I'm using JTextPane and StyledDocument for styling message and I want to clear the messages or clear only the oldest message. I can easily clear all by using:
textPane.setText("");
But if I want to clear all, except some lines, then not sure if/how it can be done. I tried
textPane.setText(textPane.getText().substring(0, Math.min(200, textPane.getText().length())));
but the issue is that it remove the content styling.
Here is simple demo that shows the issue. Is there an easy way to do it?
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyledDocument;
public class TestJTextPane {
private JTextPane infoTextPane = new JTextPane();
private StyledDocument styledDocument;
private SimpleAttributeSet attributeSet = new SimpleAttributeSet();
private JButton addText;
private JButton clearText;
public static void main(String[] argv) {
new TestJTextPane();
}
public TestJTextPane(){
addText = new JButton("add");
addText.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
try {
StyleConstants.setForeground(attributeSet, Color.GREEN);
StyleConstants.setBackground(attributeSet, Color.BLACK);
StyleConstants.setBold(attributeSet, true);
StyleConstants.setFontSize(attributeSet, 20);
styledDocument.insertString(styledDocument.getLength(), "sample text message to add\n", attributeSet);
infoTextPane.setCaretPosition(infoTextPane.getDocument().getLength());
} catch (BadLocationException e1) {
e1.printStackTrace();
}
}
});
clearText = new JButton("clear");
clearText.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
//infoTextPane.setText("");
infoTextPane.setText(infoTextPane.getText().substring(0, Math.min(200, infoTextPane.getText().length())));
}
});
styledDocument = infoTextPane.getStyledDocument();
JPanel p = new JPanel();
p.add(addText);
p.add(clearText);
p.add(infoTextPane);
JFrame f = new JFrame("HyperlinkListener");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(p);
f.setPreferredSize(new Dimension(400, 400));
f.pack();
f.setVisible(true);
}
}
Figure how to do it with Element
. For example, the below code will keep only the latest 2 messages.
Element root = infoTextPane.getDocument().getDefaultRootElement();
try {
while(root.getElementCount() > 3){
Element first = root.getElement(0);
infoTextPane.getStyledDocument().remove(root.getStartOffset(), first.getEndOffset());
}
} catch (BadLocationException e1) {
// FIXME Auto-generated catch block
e1.printStackTrace();
}