我试图在Java中使用Wolfram Alpha API作为应用程序，但在异步类方面存在问题

我有所有必要的进口货。如果有人能解释一下为什么我的输入流没有被读取，我将不胜感激。我相信是这样的，因为我的日志返回了一个异步类的问题，但更进一步地说，输入流似乎没有被读取为给定的url（尽管我可能错了）。提前谢谢

public class MainActivity extends Activity {

String[] currency;
EditText amount1;
TextView answer;
Spinner spin1;
Spinner spin2;

private InputStream OpenHttpConnection(String urlString) throws IOException
{
    InputStream in = null;

    int response = -1;

    URL url = new URL(urlString);
    URLConnection conn = url.openConnection();

    if(!(conn instanceof HttpURLConnection))
        throw new IOException("Not an HTTP Connection");
    try
    {
        HttpURLConnection httpConn = (HttpURLConnection) conn;
        httpConn.setAllowUserInteraction(false);
        httpConn.setInstanceFollowRedirects(true);
        httpConn.setRequestMethod("GET");
        httpConn.connect();
        response = httpConn.getResponseCode();
        if(response == HttpURLConnection.HTTP_OK)
        {
            in = httpConn.getInputStream();
        }

    }
    catch(Exception ex)
    {
        Log.d("Wolf Post", ex.getLocalizedMessage());
        throw new IOException("Error Connecting");
    }
    return in;
}

//method to send information and pull back xml format response
private String wolframAnswer(int currencyVal, String firstSelect, String secondSelect)
{
    //variables are assigned based of user select
    int pos1 = spin1.getSelectedItemPosition();
    firstSelect = currency[pos1];

    int pos2 = spin2.getSelectedItemPosition();
    secondSelect = currency[pos2];

    amount1 = (EditText)findViewById(R.id.editAmount1);
    answer = (TextView)findViewById(R.id.txtResult);

    InputStream in = null;

    String strWolfReturn = "";

    try
    {
        in = OpenHttpConnection("http://www.wolframalpha.com/v2/input="+currencyVal+firstSelect+"-"+secondSelect+"&appid=J6HA6V-YHRLHJ8A8Q");
        Document doc = null;
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db;

        try
        {
            db = dbf.newDocumentBuilder();
            doc = db.parse(in);
        }
        catch(ParserConfigurationException e)
        {
            e.printStackTrace();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

        doc.getDocumentElement().normalize();

        //retrieve the wolfram assumptions
        NodeList assumpElements = doc.getElementsByTagName("assumptions");

        //move through assumptions to correct one
        for (int i = 0; i < assumpElements.getLength(); i++)
        {
            Node itemNode = assumpElements.item(i);

            if(itemNode.getNodeType() == Node.ELEMENT_NODE)
            {
                //convert assumption to element
                Element assumpElly = (Element) itemNode;

                //get all the <query> elements under the <assumption> element
                NodeList wolframReturnVal = (assumpElly).getElementsByTagName("query");

                strWolfReturn = "";

                //iterate through each <query> element
                for(int j = 0; j < wolframReturnVal.getLength(); j++)
                {
                    //convert query node into an element
                    Element wolframElementVal = (Element)wolframReturnVal.item(j);

                    //get all child nodes under query element
                    NodeList textNodes = ((Node)wolframElementVal).getChildNodes();

                    strWolfReturn += ((Node)textNodes.item(0)).getNodeValue() + ". \n";
                }
            }

        }



    }
    catch(IOException io)
    {
        Log.d("Network activity", io.getLocalizedMessage());
    }

    return strWolfReturn;
}
//using async class to run a task similtaneously with the app without crashing it
private class AccessWebServiceTask extends AsyncTask<String, Void, String>
{
    protected String doInBackground(String... urls)
    {
        return wolframAnswer(100, "ZAR", "DOL");
    }
    protected void onPostExecute(String result)
    {
        Toast.makeText(getBaseContext(), result, Toast.LENGTH_LONG).show();
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    //spinner implementation from here down
    currency = getResources().getStringArray(R.array.currencies);

    spin1 = (Spinner)findViewById(R.id.spinCurr1);
    spin2 = (Spinner)findViewById(R.id.spinCurr2);

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, currency);

    spin1.setAdapter(adapter);
    spin2.setAdapter(adapter);

    //using httpget to send request to server.
    amount1 = (EditText)findViewById(R.id.editAmount1);
    answer = (TextView)findViewById(R.id.txtResult);

    Button convert = (Button)findViewById(R.id.btnConvert);

    convert.setOnClickListener(new Button.OnClickListener()
    {
        public void onClick(View v)
        {
            //apiSend();
            new AccessWebServiceTask().execute();
        }

    });


}

/*public void apiSend()
{
    int pos1 = spin1.getSelectedItemPosition();
    String firstSelect = currency[pos1];

    int pos2 = spin2.getSelectedItemPosition();
    String secondSelect = currency[pos2];

    amount1 = (EditText)findViewById(R.id.editAmount1);
    answer = (TextView)findViewById(R.id.txtResult);

    Toast.makeText(getBaseContext(), "Converting...", Toast.LENGTH_LONG).show();

    try
    {
        //encoding of url data
        String currencyVal = URLEncoder.encode(amount1.getText().toString(),"UTF-8");

        //object for sending request to server
         HttpClient client = new DefaultHttpClient();

         String url = "http://www.wolframalpha.com/v2/input="+currencyVal+firstSelect+"-"+secondSelect+"&appid=J6HA6V-YHRLHJ8A8Q";

         try
         {

             String serverString = "";

             HttpGet getRequest = new HttpGet(url);

             ResponseHandler<String> response = new BasicResponseHandler();

             serverString = client.execute(getRequest, response);
             Toast.makeText(getBaseContext(), "work 1work 1work", Toast.LENGTH_SHORT).show();
             answer.setText(serverString);
         }
         catch(Exception ex)
         {
             answer.setText("Fail 1");
         }
    }
    catch(UnsupportedEncodingException ex)
    {
        answer.setText("Fail 2");
    }

}*/

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

公共类MainActivity扩展活动{
字符串[]货币；
编辑文本数量1；
文本视图答案；
自旋器自旋1；
旋转器旋转2；
私有InputStream OpenHttpConnection（字符串urlString）引发IOException
{
InputStream in=null；
int响应=-1；
URL=新URL（URL字符串）；
URLConnection conn=url.openConnection（）；
if（！（HttpURLConnection的连接实例））
抛出新IOException（“非HTTP连接”）；
尝试
{
HttpURLConnection httpConn=（HttpURLConnection）conn；
httpConn.setAllowUserInteraction（假）；
httpConn.setInstanceFollowRedirects（真）；
httpConn.setRequestMethod（“GET”）；
httpConn.connect（）；
response=httpConn.getResponseCode（）；
if（response==HttpURLConnection.HTTP\u OK）
{
in=httpConn.getInputStream（）；
}
}
捕获（例外情况除外）
{
Log.d（“Wolf Post”，例如getLocalizedMessage（））；
抛出新IOException（“连接错误”）；
}
返回；
}
//方法发送信息并回调xml格式响应
私有字符串wolframAnswer（int currencyVal、字符串firstSelect、字符串secondSelect）
{
//变量是根据用户选择来分配的
int pos1=spin1.getSelectedItemPosition（）；
firstSelect=货币[pos1]；
int pos2=spin2.getSelectedItemPosition（）；
secondSelect=货币[pos2]；
amount1=（EditText）findViewById（R.id.editAmount1）；
答案=（TextView）findViewById（R.id.txtResult）；
InputStream in=null；
字符串strWolfReturn=“”；
尝试
{
in=OpenHttpConnection（“http://www.wolframalpha.com/v2/input=“+currencyVal+firstSelect+”-“+secondSelect+”&appid=J6HA6V-YHRLHJ8A8Q”）；
单据单据=空；
DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance（）；
文档生成器数据库；
尝试
{
db=dbf.newDocumentBuilder（）；
doc=db.parse（in）；
}
捕获（ParserConfiguration异常e）
{
e、 printStackTrace（）；
}
捕获（例外e）
{
e、 printStackTrace（）；
}
doc.getDocumentElement（）.normalize（）；
//检索wolfram假设
NodeList assumpElements=doc.getElementsByTagName（“假设”）；
//通过假设来纠正错误
对于（int i=0；iif(response == HttpURLConnection.HTTP_OK)
{
    in = httpConn.getInputStream();
}