我正在编写代码，我在JPanel上绘制多个形状然后调用repaint。我认为当我调用重绘时，JPanel中的形状应该移动到一个新位置，因为随机函数现在将提供不同的值。但形状根本不动。任何想法为什么会发生这种情况？
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
@SuppressWarnings("serial")
public class Filter extends JFrame
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
Filter mainFrame = new Filter();
mainFrame.setVisible(true);
}
});
}
public Filter()
{
//Creating the JFrame main window
setSize(800, 500);
setTitle("Particle Filter");
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
setLocation(100, 100);
getContentPane().setLayout(new BoxLayout(this.getContentPane(), BoxLayout.X_AXIS));
//creates two panels content and sidebar. Sidebar has null layout
JPanel content = new JPanel();
content.setPreferredSize(new Dimension(700,500));
content.setBackground(Color.LIGHT_GRAY);
this.getContentPane().add(content);
JPanel sidebar = new JPanel();
sidebar.setBackground(Color.LIGHT_GRAY);
sidebar.setPreferredSize(new Dimension(100,500));
this.getContentPane().add(sidebar);
sidebar.setLayout(null);
//creates three buttons in sidebar
JButton start_button = new JButton("START");
start_button.setBounds(10, 75, 77, 23);
start_button.addActionListener(new MainPanel());
sidebar.add(start_button);
JButton stop_button = new JButton("STOP");
stop_button.setBounds(10, 109, 77, 23);
sidebar.add(stop_button);
JButton reset_button = new JButton("RESET");
reset_button.setBounds(10, 381, 77, 23);
sidebar.add(reset_button);
//calls the content_Walls class and sends the number of ovals to be generated
content.add( new MainPanel());
}
}
@SuppressWarnings("serial")
class MainPanel extends JPanel implements ActionListener
{
public MainPanel()
{
setPreferredSize(new Dimension(680,450));
setBackground(Color.WHITE);
setBorder(BorderFactory.createLineBorder(Color.black));
}
public void actionPerformed(ActionEvent e)
{
if (e.getActionCommand().equals("START"))
{
repaint();
}
}
@Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
drawParticles(g);
createObstacles(g,150,225,100,40);
createObstacles(g,500,300,40,100);
createRobot(g);
}
private void createRobot(Graphics g)
{
int x=0, y=0;
int robot_radius=50;
ArrayList<Integer> robot_list= new ArrayList<Integer>();
robot_list=positionRobot(x,y);
drawRobot(g,robot_list.get(0),robot_list.get(1),robot_radius);
}
private void drawParticles(Graphics g)
{
int n=1000; // n denotes the number of particles
ArrayList<Integer> list;
list = new ArrayList<Integer>(Collections.nCopies(n, 0));
for(int i=0;i<list.size();i++)
{
generateParticles(g);
}
}
private void generateParticles(Graphics g)
{
int x=0;
int y=0;
int radius = 4;
ArrayList<Integer> list= new ArrayList<Integer>();
list=positionParticles(x,y);
g.setColor(Color.RED);
g.fillOval(list.get(0),list.get(1), radius, radius);
}
private ArrayList<Integer> positionParticles(int x, int y)
{
int radius = 4;
ArrayList<Integer> list= new ArrayList<Integer>();
x=randomInteger(2,678); // bounds of x between which the particles should be generated
y=randomInteger(2,448); // bounds of y between which the particles should be generated
x=x-(radius/2);
y=y-(radius/2);
if((x<251&&x>=150)&&(y<266&&y>=225))
{
x=0;
y=0;
positionParticles(x,y);
}
if((x<541&&x>499)&&(y<401&&y>299))
{
x=0;
y=0;
positionParticles(x,y);
}
list.add(x);
list.add(y);
return list;
}
private ArrayList<Integer> positionRobot(int x, int y)
{
int robot_radius=50;
ArrayList<Integer> list= new ArrayList<Integer>();
x=randomInteger(25,655);//so that it stays inside the content_Walls panel
y=randomInteger(25,425); //so that it stays inside the content_Walls panel
x=x-(robot_radius/2);
y=y-(robot_radius/2);
if((x<250&&x>=150)&&(y<=265&&y>=225))
{
x=0;
y=0;
positionRobot(x,y);
}
if((x<=540&&x>=500)&&(y<=400&&y>=300))
{
x=0;
y=0;
positionRobot(x,y);
}
list.add(x);
list.add(y);
return list;
}
private void createObstacles(Graphics g, int x, int y, int width, int height)
{
g.setColor(Color.BLACK);
g.fillRect(x, y, width, height);
}
private void drawRobot(Graphics g, int x, int y, int radius)
{
g.setColor(Color.GREEN);
g.fillOval(x, y, radius, radius);
}
private static int randomInteger(int min, int max)
{
Random rand = new Random();
int randomNum = rand.nextInt((max - min) + 1) + min;
return randomNum;
}
}
答案 0 :(得分：5)
基本问题是，响应MainPanel的{{1}}实例与屏幕上JButton的实例不同...
MainPanel相反，创建一个实例并在两种情况下使用它......
// Instance one...
start_button.addActionListener(new MainPanel());
//...
// Instance two...
//calls the content_Walls class and sends the number of ovals to be generated
content.add(new MainPanel());
当你开始插入停止按钮的功能时，再次使用相同的实例。
答案 1 :(得分：0)
那可能是因为你没有使用种子值，对于Random的cunstructor。但不确定这是用Java还是用其他语言。 （阅读文档，也许是另一种语言）
Random rand = new Random();
您可以将时间用作种子值：
Random rand = new Random(System.currentTimeMillis());
也可以将rand作为一个字段并且只对它进行一次修改：
private static Random rand;
private static int randomInteger(int min, int max)
{
if (rand == null)
rand = new Random();
int randomNum = rand.nextInt((max - min) + 1) + min;
return randomNum;
}
代码不是testet。对不起，我快要睡了。