使用JScrollPane时Java Swing JTable不显示滚动条

Question

I have a tablePanel which is a JScrollPane ,and initialized with a JTable , the JTable initialized with a defaultTableModel ．When I trying to add some rows to the table, but didn't see the scroll bar, appriciated for any reply.

JFrame jFrame = new JFrame();

//rows will be added dynamically.
DefaultTableModel defautTableModel = new DefaultTableModel(null,columnNames){
  @Override
  public boolean isCellEditable(int row, int column) {
    return false;
  }
};

JTable jTable = new JTable(defautTableModel);
jTable.setLocation(20,60);
jTable.setSize(950,450);
jTable.setRowHeight(25);

jTable.getColumn("No.").setMaxWidth(45);
jTable.getColumn("position").setMaxWidth(45);
...

JTableHeader jTableHeader = jTable.getTableHeader();
jTableHeader.setLocation(20,30);
jTableHeader.setSize(950,30);
jTableHeader.setFont(new Font(null, Font.BOLD, 16));
jTableHeader.setResizingAllowed(true);
jTableHeader.setReorderingAllowed(true);

JScrollPane tablePanel = new JScrollPane(jTable);
tablePanel.setLayout(null);
tablePanel.add(jTableHeader);
tablePanel.add(jTable);

jFrame.setContentPane(tablePanel);

Answer 1

tablePanel.setLayout(null); is the primary cause of your problem. A JScrollPane has its own layout manager which is used to manage the scrollbars, view port and headers.

tablePanel.add is your next problem, as you shouldn't be adding components to the JScrollPane . Instead, you should be setting the JScrollPane 's JViewPort .

But, since you're using JScrollPane tablePanel = new JScrollPane(jTable); , there's actually no need for the three lines which follow it.

I would highly recommend that you take a closer look at:

• How to us tables
• How to use scroll panes
• Laying Out Components Within a Container

Now, before you tell me how nothing I've suggested actually works, go and re-read Laying Out Components Within a Container - this is the corner stone concept you will need to understand and master before Swing really begins to work for you

Answer 2

JScrollPane tablePanel = new JScrollPane(jTable);

// No need for the below code

/*tablePanel.setLayout(null);

tablePanel.add(jTableHeader);

tablePanel.add(jTable);*/

jFrame.setContentPane(tablePanel);