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[web] Flash AS3 KeyboardEvent madness

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I am really new to the FLASH and Actionscript. I am making this simple game where you control a small spacecraft with keys. The problem is that, if I keep pressed one of the buttons (UP/DOWN/LEFT/RIGHT) for more than 2 seconds, FPS suddenly drops from 60 to below 40. But that's not all. If I press another key, while holding that LEFT/RIGHT/WHATEVER key down, fps quickly jumps back to stable 60. Any ideas why? PS I have a boolean array where I keep track which keys are pressed and released.

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This is class I use for keyboard input management. I found it somewhere on the web, though it is very simple.


// Key.as
package {

import flash.display.Stage;
import flash.events.Event;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;

/**
* The Key class recreates functionality of
* Key.isDown of ActionScript 1 and 2. Before using
* Key.isDown, you first need to initialize the
* Key class with a reference to the stage using
* its Key.initialize() method. For key
* codes use the flash.ui.Keyboard class.
*
* Usage:
* Key.initialize(stage);
* if (Key.isDown(Keyboard.LEFT)) {
* // Left key is being pressed
* }
*/
public class Key {

private static var initialized:Boolean = false; // marks whether or not the class has been initialized
private static var keysDown:Object = new Object(); // stores key codes of all keys pressed
/**
* Initializes the key class creating assigning event
* handlers to capture necessary key events from the stage
*/
public static function initialize(stage:Stage) {
if (!initialized) {
// assign listeners for key presses and deactivation of the player
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);
stage.addEventListener(Event.DEACTIVATE, clearKeys);
// mark initialization as true so redundant
// calls do not reassign the event handlers
initialized = true;
}
}

/**
* Returns true or false if the key represented by the
* keyCode passed is being pressed
*/
public static function isDown(keyCode:uint):Boolean {
if (!initialized) {
// throw an error if isDown is used
// prior to Key class initialization
throw new Error("Key class has yet been initialized.");
}
return Boolean(keyCode in keysDown);
}

/**
* Event handler for capturing keys being pressed
*/
private static function keyPressed(event:KeyboardEvent):void {
// create a property in keysDown with the name of the keyCode
keysDown[event.keyCode] = true;
}

/**
* Event handler for capturing keys being released
*/
private static function keyReleased(event:KeyboardEvent):void {
if (event.keyCode in keysDown) {
// delete the property in keysDown if it exists
delete keysDown[event.keyCode];
}
}

/**
* Event handler for Flash Player deactivation
*/
private static function clearKeys(event:Event):void {
// clear all keys in keysDown since the player cannot
// detect keys being pressed or released when not focused
keysDown = new Object();
}
}
}


And then, every frame I check the keyboard state like this:



// I call for Key.initialize(stage); earlier


if (Key.isDown(Keyboard.LEFT))
auto.rotation-=turn_angle;
else if (Key.isDown(Keyboard.RIGHT))
auto.rotation+=turn_angle;
else if (Key.isDown(Keyboard.UP))
speed+=acceleration;
else if (Key.isDown(Keyboard.DOWN))
{
speed-=acceleration;
if (speed<0)
speed = 0;

}

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