Question

如何使用paint方法，在一个Panel中画圆，或者矩形

Answer 1

import java.awt.*;

import java.awt.geom.*;

import javax.swing.*;

public class DrawDemo {

public static void main(String[] args) {

DrawFrame frame = new DrawFrame();

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.show();

}

}/**

一个frame中包含一个panel用来画图

*/

class DrawFrame extends JFrame {

public DrawFrame() {

setTitle("DrawDemo");

setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

// 将 panel 加到 frame

DrawPanel panel = new DrawPanel();

Container contentPane = getContentPane();

contentPane.add(panel);

}

public static final int DEFAULT_WIDTH = 400;

public static final int DEFAULT_HEIGHT = 400;

}/**

用来显示矩形和椭圆的panel

*/

class DrawPanel extends JPanel {

public void paintComponent(Graphics g) {

super.paintComponent(g);

Graphics2D g2 = (Graphics2D) g;

// 画矩形

double leftX = 100;

double topY = 100;

double width = 200;

double height = 150;

Rectangle2D rect = new Rectangle2D.Double(leftX, topY, width, height);

g2.draw(rect);

// 画rect的内切椭圆

Ellipse2D ellipse = new Ellipse2D.Double();

ellipse.setFrame(rect);

g2.draw(ellipse);

// 画一条对角线

g2.draw(new Line2D.Double(leftX, topY, leftX + width, topY + height));

// 画一个同心的圆

double centerX = rect.getCenterX();

double centerY = rect.getCenterY();

double radius = 150;

Ellipse2D circle = new Ellipse2D.Double();

circle.setFrameFromCenter(centerX, centerY, centerX + radius, centerY

+ radius);

g2.draw(circle);

}

}以上不知道符合不符合要求。