我试图在g.drawImage内使用Canvas Jframe显示背景图片，但我没有显示任何内容，屏幕仍为白色，当我尝试使用任何颜色填充屏幕时使用g.fillRect
这是Main类：
import org.jbox2d.collision.shapes.PolygonShape;
import org.jbox2d.common.Vec2;
import org.jbox2d.dynamics.Body;
import org.jbox2d.dynamics.BodyDef;
import org.jbox2d.dynamics.FixtureDef;
import org.jbox2d.dynamics.World;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
import java.util.Iterator;
import javax.swing.ImageIcon;
public class Main extends Canvas implements Runnable, KeyListener {
private static final long serialVersionUID = 1L;
public static final int WIDTH = 600, HEIGHT = WIDTH / 12 * 9;
// rate to convert meters to pixels in the physics engine
public static final float RATE = 30;
// counts how many loops are made in the main thread
private int counter = 49;
// image and graphics used for double buffering
private ImageIcon bgImage = new ImageIcon("res/bgImage.png");
private Image dbImage;
private Graphics dbg;
/* boolean to define when the game will be started and stopped */
private boolean running = false;
// variables for the Box2D world
Vec2 gravity = new Vec2(0.0f, 10.0f);
boolean doSleep = true;
World world = new World(gravity, doSleep);
// new array list to hold Ball references
ArrayList<Ball> balls = new ArrayList<Ball>();
// create a new player
Player character = new Player(world);
public Main() {
addKeyListener(this);
// add a ground floor to our Box2D world
BodyDef groundBodyDef = new BodyDef();
groundBodyDef.position.set(300.0f / RATE, 400.0f / RATE);
Body groundBody = world.createBody(groundBodyDef);
PolygonShape groundBox = new PolygonShape();
groundBox.setAsBox(300.0f / RATE, 0);
groundBody.createFixture(groundBox, 0.0f);
// wall fixture
FixtureDef fixtureDef = new FixtureDef();
fixtureDef.shape = groundBox;
fixtureDef.density = 2.0f;
fixtureDef.filter.groupIndex = -1;
// left wall
groundBodyDef.position.set(0.0f / RATE, 350.0f / RATE);
groundBody = world.createBody(groundBodyDef);
groundBox.setAsBox(0, 50.0f / RATE);
groundBody.createFixture(fixtureDef);
// right wall
groundBodyDef.position.set(600.0f / RATE, 350.0f / RATE);
groundBody = world.createBody(groundBodyDef);
groundBox.setAsBox(0, 50.0f / RATE);
groundBody.createFixture(fixtureDef);
/**
* @WIDHT : width of jpanel screen
* @HEIGHT : height of the jpanel screen
* @param : title of jpanel screen
* @this : refered to our main game instance
*/
new Window(WIDTH, HEIGHT, "Apocalypse 2D v0.0", this);
}
@Override
public int getWidth() { // Width of the CustomPanel
return WIDTH;
}
@Override
public int getHeight() { // Height of the CustomPanel
return HEIGHT;
}
@Override
public Dimension getPreferredSize() { // Dimension of the CustomPanel
return new Dimension(getWidth(), getHeight());
}
public void start() {
// starts a new thread
running = true;
Thread th = new Thread(this);
th.start();
}
public void stop() {
running = false;
}
public void destroy() {
}
public void run() {
Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
while (running) {
counter++;
// Simulate the world
float timeStep = 1.0f / 60.0f;
int velocityIterations = 6;
int positionIterations = 2;
world.step(timeStep, velocityIterations, positionIterations);
// add new balls to the world every 50th loop
if (counter % 80 == 0)
balls.add(new Ball(world));
repaint();
// pause for 10 milliseconds
try {
Thread.sleep(10);
} catch (InterruptedException ex) {
// do nothing
}
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
}
}
public void paint(Graphics g) {
/*g.setColor(Color.black);*/
/*g.fillRect(0, 0, getWidth(), getHeight());*/
g.drawImage(bgImage, getWidth(), getHeight(), null);
// loop through each ball and call it's draw method
Iterator<Ball> itr = balls.iterator();
while (itr.hasNext()) {
Ball b = itr.next();
b.DrawBall(g);
// if the ball should be removed then remove it
if (b.shouldDelete())
itr.remove();
}
// draw the main character.
character.draw(g);
}
// sets up double buffering for graphics
public void update(Graphics g) {
if (dbImage == null) {
dbImage = createImage(this.getSize().width, this.getSize().height);
dbg = dbImage.getGraphics();
}
dbg.setColor(getBackground());
dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);
dbg.setColor(getForeground());
paint(dbg);
g.drawImage(dbImage, 0, 0, this);
character.animplayer();
for (Ball ball : balls) {
ball.animBalls();
}
}
public void keyPressed(KeyEvent key) {
character.keyPress(key);
}
public void keyReleased(KeyEvent key) {
character.keyRelease(key);
}
public void keyTyped(KeyEvent key) {
}
public static void main(String[] args) {
new Main();
}
}
这是我尝试将图像填充到屏幕的绘画方法：
public void paint(Graphics g) {
/*g.setColor(Color.black);*/
/*g.fillRect(0, 0, getWidth(), getHeight());*/
g.drawImage(bgImage, getWidth(), getHeight(), null);
// loop through each ball and call it's draw method
Iterator<Ball> itr = balls.iterator();
while (itr.hasNext()) {
Ball b = itr.next();
b.DrawBall(g);
// if the ball should be removed then remove it
if (b.shouldDelete())
itr.remove();
}
// draw the main character.
character.draw(g);
}
答案 0 :(得分：1)
drawImage()方法有多个重载，您使用的方法是drawImage(BufferedImage img, int x, int y, ImageObserver observer)，x和y是画布上的左上角坐标。现在这些是画布的宽度和高度，因此图像被绘制在面板之外。尝试拨打g.drawImage(dbImage, 0, 0, null)。
假设您的图片尺寸与画布不同，请使用g.drawImage(dbImage, 0, 0, getWidth(), getHeight(), null)在图片上填充图片。