XMLPullParser getName() returns null

Question

我正在尝试解析openweathermap api http://api.openweathermap.org/data/2.5/weather?q=London&mode=xml。我通过XmlPullParserFactory.newPullParser()使用KXmlParser，但XMLPullParser.getName()总是返回null。这可能是一个愚蠢的错误，但似乎我可能需要你的帮助来发现它。

下面是通过HTTPURLConnection读取api的代码。

 URL url = new URL(urlString);
                URLConnection urlConnection = url.openConnection();
                HttpURLConnection httpConnection = (HttpURLConnection) urlConnection;
                httpConnection.setRequestMethod("GET");
                httpConnection.connect();
                if(httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK){
                    inputStream = httpConnection.getInputStream();
                }

我用

BufferedReader buffer = new BufferedReader(
                            new InputStreamReader(inputStream));
                    String s="";
                    while ((s=buffer.readLine())!=null){
                        stringBuffer.append(s);
                        System.out.println(s);
                    }

以确保我正在成功地读取xml，并且结果证明代码正在正常运行。接下来，我将使用以下代码解析xml

XmlPullParserFactory xmlFactoryObject = XmlPullParserFactory.newInstance();
            XmlPullParser myparser = xmlFactoryObject.newPullParser();
            myparser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES
                    , false);
            myparser.setInput(inputStream, null);
            int event = myparser.getEventType();
            while (event != XmlPullParser.END_DOCUMENT){
                Log.d("XMLPullParserHandler", "sdfdsf " + myparser.getName());
                String name = myparser.getName();

但我得到java.lang.NullPointerException在myparser.getName();此外，上面的日志显示"sdfdsf null"。

我做错了什么?

Answer 1

您可以解析给定的xml或将模式更改为json并解析json

你的xml标签看起来像

<city id="2643743" name="London"> 
// tag name is city
// id and name are attributes with values 2643743 and London

注意:我只展示了几个标签的解析。但它应该可以帮助您理解并自己对其余部分进行解析。

来自文档

公共抽象字符串getName ()新增API level 1

对于START_TAG或END_TAG事件，当前事件的(本地)名称元素在启用名称空间时返回。当命名空间如果禁用处理，则返回原始名称。对于ENTITY_REF事件时，返回实体名称。如果当前事件不是START_TAG、END_TAG或ENTITY_REF，返回null。

解析xml并获取值

public class XMLPullParserHandler {

    public XMLPullParserHandler() {
    }
    public Void parse(InputStream is) {
        XmlPullParserFactory factory = null;
        XmlPullParser parser = null;
        try {
            factory = XmlPullParserFactory.newInstance();
            factory.setNamespaceAware(true);
            parser = factory.newPullParser();
            parser.setInput(is, null);
            boolean check =false;
           //factory instantiates an object
            int eventType = parser.getEventType();
            while (eventType != XmlPullParser.END_DOCUMENT) {
                switch (eventType) {
                case XmlPullParser.START_TAG:
                    String tagname = parser.getName();
                    Log.i("Tag names are ",tagname);
                    if (tagname.equalsIgnoreCase("city")) {
                        if(parser.getAttributeValue(null, "id").equals("264374"))
                        {
                             String cityname= parser.getAttributeValue(null, "name");
                             Log.i(" City Name is ",cityname);
                        }
                    }
                    if (tagname.equalsIgnoreCase("coord")) {
                             String lat= parser.getAttributeValue(null, "lat");
                             String lon= parser.getAttributeValue(null, "lon");
                             Log.i("Latitude and Longitude is","Lat= "+lat+"Lon= "+lon);
                    }
                    if (tagname.equalsIgnoreCase("sun")) {
                     String rise= parser.getAttributeValue(null, "rise");
                     String set= parser.getAttributeValue(null, "set");
                     Log.i("Sun Rise and Sun set is","Rise= "+rise+"Set= "+set);
               }
                    break;
                case XmlPullParser.TEXT:
                    break;
                case XmlPullParser.END_TAG:

                    break;
                default:
                    break;
                }
                eventType = parser.next();
            }
        } catch (XmlPullParserException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

日志

08-18 16:14:35.885: I/City Name is(31634): London
08-18 16:14:35.885: I/Latitude and Longitude is(31634): Lat= 51.51Lon= -0.13
08-18 16:14:35.885: I/Sun Rise and Sun set is(31634): Rise= 2014-08-18T04:51:39Set= 2014-08-18T19:16:53

如果你的xml标签看起来像

<cityname type="test">City is London</cityname> 

获取值

case XmlPullParser.TEXT:
       text = parser.getText();
break;
case XmlPullParser.END_TAG:
       if (tagname.equalsIgnoreCase("cityname")) {                             
        Log.i("Name is",text);
       }
break;

编辑:

Asynctask

class TheTask extends AsyncTask<Void,Void,Void>
{
@Override
protected Void doInBackground(Void... params) {
    // TODO Auto-generated method stub
    String response;
       try {
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpGet httpGet = new HttpGet("http://api.openweathermap.org/data/2.5/weather?q=London&mode=xml");
            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            response = EntityUtils.toString(httpEntity);
            InputStream is = new ByteArrayInputStream(response.getBytes(Charset.forName("UTF-8")));
            new XMLPullParserHandler().parse(is); 
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    return null;
}   
}

Answer 2

START_DOCUMENT是您总是从解析器获得的第一个事件，而getName()仅在START_TAG, END_TAG和ENTITY_REF事件的情况下返回不为空。

对于START_TAG或END_TAG事件，在启用名称空间时返回当前元素的(本地)名称。当名称空间处理被禁用时，将返回原始名称。对于ENTITY_REF事件，返回实体名称。如果当前事件不是START_TAG、END_TAG或ENTITY_REF，则返回null。

试试这个:

while (event != XmlPullParser.END_DOCUMENT) {
    if (event == XmlPullParser.START_TAG || event == XmlPullParser.END_TAG) {
        Log.d("XMLPullParserHandler", "sdfdsf " + myparser.getName());
        String name = myparser.getName();
    }
    event = myparser.next();
}