我有一个奇怪的问题。 g.drawString（）在if语句中不起作用。它在if语句之外。我在if语句中尝试过System.out.print（“TEST”）。这有效。但是，如果我添加drawString方法，则只打印测试作品
private void render() {
BufferStrategy bs = getBufferStrategy();
if (bs == null) {
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
g.setColor(Color.GREEN);
g.fillRect(0, 0, WIDTH, HEIGHT);
g.setColor(Color.BLACK);
g.drawString("Score: " + score + " Tail: " + tailLength, 20, 10);
// g.drawString("TEST", 0, 10); Works
if(gameover) g.drawString("TEST", 0, 10); // System.out.println("TEST"); works fine
snake.render(g);
cherry.render(g);
g.dispose();
bs.show();
}
整个代码：
package snake;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferStrategy;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.JFrame;
@SuppressWarnings("serial")
public class Game extends Canvas implements Runnable, KeyListener {
private static final int WIDTH = 400, HEIGHT = 350, SCALE = 10;
private static final String TITLE = "Snake";
private Thread thread;
private Snake snake;
private Cherry cherry;
private Random random = new Random();
private int score, tailLength;
private boolean running = false, paused = false, gameover = false;
// ///////////// WINDOW //////////////////////
class Window {
Window(Game game) {
Dimension dim = new Dimension(WIDTH, HEIGHT);
game.setPreferredSize(dim);
game.setMaximumSize(dim);
game.setMinimumSize(dim);
JFrame frame = new JFrame(TITLE);
frame.add(game);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(true);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
game.startGame();
}
}
// //////////////// SNAKE ////////////////////////
class Snake {
Point head;
Direction direction;
int x, y;
ArrayList<Point> snakeParts = new ArrayList<Point>();
public Snake(int x, int y) {
this.x = x;
this.y = y;
head = new Point(x, y);
direction = Direction.DOWN;
}
void tick() {
switch (direction) {
case UP:
head = new Point(x, y--);
break;
case DOWN:
head = new Point(x, y++);
break;
case LEFT:
head = new Point(x--, y);
break;
case RIGHT:
head = new Point(x++, y);
break;
}
snakeParts.add(head);
if (x == cherry.x && y == cherry.y) {
cherry = new Cherry();
score += 10;
tailLength++;
} else {
snakeParts.remove(0);
}
if (x < 0 || y < 0 || x * SCALE + SCALE > WIDTH
|| y * SCALE + SCALE > HEIGHT) {
gameover = true;
}
for (Point point : snakeParts) {
if (x == point.getLocation().x && y == point.getLocation().y) {
gameover = true;
}
}
}
void render(Graphics g) {
g.setColor(Color.BLUE);
g.fillRect(x * SCALE, y * SCALE, SCALE, SCALE);
for (Point point : snakeParts) {
g.fillRect(point.getLocation().x * SCALE, point.getLocation().y
* SCALE, SCALE, SCALE);
}
}
}
// /////////// CHERRY //////////////////
class Cherry {
int x, y;
public Cherry() {
x = random.nextInt(WIDTH / SCALE);
y = random.nextInt(HEIGHT / SCALE);
}
public void render(Graphics g) {
g.setColor(Color.RED);
g.fillRect(x * SCALE, y * SCALE, SCALE, SCALE);
}
}
// ////////////////// DIRECTION ////////////////////////
public enum Direction {
UP, DOWN, LEFT, RIGHT;
}
// //////////////// GAME METHODS ////////////////////////
public static void main(String args[]) {
Game game = new Game();
game.addKeyListener(game);
game.new Window(game);
}
public void startGame() {
thread = new Thread(this);
thread.start();
tailLength = 0;
score = 0;
gameover = false;
}
@Override
public void run() {
init();
// Tells me when the lastTime when I started the loop
long lastTime = System.nanoTime();
// Time the thread took for a loop
long loopTime = 0;
// FPS
double amountOfTicks = 10.0;
// Optimal time per frame
double ns = 1000000000 / amountOfTicks;
// Time difference as a percentage of the optimal time per frame. Above
// 1 means that the loop was slower than the optimal time.
// Multiply an animation by that time to make up for the loss of time,
double delta = 0;
// To time when the loop has begun
long timer = System.currentTimeMillis();
// To keep an eye on the amount of updates and frames in a second
int updates = 0;
int frames = 0;
// As long as the game is running.
while (running) {
// Curent time of the new loop
long now = System.nanoTime();
// Calculate the looptime/ time for 1 frame
loopTime = (now - lastTime);
// What percentage as the loopTime of the optimal time
delta += loopTime / ns;
// Reset lastTime
lastTime = now;
if (!gameover) {
// As long as the delta is higher then one, tick.
while (delta >= 1) {
// tick is the method that updates all calculations
tick();
updates++;
delta--;
}
// This is the method that draws
render();
frames++;
}
// When the loop is working for a second do this
if (System.currentTimeMillis() - timer > 1000) {
// Add a second to the timer, to make sure the new second has
// begun and can be checked.
timer += 1000;
// Reset the frames and updates per second.
frames = 0;
updates = 0;
}
}
}
private void init() {
snake = this.new Snake(0, 0);
cherry = this.new Cherry();
running = true;
}
private void tick() {
if (!paused) {
snake.tick();
}
}
private void render() {
BufferStrategy bs = getBufferStrategy();
if (bs == null) {
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
g.setColor(Color.GREEN);
g.fillRect(0, 0, WIDTH, HEIGHT);
g.setColor(Color.BLACK);
g.drawString("Score: " + score + " Tail: " + tailLength, 20, 10);
// g.drawString("TEST", 0, 10); Works
if (gameover)
g.drawString("TEST", 0, 10); // System.out.println("TEST"); works
// fine
snake.render(g);
cherry.render(g);
g.dispose();
bs.show();
}
@Override
public void keyPressed(KeyEvent e) {
switch (e.getKeyCode()) {
case KeyEvent.VK_W:
if (snake.direction != Direction.DOWN && !paused) {
snake.direction = Direction.UP;
}
break;
case KeyEvent.VK_S:
if (snake.direction != Direction.UP && !paused) {
snake.direction = Direction.DOWN;
}
break;
case KeyEvent.VK_D:
if (snake.direction != Direction.LEFT && !paused) {
snake.direction = Direction.RIGHT;
}
break;
case KeyEvent.VK_A:
if (snake.direction != Direction.RIGHT && !paused) {
snake.direction = Direction.LEFT;
}
break;
case KeyEvent.VK_SPACE:
if (gameover) {
startGame();
} else {
if (paused) {
paused = false;
} else {
paused = true;
}
}
}
}
@Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
}
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
}
PS。我是编码的新手。所以欢迎任何提示：）