我想绘制一个内切圆。一个空的圆圈，没有填充但是有一个完整的笔划。我的代码：
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package simon;
import java.awt.*;
import java.awt.event.*; //This allows us to detect user input
import java.awt.image.BufferedImage;
import javax.swing.*; //This allows us to use graphical elements, colors, etc.
/**
*
* @author User
*/
public class SimonA {
//First, we create all the elements of our program
//Here are the variables...
public static int score = 0;
public static int color = 0; //0 = yellow, 1 = red, 2 = blue, 3 = green
public static Boolean flash = false; //This is used to make the panel blink
public static Boolean running = false;
//Here are the widgets (objects)....
public static JFrame frame = new JFrame();
public static JPanel buttons = new JPanel();
public static JPanel buttons1 = new JPanel();//These buttons will all be square (the default). Different packages can be used to change the shape
public static JPanel controls = new JPanel();
public static JButton red = new JButton();
public static JButton yellow = new JButton();
public static JButton green = new JButton();
public static JButton blue = new JButton();
public static JButton toggle = new JButton("Start"); //Click this button to see a sample flash
public static JLabel scoreTxt = new JLabel("Score: " + score, SwingConstants.CENTER); //This object (a label element) displays the score variable's value
public static Timer blink = new Timer(600,new Ticker()); //This is used to time the duration of the flash
public static BufferedImage img = new BufferedImage(400, 400, BufferedImage.TYPE_INT_ARGB);
public static Graphics2D g = img.createGraphics();
public static JLabel space = new JLabel();
JPanel panelBgImg = new JPanel() {
public void paintComponent(Graphics g){
g.setStroke(new BasicStroke(8));
g.fillOval(0, 0, 400, 400);
}
};
/*Timers are important for any program in which something "moves" at set durations. In this case, every tenth of
a second, the timer will generate an event. In this case, we are using it to determine that the active tile
will flash for 600ms, or 6/10 of a second. Obvously, then, 1000 makes the timer generate an event once-per-second. */
public static void main (String[] args)
{
frame.setBackground(Color.gray);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //This means that when we close the window with [x] the program ends
frame.setSize(new Dimension(400,400));
frame.setForeground(Color.black);
frame.setTitle("Simon");
frame.setLayout(new BorderLayout()); //Remember this from the LayoutManager test?
buttons.setLayout(new GridLayout(1,2));
buttons1.setLayout(new GridLayout(1,2));//The buttons are placed in this panel, which is set as a 2x2 grid
yellow.setBackground(Color.yellow);
yellow.addActionListener(new YellowPressed()); //This triggers the "procedure" that runs when the yellow button is pressed
yellow.setPreferredSize(new Dimension(200,200));
//Note, the other buttons will take their cue for size from the above statement, since they are all in the same grid
//We do not need to specify dimensions again
red.setBackground(Color.red);
red.addActionListener(new RedPressed());
red.setPreferredSize(new Dimension(200,200));
blue.setBackground(Color.blue);
blue.addActionListener(new BluePressed());
green.setBackground(Color.green);
green.addActionListener(new GreenPressed());
green.setPreferredSize(new Dimension(200,200));
//Adding the four buttons to the panel called "buttons"
buttons1.add(yellow);
buttons.add(red);
buttons.add(green);
buttons1.add(blue);
//The control panel on the bottom is a gride of one row and two columns
controls.setLayout(new GridLayout(2,1));
controls.add(scoreTxt);
controls.add(toggle);
toggle.addActionListener(new ToggleOn());
//We now add the panels to the frame according to the border layout
frame.add(buttons,BorderLayout.NORTH);
frame.add(controls,BorderLayout.CENTER);
frame.add(buttons1,BorderLayout.SOUTH);
//This .pack() method removes any excess whitespace around your elements
//Sometimes it results in a better look, and sometimes not.
frame.pack();
frame.setVisible(true);
}
public static class ToggleOn implements ActionListener {
public void actionPerformed(ActionEvent event)
{
//This toggles the main button between Start and Stop
//If it's running, stop it from running
//If it's not running, start it running
running = !running;
if (running)
{
toggle.setText("Stop");
//To demonstrate how the code might work, a sample flash
color = 3; //Change the color to "active"
blink.start(); //Starts the 6/10 second timer
score += 10;
scoreTxt.setText("Score: " + score);
}
else
{
toggle.setText("Start");
}
}
}
public static class YellowPressed implements ActionListener {
public void actionPerformed(ActionEvent event)
{
//Right now, the buttons just print to the screen
//The "real" program would implement other instructions here
System.out.println("Yellow");
}
}
public static class RedPressed implements ActionListener {
public void actionPerformed(ActionEvent event)
{
System.out.println("Red");
}
}
public static class BluePressed implements ActionListener {
public void actionPerformed(ActionEvent event)
{
System.out.println("Blue");
}
}
public static class GreenPressed implements ActionListener {
public void actionPerformed(ActionEvent event)
{
System.out.println("Green");
}
}
public static class Ticker implements ActionListener {
public void actionPerformed(ActionEvent event)
{
//When the timer triggers, if a button is active,
//set it back to its original color 6/10 of a second later
flash = !flash;
if (flash) //If the button is to be lit, turn it white
{
if (color == 0)
yellow.setBackground(Color.white);
else if (color == 1)
red.setBackground(Color.white);
else if (color == 2)
blue.setBackground(Color.white);
else if (color == 3)
green.setBackground(Color.white);
}
else //Otherwise, change it back to its original color
{
if (color == 0)
yellow.setBackground(Color.yellow);
else if (color == 1)
red.setBackground(Color.red);
else if (color == 2)
blue.setBackground(Color.blue);
else if (color == 3)
green.setBackground(Color.green);
blink.stop();
}
}
}
}
以下是我用于创建圆圈的内容，由于某种原因，它不会创建圆圈：
JPanel panelBgImg = new JPanel() {
public void paintComponent(Graphics g){
g.setStroke(new BasicStroke(8));
g.fillOval(0, 0, 400, 400);
}
};
答案 0 :(得分：0)
首先，你永远不会（在提供的代码中）将panelBgImg添加到任何组件，因此不会显示任何内容（您必须将其添加到某个框架或其他面板）。
您还应该更改paintComponent方法......
JPanel panelBgImg = new JPanel() {
public void paintComponent(Graphics g){
//Call super method to draw background
super.paintComponent(g);
//Cast to Graphics2D to use setStroke
Graphics2D g2d = (Graphics2D) g;
//Set the color of the circle you want to draw
g2d.setColor(Color.RED);
g2d.setStroke(new BasicStroke(8));
//g2d.fillOval(0, 0, 400, 400);
//Use drawOval instead of fillOval (otherwise it will be filled with the color)
g2d.drawOval(0, 0, 400, 400);
}
};