我正在尝试从Class02类访问Class01类中的值。我整晚都在看书，但我无法让它上班。任何帮助将不胜感激。如果这看起来像一个愚蠢的问题，我很抱歉，但我对java完全不熟悉。谢谢： - ）
public class Class01
{
private JFrame frame;
private RecordValue recAction = new RecordValue();
private JButton btnAdd;
private JButton btnEdit;
// Launch the application
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Class01 window = new Class01();
window.frame.setVisible(true);
}
catch (Exception e) {
e.printStackTrace();
}
}
});
}
// Create the application
public Class01() {
initialize();
}
// Initialize the contents of the frame
private void initialize()
{
frame = new JFrame();
frame.getContentPane().setBackground(new Color(255, 228, 196));
frame.setBounds(100, 100, 197, 89);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
btnAdd = new JButton("Add");
btnAdd.setBounds(25, 11, 60, 23);
frame.getContentPane().add(btnAdd);
btnEdit = new JButton("Edit");
btnEdit.setBounds(95, 11, 60, 23);
frame.getContentPane().add(btnEdit);
btnAdd.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
recAction.setRecordValue(0); // 0 = New, 1 = Edit
Class02 ar = new Class02(recAction);
ar.recordForm();
}
});
btnEdit.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
recAction.setRecordValue(1); // 0 = New, 1 = Edit
Class02 er = new Class02(recAction);
er.recordForm();
}
});
}
public int getNewEditAction()
{
System.out.println("getNewEditAction = " + this.recAction.getRecordValue());
return this.recAction.getRecordValue();
}
}
//*************************************************************************************************
public class Class02{
private JFrame frame;
RecordValue _recordValue;
Class01 c01 = new Class01();
// Launch the application
public void recordForm() {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
// Create the application
public Class02(RecordValue recordValue)
{
_recordValue = recordValue;
initialize();
}
// Initialize contents of frame
private void initialize()
{
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(100, 100, 230, 95);
frame.getContentPane().setLayout(null);
JButton btnShowAction = new JButton("Show Action Value");
btnShowAction.setFont(new Font("Tahoma", Font.BOLD, 12));
btnShowAction.setBounds(28, 11, 163, 23);
frame.getContentPane().add(btnShowAction);
btnShowAction.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
System.out.println("Rec Value = " + _recordValue);
}
});
}
}
//*************************************************************************************************
public class RecordValue
{
public int _recordValue = 0;
public int getRecordValue()
{
return _recordValue;
}
public void setRecordValue(int val)
{
_recordValue = val;
}
}
答案 0 :(得分：1)
为什么不起作用？ 您的代码存在一些问题，但是它无法正常工作的主要原因是因为范围。除非将变量标记为 static ，否则它是包含在其中的类的成员，这意味着每个类都有自己的变量版本。可以把它想象成一支简单的笔 - 笔内的墨水是笔的一部分，没有两支笔共享墨水。如果用一支笔书写，它不会影响另一支笔中的墨水量。
如何使其发挥作用 有一种简单但不正确的方法来解决这个问题，以及一种稍微复杂但正确的方法：
我不打算向你展示简单的解决方案，因为a）它是微不足道的，而b）从编程的角度解决你的问题是错误的方法。我逐字复制了所有代码并注释掉了我没有其余代码的部分，然后进行了更改以向您显示正确的解决方案。我专注于修复你在这里描述的问题而忽略了我看到的其他问题：
public class RecordValue {
private int _recordValue = 0;
public int getRecordValue(){
return _recordValue;
}
public void setRecordValue(int val){
_recordValue = val;
}
}
public class HealthTracker {
private JFrame frame;
private JButton btnNew;
private JLabel lblHealthTrackerSystem;
private JButton btnSearch;
public JTable tblMain;
// use an object type so we can pass it around and change the value(s)
private RecordValue newEditAction = new RecordValue();
//private int neweditAction; // 0 = New, 1 = Edit
public String servId;
// Public items
//StoredProcedures sp = new StoredProcedures();
String[] inputFlds = new String[3];
private JButton btnDelete;
// Launch the application
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try{
HealthTracker window = new HealthTracker();
window.frame.setVisible(true);
}
catch (Exception e){
e.printStackTrace();
}
}
});
}
// Create the application
public HealthTracker()
{
initialize();
}
// Initialize the contents of the frame
private void initialize()
{
btnNew = new JButton("Add New Record");
btnNew.setFont(new Font("Tahoma", Font.BOLD, 11));
btnNew.setBounds(306, 276, 125, 23);
frame.getContentPane().add(btnNew);
JButton btnUpdate = new JButton("Update Record");
btnUpdate.setFont(new Font("Tahoma", Font.BOLD, 11));
btnUpdate.setBounds(576, 276, 125, 23);
frame.getContentPane().add(btnUpdate);
// Add a New Record Button
btnNew.addActionListener( new ActionListener() {
public void actionPerformed(ActionEvent e) {
newEditAction.setRecordValue(0);// = 0; // 0 = New, 1 = Edit
// WE ALREADY HAVE ONE. DON'T MAKE ANOTHER ONE.
NewEditRecord nr = new NewEditRecord(newEditAction);
nr.recordForm();
}
});
// Update a Record Button
btnUpdate.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
servId = JOptionPane.showInputDialog(frame, "Which ServiceID Record You Want to Update?");
newEditAction.setRecordValue(1);// = 1; // 0 = New, 1 = Edit
NewEditRecord ur = new NewEditRecord(newEditAction);
ur.recordForm();
}
});
}
public int getNewEditAction()
{
System.out.println("getNewEditAction = " + this.newEditAction.getRecordValue());
return this.newEditAction.getRecordValue();
}
}
public class NewEditRecord {
private JFrame frame;
// we don't need an entire tracker to do anything in here
//HealthTracker ht = new HealthTracker();
RecordValue _recordValue;
//int recAction = ht.getNewEditAction();
// Launch the application
// there is no reason for this to be static
public /*static*/ void recordForm() {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
// don't make ANOTHER instance, we're in one already!!!!!!
//NewEditRecord window = new NewEditRecord();
/*window.*/frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
// Create the application
public NewEditRecord(RecordValue recordValue) {
_recordValue = recordValue;
initialize();
}
// Initialize contents of frame
private void initialize() {
// frame = new JFrame();
// frame.setBounds(100, 100, 706, 390);
// frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// frame.getContentPane().setLayout(null);
//
// txtInstitution = new JTextField();
// txtInstitution.setBounds(100, 47, 540, 20);
// lblInstitution.setLabelFor(txtInstitution);
// frame.getContentPane().add(txtInstitution);
// txtInstitution.setColumns(10);
//
// // If Updating, Load Fields w/Record Data
// if (recAction == 1){
// String qry = "SELECT ServiceID, Institution, Doctor, CONCAT(Street,', ',City, ', ', State, ' ', ZipCode) AS Address, Date, Cost"
// + ", Caption AS ServiceType, Comments FROM Services s INNER JOIN ServiceTypes st ON s.ServiceTypeID = st.ServiceTypeID"
// + " WHERE (ServiceID = '"+ recServID + "')";
//
// try{
// Connection dbconn = StoredProcedures.dbConn();
// Statement stmt = dbconn.createStatement();
// ResultSet rs = stmt.executeQuery(qry);
//
// while (rs != null && rs.next()){
// txtInstitution.setText(rs.getString("ServiceID"));
// }
// }
// catch (Exception e){
// e.printStackTrace();
// }
// }
//
// // Close Form
// btnCancel.addActionListener(new ActionListener(){
// public void actionPerformed(ActionEvent e){
// frame.dispose();
// }
// });
}
}
我们将一个对象的单个实例传递给每个 NewEditRecord HealthTracker 中包含的整数值（对于每个实例都是不同的）。 >。这意味着所有 NewEditRecord 对象都指向相同的 RecordValue 对象，因此如果其中一个 NewEditRecord 对象更改 RecordValue的值它将反映在其他 NewEditRecord 对象中，因为它们必须转到 RecordValue 并从那里获取整数。