onPostExecute上的java.lang.NullPointerException？

Question

我有這個類在我發送SOAP請求到服務器。我有我的主類，一個AsyncTask類，一個解析器類，一個接口。我的問題是我總是得到這個NullpointerException。我想要做的是在我的主要活動我會發送一個字符串到AsyncTask，然後在AsyncTask onPostExecute的結果，我需要將它傳遞給解析器類，在這一部分我有問題。我使用我以前的問題的接口，但它不工作。

的AsyncTask類：

public class TestAsyncTask extends AsyncTask<String, Void, String> { 

public TestInterface delegate = null; 
String soapString = "http://-------------"; 
String serverString = "https:-----------"; 

@Override 
protected String doInBackground(String... sString) { 
String yourValue = sString[0]; 
String resString = null; //This will be the storage of the response. 

try { 

    //Uses URL and HttpURLConnection for server connection 
    URL url = new URL(serverString); 
    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); 
    urlConnection.setDoOutput(true); 
    urlConnection.setDoInput(true); 
    urlConnection.setUseCaches(false); 
    urlConnection.setChunkedStreamingMode(0); 
    urlConnection.addRequestProperty("SOAPAction", soapString); 
    urlConnection.addRequestProperty("Content-Type", "text/xml; charset=utf-8"); 
    urlConnection.addRequestProperty("Content-Length", "" + yourValue.length()); 
    urlConnection.setRequestMethod(HttpPost.METHOD_NAME); 

    // Using OutputStream and Writer to send a request to the server. 
    OutputStream outputStream = urlConnection.getOutputStream(); 
    Writer writer = new OutputStreamWriter(outputStream); 
    writer.write(yourValue); 
    writer.flush(); 
    writer.close(); 

    //Using InputStream to get the response of the request from the server. 
    InputStream inPutStream = urlConnection.getInputStream(); 
    BufferedReader buffReader = new BufferedReader(new InputStreamReader(inPutStream)); 
    ByteArrayBuffer byteBuffer = new ByteArrayBuffer(50); 

    int resint = urlConnection.getResponseCode(); 

    while ((resint = buffReader.read()) != -1) { 
     byteBuffer.append(resint); 
    } 

    resString = new String(byteBuffer.toByteArray()); 

    } catch (Exception aException) { 
    resString = aException.getMessage(); 
    } 

    return resString; 
} 


protected void onPostExecute(String aReturnValueString) { 
    //I THINK HERE IS WHERE THE PROBLEM EXIST 
      delegate.processFinish(aReturnValueString); 
} 
} 

接口，這林不知道：

public interface TestInterface { 
    void processFinish(String output); 
} 

解析類：

public class TestParser implements TestInterface { 

TestAsyncTask a= new TestAsyncTask(); 
TextView oTextView[], aTextView[], pTextView[], dTextView[]; //Create a new TextView array to store the parsing results. 
private LinearLayout linearLayout; 
int pars; 

Context contxt; 

//Constructor 
public TestParser(Context cContext){ 
    contxt = cContext; //Pass Context to constructor 
} 

//Getter for LinearLayout. 
    public LinearLayout getLinearLayout(){ 
     return linearLayout; 
    } 
    //Setter for LinearLayout. 
    public void setLinearLayout(LinearLayout aSetterLinearLayout){ 
     this.linearLayout = aSetterLinearLayout; 
    } 


    public void onCreate(Bundle savedInstanceState) { 
    a.delegate = this; 
    } 

public void processFinish(String output) { 
    // TODO Auto-generated method stub 
    linearLayout = new LinearLayout(this); 

    //The try/catch statement encloses some code and is used to handle errors and exceptions that might occur in that code. 
    try { 

     //Use SAXParser(Simple API for XML) to handle the parsing of XML(Response). */ 

     SAXParserFactory saxParF = SAXParserFactory.newInstance(); 
     SAXParser sAXPar = saxParF.newSAXParser(); 
     XMLReader xMLReader = sAXPar.getXMLReader(); 

     // Create handler to handle XML Tags (GBXMLHandler extends DefaultHandler).   
     TestXMLHandler xMLHandler = new TestXMLHandler(); 
     xMLReader.setContentHandler(xMLHandler); 
     InputSource inputSource = new InputSource(new StringReader(output)); 
     xMLReader.parse(inputSource); 

     TestData data = TestXMLHandler.aData; 

     int aone = data.getoName().size(); 
     int atwo = data.getDes().size(); 

     oTextView = new TextView[aone]; 
     aTextView = new TextView[aone]; 
     dTextView = new TextView[atwo]; 
     pTextView = new TextView[atwo]; 

     //The for statement provides a compact way to iterate over a range of values. 
     for (pars = 0; pars + 1 < atwo; pars++) { 

     dTextView[pars] = new TextView(getApplicationContext()); 
     dTextView[pars].setText("Description = " + data.getDes().get(pars)); 
     linearLayout.addView(dTextView[pars]); 

     pTextView[pars] = new TextView(getApplicationContext()); 
     pTextView[pars].setText("RegularSellUnitPrice = " + data.getRegularSellUnitPrice().get(pars)); 
     linearLayout.addView(pTextView[pars]); 
     } 

     for (pars = 0; pars < aone; pars++){ 
     oTextView[pars] = new TextView(getApplicationContext()); 
     oTextView[pars].setText("OperatorName = " + data.getoName().get(pars)); 
     linearLayout.addView(oTextView[pars]); 

     aTextView[pars] = new TextView(getApplicationContext()); 
     aTextView[pars].setText("type = " + data.getType().get(pars)); 
     linearLayout.addView(aTextView[pars]);  
     } 
    } catch (Exception e) { 
     System.out.println("XML Pasing Exception = " + e); 
    } 
} 
} 

Answer 1

在我看來，像你delegate對象永遠不會被instansiated 。

聲明它作爲null從來就不是調用delegate = new TestParser()