getGraphics() impedisce l'avvio del gioco [chiuso]
https://stackoverflow.com//questions/12656661
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11-12-2019 - |
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Sto imparando il doppio buffering e il libro che ho ricevuto dal mio insegnante mi dice di scrivere quello che ho scritto.Ma quando Java tenta di ottenere l'oggetto grafico dall'immagine si blocca.
cornice = Immagine
motore = Grafica
Errore
Exception in thread "main" java.lang.NullPointerException
at Engine.<init>(Engine.java:30)
at Game.<init>(Game.java:35)
at Game.main(Game.java:22)
Gioco.java
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.util.*;
import java.util.Timer;
public class Game implements ActionListener {
private static Game hosmos2;
private JFrame frmMain;
private AntiCheat holyanticheat;
private Dimension screen;
private Engine holyengine;
private int sx, sy;
private Timer timCheat;
public static void main(String[] args) throws FileNotFoundException, InterruptedException {
hosmos2 = new Game();
}
private Game() throws FileNotFoundException, InterruptedException {
frmMain = new JFrame("Hosmos 2");
frmMain.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frmMain.setSize(1366, 768);
screen = Toolkit.getDefaultToolkit().getScreenSize();
sx = (int) ((screen.getWidth() - frmMain.getWidth()) / 2);
sy = (int) ((screen.getHeight() - frmMain.getHeight()) / 2);
frmMain.setLocation(sx, sy);
holyanticheat = new AntiCheat();
holyengine = new Engine();
timCheat = new Timer();
frmMain.setVisible(true);
timCheat.schedule(holyanticheat, 500);
Thread.sleep(1000);
timCheat.cancel();
}
public void actionPerformed(ActionEvent e) {
}
}
Motore.java
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import javax.swing.*;
import java.util.*;
public class Engine extends JPanel {
private boolean countdown, quality;
private Font text, text2;
private Graphics engine;
private Image frame;
private ImageIcon background, button1, button21, button22, button3, button4, button51, button52, header;
private int weedbackground, fps, fps2;
public Rectangle box1, box2, box3, box4, box5;
public static void main(String[] args) {
}
public Engine() {
this.setBackground(Color.black);
frame = createImage(getSize().width, getSize().height);
text = new Font("Microsoft Sans Serif", Font.BOLD, 24);
text2 = new Font("Microsoft Sans Serif", Font.BOLD, 8);
engine = frame.getGraphics(); // Error
background = new ImageIcon("textures/background.png");
//background = background.GetThumbnailImage(source.ClientSize.Width, source.ClientSize.Height, null, IntPtr.Zero);
button1 = new ImageIcon("textures/button 1.png");
button21 = new ImageIcon("textures/button 2-1.png");
button22 = new ImageIcon("textures/button 2-2.png");
button3 = new ImageIcon("textures/button 3.png");
button4 = new ImageIcon("textures/button 4.png");
button51 = new ImageIcon("textures/button 5-1.png");
button52 = new ImageIcon("textures/button 5-2.png");
header = new ImageIcon("textures/header.png");
box1 = new Rectangle(20, 20, 87, 37);
box2 = new Rectangle(20, 60, 96, 37);
box3 = new Rectangle(20, 103, 182, 43);
box4 = new Rectangle(20, 146, 83, 43);
box5 = new Rectangle(20, 189, 206, 43);
}
public Rectangle GetBox1() {
return box1;
}
public Rectangle GetBox2() {
return box2;
}
public Rectangle GetBox3() {
return box3;
}
public Rectangle GetBox4() {
return box4;
}
public Rectangle GetBox5() {
return box5;
}
public void FPS()
{
fps2 = fps;
fps = 0;
}
public void Quality(boolean quality2)
{
quality = quality2;
}
public void Render(boolean music, boolean effect, int time, int spawned, int points, int cracktime, int crackend, int shieldtime, int shieldend, int weedtime, int weedend, ImageIcon malcolm, int malcolmX, int malcolmY, int item, ImageIcon crack, int crackX, int crackY, ImageIcon nuke, int nukeX, int nukeY, ImageIcon shield, int shieldX, int shieldY, ImageIcon skull, int skullX, int skullY, ImageIcon trollface, int trollfaceX, int trollfaceY, ImageIcon weed, int weedX, int weedY, LinkedList<Hosmin> hosmins) {
engine = frame.getGraphics();
super.paintComponent(engine);
if (effect == false) {
if (quality == false) {
background.paintIcon(this, engine, 0, 0);
}
else {
this.setBackground(Color.black);
}
}
else {
if (weedbackground == 1) {
this.setBackground(Color.green);
weedbackground++;
}
else if (weedbackground == 2) {
this.setBackground(Color.yellow);
weedbackground++;
}
else if (weedbackground == 3) {
this.setBackground(Color.red);
weedbackground = 1;
}
}
header.paintIcon(this, engine, 547, 10);
button1.paintIcon(this, engine, 20, 20);
if (music == false) {
button21.paintIcon(this, engine, 20, 60);
}
else {
button22.paintIcon(this, engine, 20, 60);
}
button3.paintIcon(this, engine, 20, 103);
button4.paintIcon(this, engine, 20, 146);
if (quality == false) {
button51.paintIcon(this, engine, 20, 189);
}
else {
button52.paintIcon(this, engine, 20, 189);
}
engine.setFont(text2);
engine.setColor(Color.green);
engine.drawString("FPS: " + fps2, 1293, 9);
engine.setFont(text);
engine.setColor(Color.red);
engine.drawString("Time: " + time, 1178, 22);
engine.drawString("Hosmins: " + spawned, 1124, 59);
engine.drawString("Points: " + points, 1160, 96);
engine.setFont(text2);
engine.setColor(Color.green);
engine.drawString("Developer: HolyDuFF", 1229, 708);
malcolm.paintIcon(this, engine, malcolmX, malcolmY);
if (countdown == true) {
if (crackend - cracktime == 0) {
countdown = false;
}
else if (cracktime >= 0) {
engine.setFont(text);
engine.setColor(Color.red);
crackend = crackend - cracktime;
if (crackend != 10) {
engine.drawString("" + crackend, malcolmX + 17, malcolmY - 40);
}
else {
engine.drawString("" + crackend, malcolmX + 7, malcolmY - 40);
}
}
else if (shieldtime >= 0) {
engine.setFont(text);
engine.setColor(Color.red);
shieldend = shieldend - shieldtime;
if (shieldend != 10) {
engine.drawString("" + shieldend, malcolmX + 17, malcolmY - 40);
}
else {
engine.drawString("" + shieldend, malcolmX + 7, malcolmY - 40);
}
}
else if (weedtime >= 0) {
engine.setFont(text);
engine.setColor(Color.blue);
weedend = weedend - weedtime;
if (weedend != 10) {
engine.drawString("" + weedend, malcolmX + 17, malcolmY - 40);
}
else {
engine.drawString("" + weedend, malcolmX + 7, malcolmY - 40);
}
}
}
for (int i = 0; i < hosmins.size(); i++) {
Hosmin temp = hosmins.get(i);
temp.Draw().paintIcon(this, engine, temp.GetX(), temp.GetY());
}
if (item == 1) {
crack.paintIcon(this, engine, crackX, crackY);
}
else if (item == 2) {
nuke.paintIcon(this, engine, nukeX, nukeY);
}
else if (item == 3) {
shield.paintIcon(this, engine, shieldX, shieldY);
}
else if (item == 4) {
skull.paintIcon(this, engine, skullX, skullY);
}
else if (item == 5) {
trollface.paintIcon(this, engine, trollfaceX, trollfaceY);
}
else if (item == 6) {
weed.paintIcon(this, engine, weedX, weedY);
}
engine.dispose();
repaint();
fps++;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(frame, 0, 0, this);
}
public void SetBackground(int background2) {
weedbackground = background2;
}
public void SetCountdown(boolean countdown2) {
countdown = countdown2;
}
public void SetBox2(int mode) {
if (mode == 1) {
box2.width = 96;
box2.height = 37;
}
else {
box2.width = 76;
box2.height = 43;
}
}
public void SetBox5(int mode) {
if (mode == 1) {
box5.width = 206;
}
else {
box5.width = 213;
}
}
}
Soluzione
Stai chiamando getGraphics() su una variabile Immagine nulla.Se guardi l'API per Component's createImage() vedrai perché è così:
restituisce un'immagine disegnabile fuori schermo, che può essere utilizzata per il doppio buffering. Il valore restituito può essere nullo se il componente non è visualizzabile.Ciò accadrà sempre se GraphicsEnvironment.isHeadless() restituisce true.
Il motore non è ancora visualizzato nel suo costruttore.È necessario eseguire prima il rendering della GUI chiamando pack() O setVisible(true) nella finestra di livello superiore prima che venga visualizzato questo JPanel.
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