鍵盤觸發事件 , 我們以遊戲做為例子 分別是控制角色上下左右
底下分成兩部份,先介紹as2.0早期寫法 ,再為各位介紹as3.0 有3種鍵盤寫法!
( as2.0已經不推薦使用囉 )
不論那一種AS3.0寫法 以下都只能做一個事件方向的偵測 ,
兩個方向量無法同時被觸發, 意思就是當然按下 左 & 上時 它只會觸發其一,這解決方法在下一節討論
早期AS2.0寫法
//在onEnterFrame status :
if (Key.isDown(Key.LEFT)) {
xspeed -= power;
}
if (Key.isDown(Key.RIGHT)) {
xspeed += power;
}
if (Key.isDown(Key.UP)) {
yspeed -= power;
}
if (Key.isDown(Key.DOWN)) {
yspeed -= power;
}
xspeed *= friction; //磨擦力
yspeed *= friction;
_y += yspeed;
_x += xspeed;
AS3.0鍵盤事件寫法 , 都已改為事件監聽方法, 監聽key是否DOWN 或UP
3.0鍵盤寫法1:
stage.addEventListener(Event.ENTER_FRAME, report_loop);
//場景進入立刻 ENTER_FRAME(跟onEnterFrame同道理) 不停的跑report_loop 函數
stage.addEventListener(KeyboardEvent.KEY_DOWN, reportKeyDown);
//一開始 "場景" 監聽鍵盤是否被按下或放開事件
//該report_loop不停的被觸發 接收 keyDown 所得到的 xspeed 與 yspeed 值 來做磨擦力與物件位移
function report_loop(event:Event):void {
xspeed*=friction;
yspeed*=friction;
mc.y += yspeed;
mc.x += xspeed;
}
//當事件觸發 鍵盤按下 就觸發以下條件
function reportKeyDown(event:KeyboardEvent):void {
if (event.keyCode==Keyboard.RIGHT) {
xspeed+=power;
}
if (event.keyCode==Keyboard.LEFT) {
xspeed-=power;
}
if (event.keyCode==Keyboard.UP) {
yspeed-=power;
}
if (event.keyCode==Keyboard.DOWN) {
yspeed+=power;
}
}//keyDown
3.0鍵盤寫法2:
stage.addEventListener(Event.ENTER_FRAME, report_loop);
stage.addEventListener(KeyboardEvent.KEY_DOWN, reportKeyDown);
stage.addEventListener(KeyboardEvent.KEY_UP, reportKeyUp);
function reportKeyDown(event:KeyboardEvent):void {
objKeyboard.pressed=true;
objKeyboard.keyCode=event.keyCode;
}
function reportKeyUp(evt:KeyboardEvent): void{
objKeyboard.pressed = false;
objKeyboard.keyCode = null;
}
//一樣分為KEY DOWN與UP,
//不同的是,當DOWN觸發的事件內容,透過自定參數來判斷是否按下
function reportKeyUp(evt:KeyboardEvent): void{
objKeyboard.pressed = false;
objKeyboard.keyCode = null;
}
var power:Number=0.8;
var yspeed:Number=0;
var xspeed:Number=0;
var friction:Number=0.9;
var objKeyboard:Object;
objKeyboard={pressed:true,keyCode:null};
function report_loop(event:Event):void {
xspeed*=friction;
yspeed*=friction;
mc.y+=yspeed;
mc.x+=xspeed;
if (objKeyboard.pressed) { //自定參數判斷是否按下
switch (objKeyboard.keyCode) { //利用 switch 判斷key值
case 37 :
xspeed += power;
break;
case 39 :
xspeed -= power;
break;
case 38 :
yspeed += power;
break;
case 40 :
yspeed -= power;
break;
}
}
}
3.0鍵盤寫法3:
//以下寫法大家想必都非常熟悉 ,很像 AS2.0 寫法
if (objKeyboard.keyCode==37) {
xspeed+=power;
}
if (objKeyboard.keyCode==39) {
xspeed-=power;
}
if (objKeyboard.keyCode==38) {
yspeed+=power;
}
if (objKeyboard.keyCode==40) {
yspeed-=power;
}
