Question

public class MyDataBase extends JPanel
{
    String sql;
    //String tablename;
    public MyDataBase(){}
    public MyDataBase(String sql)
    {
         System.out.printf("hai");
        ArrayList columnNames = new ArrayList();
        ArrayList data = new ArrayList();

        //  Connect to an MySQL Database, run query, get result set

          // this.tablename=tablename;
           this.sql =sql;


        // This will ensure that the sql objects are closed when the program
        // is finished with them
        try {
            Connection con=DatabaseConnection.getConnection();
            Statement stmt=con.createStatement();
            ResultSet rs = stmt.executeQuery( sql );

            ResultSetMetaData md = rs.getMetaData();
            int columns = md.getColumnCount();

            //  Get column names
            for (int i = 1; i <= columns; i++)
            {
                columnNames.add( md.getColumnName(i) );
            }

            //  Get row data
            while (rs.next())
            {
                ArrayList row = new ArrayList(columns);

                for (int i = 1; i <= columns; i++)
                {
                    row.add( rs.getObject(i) );
                }

                data.add( row );
            }
        }
        catch (SQLException e)
        {
            System.out.println( e.getMessage() );
        }

        // Create Vectors and copy over elements from ArrayLists to them
        // Vector is deprecated but I am using them in this example to keep
        // things simple - the best practice would be to create a custom defined
        // class which inherits from the AbstractTableModel class
        Vector columnNamesVector = new Vector();
        Vector dataVector = new Vector();

        for (int i = 0; i < data.size(); i++)
        {
            ArrayList subArray = (ArrayList)data.get(i);
            Vector subVector = new Vector();
            for (int j = 0; j < subArray.size(); j++)
            {
                subVector.add(subArray.get(j));
            }
            dataVector.add(subVector);
        }

        for (int i = 0; i < columnNames.size(); i++ )
            columnNamesVector.add(columnNames.get(i));

        //  Create table with database data
        JTable table = new JTable(dataVector, columnNamesVector)
        {

            public Class getColumnClass(int column)
            {
                for (int row = 0; row < getRowCount(); row++)
                {
                    Object o = getValueAt(row, column);

                    if (o != null)
                    {
                        return o.getClass();
                    }
                }

                return Object.class;
            }
        };

        JFrame frame=new JFrame();
            JScrollPane scrollPane = new JScrollPane( table );
            frame.getContentPane().add( scrollPane );

            JPanel buttonPanel = new JPanel();
            frame.getContentPane().add( buttonPanel, BorderLayout.SOUTH );


                System.out.println("Query Building"+sql);
    }

    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Please enter user name : ");
        String tablename = in.nextLine();       
        System.out.println("You entered : " + tablename);
        String sql=" SELECT * FROM "+tablename;

        JFrame frame = new JFrame();

        MyDataBase pan = new MyDataBase(sql);
        pan.setVisible(true);
        frame.add(pan);
        frame.pack();
        frame.setVisible(true);

       System.out.println("hai");
    }
}

仅显示帧的输出，而不是表数据。

Answer 1

您创建了JFrame两次。 main()中的{{}}和MyDataBase(String sql)中的第二个，您可以在其中添加表格和滚动窗格。您需要将滚动窗格添加到main()中创建的框架中。（或者，由于MyDataBase扩展了JPanel，因此将MyDataBase添加到main()中的框架应按预期工作）

此外，swing是单线程的，您应该只在事件派发线程中创建和访问swing组件。请参阅tutorial，其中详细说明了如何执行此操作。

如何从数据库输出表数据扩展jpanel与滚动条

1 个答案: