flash 滚动条代码

最近在学习flash，自己用AS3.0写了一个滚动条，不是用组件的

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import app.view.ui.friend.FriendsColumn;
import flash.display.SimpleButton;
import flash.events.MouseEvent;
import flash.events.TextEvent;
import com.iceengine.interfaces.IProcess;
import com.iceengine.input.IceInput;
import com.iceengine.core.Processer;

internal class FriendScrollBar extends IceSprite { ? ?private var _friendsColumn:FriendsColumn=null; ?private var _friends:Array = []; ?private var _page:int=0; ?private var _topBtn:SimpleButton = null; ?private var _bottomBtn:SimpleButton = null; ?private var _upBtn:SimpleButton = null; ?private var _downBtn:SimpleButton = null; ?public? var _slider:SimpleButton = null; ?public var _scrollBar:SimpleButton = null; ?private var _isDown:Boolean = false; ? ?public function FriendScrollBar (mc:DisplayObject,friendsColumn:FriendsColumn,parent:DisplayObjectContainer=null,initX:Number=0,initY:Number=0){ ??super(mc,parent); ??_friendsColumn = friendsColumn; ??_mc.x = initX; ??_mc.y = initY; ??_topBtn = _mc.topBtn; ??_bottomBtn = _mc.bottomBtn; ??_upBtn = _mc.upBtn; ??_downBtn = _mc.downBtn; ??_slider = _mc.slider? ; ??_scrollBar = _mc.bar; ?? ??_friends = _friendsColumn._friendList; ??initListeners(); //??Processer.addUpdateFunc(_update); ?} ? ?private function _update():void { ??if(_isDown){ ???if(_slider.y >_scrollBar.y +_scrollBar.height) ???{ ????_slider.y = _scrollBar.y +_scrollBar.height; ???} ???else if(_slider.y< _scrollBar.y){ ????_slider.y = _scrollBar.y; ???} ???else{_slider.y = mouseY-64;} ???//??_slider.removeEventListener(MouseEvent.MOUSE_DOWN,_sliderMouseDown); ???_friendsColumn._start =Math.max(0,(_friendsColumn._friendList.length/_scrollBar.height)*(_slider.y - _scrollBar.y)); ???_friendsColumn.showFriendItem(_friendsColumn._friendList,_friendsColumn._start); ???if(IceInput.mouseUp) { ????_slider.addEventListener(MouseEvent.MOUSE_DOWN,_sliderMouseDown); ????_isDown = false; ???} ??} ?} ? ?public function turn(param1:int) : void ?{ ??var _rows:* = 8; // Config.getNumber("flash.friendList.blocks.cols"); ??this.shift(param1 * _rows); ??return; ?}// end function ? ?public function shift(param1:int) : void ?{ ??var _rows:* = 8 ; //Config.getNumber("flash.friendList.blocks.cols"); ??var _startIndex:* = Math.max(0,_friendsColumn._friendList.length - _rows); ??_friendsColumn._start = Math.max(0,?? Math.min(_startIndex,_friendsColumn._start + param1)); ??_friendsColumn.showFriendItem(_friendsColumn._friendList,_friendsColumn._start); ??if(_friendsColumn._friendList.length-_friendsColumn._start >7 ){ ??_slider.y =(_friendsColumn._start/_friendsColumn._friendList.length)*_scrollBar.height+_scrollBar.y ??} ??return; ?}// end function ? ?public function get pages() : int ?{ ??var _rows:* = 8;?? //Config.getNumber("flash.friendList.blocks.cols"); ??return Math.ceil(this._friends.length / _rows); ?}// end function ? ?override protected function init(e:Event=null):void { ??super.init(); ?? ?} ?override protected function end(e:Event=null):void { ??super.end(); ?? ?} ? ?private? function _sliderMouseDown(event:MouseEvent):void { ??event.stopPropagation(); ??_slider.removeEventListener(MouseEvent.MOUSE_DOWN,_sliderMouseDown); ??stage.addEventListener(MouseEvent.MOUSE_MOVE,_sliderMouseMove); ??stage.addEventListener(MouseEvent.MOUSE_UP,_sliderMouseUp); ??_isDown = true; ?} ? ?private function _sliderMouseMove(event:MouseEvent):void { ??if(mouseY - 64 >_scrollBar.y+_scrollBar.height){ ???_slider.y = _scrollBar.y+_scrollBar.height-13; ??} ??else if(mouseY - 64 <_scrollBar.y){ ???_slider.y = _scrollBar.y; ??} ??else{ ???_slider.y = mouseY-64; ??} ??_friendsColumn._start =Math.max(0,(_friendsColumn._friendList.length/_scrollBar.height)*(_slider.y - _scrollBar.y)); ??_friendsColumn.showFriendItem(_friendsColumn._friendList,_friendsColumn._start); ?} ?private? function _sliderMouseUp(event:MouseEvent):void { ??_slider.addEventListener(MouseEvent.MOUSE_DOWN,_sliderMouseDown); ??stage.removeEventListener(MouseEvent.MOUSE_MOVE,_sliderMouseMove); ??stage.removeEventListener(MouseEvent.MOUSE_UP,_sliderMouseUp); ??_isDown = true; ?} ? ?private function scrollBarClick(event:MouseEvent):void { ??_slider.y = mouseY-64; ??_friendsColumn._start =Math.max(0,(_friendsColumn._friendList.length/_scrollBar.height)*(_slider.y - _scrollBar.y)); //??trace("_start="+_start); ??_friendsColumn.showFriendItem(_friendsColumn._friendList,_friendsColumn._start); ?} ? ?private function initListeners() : void{ ??_topBtn.addEventListener(MouseEvent.CLICK,function () :void{turn(-1);}); ??_bottomBtn.addEventListener(MouseEvent.CLICK,function () :void{turn(1);}); ??_upBtn.addEventListener(MouseEvent.CLICK,function () :void{shift(-1);}); ??_downBtn.addEventListener(MouseEvent.CLICK,function () :void{shift(1);}); ??_scrollBar.addEventListener(MouseEvent.CLICK,scrollBarClick); ??_slider.addEventListener(MouseEvent.MOUSE_DOWN,_sliderMouseDown); ?? ?} }