android parsing xml NullPointerException

Question

안녕하세요, 내 앱 실행에 문제가 있습니다. 그리고 그것은 나를이 가져옵니다

09-19 11:15:42.941: W/dalvikvm(6202): threadid=1: thread exiting with uncaught exception (group=0x40a71930) 
09-19 11:15:43.083: E/AndroidRuntime(6202): FATAL EXCEPTION: main 
09-19 11:15:43.083: E/AndroidRuntime(6202): java.lang.RuntimeException: Unable to start activity ComponentInfo{cz.bakalari.bakalari/cz.bakalari.bakalari.ParseActivity}: java.lang.NullPointerException 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.os.Handler.dispatchMessage(Handler.java:99) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.os.Looper.loop(Looper.java:137) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at java.lang.reflect.Method.invokeNative(Native Method) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at java.lang.reflect.Method.invoke(Method.java:511) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at dalvik.system.NativeStart.main(Native Method) 
09-19 11:15:43.083: E/AndroidRuntime(6202): Caused by: java.lang.NullPointerException 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at cz.bakalari.bakalari.XML_Parser.getValue(XML_Parser.java:112) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at cz.bakalari.bakalari.ParseActivity.onCreate(ParseActivity.java:45) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.Activity.performCreate(Activity.java:5104) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
09-19 11:15:43.083: E/AndroidRuntime(6202):  ... 11 more 

이 내 활동입니다 :

public class ParseActivity extends Activity { 



    static final String KEY_XML = "xml"; 

    static final String KEY_VERZE = "verze"; 
    static final String KEY_BKTYP = "bktyp"; 
    static final String KEY_STATUS = "status"; 
    static final String KEY_UTYP = "utyp"; 


    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_parse); 

     XML_Parser parser = new XML_Parser(); 
     String xml = "<xml><verze>1.0</verze><bktyp>LOGIN</bktyp><status>OK</status><utyp>R</utyp></xml>"; 

     Document doc = parser.getDomElement(xml); 

     NodeList nl = doc.getElementsByTagName(KEY_XML); 
     Element e = (Element) nl.item(1); 



     TextView parseview1 = (TextView) findViewById(R.id.parseview1); 
     TextView parseview2 = (TextView) findViewById(R.id.parseview2); 
     TextView parseview3 = (TextView) findViewById(R.id.parseview3); 

     parseview1.setText(parser.getValue(e,KEY_VERZE)); 
     parseview2.setText(parser.getValue(e,KEY_BKTYP)); 
     parseview3.setText(parser.getValue(e,KEY_STATUS)); 



     }; 
    } 

그리고 이것은 내 XML_Parser.class입니다 :

public class XML_Parser { 

    // constructor 
    public XML_Parser() { 

    } 

    /** 
    * Getting XML from URL making HTTP request 
    * @param url string 
    * */ 
    public String getXmlFromUrl(String url) { 
     String xml = null; 

     try { 
      // defaultHttpClient 
      DefaultHttpClient httpClient = new DefaultHttpClient(); 
      HttpPost httpPost = new HttpPost(url); 

      HttpResponse httpResponse = httpClient.execute(httpPost); 
      HttpEntity httpEntity = httpResponse.getEntity(); 
      xml = EntityUtils.toString(httpEntity); 

     } catch (UnsupportedEncodingException e) { 
      e.printStackTrace(); 
     } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
     // return XML 
     return xml; 
    } 

    /** 
    * Getting XML DOM element 
    * @param XML string 
    * */ 
    public Document getDomElement(String xml){ 
     Document doc = null; 
     DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); 
     try { 

      DocumentBuilder db = dbf.newDocumentBuilder(); 

      InputSource is = new InputSource(); 
       is.setCharacterStream(new StringReader(xml)); 
       doc = db.parse(is); 

      } catch (ParserConfigurationException e) { 
       Log.e("Error: ", e.getMessage()); 
       return null; 
      } catch (SAXException e) { 
       Log.e("Error: ", e.getMessage()); 
       return null; 
      } catch (IOException e) { 
       Log.e("Error: ", e.getMessage()); 
       return null; 
      } 

      return doc; 
    } 

    /** Getting node value 
     * @param elem element 
     */ 
    public final String getElementValue(Node elem) { 
     Node child; 
     if(elem != null){ 
      if (elem.hasChildNodes()){ 
       for(child = elem.getFirstChild(); child != null; child = child.getNextSibling()){ 
        if(child.getNodeType() == Node.TEXT_NODE ){ 
         return child.getNodeValue(); 
        } 
       } 
      } 
     } 
     return ""; 
    } 

    /** 
     * Getting node value 
     * @param Element node 
     * @param key string 
     * */ 
    public String getValue(Element item, String str) {  
      NodeList n = item.getElementsByTagName(str);   
      return this.getElementValue(n.item(0)); 
     } 
} 

당신이 그 문제를 볼 수 있을까요? 나는 새로운 안드로이드 dev에 그래서 나는 간단한 대답이 필요합니다.

Answer 1

NodeList.item은 NodeList의 index 위치에있는 노드를 반환하고, 유효한 인덱스가 아닌 경우 null을 반환합니다.

으로 XML이 단 하나의 요소 "XML",

NodeList nl = doc.getElementsByTagName(KEY_XML); 

및 yoyr 노드 목록의 크기가

Element e = (Element) nl.item(1); 

에

Element e = (Element) nl.item(0);