Question

java的鼠标监听代码，语法没错，但是运行却错了？

package package1;

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Container;
import java.awt.Frame;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class MutiListenerTest implements MouseListener, MouseMotionListener
{
JTextField jf = new JTextField(30);
public void MutiListenerTest()
{
JFrame f = new JFrame("多重监听器");
JLabel a = new JLabel("请按下鼠标且拖动");
f.add(jf,"North");
f.add(a,"South");
f.addMouseListener(this);
f.addMouseMotionListener(this);
f.setBounds(300, 300, 300, 300);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}

public static void main(String[] args)
{
new MutiListenerTest();
}
public void mouseMoved(MouseEvent arg0){

}
public void mouseClicked(MouseEvent arg0)
{

}
public void mousePressed(MouseEvent arg0){

}
public void mouseReleased(MouseEvent arg0)
{

}

public void mouseDragged(MouseEvent arg0)
{
//String str = "鼠标被拖动，当前位置："+arg0.getX()+","+arg0.getY();
//jf.setText(str);
}

public void mouseEntered(MouseEvent arg0)
{
//String str = "鼠标进入窗体";
//jf.setText(str);
}
public void mouseExited(MouseEvent arg0)
{
//String str = "鼠标离开窗体";
//jf.setText(str);
}
}

Answer 1

public void MutiListenerTest() 如果是构造函数，不应该要void关键字

界面中，被 f.add(jf,"North");
f.add(a,"South");
占据了，

却只添加jframe 的事件

f.addMouseListener(this);
f.addMouseMotionListener(this);

这样是点击不到jframe的。