问题描述
我使用 JTextPane 和 StyledDocument 来设置消息样式,我想清除消息或仅清除最旧的消息。 我可以使用以下方法轻松清除所有内容:
textPane.setText("");
但是如果我想清除所有内容,除了某些行,则不确定是否/如何完成。 我试过了
textPane.setText(textPane.getText().substring(0,Math.min(200,textPane.getText().length())));
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,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);
}
}
解决方法
了解如何使用 Element 进行操作。例如,下面的代码将只保留最新的 2 条消息
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();
}