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);
}
}

当我从网站api获得lasttradeprice时，我什么都没得到。因此，当我运行应用程序时，textview只是null。这个问题可能是因为即使我在清单中给出了许可，app也无法访问Android吗？

Answer 1

该url的json结构返回，

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

因此，定位lasttradeprice值如下，

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

来自网站api的值不断返回为null

1 个答案: