http://www.iteye.com/topic/162463#
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用flex开发互动应用的时候经常会遇到显示对象与键盘鼠标的互动响应，通常的做法是添加侦听器来检测输入事件：
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package {
import flash.display.Sprite;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
public class FlexTest extends Sprite
{
private var circle_sprite:Sprite;
private var isUp:Boolean;
private var isDown:Boolean;
private var isLeft:Boolean;
private var isRight:Boolean;
private const MOVE_SPEED:int=2;
public function FlexTest()
{
circle_sprite=new Sprite();
circle_sprite.graphics.beginFill(0xff0000);
circle_sprite.graphics.drawCircle(100,100,20);
circle_sprite.graphics.endFill();
addChild(circle_sprite);
stage.addEventListener(KeyboardEvent.KEY_DOWN,key_down);
}
private function key_down(evt:KeyboardEvent):void{
if (evt.keyCode==Keyboard.LEFT){
circle_sprite.x-=MOVE_SPEED;
}
if (evt.keyCode==Keyboard.RIGHT){
circle_sprite.x+=MOVE_SPEED;
}
if (evt.keyCode==Keyboard.UP){
circle_sprite.y-=MOVE_SPEED;
}
if (evt.keyCode==Keyboard.DOWN){
circle_sprite.y+=MOVE_SPEED;
}
}
}
}
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以上实现，在使用过程中用方向键控制MC移动的时候为没有那么流畅,MC的移动明显有点卡，这是因为键盘按键如果一直按住不放，它也是间隔开来不断的重复触发按键事件，键盘的键值扫描有一定的间隔频率，因此产生了断断续续的感觉。
要想得到平滑的移动效果，可以通过添加事件侦听器侦听Event.ENTER_FRAME事件来解决
package {
import flash.display.Sprite;
import flash.events.Event;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
public class FlexTest extends Sprite
{
private var circle_sprite:Sprite;
private var isUp:Boolean;
private var isDown:Boolean;
private var isLeft:Boolean;
private var isRight:Boolean;
private const MOVE_SPEED:int=2;
public function FlexTest()
{
circle_sprite=new Sprite();
circle_sprite.graphics.beginFill(0x0080c0);
circle_sprite.graphics.drawCircle(100,100,20);
circle_sprite.graphics.endFill();
addChild(circle_sprite);
stage.addEventListener(KeyboardEvent.KEY_DOWN,key_down);
stage.addEventListener(KeyboardEvent.KEY_UP,key_up);
stage.addEventListener(Event.ENTER_FRAME,enter_frame);
}
private function key_down(event:KeyboardEvent):void {
if(event.keyCode==Keyboard.UP){
isUp=true;
}
if (event.keyCode==Keyboard.DOWN) {
isDown=true;
}
if(event.keyCode==Keyboard.LEFT){
isLeft=true;
}
if(event.keyCode==Keyboard.RIGHT){
isRight=true;
}
}
private function key_up(event:KeyboardEvent):void{
if(event.keyCode==Keyboard.UP){
isUp=false;
}
if (event.keyCode==Keyboard.DOWN) {
isDown=false;
}
if(event.keyCode==Keyboard.LEFT){
isLeft=false;
}
if(event.keyCode==Keyboard.RIGHT){
isRight=false;
}
}
public function enter_frame(event:Event):void{
if(isUp){
circle_sprite.y-=MOVE_SPEED;
}
if(isRight){
circle_sprite.x+=MOVE_SPEED;
}
if(isDown){
circle_sprite.y+=MOVE_SPEED;
}
if(isLeft){
circle_sprite.x-=MOVE_SPEED;
}
}
}
}
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