import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;import javax.swing.*;public class mydrawapplication extends JFrame
{
private myColorPanel panel=new myColorPanel();
public mydrawapplication()
{
super("testing!");
getContentPane().add(panel);
setSize(400,400);
setVisible(true);
}
public void paint(Graphics g)
{
super.paint(g);
Graphics2D g2d=(Graphics2D)g;
g2d.setPaint(new Color(panel.redValue(),panel.blueValue(),panel.greenValue()));
g2d.draw3DRect(100,100,80,80,true);
}
public static void main(String args[])
{
mydrawapplication application=new mydrawapplication();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
} 提示的错误
Exception in thread "main" java.lang.NullPointerException
at JPaneltest.myColorPanel.<init>(myColorPanel.java:16)
at JPaneltest.mydrawapplication.<init>(mydrawapplication.java:10)
at JPaneltest.mydrawapplication.main(mydrawapplication.java:27)
import java.awt.event.*;
import java.awt.geom.Ellipse2D;import javax.swing.*;public class mydrawapplication extends JFrame
{
private myColorPanel panel=new myColorPanel();
public mydrawapplication()
{
super("testing!");
getContentPane().add(panel);
setSize(400,400);
setVisible(true);
}
public void paint(Graphics g)
{
super.paint(g);
Graphics2D g2d=(Graphics2D)g;
g2d.setPaint(new Color(panel.redValue(),panel.blueValue(),panel.greenValue()));
g2d.draw3DRect(100,100,80,80,true);
}
public static void main(String args[])
{
mydrawapplication application=new mydrawapplication();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
} 提示的错误
Exception in thread "main" java.lang.NullPointerException
at JPaneltest.myColorPanel.<init>(myColorPanel.java:16)
at JPaneltest.mydrawapplication.<init>(mydrawapplication.java:10)
at JPaneltest.mydrawapplication.main(mydrawapplication.java:27)
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很显然是myColorPanel类抛出来的错误, 检查一下是不是类没有实例化就调用它的方法了.
要不把完整代码贴出来.
myColorPanel的情况该列出来呀!