编译通过,但运行时出现空指针异常,可是找不到哪里出现了空指针。
代码如下:
import java.awt.*;
import javax.swing.*;
public class MyDrawPanel extends JPanel
{
public void paintComponent(Graphics g)
{
Graphics2D g2d=(Graphics2D) g;
int red=(int)(Math.random()*255);
int green=(int)(Math.random()*255);
int blue=(int)(Math.random()*255);
Color startColor=new Color(red,green,blue);
int red2=(int)(Math.random()*255);
int green2=(int)(Math.random()*255);
int blue2=(int)(Math.random()*255);
Color endColor=new Color(red2,green2,blue2);
GradientPaint gradient=new GradientPaint(70,70,startColor,150,150,endColor);
g2d.setPaint(gradient);
g2d.fillOval(70,70,100,100);
}
public static void main(String[] args)
{
MyDrawPanel my=new MyDrawPanel();
Graphics f=my.getGraphics();
my.paintComponent(f);
}
}
运行结果如下:
请问应该如何解决呢?谢谢~