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POUsing Key Bindings with Arrow Keys
 

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    <p>I'm creating a game that uses the arrow keys to move a sprite. I've added key bindings for the arrow keys and the letter n, but arrow keys aren't working. Here's my code:</p> <pre><code>public class MyPanel extends JPanel { Sprite sprite = new Sprite(); Timer gameClock = new Timer(DELAY, new ActionListener(){ public void actionPerformed(ActionEvent e){ sprite.move(); // omit other methods } }); // omit other member variables public MyPanel(){ Abstract Action newGameAction = new AbstractAction("new game") { public void actionPerformed(ActionEvent e){ doNewGame(); } } setFocusable(true); addKeyBinding(new Pair&lt;String, Action&gt;("N", newGameAction)); ArrayList&lt;Pair&lt;String, Action&gt;&gt; pairs = sprite.findKeyBindingPairs(); for (Pair&lt;String, Action&gt; p : pairs) addKeyBindings(p); gameClock.start(); // omit other panel init } private void addKeyBindings(Pair&lt;String, Action&gt; pair) { String key = pair.getFirstElement(); Action action = pair.getSecondElement(); String desc = action.getValue(AbstractAction.NAME).toString(); getInputMap().put(KeyStroke.getKeyStroke(key), desc); getActionMap().put(desc, action); } // omit other methods } public class Sprite { private class ChangeDirAction extends AbstractAction { int dx, dy; ChangeDirAction(String name, int dx, int dy){ super(name); this.dx = dx; this.dy = dy; } public void actionPerformed(ActionEvent e){ setVelocity(dx, dy); } } private int dx_, dy_; Point pos; // omit other instance variables public void move(){ // With printlns dx_ and dy_ are both 0 here. Why? Point newPos = new Point(pos); newPos.translate(dx_, dy_); // omit code to test whether newPos is valid if (isWall(newPos) || isOutsidePanel(newPos)) setVelocity(0, 0); else pos = newPos; } private void setVelocity(int dx, int dy){ dx_ = dx; dy_ = dy; // With printlns dx_ and dy_ change when arrow keys are pressed } public ArrayList&lt;Pair&lt;String, Action&gt;&gt; findKeyBindingPairs(){ Pair&lt;String, Action&gt; leftPair = new Pair&lt;String, Action&gt;("LEFT", new ChangeDirAction("left", -1, 0)); Pair&lt;String, Action&gt; rightPair = new Pair&lt;String, Action&gt;("RIGHT", new ChangeDirAction("right", 1, 0)); Pair&lt;String, Action&gt; upPair = new Pair&lt;String, Action&gt;("UP", new ChangeDirAction("up", 0, -1)); Pair&lt;String, Action&gt; downPair = new Pair&lt;String, Action&gt;("DOWN", new ChangeDirAction("down", 0, 1)); ArrayList&lt;Pair&lt;String, Action&gt;&gt; result = new ArrayList&lt;Pair&lt;String, Action&gt;&gt;(); result.add(leftPair); result.add(rightPair); result.add(upPair); result.add(downPair); return result; } // omit other methods } </code></pre>
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    1. COI figured it out while trying to do an SSCCE. When I start a new game, I create a new Sprite object without the key bindings of the old one, so my key binding data is lost. I moved my code to add key bindings to the doNewGame() method and it works now.
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    2. COthat's one of reasons SSCCE is so highly recommended :-) BTW, you can add an answer to your question yourself and accept it.
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