我无法从JTable中获取所选行，然后运行SQL Query以根据membId删除该行。我被困在这个上大约6个小时！
我使用TableModel来包含来自另一个文件的表 - 意思是我可以在任何地方使用该表。文件名：MemTableModel.Java
我得到了这个例外 - 我想我已经将它缩小到一行member m = memberTableModel.getRow(selectedRow); - 但我看不出错误是什么，我在整个谷歌搜索试图找到解决方案，但我可以'找到一个。
这可能是数据库问题，我知道我的数据库正在运行，因为它正确打印到JTable并且adding into the database works所以我不认为这是问题。
public class searchAll extends JFrame implements ActionListener {
private MemTableModel memberTableModel;
private int selectedRow;
//GUI RELATED
private JTable table = new JTable();
//JButtons
private JButton btnDelete = new JButton("Delete");
private JButton btnEdit = new JButton("Edit");
//Containers, panels
Container mainCon = this.getContentPane();
JPanel formPanel = new JPanel();
//Form GUI Components
//Buttons
private static JButton submitMember = new JButton("Add Member");
/*TEXT FIELDS BOXES *******************************/
private JLabel lblName = new JLabel("Name: ");
private JTextField txtName = new JTextField("", 15);
private JLabel lblEmail = new JLabel("Email: ");
private JTextField txtEmail = new JTextField("", 15);
private JLabel lblDescription = new JLabel("Description about you: ");
private JTextArea txtDescription = new JTextArea("", 5, 15);
/*TEXT FIELDS BOXES *******************************/
/*COMBO BOXES *******************************/
private JLabel lblCountry = new JLabel();
private JComboBox comCountry = new JComboBox();
private JLabel lblGenre = new JLabel();
private JComboBox comGenre = new JComboBox();
/*COMBO BOXES *******************************/
/*RADIO BUTTONS *******************************/
private JLabel lblMaleFemale = new JLabel("Gender: ");
private JRadioButton radMale = new JRadioButton("Male: ");
private JRadioButton radFemale = new JRadioButton("Female: ");
private ButtonGroup buttonGroupMF = new ButtonGroup();
private JLabel lblFreePaid = new JLabel("Membership Type: ");
private JRadioButton radFree = new JRadioButton("Free: ");
private JRadioButton radPaid = new JRadioButton("Paid: ");
private ButtonGroup buttonGroupFP = new ButtonGroup();
/*RADIO BUTTONS *******************************/
/*PAID MEMBER STUFF *******************************/
private JLabel lblCardNo = new JLabel("Card Number: ");
private JTextField txtCardNo = new JTextField("", 15);
private JLabel lblExpiry = new JLabel();
private JComboBox comExpiry = new JComboBox();
/*PAID MEMBER STUFF *******************************/
public searchAll(){
super("Search/Edit/Delete");
this.setBounds(400, 500, 854,400);
this.setVisible(true);
MemTableModel tblMembers = new MemTableModel();
//Add table and GUI components
mainCon.add(formPanel);
formPanel.add(table);
formPanel.add(btnDelete);
formPanel.add(btnEdit);
//Add action listeners
btnEdit.addActionListener(this);
btnDelete.addActionListener(this);
table.setModel(tblMembers);
//Set Selection model for table
table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
ListSelectionModel rowSM = table.getSelectionModel();
rowSM.addListSelectionListener(new ListSelectionListener() {
@Override
public void valueChanged(ListSelectionEvent e){
ListSelectionModel lsm = (ListSelectionModel) e.getSource();
selectedRow = lsm.getMinSelectionIndex();
}
});
}
//Connection Method
public Connection getConnection(){
Connection conDB = null;
/****** DEFAULT MYSQL DRIVERS **************************/
String url = connection.geturl();
String username = connection.getUsername();
String password = connection.getPassword();
try{
//load the MYSQL driver
Class.forName(connection.getDriver());
conDB = DriverManager.getConnection(url, username, password);
}
catch(Exception e){
System.out.println("Error was: " + e);
}
return conDB;
}
/*-------ACTION PERFORMED ------------------------------*/
public void actionPerformed(ActionEvent e) {
Connection conDB = null;
Statement stmt = null;
ResultSet r = null;
System.out.println("After result set variables");
//Get the selected row everytime theres an action
member m = memberTableModel.getRow(selectedRow);
System.out.println("AFTER get row from tableModel");
if(e.getSource() == btnDelete){
try{
//Connection + Statement
conDB = getConnection();
stmt = conDB.createStatement();
String sqlDeleteMem = "delete from members where membId = " + m.getmembId();
// String sqlDeletePlay = "delete from playlist where membId = " + m.getmembId();
stmt.executeUpdate(sqlDeleteMem);
// stmt.executeUpdate(sqlDeletePlay);
// stmt.executeUpdate(sqlDeletePlay);
conDB.close();
}
catch(SQLException er){
System.out.println("Error was: " + er);
}
memberTableModel.LoadTableFromDB();
memberTableModel.fireTableRowsDeleted(selectedRow, selectedRow);
}
if(e.getSource() == btnEdit){
showInputFields();
}
if(e.getSource() == submitMember){
System.out.println("Submitted");
}
}
//Add in later --
public void showInputFields(){
formPanel.setLayout(new FlowLayout());
/*TEXT FIELDS BOXES *******************************/
formPanel.add(lblName);
formPanel.add(txtName);
formPanel.add(lblEmail);
formPanel.add(txtEmail);
formPanel.add(lblDescription);
formPanel.add(txtDescription);
/*TEXT FIELDS BOXES *******************************/
/*COMBO BOXES *******************************/
//Combo Box ( Countrys )
formPanel.add(lblCountry);
formPanel.add(comCountry);
comCountry.addItem("Australia");
comCountry.addItem("New Zealand");
comCountry.addItem("Tasmania");
comCountry.addActionListener(this);
//Combo Box ( Fav Genre )
formPanel.add(lblGenre);
formPanel.add(comGenre);
comGenre.addItem("Pop");
comGenre.addItem("Rock");
comGenre.addItem("Alternative");
comGenre.addItem("Jazz");
comGenre.addItem("Hip/Hop");
comGenre.addActionListener(this);
/*COMBO BOXES *******************************/
/*RADIO BUTTONS BOXES *******************************/
//Radio Buttons (Male/Female)
buttonGroupMF.add(radMale);
buttonGroupMF.add(radFemale);
formPanel.add(radMale);
formPanel.add(radFemale);
radMale.addActionListener(this);
radFemale.addActionListener(this);
//Free or paid members ------
buttonGroupFP.add(radFree);
buttonGroupFP.add(radPaid);
formPanel.add(radFree);
formPanel.add(radPaid);
radFree.addActionListener(this);
radPaid.addActionListener(this);
//Free or paid members ------
/*RADIO BUTTONS BOXES *******************************/
/*PAID MEMBER GUI *******************************/
formPanel.add(lblCardNo);
formPanel.add(txtCardNo);
//Hide
lblCardNo.setVisible(true);
txtCardNo.setVisible(true);
formPanel.add(lblExpiry);
formPanel.add(comExpiry);
comExpiry.addItem("2017");
comExpiry.addItem("2018");
comExpiry.addItem("2019");
//Hide
lblExpiry.setVisible(true);
comExpiry.setVisible(true);
comExpiry.addActionListener(this);
/*PAID MEMBER GUI *******************************/
//Add the button after everything
formPanel.add(submitMember);
submitMember.addActionListener(this);
}
}
MembTableModel.Java
public class MemTableModel extends AbstractTableModel{
private ArrayList<member> members = new ArrayList<member>();
private String[] columnNames = {"ID", "Name", "Email", "Country", "Genre",
"Gender", "Description", "Type", "Limit", "Card No", "Expiry Date"};
public MemTableModel(){
LoadTableFromDB();
}
public int getRowCount(){
return members.size();
}
public int getColumnCount(){
return columnNames.length;
}
public Object getValueAt(int row, int col){
//Get the row from the about get method
member f = members.get(row);
switch(col){
case 0: return f.getmembId();
case 1: return f.getname();
case 2: return f.getemail();
case 3: return f.getcountry();
case 4: return f.getfavGenre();
case 5: return f.getgender();
case 6: return f.getdescription();
case 7: return f.getmemberType();
case 8: return f.getsongLimit();
case 9: return f.getcard_no();
case 10: return f.getexpiry_date();
}
return null;
}
public String getColumnName(int col){
return columnNames[col];
}
public member getRow(int row){
member c = members.get(row);
return c;
}
public Connection getConnection(){
Connection conDB = null;
/****** DEFAULT MYSQL DRIVERS **************************/
String url = connection.geturl();
String username = connection.getUsername();
String password = connection.getPassword();
try{
//load the MYSQL driver
Class.forName(connection.getDriver());
conDB = DriverManager.getConnection(url, username, password);
}
catch(Exception e){
}
return conDB;
}
//Load all DB values into ARRAY
public void LoadTableFromDB(){
Connection conDB = null;
Statement stmt = null;
ResultSet r = null;
try{
//Connection + Statement
conDB = getConnection();
stmt = conDB.createStatement();
//Queries
String sqlSelectAll = "SELECT * FROM members";
r = stmt.executeQuery(sqlSelectAll);
members.clear();
//Loop through the resultset
while(r.next()){
members.add(new member(r.getInt("membId"), r.getString("name"),
r.getString("email"), r.getString("country"), r.getString("favGenre"),
r.getString("gender"), r.getString("description"), r.getString("memberType"),
r.getString("songLimit"), r.getString("card_no"), r.getString("expiry_date")));
}
conDB.close(); // Close the DB connection
}//End of TRY
catch(Exception er){
System.out.println("Error was: " + er);
}
}
}
我得到的例外：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at GUI.searchAll.actionPerformed(searchAll.java:164)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6527)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6292)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4883)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:719)
at java.awt.EventQueue$4.run(EventQueue.java:717)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at GUI.searchAll.actionPerformed(searchAll.java:164)