我正在将 Flex 3.0 应用程序升级到 Flex 3.6 SDK。该应用程序具有用于输入文本、组合框等的自定义控件。当我单击组合框时，调用 super.commitProperties() 时出现异常。这适用于 Flex 3.0 SDK。
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at mx.controls::ComboBox/destroyDropdown()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\ComboBox.as:1681]
at mx.controls::ComboBox/styleChanged()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\ComboBox.as:1177]
at mx.core::UIComponent/setBorderColorForErrorString()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\core\UIComponent.as:5048]
at mx.core::UIComponent/commitProperties()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\core\UIComponent.as:6033]
at mx.controls::ComboBase/commitProperties()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\ComboBase.as:993]
at mx.controls::ComboBox/commitProperties()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\ComboBox.as:1291]
at com.hanover.utility.controls.autotestcontrols::AutotestComboBox/commitProperties()[C:\App\Control\PLCustomComboBox.as:59]
at mx.core::UIComponent/validateProperties()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\core\UIComponent.as:5966]
at mx.managers::LayoutManager/validateProperties()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\managers\LayoutManager.as:539]
at mx.managers::LayoutManager/doPhasedInstantiation()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\managers\LayoutManager.as:689]
at mx.managers::LayoutManager/validateNow()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\managers\LayoutManager.as:748]
at mx.controls::ComboBox/displayDropdown()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\ComboBox.as:1638]
at mx.controls::ComboBox/downArrowButton_buttonDownHandler()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\ComboBox.as:1796]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\core\UIComponent.as:9590]
at mx.controls::Button/http://www.adobe.com/2006/flex/mx/internal::buttonPressed()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\Button.as:2504]
at mx.controls::Button/mouseDownHandler()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\Button.as:2750]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\core\UIComponent.as:9590]
at mx.controls::ComboBase/textInput_mouseEventHandler()[C:\autobuild\3.x\frameworks\projects\framework\src\mx\controls\ComboBase.as:1384]
PLCustomCombobox.as 伪源代码，第 59 行如下所示
package com
{
import com.name.utility.events.PLControlEvent;
import com.name.utility.managers.ComboToolTipManager;
import flash.events.Event;
import mx.controls.ComboBox;
import mx.events.FlexEvent;
[Event(name="controlInitComplete", type="com.events.PLControlEvent")]
[Event(name="plusControlValueChanged", type="com.name.utility.events.PLControlEvent")]
public class PLControlComboBox extends ComboBox
implements IPLControlControl
{
/**
* A flag that indicates whether the control need to refresh.
*/
protected var isNeedRefresh:Boolean = false;
/**
* A flag that indicates whether the value of control is changed.
*/
protected var isValueChanged:Boolean = false;
/**
* Constructor.
*/
public function PLControlComboBox()
{
super();
this.addEventListener(FlexEvent.CREATION_COMPLETE, onCreationComplete);
}
/**
* @private
* override commitProperties for avoid dispatch event many times.
*/
override protected function commitProperties():void
{
super.commitProperties(); // <---- line # 59 is here
if(isNeedRefresh)
{
this.dispatchEvent(new PLControlEvent(PLControlEvent.VALUE_CHANGED));
isNeedRefresh = false;
}
if(isValueChanged)
{
this.dispatchEvent(new Event("PLControlComboboxChanged"));
isValueChanged = false;
}
}
/**
* Add item's tooltip.
* @private
*/
override public function set measuredWidth(value:Number):void
{
super.measuredWidth = value;
if(collection && collection.length > 0)
{
ComboToolTipManager.showItemToolTip(this);
}
}
protected function onCreationComplete(event:FlexEvent):void
{
this.removeEventListener(FlexEvent.CREATION_COMPLETE, onCreationComplete);
this.dispatchEvent(new PLControlEvent(PLControlEvent.INIT_COMPLETE));
}
public function checkValidity():void
{
if(_required && dataProvider && dataProvider.length > 0 && _defaultItemIndex == selectedIndex)
{
_validity = false;
errorString = "please select one";
}
else
{
_validity = true;
errorString = "";
}
}
// ======================================
// public function
// ======================================
private function itemChanged():void
{
isNeedRefresh = true;
isValueChanged = true;
checkValidity();
}
// ======================================
// properties
// ======================================
private var _required:Boolean = false;
private var _validity:Boolean = false;
private var _defaultItemIndex:int = 0;
public function get required():Boolean
{
return _required;
}
[Inspectable(defaultValue=false, category="Other")]
public function set required(value:Boolean):void
{
_required = value;
isNeedRefresh = true;
checkValidity();
}
[Bindable("PLControlComboboxChanged")]
public function get controlValue():Object
{
return this.selectedIndex;
}
public function set controlValue(value:Object):void
{
if(value is Number)
{
this.selectedIndex = int(value);
itemChanged();
}
}
/**
* @copy IPLControlControl#validity
*/
public function get validity():Boolean
{
return _validity;
}
/**
* @copy IPLControlControl#type
*/
public function get type():String
{
return PLControlTypeList.CONTROL_TYPE_COMBOBOX;
}
/**
* If required is true, the default Item can not be selected.
*/
public function get defaultItemIndex():int
{
return _defaultItemIndex;
}
[Inspectable(defaultValue=0, type="Number", category="Other")]
public function set defaultItemIndex(index:int):void
{
_defaultItemIndex = index;
isNeedRefresh = true;
checkValidity();
}
/**
* Override for check validity.
*/
override public function set selectedIndex(value:int):void
{
super.selectedIndex = value;
itemChanged();
}
/**
* Override for check validity.
*/
override public function set selectedItem(value:Object):void
{
super.selectedItem = value;
itemChanged();
}
}
}
它来自 mx.controls.Comboxbox 第 1681 行，因为补间为空。
private function destroyDropdown():void
{
if (inTween)
tween.endTween();//<---- exception on this line
displayDropdown(false, null, false);
}
关于为什么会发生这种情况的任何建议？