我有一个移动球的情况。然而，在与队列进行斗争后，repaint（）将paintComponent（Graphics g）置于其中。我使用了paintImmediately。现在的问题是，如果无法访问super.paintComponent（g），我不知道如何在绘制前每次清除画布。因此，我的问题的一个可能的答案是一种清除画布的方法。我还发现Threads可能是一种可能的解决方案，但在经过多次尝试实现这个想法之后，我仍然不明白，如果有人能够显示正确的实现，我将非常感激。
这是我的代码：
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import java.awt.Color;
import javax.swing.JButton;
public class PhysicsEngine extends JPanel {
double x, y;
JPanel pan;
JButton b1;
JButton b2;
JButton b3;
JButton b4;
JButton b5;
public static void main(String[] args) {
JFrame frame = new JFrame("Ball Engine");
PhysicsEngine gui = new PhysicsEngine();
frame.add(gui, BorderLayout.CENTER);
frame.setSize(600, 600);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public PhysicsEngine() {
b1 = new JButton("1");
b1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
try {
startFirst();
} catch (InterruptedException exception) {
}
}
});
this.add(b1);
b2 = new JButton("2");
b2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
try {
startSecond();
} catch (InterruptedException exception) {
}
}
});
this.add(b2);
b3 = new JButton("3");
b3.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
try {
startThird();
} catch (InterruptedException exception) {
}
}
});
this.add(b3);
b4 = new JButton("4");
b4.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
try {
startFourth();
} catch (InterruptedException exception) {
}
}
});
this.add(b4);
b5 = new JButton("5");
b5.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
try {
startFifth();
} catch (InterruptedException exception) {
}
}
});
this.add(b5);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println("" + y);
Graphics2D g2d = (Graphics2D) g;
g2d.setColor(Color.RED);
g2d.fillOval((int) x, (int) y, 30, 30);
}
public void startFirst() throws InterruptedException {
x = 300;
y = 80;
// xPos= 0*t*t + 0*t + 300 this is constant at 300
for(int t = 1; t<70;t++){
y = .1 * t * t + 0 * t + 80; // parametric equation for y
repaint();
paintImmediately((int)x, (int)y, 30, 30);
Thread.sleep(10);
}
}
public void startSecond() throws InterruptedException {
x = 300;
y = 550;
for (int t = 1;t<150; t++) {
// xPos= 0*t*t + 0*t + 300 this is constant at 300
y = .1 * t * t - 15 * t + 550; // parametric equation for y
repaint();
paintImmediately((int)x, (int)y, 30, 30);
Thread.sleep(10);
}
}
public void startThird() throws InterruptedException {
y = 550;
x = 50;
for (int t = 1;t<150; t++) {
y = .1 * t * t - 15 * t + 550; // parametric equation for y
x = 0 * t * t + 3 * t + 50; // parametric equation for x
repaint();
paintImmediately((int)x, (int)y, 30, 30);
Thread.sleep(10);
}
}
public void startFourth() throws InterruptedException {
y = 50;
x = -4;
for (int t = 1;t<110; t++) {
// xPos= 0*t*t + 0*t + 300 this is constant at 300
y = .001*t * t * t + 50; // given parametric equation for y
x = t - 4; // given parametric equation for x
repaint();
paintImmediately((int)x, (int)y, 30, 30);
Thread.sleep(10);
}
}
public void startFifth() throws InterruptedException {
for (int t = 1; t < 130 /* goes for 1.5 seconds */; t++) {
y = 200 * Math.sin(.05*t) + 300; // given parametric equation for y
x = 200 * Math.cos(.05*t) + 300; // given parametric equation for x
repaint();
paintImmediately((int)x, (int)y, 30, 30);
Thread.sleep(10);
}
}
}
答案 0 :(得分：1)
您的问题不在于＃34;绘制队列＆＃34;，通过调用Thread.sleep，您违反了API的单线程特性在美国东部时间的背景下。
不应在for-loop中使用Thread.sleep，而应使用Swing Timer来更新变量paintComponent所依赖的状态（并调用repaint）
Swing Timer可以被认为是一个伪循环，其ActionListener在EDT的上下文中被调用，从而可以安全地更新UI
首先查看Concurrency in Swing和How to Use Swing Timers了解更多详情
作为一个概念性的例子......
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private PhysicsPane physicsPane;
public TestPane() {
physicsPane = new PhysicsPane();
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = gbc.REMAINDER;
JButton b1 = new JButton("1");
b1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
startFirst();
}
});
this.add(b1, gbc);
this.add(physicsPane, gbc);
}
protected void startFirst() {
physicsPane.startFirst();
}
}
public class PhysicsPane extends JPanel {
private Timer timer;
private double xPos, yPos;
private int tick;
public PhysicsPane() {
setBackground(Color.BLUE);
}
protected void stopTimer() {
if (timer == null) {
return;
}
timer.stop();
timer = null;
}
public void startFirst() {
stopTimer();
xPos = 300;
yPos = 500;
tick = 0;
timer = new Timer(10, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
if (tick >= 150) {
stopTimer();
return;
}
yPos = .1 * tick * tick - 15 * tick + 550;
tick++;
repaint();
}
});
timer.start();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(600, 600);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.RED);
g2d.fillOval((int) xPos, (int) yPos, 30, 30);
g2d.dispose();
}
}
}