在Eclipse中寫入文件的問題

Question

我一直在自己的遊戲中工作，並且遇到寫入我用來保存登錄面板數據的簡單文本文件的問題。我使用java.swing來創建一切。只是想知道是否有人能看到我的問題。

public class Main { 

private static String username; 
private static String password; 

public static void main(String[] args) { 

    try { FileWriter fw = new FileWriter("data.txt", true); //creates txt file for data 
      PrintWriter pw = new PrintWriter(fw); //creates writer to move data to txt file 
     } 

    catch (IOException e) { e.printStackTrace(); } //catches error with writing to txt file 



    getVariables(); //sets private variables to login info on text file 
    login(); //opens login frame 
} 

public static void login(){ 

    JFrame frame = new JFrame("");  //creates JFrame for login window 

    frame.setResizable(false);        
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //FRAME SETTINGS 
    frame.setSize(180,140); 
    frame.setLocationRelativeTo(null); 

    JPanel panel = new JPanel(); //creates panel for login window 
    panel.setLayout(null); 

    JLabel usernameL = new JLabel("Username:"); //username label for login window 
    usernameL.setSize(100,20); 
    usernameL.setLocation(5,5); 

    JLabel passwordL = new JLabel("Password:"); //password label for login window 
    passwordL.setSize(100,20); 
    passwordL.setLocation(5,25); 


    final JTextField usernameField = new JTextField("",15); //username field for login window 
    usernameField.setSize(100,20); 
    usernameField.setLocation(70,5); 

    final JPasswordField passwordField = new JPasswordField("",15); //password field for login window 
    passwordField.setSize(100,20); 
    passwordField.setLocation(70,25); 

    JButton confirmLogin = new JButton("Log In");  //button to login 
    confirmLogin.setSize(80,20); 
    confirmLogin.setLocation(45,50); 
    confirmLogin.addActionListener(new ActionListener(){ 
     public void actionPerformed(ActionEvent e) {  //checks to see if login is correct 
      if(usernameField.getText().equals(username) && passwordField.getText().equals(password)){ 
       gameMenu();   //calls game menu 
      } 
      else { 
       String message = "Your username or password is wrong!"; 
       JOptionPane.showMessageDialog       //displays panel stating login was incorrect 
       (new JFrame(), message, "Login Failed", 
       JOptionPane.ERROR_MESSAGE); 
      } 
     } 
    }); 

    JButton createAccount = new JButton("Create Account"); //button to create account 
    createAccount.setSize(122,20); 
    createAccount.setLocation(25,75); 
    createAccount.addActionListener(new ActionListener(){ 
     public void actionPerformed(ActionEvent e) {  //calls method to create account 
      createAccount(); 
     } 
    }); 

    panel.add(createAccount); 
    panel.add(passwordField); 
    panel.add(usernameField); 
    panel.add(usernameL);   //add components to window 
    panel.add(passwordL); 
    panel.add(confirmLogin); 

    frame.add(panel); 
    frame.setVisible(true); 
} 

protected static void createAccount() { 
    final JFrame frame2 = new JFrame("Account Creation");  //creates window for account creation 
    frame2.setSize(290,110); 
    frame2.setLocationRelativeTo(null); 
    frame2.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);  //window settings 
    frame2.setResizable(false); 

    JPanel panel2 = new JPanel(); 
    panel2.setLayout(null);     //creates panel for account creation window 

    JLabel usernameL2 = new JLabel("Username:"); 
    usernameL2.setSize(100,20);    //creates username label for window 
    usernameL2.setLocation(55,5); 

    JLabel passwordL2 = new JLabel("Password:"); //creates password label for window 
    passwordL2.setSize(100,20); 
    passwordL2.setLocation(55,25); 

    final JTextField usernameField2 = new JTextField("",15); 
    usernameField2.setSize(100,20);    //creates username field for window 
    usernameField2.setLocation(120,5); 

    final JPasswordField passwordField2 = new JPasswordField("",15); 
    passwordField2.setSize(100,20);   //creates password field for window 
    passwordField2.setLocation(120,25); 

    JButton confirm = new JButton("Confirm Creation"); 
    confirm.setSize(130,20);   //creates button to confirm account creation 
    confirm.setLocation(75,50); 
    confirm.addActionListener(new ActionListener(){ 
     public void actionPerformed(ActionEvent e) { 
      try { FileWriter fw = new FileWriter("out.txt", false);   //doesnt append (should overwrite data) 
       PrintWriter pw = new PrintWriter(fw);      

       pw.println(usernameField2.getText());   //gets info from textfield and pushes to data txt file 
       pw.println(passwordField2.getText());   //gets info from textfield and pushes to data txt file 
       pw.close();        //closes printwriter and saves data file 

       String message = "Account created succesfully!"; 
       JOptionPane.showMessageDialog 
       (new JFrame(), message, "",     //displays panel stating account creation was succesful 
       JOptionPane.INFORMATION_MESSAGE); 

       frame2.dispose(); 

     } 
      catch (IOException g) { g.printStackTrace(); } 

     }}); 

    panel2.add(confirm); 
    panel2.add(usernameL2); 
    panel2.add(passwordL2);   //add components to account creation window 
    panel2.add(usernameField2); 
    panel2.add(passwordField2); 
    frame2.add(panel2); 
    frame2.setVisible(true); 

} 

public static void gameMenu(){ 

    System.out.println("IT WORKS!");   //testing to make sure filewriting works 
} 

public static void getVariables(){ 

    try { 
     FileReader fr = new FileReader("data.txt");   //gets ready to read from data file 
     BufferedReader br = new BufferedReader(fr); 

     String str; 
     for(int i = 0; i < 2; i++){ 
      if((str = br.readLine()) != null && i == 0) {   //reads first line and saves it 
       username = str; 
      } 
      if((str = br.readLine()) != null && i == 1) {   //reads second line and saves it 
       password = str; 
      } 
     } 

     br.close();      //closes reader 

    } catch(IOException e) { 
     System.out.println("File not found."); 
    } 

} 
} 

Answer 1

嘗試使用：

for(int i = 0; i < 2; i++){ 
     if(i == 0 && (str = br.readLine()) != null) { 
      username = str; 
     } 
     if(i == 1 && (str = br.readLine()) != null) { 
      password = str; 
     } 
    } 

，您使用的是不工作，因爲第一個if語句將消耗第二行即使i不0代碼。

讀取線將是這方面的一個簡單的方法：

for(int i = 0; (str = br.readLine())!=null && i < 2;i++){ 
    if(i == 0){ 
     username = str; 
    }else{ 
     password = str; 
    } 
} 

另外，在getVariables()方法你應該閱讀out.txt文件，而不是data.txt。從您發佈的代碼看來，沒有數據寫入data.txt文件。