[英]Why doesn't my method repaint correctly?
我最近才開始學習Java,我的目標是用它制作一個簡單的圖形游戲,以便隨時指出任何樣式錯誤。
從我的主標題屏幕過渡到主屏幕時,我的舊標題屏幕沒有刷新,用於單擊以轉到主屏幕的按鈕被凍結,基本上,圖像被凍結,主屏幕上的paintComponent沒有被調用,並且程序只是進入無限循環而不會關閉(必須通過任務管理器關閉)。
需要注意的有趣一點是,沒有while循環,它就可以正常工作,paintComponent被調用,並且一切都可以正常工作,當重新引入while循環時,同樣的問題仍然存在。
public class Game {
private static final int HEIGHT = 650;
private static final int WIDTH = 820;
private static final int FRAMES_PER_SEC = 60;
private JFrame frame = new JFrame("Game");
private boolean inIntroScreen = true;
private boolean game_running = false;
private int x = 1;
private int y = 1;
private int dx = 1;
private int dy = 1;
/* method to set up GUI for the game. */
public void initGUI () {
//Build Frame
frame.setSize(WIDTH, HEIGHT);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);
//End Build Frame
/* Intro screen build */
class drawIntro extends JPanel {
public void paintComponent(Graphics g) {
if (inIntroScreen) {
Graphics2D g2d = (Graphics2D) g;
//Background
g2d.setPaint(Color.BLACK);
g2d.fillRect(0, 0, 820, 650);
//Title
BufferedImage img = null;
try { img = ImageIO.read(new File("game.png")); }
catch (IOException e) { System.out.println("Error image"); }
g2d.drawImage(img, 180, 52, null);
g2d.setPaint(Color.WHITE);
g2d.fillOval(550, 60, 40, 40);
g2d.fillOval(195, 60, 40, 40);
System.out.println("Intro screen painted");
}
} //end paint
} //end draw inner class
final drawIntro introScreen = new drawIntro();
final JPanel introPanel = new JPanel();
final JButton startButton = new JButton("Start");
frame.getContentPane().add(introPanel,BorderLayout.SOUTH);
introPanel.setBackground(Color.BLACK);
frame.getContentPane().add(introScreen, BorderLayout.CENTER);
startButton.setPreferredSize(new Dimension(100,50));
startButton.setBackground(Color.BLACK);
startButton.setForeground(Color.WHITE);
introPanel.add(startButton);
introScreen.repaint();
//End intro screen build
startButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
introPanel.removeAll();
introPanel.revalidate();
inIntroScreen = false;
game_running = true;
System.out.println("button clicked");
Start();
}
});
} //End initGUI
/* Level building class */
class Level extends JPanel {
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
//Background
g2d.setPaint(Color.BLACK);
g2d.fillRect(0, 0, 820, 650);
//Anti-aliasing
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setPaint(Color.BLUE);
g2d.fillOval(x, y, 70, 70);
x += dx;
y += dy;
System.out.println("Main screen painted");
} //End paint component
}
/* Game loop */
public void Start () {
Level player = new Level();
frame.add(player);
player.repaint();
int FPS = 1000 / FRAMES_PER_SEC;
while(game_running) { /* PROBLEM HERE, if while loop is removed everything works as intended */
frame.repaint();
try { Thread.sleep(FPS); }
catch (InterruptedException e) {}
}
}
public static void main(String[] args) {
Game game = new Game();
game.initGUI();
System.out.println("Program terminated");
}
} //end game class
您的問題是經典的Swing線程問題,您需要在Swing事件線程上執行長時間運行的任務。 實際上,您似乎正在使用繪畫方法執行長時間運行的代碼,因此絕對不應執行某些操作,因為這將在每次執行重新繪畫時重復執行此任務,從而使繪畫速度變慢。
建議:
while (game_running) {
循環正在做同樣的事情-綁定Swing事件線程,凍結GUI。 為此,請使用Swing計時器。 例如:
// start method name should start with a lower-case letter
public void start() {
final Level player = new Level();
frame.add(player);
player.repaint();
int fps = 1000 / FRAMES_PER_SEC;
// use a field called timer
timer = new Timer(fps, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// get this out of the paintComponent method
x += dx;
y += dy;
player.repaint();
}
});
timer.start();
}
例如:
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
@SuppressWarnings("serial")
public class Game2 extends JPanel {
public static final String INTRO = "intro";
public static final String GAME = "game";
public static final int FPS = 15;
private CardLayout cardLayout = new CardLayout();
public Game2() throws IOException {
URL imgUrl = new URL(IntroScreen.IMAGE_PATH);
BufferedImage img = ImageIO.read(imgUrl);
IntroScreen introScreen = new IntroScreen(img);
introScreen.setLayout(new BorderLayout());
JButton startButton = new JButton(new StartAction("Start"));
JPanel bottomPanel = new JPanel();
bottomPanel.setOpaque(false);
bottomPanel.add(startButton);
introScreen.add(bottomPanel, BorderLayout.PAGE_END);
setLayout(cardLayout);
add(introScreen, INTRO);
}
private class StartAction extends AbstractAction {
public StartAction(String name) {
super(name);
int mnemonic = (int) name.charAt(0);
putValue(MNEMONIC_KEY, mnemonic);
}
@Override
public void actionPerformed(ActionEvent e) {
GamePanel gamePanel = new GamePanel(FPS);
Game2.this.add(gamePanel, GAME);
cardLayout.show(Game2.this, GAME);
gamePanel.start();
}
}
private static void createAndShowGui() {
Game2 game2 = null;
try {
game2 = new Game2();
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
JFrame frame = new JFrame("Game");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(game2);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
@SuppressWarnings("serial")
class IntroScreen extends JPanel {
public static final String IMAGE_PATH = "https://duke.kenai.com/"
+ "glassfish/GlassFishMedium.jpg";
private BufferedImage img;
public IntroScreen(BufferedImage img) {
this.img = img;
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
g.drawImage(img, 0, 0, this);
}
}
@Override
public Dimension getPreferredSize() {
if (img != null) {
int width = img.getWidth();
int height = img.getHeight();
return new Dimension(width, height);
}
return super.getPreferredSize();
}
}
@SuppressWarnings("serial")
class GamePanel extends JPanel {
protected static final int DX = 2;
protected static final int DY = DX;
private int x;
private int y;
private Timer timer;
private int fps = 0;
public GamePanel(int fps) {
this.fps = fps;
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
//Background
g2d.setPaint(Color.BLACK);
g2d.fillRect(0, 0, 820, 650);
//Anti-aliasing
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setPaint(Color.BLUE);
g2d.fillOval(x, y, 70, 70);
}
public void start() {
// use a field called timer
timer = new Timer(fps, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
// get this out of the paintComponent method
x += DX;
y += DY;
repaint();
}
});
timer.start();
}
}
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