画图问题 你的整个init函数就没有被调用,怎么可能显示出来.找本书看些例子就知道了 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 如楼上所说,你的init方法没有调用,而且你的Graphics是在什么上面画图,也没有定义。给你一个简单的例子:拖动鼠标可以划线import javax.swing.*;import java.awt.*;import java.awt.geom.Ellipse2D;import java.awt.event.MouseListener;import java.awt.event.MouseEvent;import java.awt.geom.Line2D;import java.awt.Graphics2D;public class Drawing extends JPanel{ private Paint paint; private Point start,end; protected Graphics2D g2; public Drawing() { paint = Color.red; this.addMouseListener(new MouseClickListener()); } public void paintComponent(Graphics g) { super.paintComponent(g); g2 = (Graphics2D)g; g2.setPaint(paint); } public static void main(String[] args) { JFrame frame = new JFrame("Test"); Drawing draw = new Drawing(); draw.setLayout(new BorderLayout()); frame.getContentPane().add(draw,BorderLayout.CENTER); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(800,600); frame.show(); } class MouseClickListener implements MouseListener { public void mouseClicked(MouseEvent e) { } public void mouseEntered(MouseEvent e) { } public void mouseExited(MouseEvent e) { } public void mousePressed(MouseEvent e) { start = e.getPoint(); } public void mouseReleased(MouseEvent e) { end = e.getPoint(); g2 = (Graphics2D) Drawing.this.getGraphics(); g2.drawLine(start.x,start.y,end.x,end.y); } }} 请教:java连接数据库 object和object数组什么联系和区别? 关于resultset的问题? 怎么把中文数字(不是金额)转换成整数 jcreator的配置问题 求telnet客户端源程序学习 按 上一个 这个按纽 怎么没反应啊!!各位帮我看看。 write的用法 菜鸟提问了....... ·········itext 问题!!! 用java调用url接口的问题。 如何判断对象a是否为类A的实例?
而且你的Graphics是在什么上面画图,
也没有定义。
给你一个简单的例子:拖动鼠标可以划线
import javax.swing.*;
import java.awt.*;
import java.awt.geom.Ellipse2D;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import java.awt.Graphics2D;public class Drawing extends JPanel{
private Paint paint;
private Point start,end;
protected Graphics2D g2;
public Drawing() {
paint = Color.red;
this.addMouseListener(new MouseClickListener());
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g2 = (Graphics2D)g;
g2.setPaint(paint); } public static void main(String[] args) {
JFrame frame = new JFrame("Test");
Drawing draw = new Drawing();
draw.setLayout(new BorderLayout());
frame.getContentPane().add(draw,BorderLayout.CENTER);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(800,600);
frame.show();
}
class MouseClickListener implements MouseListener
{
public void mouseClicked(MouseEvent e) {
} public void mouseEntered(MouseEvent e) {
} public void mouseExited(MouseEvent e) {
} public void mousePressed(MouseEvent e) {
start = e.getPoint();
} public void mouseReleased(MouseEvent e) {
end = e.getPoint();
g2 = (Graphics2D) Drawing.this.getGraphics();
g2.drawLine(start.x,start.y,end.x,end.y);
} }}