StackOverflow2013

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plurals

PO
primarykey
Id
17740321
data
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0
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ClosedDate
CommentCount
11
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2013-07-19T07:23:22.273
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2013-07-19T08:04:14.410
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2013-07-19T08:04:14.410
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992484
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17740163
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2
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text
Body
Start by trying to call <code>repaint</code> to request that the panel should be repainted... <pre><code>public void spawnEnemy(int type, int amount) { aliens = new ArrayList(); for (int i = 1; i < amount + 1; i++) { aliens.add(new Enemy(0 - i * 40, 400)); System.out.println("Attack Message Recieved " + i); } repaint() // <<-- } </code></pre> Also, it is recommended that should be overriding <code>paintComponent</code> instead of <code>paint</code> Updated Don't dispose of any resource you didn't create... <pre><code>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(); g2d.setColor(Color.BLACK); g2d.drawString("BattleView: ", 5, 15); Toolkit.getDefaultToolkit().sync(); // This is a bad idea.. //g.dispose(); } </code></pre> <code>Graphics</code> is a shared resource, meaning that other components in your application may need to use them. Also disposing may prevent Swing from begin able to paint anything at all... Updated You define a <code>ArrayList</code> as an instance field, but you never initialise until the <code>spawnEnemy</code> method is called. <code>paint</code> is likely to called a long time before that. <pre><code>public class BattleView extends JPanel implements ActionListener { //...// private ArrayList aliens; //..// public void spawnEnemy(int type, int amount) { aliens = new ArrayList(); </code></pre> You have a number of options. You could check for to see if the <code>aliens</code> list is <code>null</code> before painting... <pre><code>if (aliens != null) { ... } </code></pre> But there is a problem here, what happens if you get more enemies? You could actually lose some (if <code>paint</code> isn't called before more updates arrive) Instead, you should create the <code>aliens</code> list in the constructor and simply update it as new enemies arrive... <pre><code>public BattleView(Player player) { aliens = new ArrayList(); //...// } </code></pre> Add new enemies to the list as they arrive... <pre><code>public void spawnEnemy(int type, int amount) { for (int i=1; i<amount+1; i++ ) { aliens.add(new Enemy(0-i*40,400)); System.out.println("Attack Message Recieved "+i); } repaint(); } </code></pre> And then paint... <pre><code>for (int i = 0; i < aliens.size(); i++) { Enemy a = (Enemy)aliens.get(i); if (a.isVisible()) g2d.drawImage(a.getImage(), a.getX(), a.getY(), this); } </code></pre>
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1. This table or related slice is empty.
PostParentId
1. POSprite spawning on particular JPanel
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PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. USMadProgrammer
UserOwnerUserId
1. USMadProgrammer
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1. This table or related slice is empty.
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1. This table or related slice is empty.
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1. This table or related slice is empty.
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1. VO
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