How to always scroll to bottom of text area?

问题

How do I make it so the scroll pane is always located the bottom of the scroll pane where the new data is being written? I can't see the new text coming in as it is written.

JTextArea itTextArea = new JTextArea(10,80);
new JScrollPane(itTextArea);
xmlTextArea.setEditable(true);

回答1:

This is what I use:

DefaultCaret caret = (DefaultCaret) textArea.getCaret();
caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);

Here's how you implement it:

public class Test
{
    public static void createFrame()
    {
        EventQueue.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {
                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                try 
                {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception e) {
                    e.printStackTrace();
                }
                JPanel panel = new JPanel();
                panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
                panel.setOpaque(true);
                JTextArea textArea = new JTextArea(15, 50);
                textArea.setWrapStyleWord(true);
                textArea.setEditable(false);
                textArea.setFont(Font.getFont(Font.SANS_SERIF));
                JScrollPane scroller = new JScrollPane(textArea);
                scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
                scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
                JPanel inputpanel = new JPanel();
                inputpanel.setLayout(new FlowLayout());
                JTextField input = new JTextField(20);
                JButton button = new JButton("Enter");
                DefaultCaret caret = (DefaultCaret) textArea.getCaret();
                caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);
                panel.add(scroller);
                inputpanel.add(input);
                inputpanel.add(button);
                panel.add(inputpanel);
                frame.getContentPane().add(BorderLayout.CENTER, panel);
                frame.pack();
                frame.setLocationByPlatform(true);
                frame.setVisible(true);
                frame.setResizable(false);
                input.requestFocus();
            }
        });
    }

    public static void main(String... args)
    {
        createFrame();
    }
}

What that should look like:

回答2:

For a little fancier solution you can use Smart Scrolling.

回答3:

itTextArea.setCaretPosition(itTextArea.getText().length());

Take a look at JTextComponent#setCaretPosition for more details

来源：https://stackoverflow.com/questions/15623287/how-to-always-scroll-to-bottom-of-text-area

标签

java

swing

scroll

jtextarea

caret