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POSprite spawning on particular JPanel
 

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  1. POSprite spawning on particular JPanel
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    <p>I am working on multiplayer game where when the server sends distinct message, ie. type of enemy and number of enemies. that particular sprite loads onto screen. I have 4 views, seperated by CardLayout and buttons on the top to switch between screens.</p> <p>Here's the chain that I have set up. When I try to draw the enemies.. I get an error.</p> <p>In Main class I have this method:</p> <pre><code>public void handleAttack(String message){ ViewA.spawnEnemy(type,amt); } </code></pre> <p>This is the class for <code>ViewA</code> which has the <code>spawnEnemy()</code> method.</p> <pre><code>public class BattleView extends JPanel implements ActionListener { private Player player; private Timer timer; private int B_WIDTH; private int B_HEIGHT; private boolean ingame; private ArrayList aliens; public BattleView(Player player) { this.player = player; addKeyListener(new TAdapter()); setFocusable(true); setBackground(Color.RED); setDoubleBuffered(true); setSize(652, 480); ingame = true; timer = new Timer(5, this); timer.start(); } public void addNotify() { super.addNotify(); B_WIDTH = getWidth(); B_HEIGHT = getHeight(); super.setPreferredSize(new Dimension(B_WIDTH,B_HEIGHT)); } public void spawnEnemy(int type, int amount) { aliens = new ArrayList(); for (int i=1; i&lt;amount+1; i++ ) { aliens.add(new Enemy(0-i*40,400)); System.out.println("Attack Message Recieved "+i); } } public void paint(Graphics g) { super.paint(g); Graphics2D g2d = (Graphics2D)g; g2d.drawImage(background, 0, 0, null); if (player.isVisible()){ g2d.drawImage(player.getImage(), player.getX(), player.getY(), this); } ArrayList ms = player.getMissiles(); /* for (int i = 0; i &lt; ms.size(); i++) { Missile m = (Missile)ms.get(i); g2d.drawImage(m.getImage(), m.getX(), m.getY(), this); }*/ /* for (int i = 0; i &lt; aliens.size(); i++) { Enemy a = (Enemy)aliens.get(i); if (a.isVisible()){ g2d.drawImage(a.getImage(), a.getX(), a.getY(), this); } }*/ g2d.setColor(Color.BLACK); g2d.drawString("BattleView: ", 5, 15); Toolkit.getDefaultToolkit().sync(); g.dispose(); } @Override public void actionPerformed(ActionEvent e) { /* if (aliens.size()==0) { //send message to server that enemies have been killed }*/ ArrayList ms = player.getMissiles(); /* for (int i = 0; i &lt; ms.size(); i++) { Missile m = (Missile) ms.get(i); if (m.isVisible()){ m.move(); }else{ ms.remove(i); } }*/ /* for (int i = 0; i &lt; aliens.size(); i++) { Enemy a = (Enemy) aliens.get(i); if (a.isVisible()){ a.move(); }else{ aliens.remove(i); } }*/ player.move(); checkCollisions(); repaint(); } public void checkCollisions() { /* Rectangle r3 = player.getBounds(); for (int j = 0; j&lt;aliens.size(); j++) { Enemy a = (Enemy) aliens.get(j); Rectangle r2 = a.getBounds(); if (r3.intersects(r2)) { player.setVisible(false); a.setVisible(false); ingame = false; } }*/ ArrayList ms = player.getMissiles(); /* for (int i = 0; i &lt; ms.size(); i++) { Missile m = (Missile) ms.get(i); Rectangle r1 = m.getBounds(); for (int j = 0; j&lt;aliens.size(); j++) { Enemy a = (Enemy) aliens.get(j); Rectangle r2 = a.getBounds(); if (r1.intersects(r2)) { m.setVisible(false); a.setVisible(false); } // r1.intersects } // for aliens.size() }*/ // for ms.size() } private class TAdapter extends KeyAdapter { public void keyReleased(KeyEvent e) { player.keyReleased(e); } public void keyPressed(KeyEvent e) { player.keyPressed(e); } } } </code></pre> <p>This part fires five <code>System.out.println("Attack Message Recieved "+i);</code> when server sends message. So if server sends 1,5.. 5 units of type 1 are "recieved" and <code>System.out.println</code> prints 5 times.</p> <p>Now when I try to use <code>paint(g)</code> to draw the enemy units using the for-loop.. I get an error When I comment out the for-loop everything compiles fine and loads (but no screen sprites are created of the enemy, only the <code>System.out.println</code> fires the N number of times sent via the server.</p> <p>How can I get it to draw the enemies right after the <code>System.out.println</code> fires?</p> <p>This is the error:</p> <pre><code>at ViewA.paint(ViewA.java:85) at javax.swing.JComponent.paintToOffscreen(Unknown Source) at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source) at javax.swing.RepaintManager$PaintManager.paint(Unknown Source) at javax.swing.RepaintManager.paint(Unknown Source) at javax.swing.JComponent._paintImmediately(Unknown Source) at javax.swing.JComponent.paintImmediately(Unknown Source) at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source) at javax.swing.RepaintManager.access$700(Unknown Source) at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source) at java.awt.event.InvocationEvent.dispatch(Unknown Source) at java.awt.EventQueue.dispatchEventImpl(Unknown Source) at java.awt.EventQueue.access$000(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source) </code></pre> <p>at ViewA.paint(ViewA.java:85)</p> <p>corresponds to this line:</p> <blockquote> <pre><code> for (int i = 0; i &lt; aliens.size(); i++) { Enemy a = (Enemy)aliens.get(i); if (a.isVisible()) g2d.drawImage(a.getImage(), a.getX(), a.getY(), this); } g2d.setColor(Color.BLACK); g2d.drawString("BattleView: ", 5, 15); </code></pre> </blockquote>
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    1. COYou shouldn't be calling `paint(g)` yourself, use `repaint` to request that the panel be repainted
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    2. COcan you remove commented lines, that aren't necessary?
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    3. COOkay that tells us where not what...included the actual exception as well (I know, we're meanies)
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