我正在尝试学习Java，来自C / assembly嵌入式系统背景。经过几周的学习，我认为尝试制作一款游戏会很有趣，但我遇到的问题是JPanel以不一致的速度重新粉刷。
我的“游戏”GUI由一个包含JPanel的JFrame组成。如您所见，JFrame的主线程休眠30毫秒，然后更新“游戏”逻辑并重绘JFrame和JPanel。每次重绘JPanel时，我都会检查它是否需要大约30毫秒。正如您所料，帧重绘之间的时间永远不会超过32毫秒。
尽管JPanel每30毫秒左右肯定会被重新绘制，但它中的动画可能非常不稳定。在Ubuntu 14.10上，非常明显，即使调用我的JPanel的repaint（）之间的时间仍然不超过32ms。
最令人烦恼的是，如果我取消注释行
//this.resize(300 + a, 300);
//a = (a == 1)?(0):1;
是否有某种方法可以强制JFrame以我想要的速率更新而不进行荒谬的.resize调用？
Main.java
package jdemo;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class Main
{
public static void main(String[] args)
{
SimFrame s = new SimFrame();
Thread t = new Thread(s);
t.start();
}
}
Sim.java
package jdemo;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.Timer;
import javax.swing.JPanel;
import javax.swing.JFrame;
public class Sim extends JPanel implements KeyListener
{
/**
*
*/
private static final long serialVersionUID = 1L;
private int keys[] = new int[1024];
double x = 100;
double y = 100;
double dx = 0;
double dy = 0;
double theta = 0.0;
private int size = 0;
private int dsize = 1;
public Sim()
{
this.addKeyListener(this);
this.setFocusable(true);
}
long prevmillis;
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Graphics2D drawing = (Graphics2D)g;
//clear the background.
drawing.setColor(Color.WHITE);
drawing.fillRect(0, 0, this.getWidth() - 1, this.getHeight() - 1);
//System.out.printf("dt = %d\n", System.currentTimeMillis() - prevmillis);
prevmillis = System.currentTimeMillis();
drawing.setColor(Color.BLACK);
drawing.drawRect(0, 0, size, size);
drawing.setColor(Color.BLACK);
int[] xpoints = {(int)(x + 10 * Math.cos(Math.toRadians(theta))),
(int)(x + 5 * Math.cos(Math.toRadians(theta - 150))),
(int)(x + 5 * Math.cos(Math.toRadians(theta + 150)))};
int[] ypoints = {(int)(y + 10 * Math.sin(Math.toRadians(theta))),
(int)(y + 5 * Math.sin(Math.toRadians(theta - 150))),
(int)(y + 5 * Math.sin(Math.toRadians(theta + 150)))};
drawing.drawPolygon(xpoints, ypoints, 3);
}
public void updateLogic()
{
if(keys[KeyEvent.VK_UP] == 1)
{
size++;
}
else if(keys[KeyEvent.VK_DOWN] == 1)
{
size--;
}
//update theta.
if(keys[KeyEvent.VK_LEFT] == 1)
{
theta += 5;
}
if(keys[KeyEvent.VK_RIGHT] == 1)
{
theta -= 5;
}
if(theta > 360.1)
{
theta -= 360;
}
if(theta < -0.1)
{
theta += 360;
}
//update acceleration
if(keys[KeyEvent.VK_SPACE] == 1)
{
dx += 0.08* Math.cos(Math.toRadians(theta));
dy += 0.08 * Math.sin(Math.toRadians(theta));
}
dx *= 0.99;
dy *= 0.99;
//update position
x = x + dx;
y = y + dy;
System.out.printf("%f, %f\n", dx, dy);
//update size
if(size > 150)
{
dsize = -1;
}
if(size < 10)
{
dsize = 1;
}
size += dsize;
}
@Override
public void keyPressed(KeyEvent arg0)
{
// TODO Auto-generated method stub
keys[arg0.getKeyCode()] = 1;
System.out.printf("%d\n", arg0.getKeyCode());
}
@Override
public void keyReleased(KeyEvent arg0)
{
// TODO Auto-generated method stub
keys[arg0.getKeyCode()] = 0;
}
@Override
public void keyTyped(KeyEvent arg0)
{
// TODO Auto-generated method stub
}
}
SimFrame.java
package jdemo;
import jdemo.Sim;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class SimFrame extends JFrame implements Runnable
{
private Sim s;
public SimFrame()
{
this.s = new Sim();
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setContentPane(this.s);
this.pack();
this.setLocationRelativeTo(null);
this.setSize(200, 200);
}
@Override
public void run()
{
int a = 0;
this.setVisible(true);
while(true)
{
//repaint
s.updateLogic();
this.getContentPane().revalidate();
this.repaint();
//this.resize(300 + a, 300);
//a = (a == 1)?(0):1;
try
{
Thread.sleep(30);
}
catch(InterruptedException e)
{
System.out.printf("failed");
break;
}
}
}
}
非常感谢。
答案 0 :(得分：1)
试试这个，如果有效，我会将其转换为真正的答案（我只是不知道它是否会比你当前的代码更好地在你的系统上运行）：
public class SimFrame extends JFrame {
public SimFrame() {
setContentPane(new Sim());
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setLocationRelativeTo(null);
setVisible(true);
}
private class Sim extends JPanel {
double x = 100;
double y = 100;
double dx = 0;
double dy = 0;
double theta = 0.0;
private int size = 0;
private int dsize = 1;
public Sim() {
addKeyListener(new Controller());
setFocusable(true);
setBackground(Color.WHITE);
new Timer(30, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
dx *= 0.99;
dy *= 0.99;
// update position
x = x + dx;
y = y + dy;
// update size
if (size > 150)
dsize = -1;
if (size < 10)
dsize = 1;
size += dsize;
// update theta.
if (theta > 360.1) {
theta -= 360;
}
if (theta < -0.1) {
theta += 360;
}
repaint();
}
}).start();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
};
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D drawing = (Graphics2D) g;
drawing.setColor(Color.BLACK);
drawing.drawRect(0, 0, size, size);
drawing.setColor(Color.BLACK);
int[] xpoints = {(int) (x + 10 * Math.cos(Math.toRadians(theta))), (int) (x + 5 * Math.cos(Math.toRadians(theta - 150))),
(int) (x + 5 * Math.cos(Math.toRadians(theta + 150)))};
int[] ypoints = {(int) (y + 10 * Math.sin(Math.toRadians(theta))), (int) (y + 5 * Math.sin(Math.toRadians(theta - 150))),
(int) (y + 5 * Math.sin(Math.toRadians(theta + 150)))};
drawing.drawPolygon(xpoints, ypoints, 3);
}
private class Controller extends KeyAdapter {
@Override
public void keyPressed(KeyEvent evt) {
switch (evt.getKeyCode()) {
case KeyEvent.VK_UP:
size++;
break;
case KeyEvent.VK_DOWN:
size--;
break;
case KeyEvent.VK_LEFT:
theta += 5;
break;
case KeyEvent.VK_RIGHT:
theta -= 5;
break;
case KeyEvent.VK_SPACE:
dx += 0.08 * Math.cos(Math.toRadians(theta));
dy += 0.08 * Math.sin(Math.toRadians(theta));
break;
}
}
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new SimFrame();
}
});
}
}
是的，我知道操作系统在按住密钥时会出现延迟，如果有效，我们会接受它。
更简单的动画：
public class CopyOfSimFrame extends JFrame {
public CopyOfSimFrame() {
setContentPane(new Sim());
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setLocationRelativeTo(null);
setVisible(true);
}
private class Sim extends JPanel {
private int size = 0;
private int dsize = 1;
public Sim() {
setBackground(Color.WHITE);
new Timer(30, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// update size
if (size >= 150)
dsize = -1;
if (size <= 0)
dsize = 1;
size += dsize;
repaint();
}
}).start();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(150, 150);
};
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLACK);
g.drawRect(0, 0, size, size);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new CopyOfSimFrame();
}
});
}
}