如何再次拨打JTable function

Question

我正在尝试使用 java swing 创建一个 GUI 界面，它能够将用户添加到我视为数据库的文本文件中。 GUI 界面有一个 JTable，它提取文本文件中的现有项目并最初显示它。 一旦我 go 添加新项目，它就会在文本文件上更新，但不会在 JTable 上更新。这主要是因为我只调用 JTable 一次我设置代码的方式。 我想知道如何多次调用 JTable 或为其创建一个按钮来调用表格的刷新并在旧项目旁边显示新添加的项目。

我希望它能够在updateList function 中调用表的刷新，或者一旦按下viewButton触发一个 else if 语句，该语句可以在actionPerformed function 中执行此操作。

这是我的代码：

class UserManager extends JFrame implements ActionListener {

  private JTextField firstNameField, lastNameField, salaryField;
  private JButton addButton, removeButton, viewButton, sortButton, getButton;
  private JList<Employee> userList;
  private ArrayList<Employee> users;

  public UserManager() {
    setTitle("Employee Manager");
    setSize(300, 300);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    firstNameField = new JTextField(20);
    lastNameField = new JTextField(20);
    salaryField = new JTextField(20);
    addButton = new JButton("Add");
    addButton.addActionListener(this);
    removeButton = new JButton("Remove");
    removeButton.addActionListener(this);
    viewButton = new JButton("Refresh List"); // POTENTIAL BUTTON TO REFRESH JTABLE?
    viewButton.addActionListener(this);
    sortButton = new JButton("Sort List");
    sortButton.addActionListener(this);

    // Pulling data from text file database
    ArrayList<ArrayList<String>> databaseData = ReadFile();

    users = new ArrayList<Employee>();

    // Adding existing databaseData to users
    for (int i = 0; i < databaseData.size(); i++) {
      Employee user = new Employee(databaseData.get(i).get(0), databaseData.get(i).get(1), Integer.valueOf(databaseData.get(i).get(2)));
      users.add(user);
    }
    
    userList = new JList<Employee>(users.toArray(new Employee[0]));
    userList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);


    JPanel firstNamePanel = new JPanel();
    firstNamePanel.add(new JLabel("First Name:"));
    firstNamePanel.add(firstNameField);

    JPanel lastNamePanel = new JPanel();
    lastNamePanel.add(new JLabel("Last Name:"));
    lastNamePanel.add(lastNameField);

    JPanel salaryPanel = new JPanel();
    salaryPanel.add(new JLabel("Salary:"));
    salaryPanel.add(salaryField);

    JPanel buttonPanel = new JPanel();
    buttonPanel.add(addButton);
    buttonPanel.add(removeButton);
    buttonPanel.add(viewButton);
    buttonPanel.add(sortButton);

    
    // Converting 2D arraylist to normal 2D array for JTable
    String[][] data = databaseData.stream().map(u -> u.toArray(new String[0])).toArray(String[][]::new);

    // Initializing column names of JTable
    String[] columnNames = { "FName", "LName", "Salary" };
    
    // Initializing the JTable (THIS IS WHAT I NEED TO REFRESH)
    JTable j = new JTable(data, columnNames);
    j.setBounds(1000, 1000, 900, 900);

    // adding it to JScrollPane
    JScrollPane table = new JScrollPane(j);
    
    JPanel mainPanel = new JPanel(new GridLayout(5, 3));
    mainPanel.add(firstNamePanel);
    mainPanel.add(lastNamePanel);
    mainPanel.add(salaryPanel);
    mainPanel.add(buttonPanel);
    mainPanel.add(table);

    
    add(mainPanel);
  }

  public void actionPerformed(ActionEvent e) {
    // "Add" button is clicked
    if (e.getSource() == addButton) {
      String firstName = firstNameField.getText();
      String lastName = lastNameField.getText();
      int salary = 0;
      
      try {
          salary = Integer.parseInt(salaryField.getText());
      } 
      catch (NumberFormatException nfe) {
        JOptionPane.showMessageDialog(this, "Please enter a valid salary", "Error", JOptionPane.ERROR_MESSAGE);
        return;
      }

      // Error check to see if full name and age is entered
      if (!firstName.equals("") && !lastName.equals("")) {
        Employee user = new Employee(firstName, lastName, salary);
        users.add(user);
        updateList();
        firstNameField.setText("");
        lastNameField.setText("");
        salaryField.setText("");

      }
      else {
        JOptionPane.showMessageDialog(this, "Please enter a valid full name", "Error", JOptionPane.ERROR_MESSAGE);
      }

    } 


    // POTENTIAL BUTTON THAT REFRESHES JTABLE? 
    else if (e.getSource() == viewButton) {
      
    }
  }

  // Updates the list after a CRUD operation is called
  private void updateList() {
    userList.setListData(users.toArray(new Employee[0]));

    try {
      FileWriter fw = new FileWriter("db.txt", false);
      // BufferedWriter bw = new BufferedWriter(fw);
      // PrintWriter pw = new PrintWriter(bw);

      // Loop through each student and write to the text file
      for (int i = 0; i < users.size(); i++) {
        fw.write(toString(users.get(i).getFirstName(), users.get(i).getLastName(), users.get(i).getSalary()));
      }
      fw.close();

      // CALL A REFRESH FOR THE TABLE HERE??
    }
    catch (IOException io) {

    }

  }


  
  
  // Combing multiple string and ints into a string
  public String toString(String firstName, String lastName, int salary) {
      return firstName + ", " + lastName + ", " + salary + "\n";
  }



  // Reading database
  public static ArrayList<ArrayList<String>> ReadFile() {
    try {
      // Choose grades.txt file to look at
      File myObj = new File("db.txt");

      // Create scanner object
      Scanner myReader = new Scanner(myObj);

      // Create 2d list array to hold all the single list arrays of single information
      ArrayList<ArrayList<String>> combinedArr = new ArrayList<ArrayList<String>>();
    
      // While the file reader is still reading lines in the text
      while (myReader.hasNextLine()) {
        // Read strings of text in txt file
        String data = myReader.nextLine();

        // Get first and last name from a string
        ArrayList<String> temp = GetName(data); 

        // Add the person and their salary to the combined array that holds everyones
        combinedArr.add(temp);
      }

      // Close file once there are no more lines to read
      myReader.close();

      return combinedArr;
    } 
    catch (FileNotFoundException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }

    // Return invalid list string with nothing if error
    ArrayList<ArrayList<String>> Invalid = new ArrayList<ArrayList<String>>();
    return Invalid;
  }



  // Parses name in db
  public static ArrayList<String> GetName(String data) {
    String first = "";
    String last = "";
    String sal = "";
    // System.out.println(data[0])
    for (int i = 0; i < data.length(); i++) {
      if (data.charAt(i) == ',') {
        // Start from 2 indexes after the first occurance of the comma
        for (int j = i+2; j < data.length(); j++) {
          if (data.charAt(j) == ',') {
            for (int n = j+2; n < data.length(); n++) {
              sal += data.charAt(n);
            }
            break;
          }
          last += data.charAt(j);
        }
        break;
      }
      first += data.charAt(i);
    }

    // Initializing package array to send all values
    ArrayList<String> arr = new ArrayList<String>();
    arr.add(first);
    arr.add(last);
    arr.add(sal);
    
    return arr;
  }


  public static void main(String[] args) {
      UserManager frame = new UserManager();
      frame.setVisible(true);
  }
}

class Employee {
  // Initalizing variables
  private String firstName;
  private String lastName;
  private int salary;

  // Assigning variables
  public Employee(String firstName, String lastName, int salary) {
      this.firstName = firstName;
      this.lastName = lastName;
      this.salary = salary;
  }

  // return first name
  public String getFirstName() {
    return firstName;
  }

  // return last name
  public String getLastName() {
    return lastName;
  }

  // return salary
  public int getSalary() {
    return salary;
  }
}

Answer 1

初始化 JTable（这是我需要刷新的）

你不刷新表。 所有 Swing 组件的数据都包含在一个“模型”中。 您更改 model 中的数据。当对 model 进行更改时，将重新绘制表以反映更改。

所以你可以：

1. 创建一个新的DefaultTableModel （这是不必要的）
2. 更新现有的DefaultTableModel ，每次将新项目写入文件时，使用 addRow addRow(...)方法更新 model。

而不是使用如下代码：

JTable j = new JTable(data, columnNames);

您可以使用：

model = new DefaultTableModel(data, columnNames)
table = new JTable(model)

现在，您可以随时通过在 class 中创建实例变量或使用table.getModel()方法来访问 DefaultTableModel。

Answer 2

通常列表和表格通过它们的模型更新。 它们代表向用户显示的信息。 你可以试试这个。

在您的 class 中创建一个新字段。 在构造函数中初始化表时使用此字段。

private JTable userTable;

在您的更新 function 中，试试这个：

DefaultTableModel model = new DefaultTableModel();
users = // fetch here for your users
for (int i = 0, i < user.length, i++)
    model.addRow(users[i]);
}
// finally set new model in your table
userTable.setModel(model);
userTable.doLayout();