这是我在stackoverflow上的第一篇文章，我希望有人可以帮助我解决我在这里遇到的问题。
我正在处理的问题是repaint()问题，有些人会认为我在这些论坛上没有足够的搜索来解决我的问题，但我已经看了很多，但没有任何工作。在下面的代码中，我尝试在for循环中调用drawB，无论数组多大，这个代码都能正常运行。 for循环调用drawB 20次左右。在drawB中，我希望设置一个图像（它将根据数组中的数字而不同）然后调用repaint()，然后调用子类GameCanvas中的paintComponent()。
问题是paintComponant根本没有在这个初始化中运行。然而，repaint() DOES在我制作gameLoop()的循环中运行，但我需要在gameLoop()之前进行初始化。
任何人都知道发生了什么，或者如何解决它？
package engine;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
public class GameMain extends JFrame // main class for the game as a Swing application
{
// Define constants for the game
static final int CANVAS_WIDTH = 800; // width and height of the game screen
static final int CANVAS_HEIGHT = 600;
static final int UPDATE_RATE = 4; // number of game update per second
static final long UPDATE_PERIOD = 1000000000L / UPDATE_RATE; // nanoseconds
String path;
BufferedImage image;
private GameCanvas canvas;
// Constructor to initialize the UI components and game objects
public GameMain()
{
gameInit();
image = null;
canvas = new GameCanvas();
canvas.setPreferredSize(new Dimension(CANVAS_WIDTH, CANVAS_HEIGHT));
this.setContentPane(canvas);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.pack();
this.setTitle("Blockcraft!");
this.setVisible(true);
}
public void gameInit()
{
dispArray();
gameStart();
}
public void dispArray()
{
int tempLevel[][] = new int[][] {{1,1,1,1},{6,2,2,2},{3,3,3,3},{4,4,4,4},{4,4,4,4},{4,4,4,4},{4,4,4,4},{4,4,4,4},{4,4,4,4}};
int widthTemp = tempLevel[0].length;
int heightTemp = tempLevel.length;
for(int i = 0; i < heightTemp; i++)
{
for(int j = 0; j < widthTemp; j++)
{
try
{
image = ImageIO.read(getFile());
}
catch (Exception e)
{
e.printStackTrace();
}
drawB(image);
}
}
}
public File getFile()
{
path = "images//1.jpg";
File file = new File(path);
return file;
}
public void drawB(BufferedImage imgTemp)
{
image = imgTemp;
repaint();
}
private void gameLoop()
{
long beginTime, timeTaken, timeLeft;
while (true)
{
repaint();
beginTime = System.nanoTime();
timeTaken = System.nanoTime() - beginTime;
timeLeft = (UPDATE_PERIOD - timeTaken) / 1000000L; // in milliseconds
if (timeLeft < 10) timeLeft = 10; // set a minimum
try
{
Thread.sleep(timeLeft);
}
catch (InterruptedException ex)
{
//
}
}
}
// Refresh the display. Called back via repaint(), which invoke the paintComponent().
private void gameDraw(Graphics2D g2d)
{
g2d.drawImage(image, 0, 0, 15, 15, this);
}
public void gameKeyPressed(int keyCode)
{
//
}
public void gameKeyReleased(int keyCode)
{
//
}
public void gameKeyTyped(char keyChar)
{
//
}
class GameCanvas extends JPanel implements KeyListener
{
boolean paintAll;
int xPos, yPos;
Image img;
public GameCanvas()
{
setFocusable(true);
requestFocus();
addKeyListener(this);
}
// Override paintComponent to do custom drawing.
// Called back by repaint()... sometimes?
@Override
public void paintComponent(Graphics g)
{
System.out.println("repainting");
Graphics2D g2d = (Graphics2D)g;
// Draw the game objects
gameDraw(g2d);
}
// KeyEvent handlers
@Override
public void keyPressed(KeyEvent e)
{
gameKeyPressed(e.getKeyCode());
}
@Override
public void keyReleased(KeyEvent e)
{
gameKeyReleased(e.getKeyCode());
}
@Override
public void keyTyped(KeyEvent e)
{
gameKeyTyped(e.getKeyChar());
}
}
// To start and re-start the game.
public void gameStart()
{
// Create a new thread
Thread gameThread = new Thread()
{
// Override run() to provide the running behavior of this thread.
@Override
public void run()
{
gameLoop();
}
};
// Start the thread. start() calls run(), which in turn calls gameLoop().
gameThread.start();
}
// main
public static void main(String[] args)
{
// Use the event dispatch thread to build the UI for thread-safety.
SwingUtilities.invokeLater(new Runnable()
{
@Override
public void run()
{
new GameMain();
}
});
}
}
从初始化代码开始，在初始化期间没有响应是有意义的：
public void dispArray() {
int tempLevel[][] = new int[][] { { 1, 1, 1, 1 }, { 6, 2, 2, 2 },
{ 3, 3, 3, 3 }, { 4, 4, 4, 4 }, { 4, 4, 4, 4 }, { 4, 4, 4, 4 },
{ 4, 4, 4, 4 }, { 4, 4, 4, 4 }, { 4, 4, 4, 4 } };
int widthTemp = tempLevel[0].length;
int heightTemp = tempLevel.length;
for (int i = 0; i < heightTemp; i++) {
for (int j = 0; j < widthTemp; j++) {
try {
image = ImageIO.read(getFile());
} catch (Exception e) {
e.printStackTrace();
}
drawB(image);
}
}
}
public File getFile() {
path = "images//1.jpg";
File file = new File(path);
return file;
}
public void drawB(BufferedImage imgTemp) {
image = imgTemp;
repaint();
}
包括读入图像文件，都是在Swing事件线程上完成的，这是你永远不应该做的事情。
解决方案：不要这样做。而是使用后台线程，例如SwingWorker提供的后台线程。有关这方面的更多信息，请阅读Concurrency in Swing。