Question

我想从free.worldweatheronline.com获取xml数据我尝试了以下方式： -

<fx:Script>
    <![CDATA[
        import mx.rpc.events.FaultEvent;
        import mx.rpc.events.ResultEvent;
        private var main_xml_url:String = "http://free.worldweatheronline.com/feed/weather.ashx?q="+cityName.text.toString()+"&format=xml&num_of_days=2&key=my_api_key"; // there I put my api key not showing here//


        protected function weatherService_resultHandler(event:ResultEvent):void
        {
            // TODO Auto-generated method stub
            var result_weather_data:Object = event.result;
            cityNameData.text = data.request.query;

        }

        protected function weatherService_faultHandler(event:FaultEvent):void
        {
            // TODO Auto-generated method stub
            cityNameData.text = event.message.toString();
        }

    ]]>
</fx:Script>

<fx:Declarations>       
    <s:HTTPService id="weatherService"
                   url="main_xml_url"
                   resultFormat="object"
                   result="weatherService_resultHandler(event)"
                   fault="weatherService_faultHandler(event)"/>
    <!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>
<s:TextInput id="cityName" text="Hyderabad" x="10" y="10" width="219" fontWeight="bold" prompt="Enter city Name"/>

<s:Label id="cityNameData" x="108" y="109" width="202" fontSize="20" fontWeight="bold"/>

但是有一个错误说：无法访问null对象引用的属性或方法。在private var main_xml_url：String

请提前解决，请先帮忙。

Answer 1

上面的代码表示您正在尝试在对象初始化时检索并分配cityName.text.toString()的值。

作为cityName的显示对象TextInput在分配时不会添加到显示中。因此，你正在获得NPE。

您可以按如下方式更正此问题：

<fx:Declarations>
    <s:HTTPService id="weatherService"
        url="{BASE_URL}"
        resultFormat="object"
        result="weatherService_resultHandler(event)"
        fault="weatherService_faultHandler(event)">
        <s:request xmlns="">
            <q>{cityName.text.toString()}</q>
            <format>{FORMAT}</format>
            <num_of_days>{NUMBER_OF_DAYS}</num_of_days>
            <key>{API_KEY}</key>
        </s:request>
    </s:HTTPService>
    <!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>

<fx:Script>
    <![CDATA[
        import mx.rpc.events.FaultEvent;
        import mx.rpc.events.ResultEvent;

        private static const BASE_URL:String="http://free.worldweatheronline.com/feed/weather.ashx"
        private static const API_KEY:String="your API key here"
        private static const NUMBER_OF_DAYS:uint=2;
        private static const FORMAT:String="xml";

        protected function weatherService_resultHandler(event:ResultEvent):void
        {
            // TODO Auto-generated method stub
            var result_weather_data:Object=event.result;
            cityNameData.text=result_weather_data.request.query;

        }

        protected function weatherService_faultHandler(event:FaultEvent):void
        {
            // TODO Auto-generated method stub
            cityNameData.text=event.message.toString();
        }
    ]]>
</fx:Script>
<s:layout>
    <s:VerticalLayout/>
</s:layout>
<s:TextInput id="cityName"
    width="219"
    text="Hyderabad"
    x="10"
    y="10"
    fontWeight="bold"
    prompt="Enter city Name"/>

<s:Label id="cityNameData"
    width="202"
    x="108"
    y="109"
    fontSize="20"
    fontWeight="bold"/>

<s:Button label="Send" click="{weatherService.send()}"/>

此外，您忘记拨打send()对象上的weatherService。这意味着无论如何都不会触发您的Web服务调用。

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无法从flex中的xml服务获取数据

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