exist, create it
if (!directory.exists()) {
System.out.println("Creating Directory... ");
boolean result = false;
try {
directory.mkdir();
result = true;
} catch (SecurityException se) {
//handle it
}
if (result) {
System.out.println("Directory Created");
}
}
return directory;
}
public JButton getButton()
{
return uploadBtn;
}
private void logOffBtnActionPerformed(java.awt.event.ActionEvent evt) {
// try {
String hostname = hostTxt.getText();
String port = portTxt.getText();
username = usernameTxt.getText();
String password = passwordTxt.getText();
hostTxt.setEditable(true);
portTxt.setEditable(true);
usernameTxt.setEditable(true);
passwordTxt.setEditable(true);
loginBtn.setEnabled(true);
connectionLbl.setText("Not Connected");
connectionLbl.setForeground(Color.red);
// ClientHelper helper
// = new ClientHelper(hostname, port, username, password);
//
// String serverResponse =helper.sendMessageLogOff(username);
// System.out.println(serverResponse);
//
//
// } catch (SocketException ex) {
// Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
// } catch (UnknownHostException ex) {
// Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
// } catch (IOException ex) {
// Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
// }
}
public void createFile(String fileName) {
String sb = "TEST CONTENT";
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("C:\\" + fileName));
int retrieval = chooser.showSaveDialog(null);
if (retrieval == JFileChooser.APPROVE_OPTION) {
try {
FileWriter fw = new FileWriter(chooser.getSelectedFile() + ".txt");
fw.write(sb.toString());
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
public void createServerFile() throws IOException
{
String str = "This is a server file!";
File newTextFile = new File("C:\\ServerFolder\\serverFile.txt");
FileWriter fw = new FileWriter(newTextFile);
fw.write(str);
fw.close();
System.out.println("\n904 - Server file created - 'serverFile.txt'");
}
private void createFileActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
createFile(username);
notifyLbl.setText("File Created!");
Timer timer = new Timer(5000, e -> notifyLbl.setText(""));
timer.setRepeats(false);
timer.start();
}
private void uploadBtnActionPerformed(java.awt.event.ActionEvent evt) {
try {
// TODO add your handling code here:
String fileName = fileNameTxt.getText();
String hostname = hostTxt.getText();
String port = portTxt.getText();
String username = usernameTxt.getText();
String password = passwordTxt.getText();
String text = "This is " + username + "'s file!";
ClientHelper helper
= new ClientHelper(hostname, port, username, password);
File file = new File("C:\\" + username + "\\" + fileName + ".txt");
if (!file.exists()) {
System.out.println("File not found!");
} else {
String myFile = helper.writeFileAndSend(fileName, username, text);
System.out.println("Response:\n" + "File name: " + myFile + " User: " + username);
notifyLbl.setText("File Uploaded");
Timer timer = new Timer(5000, e -> notifyLbl.setText(""));
timer.setRepeats(false);
timer.start();
}
} catch (SocketException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (UnknownHostException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
}
}
private void downloadBtnActionPerformed(java.awt.event.ActionEvent evt) {
try {
// TODO add your handling code here:
String hostname = hostTxt.getText();
String port = portTxt.getText();
username = usernameTxt.getText();
String password = passwordTxt.getText();
String fileToDownload = downloadFileNameTxt.getText();
String messageInFile = "User Downloaded: " + username + " *********This is a server File!**********";
ClientHelper helper
= new ClientHelper(hostname, port, username, password);
File file = new File("C:\\ServerFolder\\" + fileToDownload + ".txt");
if (!file.exists()) {
System.out.println("File not found!");
} else {
helper.readFileAndSend(fileToDownload, messageInFile);
System.out.println("\nResponse:\n" + "File name: " + fileToDownload + " User: " + username);
notifyLbl.setText("File Downloaded");
Timer timer = new Timer(5000, e -> notifyLbl.setText(""));
timer.setRepeats(false);
timer.start();
}
} catch (SocketException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (UnknownHostException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(ClientGUI.class.getName()).log(Level.SEVERE, null, ex);
}
}
public boolean validateUsername(String username) {
username = username.trim();
if (username == null || username.equals("")) {
return false;
}
if (!username.matches("[a-zA-Z]*")) {
return false;
}
return true;
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
ClientGUI client = new ClientGUI(new Server());
client.createUserFolder("DownloadedFiles");
//client.createServerFile("serverFile");
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new ClientGUI().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel connectionLbl;
private javax.swing.JButton createFile;
private javax.swing.JButton downloadBtn;
private javax.swing.JTextField downloadFileNameTxt;
private javax.swing.JTextField fileNameTxt;
private javax.swing.JTextField hostTxt;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JPanel jPanel1;
private javax.swing.JButton logOffBtn;
private javax.swing.JButton loginBtn;
private javax.swing.JLabel notifyLbl;
private javax.swing.JTextField passwordTxt;
private javax.swing.JTextField portTxt;
public javax.swing.JButton uploadBtn;
private javax.swing.JTextField usernameTxt;
// End of variables declaration
}
Server.java
public class Server implements ActionListener {
JButton button = new JButton();
public static void main(String[] args) {
ClientGUI client = new ClientGUI();
client.createUserFolder("ServerFolder");
Server server = new Server();
server.button = client.getButton();
int serverPort = 7; // default port
if (args.length == 1) {
serverPort = Integer.parseInt(args[0]);
}
try {
// instantiates a datagram socket for both sending
// and receiving data
ServerDatagramSocket mySocket = new ServerDatagramSocket(serverPort);
System.out.println("Server Ready...");
while (true) { // forever loop
//Login
DatagramMessage request = mySocket.receiveMessageAndSender();
System.out.println("201 - Request Received to Login");
String message = request.getMessage();
System.out.println("204 - Login Successful - Welcome " + message);
// Now send the echo to the requestor
mySocket.sendMessage(request.getAddress(),
request.getPort(), message);
//End Login
// //LogOff
// DatagramMessage requestToLogOff = mySocket.receiveMessageAndSender();
// System.out.println("\n401 - Request Received to Log off");
// String response = requestToLogOff.getMessage();
//
// System.out.println("402 - Log off Successful - Goodbye " + response);
// // Now send the echo to the requestor
// mySocket.sendMessage(request.getAddress(),
// request.getPort(), response);
// //End LogOff
// //Upload
// System.out.println("\n304 - Upload Requested...");
// byte[] receiveData = new byte[MAX_LEN];
// byte[] sendData = new byte[MAX_LEN];
// DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
// mySocket.receive(receivePacket);
//
// String sentence = new String(receivePacket.getData());
// SimpleDateFormat df = new SimpleDateFormat("EEE, MMM d, ''yy");
//
// File moddedFile = new File("C:\\ServerFolder\\");
//
// mySocket.sendMessage(request.getAddress(), request.getPort(), "Last upload on " + df.format(moddedFile.lastModified()));
// System.out.println("305 - Last upload on " + df.format(moddedFile.lastModified()));
// System.out.println("306 - Recieved Data: " + sentence);
//
// InetAddress IPAddress = receivePacket.getAddress();
// int port = receivePacket.getPort();
// String capitalizedSentence = sentence.toUpperCase();
// sendData = capitalizedSentence.getBytes();
// DatagramPacket sendPacket
// = new DatagramPacket(sendData, sendData.length, IPAddress, port);
// mySocket.send(sendPacket);
//
// System.out.println("\n307 - File Recieved and ready for upload...");
// Writer writer = null;
//
// String todaysDate = df.format(new Date());
//
// writer = new BufferedWriter(new OutputStreamWriter(
// new FileOutputStream("C:\\ServerFolder\\" + message.trim() + "\\" + todaysDate + ".txt"), "utf-8"));
// writer.write(sentence);
// System.out.println("308 - File upload complete!");
// writer.close();
//
// //End Upload
//Start Download
client.createServerFile();
System.out.println("\n504 - Download Requested...");
File downloadFolder = new File("C:\\ServerFolder\\serverFile.txt");
String myFile = null;
BufferedReader reader = new BufferedReader(new FileReader(downloadFolder));
StringBuilder sb = new StringBuilder();
String line = reader.readLine();
while(line != null)
{
sb.append(line);
sb.append(System.lineSeparator());
line = reader.readLine();
}
myFile = sb.toString();
mySocket.sendMessage(request.getAddress(), request.getPort(), myFile + "\n\n501 - Download Complete");
//System.out.println("\n508 - Download Requested...");
JOptionPane.showMessageDialog(null, "File download complete!");
System.out.println("508 - File download complete!");
//End Download
} //end while
} // end try
catch (Exception ex) {
ex.printStackTrace();
} // end catch
}//end main
@Override
public void actionPerformed(ActionEvent e) {
if(button.getModel().isPressed())
System.out.println("the button is pressed");
}
} // end class
答案 0 :(得分：1)
当您使用带有ActionListener参数的构造函数时，您不会调用initComponents()，因此没有任何组件被初始化并且所有组件都保持为null。所以改变这个：
public ClientGUI(ActionListener listen)
{
uploadBtn.addActionListener(listen);
}
到此：
public ClientGUI(ActionListener listen)
{
this(); // call the default constructor first which calls initComponents.
uploadBtn.addActionListener(listen);
}
或者您可以直接调用initComponents：
public ClientGUI(ActionListener listen)
{
initComponents();
uploadBtn.addActionListener(listen);
}
但我也不喜欢这个第二个解决方案，因为如果你将其他初始化代码放在默认构造函数中，你需要在两个构造函数中显式调用它。