Issue creating Scrollable Pane with Swing

Question

I have the following class...

public class MessageFrame extends JFrame {

public MessageFrame(List<HistoryMessage> messages){
    setLayout(null);
    JPanel container = new JPanel();
    JScrollPane scrPane = new JScrollPane(container);
    getContentPane().add(scrPane);
    int i = 1;
    for(HistoryMessage m : messages){
        //TODO: needs to be StringBuilder
        StringBuilder sb = new StringBuilder();
        sb.append("<html> <strong>");
        sb.append(m.getSender());
        sb.append(" ");
        Date d = new Date(m.getDate());
        sb.append(d);
        sb.append(":</strong>");
        sb.append(m.getPayload());
        sb.append("</html>");
        JLabel l = new JLabel(sb.toString());
        l.setBounds(30, i, 400, 50);
        i += 125;
        container.add(l);
    }
    setTitle("Messages");
    setSize(500,500);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setVisible(true);
}

}

This shows me nothing, however, if I don't use the scroll pane this works...

public MessageFrame(List<HistoryMessage> messages){
    setLayout(null);
    int i = 1;
    for(HistoryMessage m : messages){
        //TODO: needs to be StringBuilder
        StringBuilder sb = new StringBuilder();
        sb.append("<html> <strong>");
        sb.append(m.getSender());
        sb.append(" ");
        Date d = new Date(m.getDate());
        sb.append(d);
        sb.append(":</strong>");
        sb.append(m.getPayload());
        sb.append("</html>");
        JLabel l = new JLabel(sb.toString());
        l.setBounds(30, i, 400, 50);
        i += 125;
        add(l);
    }
    setTitle("Messages");
    setSize(500,500);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setVisible(true);
}

But no scrolling so only the first few show up, can someone help me with what I am missing?

score 2 · Accepted Answer · answered Nov 15 '13 at 17:34

2

setLayout(null);

Don't use a null layout.

l.setBounds(30, i, 400, 50);

Don't use setBounds(...).

Scrollbars will appear automatically when the preferred size of the component added to the scrollpane is greater than the size of the scroll pane.

Let the layout managers to their jobs. Read the section from the Swing tutorial on Layout Managers and use an appropriate layout manager or combination of nested layout managers.

answered Nov 15 '13 at 17:34

camickr

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The scrollpane is added to the content pane of the frame so it will take whatever space is remaining in the frame after the frame borders and title bars are painted. – camickr Nov 15 '13 at 17:36

score 0 · Answer 2 · answered Nov 15 '13 at 17:40

Here is the new version that works after +camickr's changes....

public class MessageFrame extends JFrame {

public MessageFrame(List<HistoryMessage> messages){
    JPanel container = new JPanel();
    container.setLayout(new BoxLayout(container, BoxLayout.PAGE_AXIS));
    JScrollPane scrPane = new JScrollPane(container);
    getContentPane().add(scrPane);
    int i = 1;
    for(HistoryMessage m : messages){
        //TODO: needs to be StringBuilder
        StringBuilder sb = new StringBuilder();
        sb.append("<html> <strong>");
        sb.append(m.getSender());
        sb.append(" ");
        Date d = new Date(m.getDate());
        sb.append(d);
        sb.append(":</strong>");
        sb.append(m.getPayload());
        sb.append("</html>");
        JLabel l = new JLabel(sb.toString());
        i += 125;
        container.add(l);
    }
    setTitle("Messages");
    setSize(500,500);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setVisible(true);
}

}

Issue creating Scrollable Pane with Swing

2 Answers2