我编写一个简单的类,就是画一条直线
import java.awt.Graphics;
public class MyLine {
private int x1,y1,x2,y2;
public MyLine() {
x1=0; y1=0; x2=0; y2=0;
}
public MyLine(int X1,int Y1,int X2,int Y2){
x1=X1; y1=Y1; x2=X2; y2=Y2;
}
public void draw(Graphics g)
{
g.drawLine(x1,y1,x2,y2);
}
}
写的测试applet如下:
import java.awt.*;
import javax.swing.*;
public class MyLineTest extends JApplet {
MyLine line;
public void init() {
MyLine line=new MyLine(10,10,100,10);
}
public void paint(Graphics g)
{
line.draw(g);
}
}
运行之后总是提示NullPointerException错误,appletviewer中也没有直线出来!我是java初学者,还没有经验,遇到这种问题还不能解决,请各位大虾指点
import java.awt.Graphics;
public class MyLine {
private int x1,y1,x2,y2;
public MyLine() {
x1=0; y1=0; x2=0; y2=0;
}
public MyLine(int X1,int Y1,int X2,int Y2){
x1=X1; y1=Y1; x2=X2; y2=Y2;
}
public void draw(Graphics g)
{
g.drawLine(x1,y1,x2,y2);
}
}
写的测试applet如下:
import java.awt.*;
import javax.swing.*;
public class MyLineTest extends JApplet {
MyLine line;
public void init() {
MyLine line=new MyLine(10,10,100,10);
}
public void paint(Graphics g)
{
line.draw(g);
}
}
运行之后总是提示NullPointerException错误,appletviewer中也没有直线出来!我是java初学者,还没有经验,遇到这种问题还不能解决,请各位大虾指点
import javax.swing.*;
public class MyLineTest extends JApplet {
MyLine line;
public void init() {
line=new MyLine(10,10,100,10);
}
public void paint(Graphics g)
{
line.draw(g);
}
}
太感谢你了,boby!