带有ScrollPane自动滚动错误的JList

Question

I have a JList with a ScrollPane. When i press a button, a new line is added to the JList.But the problem is that it doesn't scroll to the last element, but the second last element. Here is a portion of code used : There are no erros. Everything works good except this .

DefaultListModel<String> model = new DefaultListModel<String>();
JList<String> list = new JList<String>(model);
JPanel panel = new JPanel(new GridLayout(0,1));
panel.add(list);
scroll = new JScrollPane(panel);
JPanel p = new JPanel(new BorderLayout());
p.add(scroll, BorderLayout.CENTER);
p.add(buttonPanel, BorderLayout.SOUTH); // here are more button's including the one with the action described below

public void actionPerformed(ActionEvent e) {
        list.setFont(new Font("Times new Roman", Font.PLAIN, 30));      
        model.add(list.getModel().getSize(), "Some text randomly"+ i++);        
        panel.repaint();panel.revalidate();     
        scroll.getVerticalScrollBar().setValue(scroll.getVerticalScrollBar().getMaximum());
}

Answer 1

I think that the actual repainting happens after this method has ended. Try calling the last line using SwingUtilities.invokeLater() like this:

SwingUtilities.invokeLater(new Runnable() { public void run() { 
        scroll.getVerticalScrollBar().setValue(scroll.getVerticalScrollBar().getMaximum(‌));
    }
}); 

Beware while copy-pasting this into your IDE: There is a hidden character (zero-width non-joiner) in the HTML that is not allowed in your Java code. Just remove everything between the braces after getMaximum() .

(In Java 8 you can use a Lambda expression to make this statement smaller and better readable.)