Flash Flex TabNavigator空对象问题
我在TabNavigator中遇到问题,因为它总是发送错误:Flash Flex TabNavigator空对象问题,flash,apache-flex,flash-builder,tabnavigator,Flash,Apache Flex,Flash Builder,Tabnavigator,我在TabNavigator中遇到问题,因为它总是发送错误: TypeError: Error #1009: Cannot access a property or method of a null object reference. at mx.containers::TabNavigator/keyDownHandler()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/mx/src/mx/contain
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at mx.containers::TabNavigator/keyDownHandler()[/Users/justinmclean/Documents/ApacheFlex4.11.0/frameworks/projects/mx/src/mx/containers/TabNavigator.as:903]
示例代码:
<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" applicationComplete="init(event)">
<fx:Script>
<![CDATA[
import mx.events.FlexEvent;
protected function init(event:FlexEvent):void
{
stage.addEventListener(KeyboardEvent.KEY_DOWN, handleKeyDown);
}
public function handleKeyDown(event:KeyboardEvent):void
{
if(event.keyCode == Keyboard.F1){
if(currentState=="State1"){
currentState = "setting";
}else{
currentState = "State1";
}
}
}
]]>
</fx:Script>
<fx:Declarations>
<!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>
<s:states>
<s:State name="State1"/>
<s:State name="setting"/>
</s:states>
<s:BorderContainer left="0" right="0" top="0" bottom="0" includeIn="setting">
<mx:TabNavigator id="TabNavigator" left="10" right="10" top="110" bottom="10" creationPolicy="all">
<!-- General Tab -->
<s:NavigatorContent id="generaltab" width="100%" height="100%" label="General">
<s:Group id="generalcontainer">
</s:Group>
</s:NavigatorContent>
<!-- Screen Tab -->
<s:NavigatorContent id="screentab" width="100%" height="100%" label="Screen">
<s:Group id="screencontainer" width="100%" height="100%">
</s:Group>
</s:NavigatorContent>
<!-- Playlist Tab -->
<s:NavigatorContent id="playlisttab" width="100%" height="100%" label="Playlist">
<s:Group id="playlistcontainer">
</s:Group>
</s:NavigatorContent>
</mx:TabNavigator>
</s:BorderContainer>
</s:WindowedApplication>
当我按F1时,它将跳转到设置页面。这将显示选项卡导航器。再次按F1键将其隐藏
基本上,反复显示和隐藏选项卡导航器没有问题。但是,如果我在隐藏选项卡导航器之前单击了任何选项卡,当我试图通过按键盘上的F1键再次显示选项卡导航器时,它会出现如上所示的错误
如何解决/防止错误发生
谢谢。看起来您在SDK中偶然发现了一个bug(坦白地说,这让我有点担心,因为这意味着一些事件侦听器没有被正确处理) 查看错误发生的来源:
override protected function keyDownHandler(event:KeyboardEvent):void
{
if (focusManager.getFocus() == this)
{
// Redispatch the event from the TabBar so that it can handle it.
tabBar.dispatchEvent(event);
}
}
发生的情况是,当您从State1
转到setting
时,TabNavigator
最初不在显示列表上(您正在通过includeIn
添加它),因此它没有focusManager
。这是完全正常的;不正常的是,对当前不在显示列表上的组件执行keyDownHandler
方法。这最终会导致空指针异常,因为在执行方法时没有focusManager
。当TabNavigator的父项被删除时,框架似乎不会清理事件侦听器。当使用
includeIn
本身添加/删除TabNavigator时,它确实可以正常工作,因此幸运的是,解决方法非常简单:
<s:BorderContainer includeIn="setting">
<mx:TabNavigator id="TabNavigator" includeIn="setting" creationPolicy="all">
您可能希望在中注册此错误。我刚刚找到了一种防止此错误发生的方法。即通过添加
TabNavigator.stage.focus=null代码>将状态更改回状态1
Hi RIAstar之前。非常感谢你的解释。我将把这个bug提交给ApacheFlexJira。但与此同时,你有什么建议我如何才能防止错误的发生?我简直等不及修复这个bug继续这个项目了。@user1995781在TabNavigator上应用includeIn=“setting”
本身(正如我上面解释的)对我很有效。这对你不管用吗?我真的很想念你的变通方法。不管怎样,我刚试过,但似乎对我不起作用。也许它适用于这里的简化示例,但不适用于实际代码。无论如何,非常感谢你的帮助。:)