NullPointerException

[nephilim89]

ciao!
errore:

Exception in thread "main" java.lang.NullPointerException
at java.awt.Container.addImpl(Container.java:1045)
at javax.swing.JToolBar.addImpl(JToolBar.java:561)
at java.awt.Container.add(Container.java:365)
at src.myApp.<init>(myApp.java:39)
at src.myApp.main(myApp.java:90)

codice:

 package src;
import java.awt.*;
import java.awt.event.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.sql.*;
import javax.swing.table.DefaultTableModel;
import javax.swing.JTable;
import java.util.Vector;

class myApp extends JFrame implements ActionListener{

private Button ok;
private Button annulla;
private JPanel northPanel;
private JTable mainTable;
private JPanel statusBar;
private JProgressBar progressBar;
private JMenuBar menuBar;
private JMenu fileMenu;
private JMenuItem nuovoFile;
private BorderLayout borderLayout;
private JToolBar toolBar;


public myApp(){
    
    borderLayout = new BorderLayout();
    this.setLayout(borderLayout);    
        
        northPanel = new JPanel(new GridLayout(2,1));

        menuBar = new JMenuBar();
            menuBar.add(fileMenu = new JMenu("File"));
                fileMenu.add(nuovoFile = new JMenuItem("Nuovo"));

        toolBar = new JToolBar("toolBar",JToolBar.HORIZONTAL);
            toolBar.add(ok);
            toolBar.add(annulla);

      ok = new Button("Ok");
    ok.addActionListener(this);
    
    annulla = new Button("Annulla");
    annulla.addActionListener(this);

        statusBar = new JPanel(new GridLayout(1,1));

        northPanel.add(menuBar);
        northPanel.add(toolBar);




        this.add(northPanel,BorderLayout.NORTH);
    this.add(mainTable,BorderLayout.CENTER);
    this.add(statusBar,BorderLayout.SOUTH);
    this.setTitle("mia finestra");
    this.setSize(900,600);
    this.setVisible(true);

    this.addWindowListener(new WindowAdapter(){
        public void windowClosing(WindowEvent e){
            dispose();
        }
        public void windowIconified(WindowEvent e){
            setTitle("Ridotto a Icona");
        }
        public void windowDeiconified(WindowEvent e){
            setTitle("mia finestra");
        }
        } ) ;
    
}



public void actionPerformed(ActionEvent e){

System.out.println(e);
}

public static void main(String arg[])
{

    myApp launch = new myApp();

}

} 

soluzione?

[andbin]

Originariamente inviato da nephilim89

toolBar.add(ok);

ok = new Button("Ok"); 

soluzione?

La add() è stata fatta prima di aver assegnato qualcosa a 'ok'. Tutto qui ...

[nephilim89]

ho modificato cosi:

ok = new Button("Ok");
    ok.addActionListener(this);
    
    annulla = new Button("Annulla");
    annulla.addActionListener(this);

        toolBar = new JToolBar("toolBar",JToolBar.HORIZONTAL);
            toolBar.add(ok);
            toolBar.add(annulla); 

ma l'errore resta!

Exception in thread "main" java.lang.NullPointerException
at java.awt.Container.addImpl(Container.java:1041)
at java.awt.Container.add(Container.java:959)
at javax.swing.JFrame.addImpl(JFrame.java:540)
at java.awt.Container.add(Container.java:927)
at src.myApp.<init>(myApp.java:60)
at src.myApp.main(myApp.java:90)

[google01]

manca la new per mainTable ?

this.add(mainTable,BorderLayout.CENTER); 

[nephilim89]

no la parte della table l'ho tolta perchè era lunga ed ero sicuro al 100% che fosse giusta perchè con o senza da errore uguale

 try{
            String driver = "org.apache.derby.jdbc.EmbeddedDriver";
            Class.forName(driver).newInstance();

            String protocol = "jdbc:derby:zmovies;";
            Connection c = DriverManager.getConnection( protocol );

            Statement exe = c.createStatement();
            ResultSet rs = exe.executeQuery("SELECT * FROM movies;");
            ResultSetMetaData m = rs.getMetaData();

            DefaultTableModel model = new DefaultTableModel();
            JTable jTable1 = new JTable(model);

            // Aggiungi le colonne "manualmente"
            model.addColumn("ID");
            model.addColumn("Titolo");
            model.addColumn("Genere");
            model.addColumn("Anno");
            model.addColumn("Regista");
            model.addColumn("Attori");
            model.addColumn("Copertina");
            model.addColumn("Conservato in");

            // Aggiungi le righe leggendo dal db;
            while(rs.next()) {
              Vector<String> row = new Vector<String>();
              row.addElement(rs.getString("ID"));
              row.addElement(rs.getString("Title"));
              row.addElement(rs.getString("Genre"));
              row.addElement(rs.getString("Release"));
              row.addElement(rs.getString("Director"));
              row.addElement(rs.getString("Actor"));
              row.addElement(rs.getString("Cover"));
              row.addElement(rs.getString("Stored"));

              model.addRow(row);
            }

            rs.close();
            exe.close();
            c.close();
        }
        catch (ClassNotFoundException e){ System.out.println(e); }
        catch (SQLException e){ System.out.println(e); }
        catch (InstantiationException e){ System.out.println(e); }
        catch (IllegalAccessException e){ System.out.println(e); } 

[desa]

Ha ragione google01: l'errore è che non inizializzi mainTable.
Ma se poi hai modificato il codice e ricevi un errore diverso da quello che hai postato noi non abbiamo modo di saperlo...