來自網站API的值總是返回爲零

Question

public class MainActivity extends Activity { 

TextView httpStuff; 
HttpClient client; 
JSONObject json; 
final static String URL = "http://pubapi.cryptsy.com/api.php?method=singlemarketdata&marketid=462"; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    //StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build(); 
    //StrictMode.setThreadPolicy(policy); 
    httpStuff = (TextView) findViewById(R.id.price); 
    client = new DefaultHttpClient(); 
    new Read().execute("lasttradeprice"); 
} 
public JSONObject lastPrice(String username) 
     throws ClientProtocolException, IOException, JSONException{ 
    StringBuilder url = new StringBuilder(URL); 
    //url.append(username); 


    HttpGet get = new HttpGet(url.toString()); 
    HttpResponse r = client.execute(get); 
    int status = r.getStatusLine().getStatusCode(); 
    if (status == 200){ 
     HttpEntity e = r.getEntity(); 
     String data = EntityUtils.toString(e); 
     JSONArray timeline = new JSONArray(data); 
     JSONObject last = timeline.getJSONObject(0); 
     return last; 
    }else{ 
     //Toast.makeText(HttpExample.this, "error", Toast.LENGTH_LONG); 
     return null; 
    } 
} 

public class Read extends AsyncTask<String, Integer, String>{ 

    @Override 
    protected void onPostExecute(String result) { 
     httpStuff.setText("Price" + result + "357"); 
    } 

    @Override 
    protected String doInBackground(String... params) { 
     try { 
      json = lastPrice("lasttradeprice"); 
      return json.getString(params[0]); 
     } catch (ClientProtocolException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } catch (JSONException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
     return null; 
    } 

} 


@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; 

} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 
    if (id == R.id.action_settings) { 
     return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 
} 

當我從網站api獲取lasttradeprice時，我什麼也得不到。 所以當我運行應用程序時，textview只是null。 這個問題可能是因爲應用程序無法訪問android，即使我在清單中給予權限？

Answer 1

該URL的JSON結構返回因爲如此，

{ 
    "success":1, 
    "return":{ 
     "markets":{ 
     "CLAM":{ 
      "marketid":"462", 
      "label":"CLAM\/BTC", 
      "lasttradeprice":"0.00280009", 
      ...... 

所以，針對lasttradeprice值將如下所示，

json = lastPrice("lasttradeprice"); 
    return json.getJSONObject("return") 
       .getJSONObject("markets") 
       .getJSONObject("CLAM") 
       .getString(params[0]);