怎么用java画矩形?并且可以在后续添加直线?
下面的这个函数用了Graphics.drawPolyline(int[] a,int[] b,int n);方法,
用main()调用时为什么会出错呢?import java.applet.Applet;
import java.awt.Graphics;/**
*
* @author Administrator
* 画矩形
*/
public class Grid extends Applet{
Graphics g;
public Grid(){
int[] xPoints={0,700,700,0,0};
int[] yPoints={0,0,700,700,0};
int nPoints=5;
g.drawPolyline(xPoints, yPoints, nPoints);
}}
下面的这个函数用了Graphics.drawPolyline(int[] a,int[] b,int n);方法,
用main()调用时为什么会出错呢?import java.applet.Applet;
import java.awt.Graphics;/**
*
* @author Administrator
* 画矩形
*/
public class Grid extends Applet{
Graphics g;
public Grid(){
int[] xPoints={0,700,700,0,0};
int[] yPoints={0,0,700,700,0};
int nPoints=5;
g.drawPolyline(xPoints, yPoints, nPoints);
}}
这个不行吗?
g.drawPolygon(xPoints, yPointts,nPoints);
程序这样修改后就应该没问题了.
import java.awt.Graphics; /**
*
* @author Administrator
* 画矩形
*/
public class Grid extends Applet{
int[] xPoints;
int[] yPoints;
int nPoints;
public void init(){
xPoints=new int[]{0,700,700,0,0};
yPoints=new int[]{0,0,700,700,0};
nPoints=5;
}
public void paint(Graphics g){
g.drawPolyline(xPoints, yPoints, nPoints);
}
} applet程序里画图需要使用Applet类的paint方法。