package untitled9;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.*;
class Untitled1 extends Frame //extends mouseAdapter
{
private static Untitled1 frame;// private Untitled1 frame;
private static boolean is;
public static void main(String[] args)
{ frame =Untitled1.frame;
//frame = new JFrame("ddd");
frame.addMouseListener(new MouseAdapter() {
public void mouseEntered(MouseEvent e) {
//repaint();
is = true;
} public void mouseExited(MouseEvent e) {
//repaint();
is = false;
} public void paint(Graphics g) { //super.paint(g);
if (is) {
g.fillRect(60, 60, 60, 120);
g.setColor(Color.red);
}
else {
g.fillRect(60, 60, 180, 120);
g.setColor(Color.red);
}
} });
frame.setSize(500,500);
frame.setVisible(true);
}
}
java.lang.NullPointerException
at untitled9.Untitled1.main(Untitled1.java:16)
Exception in thread "main
有谁帮忙过去运行一下 ,看什么错误
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.*;
class Untitled1 extends Frame //extends mouseAdapter
{
private static Untitled1 frame;// private Untitled1 frame;
private static boolean is;
public static void main(String[] args)
{ frame =Untitled1.frame;
//frame = new JFrame("ddd");
frame.addMouseListener(new MouseAdapter() {
public void mouseEntered(MouseEvent e) {
//repaint();
is = true;
} public void mouseExited(MouseEvent e) {
//repaint();
is = false;
} public void paint(Graphics g) { //super.paint(g);
if (is) {
g.fillRect(60, 60, 60, 120);
g.setColor(Color.red);
}
else {
g.fillRect(60, 60, 180, 120);
g.setColor(Color.red);
}
} });
frame.setSize(500,500);
frame.setVisible(true);
}
}
java.lang.NullPointerException
at untitled9.Untitled1.main(Untitled1.java:16)
Exception in thread "main
有谁帮忙过去运行一下 ,看什么错误
我修改了下你的代码 ,现在能达到你要得动态画图效果
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.*;
class Untitled1 extends Frame //extends mouseAdapter
{
private static Untitled1 frame=new Untitled1();// private Untitled1 frame;
private static boolean is=true;
Untitled1(){
super("ddd");
}
public static void main(String[] args)
{ frame =Untitled1.frame;
//frame = new JFrame("ddd"); frame.addMouseListener(new MouseAdapter() {
public void mouseEntered(MouseEvent e) {
//repaint();
is = true;
frame.repaint();
} public void mouseExited(MouseEvent e) {
//repaint();
is = false;
frame.repaint();
} public void paint(Graphics g) { //super.paint(g);
if (is) {
g.fillRect(60, 60, 60, 120);
g.setColor(Color.red);
}
else {
g.fillRect(60, 60, 180, 120);
g.setColor(Color.red);
}
} });
frame.setSize(500,500);
frame.setVisible(true);
}
public void paint(Graphics g) { //super.paint(g);
if (is) {
g.fillRect(60, 60, 60, 120);
g.setColor(Color.red);
}
else {
g.fillRect(60, 60, 180, 120);
g.setColor(Color.red);
}
}
}