Question

我正在尝试创建一个可以更新多个城市天气的应用程序。每行都有不同的温度，所以我使用了AsynkTask。但是我从API获得响应后无法更新UI。

我的主要活动

public class MainActivity extends Activity {
    LinearLayout depart_arrivals_details;
    LayoutInflater inflater;
    TextView depart_time,
    depart_airport_city, depart_airport, arrival_time,
    arrival_airport_city, arrival_airport, pnr_number,temprature,humidity;
    ImageView flight_depart_image;
    public static String url = "";
    WeatherResponse response;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        depart_arrivals_details = (LinearLayout) findViewById(R.id.depart_arrivals_details);
        inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        setSectorData();
    }

    void setSectorData() {
        for (int i = 0; i < 1; i++) {
            inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            RelativeLayout layout = (RelativeLayout) inflater.inflate(
                    R.layout.sector_details, depart_arrivals_details, false);
            depart_time = (TextView)layout.findViewById(R.id.depart_time);
            depart_airport_city = (TextView)layout.findViewById(R.id.depart_airport_city);
            temprature = (TextView)layout.findViewById(R.id.temprature);
            humidity = (TextView)layout.findViewById(R.id.humidity);
            flight_depart_image = (ImageView)layout.findViewById(R.id.flight_depart_image);
            WeatherResponse responseUpdate = requestWeatherUpdate("DEL");

        depart_time.setText("20:45");
        depart_airport_city.setText("Mumbai");
        /*
         * This part will be updated when we will se the request and get the response 
         * then we have to set the temp and humidity for each city that we have recived
         * */
        temprature.setText(responseUpdate.getTempInC()+(char) 0x00B0);//Here it is showing null pointer exception after that the respone is coming from the server .So can we do this 
        humidity.setText(responseUpdate.getHumidity());

            flight_depart_image.setImageResource(R.drawable.f1);

            depart_arrivals_details.addView(layout, i);
        }
    }

    /*
     * Here the location will be dynamic and have to send the request for all the location i have 
     * */
    private WeatherResponse requestWeatherUpdate(String location) {
        url = "http://api.worldweatheronline.com/free/v1/weather.ashx?&format=xml&num_of_days=2&key=uysakmq923nbd5y549yz3aaw&q="
                + location;
        Log.d("URL for Weather Upadate", url);
        WeatherUpdateAsyncTask weatherReq = new WeatherUpdateAsyncTask(new CallBack() {
            @Override
            public void run(Object result) {
                try {
                    String AppResponse = (String) result;
                    response = ParseWeatherResponseXML
                            .parseMyTripXML(AppResponse);
                } catch (Exception e) {
                    Log.e("TAG Exception Occured",
                            "Exception is " + e.getMessage());
                }
            }
        });
        weatherReq.execute(url);
        return response;

    }

这是我的 requestWeatherUpdate

   private WeatherResponse requestWeatherUpdate(String location) {
        url = ""
                + location;
        Log.d("URL for Weather Upadate", url);
        WeatherUpdateAsyncTask weatherReq = new WeatherUpdateAsyncTask(new CallBack() {
            @Override
            public void run(Object result) {
                try {
                    String AppResponse = (String) result;
                    response = ParseWeatherResponseXML
                            .parseMyTripXML(AppResponse);
                } catch (Exception e) {
                    Log.e("TAG Exception Occured",
                            "Exception is " + e.getMessage());
                }
            }
        });
        weatherReq.execute(url);
        return response;

    }

如果我尝试设置我收到的值是抛出空指针异常

Answer 1

使用Views的{{1}}获得结果后，您可以更新在用户界面Thread上运行的AsyncTask。此外，您需要致电onPostExecute() AsyncTask，execute()才能真正开始。

Answer 2

试试这个

首先在 for循环

中

depart_arrivals_details.removeAllViews();
 for (int i = 0; i < 2; i++) {
            requestWeatherUpdate("BLR");
            }

功能WeatherResponse

private WeatherResponse requestWeatherUpdate(String location) {
        url = ""
                + location;
        Log.d("URL for Weather Upadate", url);
        WeatherUpdateAsyncTask weatherReq = new WeatherUpdateAsyncTask();
        String weatherRequestResponse="";
        try {
            weatherRequestResponse=weatherReq.execute(url).get();
            parsedWeatherResponse = ParseWeatherResponseXML
                    .parseMyTripXML(weatherRequestResponse);
        } catch (InterruptedException e) {

            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ParserConfigurationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return parsedWeatherResponse;

    }

然后 AsynkTask

public class WeatherUpdateAsyncTask extends AsyncTask<String, Void, String> {
    Context context;
    CallBack callBack;

   @Override
    protected String doInBackground(String... arg0) {
        String responseString = "";
        HttpClient client = null;
        try {
            client = new DefaultHttpClient();
            HttpGet get = new HttpGet(arg0[0]);
            client.getParams().setParameter("http.socket.timeout", 6000);
            client.getParams().setParameter("http.connection.timeout", 6000);
            HttpResponse responseGet = client.execute(get);
            HttpEntity resEntityGet = responseGet.getEntity();
            if (resEntityGet != null) {
                responseString = EntityUtils.toString(resEntityGet);
                Log.i("GET RESPONSE", responseString.trim());
            }
        } catch (Exception e) {
            Log.d("ANDRO_ASYNC_ERROR", "Error is " + e.toString());
        }
        Log.d("ANDRO_ASYNC_RESPONSE", responseString.trim());
        client.getConnectionManager().shutdown();
        return responseString.trim();

    }

    @Override
    protected void onPostExecute(String result) {
       super.onPostExecute(result);
    }

}

异步任务调用循环不给值返回

2 个答案: