JTextArea中光标的操作

import javax.swing.*;
import javax.swing.event.CaretEvent;
import javax.swing.event.CaretListener;
import javax.swing.text.BadLocationException;
import java.awt.*;

public class Test extends JFrame {

public static void main(String[]args){
new Test().launch();
}

public void launch(){
try{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}   catch(Exception e){
e.printStackTrace();
}
Box content = Box.createVerticalBox();
final JTextArea textArea = new JTextArea();
final JTextField info = new JTextField();
info.setMinimumSize(new Dimension(300,50));
info.setMaximumSize(new Dimension(300,50));
textArea.addCaretListener(new CaretListener() {
@Override
public void caretUpdate(CaretEvent e) {
try{
//获取光标位置，距离起始位置的偏移量
int posi = textArea.getCaretPosition();
//计算行数，比较奇芭，能用，有待搞懂
Rectangle rec = textArea.modelToView(posi);
int rows = rec.y / rec.height + 1;
//计算列数用上面的方法就不行了，先获取所在行r,但是如果设置了自动换行的话，这个r目测不好用，
int r = textArea.getLineOfOffset(posi);
//用光标偏移量减去行首偏移量就是列数了，
int columns = posi - textArea.getLineStartOffset(r) + 1;
info.setText("行数：" + rows + "    列数：" + columns);
}   catch(BadLocationException badlocation){
System.out.println("bad location");
}
}
});
content.add(info);
content.add(textArea);
this.add(content);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocation(300,200);
setSize(300,200);
setVisible(true);
}
}