我正在开发一个程序，当管理员使用ID登录他们的帐户时，他们会进入Manager屏幕。在Manager屏幕上，有一个JList，其中包含所有员工的姓名（从数据库中检索）和按钮，允许经理更新员工的信息，更新他们的日程安排，添加新员工等。按下按钮时，它切换到一个不同的屏幕，该屏幕是与ManagerLogIn类不同的类。
第一次显示经理屏幕时，员工姓名列表显示正常。我遇到的问题是当我点击任何按钮时（我将使用“更新员工信息”按钮作为示例）。我单击“更新员工信息”按钮，它会切换屏幕/类，但是当我在更新员工信息按钮上单击确定并切换回管理器屏幕时，JList会以奇怪的顺序列出每个名称两次。
我在将模型添加到JList之前使用了DefaultListModel来添加名称，我尝试在actionListener中清除JList和模型，以便在切换到新屏幕之前按下按钮，但是没有做任何事。
我的managerScreen和我的updateEmployeeInformation代码如下。我意识到他们有点长，而且组织得不好。有关如何解决问题或为何发生这种情况的任何建议？谢谢！
**我解决了这个问题。当我从数据库中选择员工时，我没有创建新的ArrayList来保存员工信息，所以一切都出现了多次
public static void main(String[] args) throws SQLException
{
ManagerLogIn m = new ManagerLogIn();
m.setVisible(true);
}
public ManagerLogIn() throws SQLException
{
setTitle("Manager");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(WIDTH, HEIGHT);
JPanel panel = new JPanel();
JPanel buttonPanel = new JPanel();
JPanel listPanel = new JPanel();
panel.setLayout(new BorderLayout());
buttonPanel.setLayout(new GridLayout(5, 1));
listPanel.setLayout(new BorderLayout());
/**get employees' names for a JList to appear on the Manager screen
* Will be easy to select an employee name to grab their data and
* view their hours, change information, generate pay stub, etc.
*/
runDatabase();
listData = new String[employees.size()];
for(int i = 0; i < employees.size(); i++)
{
listData[i] = String.format(employees.get(i).getID() + " " + employees.get(i).getName());
listModel.addElement(listData[i]);
}
//JList code
employeeList = new JList<String>(listModel);
employeeList.setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
employeeList.setLayoutOrientation(JList.VERTICAL_WRAP);
ListListener lsl = new ListListener();
employeeList.addListSelectionListener(lsl);
//scrollpane for the JList
scrollPane = new JScrollPane(employeeList);
scrollPane.setPreferredSize(new Dimension(250, 100));
scrollPane.getVerticalScrollBar().setValue(0);
//buttons disabled until a name is selected from JList
updateInfoB.setEnabled(false);
generatePayStubB.setEnabled(false);
updateScheduleB.setEnabled(false);
ButtonHandler bh = new ButtonHandler();
//adds button handler to all buttons
updateInfoB.addActionListener(bh);
generatePayStubB.addActionListener(bh);
createNewEmpB.addActionListener(bh);
logOutB.addActionListener(bh);
updateScheduleB.addActionListener(bh);
addToScheduleB.addActionListener(bh);
addShiftB.addActionListener(bh);
buttonPanel.add(updateInfoB);
buttonPanel.add(generatePayStubB);
buttonPanel.add(updateScheduleB);
buttonPanel.add(createNewEmpB);
buttonPanel.add(addToScheduleB);
buttonPanel.add(addShiftB);
buttonPanel.add(logOutB);
listPanel.add(empLabel, BorderLayout.NORTH);
listPanel.add(scrollPane, BorderLayout.CENTER);
panel.add(listPanel, BorderLayout.CENTER);
panel.add(buttonPanel, BorderLayout.EAST);
this.add(panel);
}
//gets the name and ID of the employee selected from the JList
private class ListListener implements ListSelectionListener
{
/**gets name and ID of employee selected from JList and splits it into
* an array to retrieve just the ID number. Sends the selected ID number
* to update classes to update that particular employee's information*/
public void valueChanged(ListSelectionEvent e)
{
if(employeeList.getSelectedValuesList().size() > 0)
{
//enables 3 buttons when a name is selected
updateInfoB.setEnabled(true);
generatePayStubB.setEnabled(true);
updateScheduleB.setEnabled(true);
//gets the name and ID of the employee selected and splits them into an array
selectedEmployee = listData[employeeList.getSelectedIndex()];
String[] employeeInfo = selectedEmployee.split(" ");
//gets the ID of the selected employee
selectedID = employeeInfo[0];
UpdateEmpInfoGUI ue = new UpdateEmpInfoGUI();
ue.setID(selectedID);
UpdateScheduleGUI us = new UpdateScheduleGUI();
ue.setID(selectedID);
GeneratePayStubGUI g = new GeneratePayStubGUI();
g.setID(selectedID);
}
//disables buttons if a name is not selected
else
{
updateInfoB.setEnabled(false);
generatePayStubB.setEnabled(false);
updateScheduleB.setEnabled(false);
}
}
}
private class ButtonHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
//update information button pressed AND an employee's name is selected from JList
if(e.getActionCommand().equals("Update Employee Information"))
{
setVisible(false);
new UpdateEmpInfoGUI().setVisible(true);
}
//generate pay stub button pressed AND an employee's name is selected from JList
else if(e.getActionCommand().equals("Generate Pay Stub"))
{
setVisible(false);
new GeneratePayStubGUI().setVisible(true);
}
//create new employee button pressed
else if(e.getActionCommand().equals("Create New Employee"))
{
setVisible(false);
new CreateNewEmpGUI().setVisible(true);
}
//add to schedule button pressed
else if(e.getActionCommand().equals("Add to Schedule"))
{
setVisible(false);
new AddToScheduleGUI().setVisible(true);
}
//update schedule button pressed
else if(e.getActionCommand().equals("Update Schedule"))
{
setVisible(false);
new UpdateScheduleGUI().setVisible(true);;
}
//update shift button pressed
else if(e.getActionCommand().equals("Add Shift"))
{
setVisible(false);
new AddShiftGUI().setVisible(true);;
}
else //log out button
{
System.exit(0);
}
}
}
public static void main(String[] args)
{
UpdateEmpInfoGUI u = new UpdateEmpInfoGUI();
u.setVisible(true);
}
//GUI window
public UpdateEmpInfoGUI()
{
setTitle("Update Employee Information");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(WIDTH, HEIGHT);
JPanel panel = new JPanel();
JPanel answerPanel = new JPanel();
JPanel buttonPanel = new JPanel();
panel.setLayout(new BorderLayout());
answerPanel.setLayout(new BoxLayout(answerPanel, BoxLayout.PAGE_AXIS));
ButtonHandler bh = new ButtonHandler();
runDatabase();
nameTF.setText(emp.getName());
idTF.setText(selectedID);
payRateTF.setText(String.valueOf(emp.getPayRate()));
ok.addActionListener(bh);
cancel.addActionListener(bh);
answerPanel.add(nameL, Component.LEFT_ALIGNMENT);
answerPanel.add(nameTF, Component.RIGHT_ALIGNMENT);
answerPanel.add(idL, Component.LEFT_ALIGNMENT);
answerPanel.add(idTF, Component.RIGHT_ALIGNMENT);
answerPanel.add(payRateL, Component.LEFT_ALIGNMENT);
answerPanel.add(payRateTF, Component.RIGHT_ALIGNMENT);
buttonPanel.add(ok);
buttonPanel.add(cancel);
panel.add(answerPanel, BorderLayout.CENTER);
panel.add(buttonPanel, BorderLayout.SOUTH);
this.add(panel);
}
//gets the ID selected by the manager in the ManagerScreen class
public void setID(String id)
{
selectedID = id;
}
//handles buttons when pushed
public class ButtonHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
//updates the employee's information when pressed
if(e.getActionCommand().equals("Ok"))
{
try
{
updateInfo();
new ManagerScreen().setVisible(true);
}
catch (SQLException e1)
{
e1.printStackTrace();
}
}
//goes back to the Manager log in screen
else
{
try
{
new ManagerScreen().setVisible(true);
}
catch (SQLException e1)
{
e1.printStackTrace();
}
}
}
}
//updates the employee's information
public static void updateInfo()
{
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
// Method 1: direct access to a Microsoft access database file
String filename = "./database.accdb";//use the name of your database!
String database = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=";
database+= filename.trim() + ";DriverID=22;READONLY=true}"; // add on to the end
// now we can get the connection from the DriverManager
Connection con = DriverManager.getConnection(database ,"","");
// try and create a java.sql.Statement so we can run queries
Statement s = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
//gets the text from the text fields
String employeeName = nameTF.getText();
String id = idTF.getText();
Double payRate = Double.valueOf(payRateTF.getText());
//update statement
PreparedStatement ps = con.prepareStatement("UPDATE employee SET ID=?, name=?, payRate=? WHERE ID='"+selectedID+"'");
ps.setString(1, id);
ps.setString(2, employeeName);
ps.setDouble(3, payRate);
ps.executeUpdate();
ps.close();
successMessage();
}
catch (Exception err)
{
err.printStackTrace();
String message = "An error occurred.\n"
+ "Employee " + emp.getID() + "not updated.";
String title = "Error";
JOptionPane.showMessageDialog(null, message, title, JOptionPane.WARNING_MESSAGE);
err.printStackTrace();
}
}
public static void successMessage()
{
String message = "Employee " + idTF.getText() + " successfully updated.";
String title = "Success";
JOptionPane.showMessageDialog(null, message, title, JOptionPane.INFORMATION_MESSAGE);
}
//gets the row with the selected ID number
public static void runDatabase()
{
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
// Method 1: direct access to a Microsoft access database file
String filename = "./database.accdb";//use the name of your database!
String database = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb, *.accdb)};DBQ=";
database+= filename.trim() + ";DriverID=22;READONLY=true}"; // add on to the end
// now we can get the connection from the DriverManager
Connection con = DriverManager.getConnection(database ,"","");
// try and create a java.sql.Statement so we can run queries
java.sql.Statement s = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
String query=("select name, payRate from employee where ID = '"+selectedID+"'");
s.execute(query);
ResultSet rs = s.getResultSet();// get any ResultSet that came from our query
if (rs != null)
{
// if rs == null, then there is no ResultSet to view
while ( rs.next()) // this will step through our data row-by-row
{
//the next line will get the first column in our current row's ResultSet
String name = rs.getString("name");
Double payRate = rs.getDouble("payRate");
//creates a new employee
emp = new Employee(selectedID, name, payRate);
}
}
s.close(); // close the Statement to let the database know we're done with it
}
catch (Exception err)
{
System.out.println("ERROR: " + err);
}
}