Android 4.0中的类无响应-在2.3及以下版本中有效

Question

I've got a class, GetWeather.java, which fetches weather data from an API. It is called from the main activity of my app periodically via a separate thread. The thread hits the GetWeather class and posts the returned data to a TextView.

In either case a System.out.println of the returned data from within the GetWeather class shows that the data is indeed being returned.

Below is GetWeather.java:

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.net.Uri;
import android.util.Log;

public class GetWeather {

    InputStream is = null;

    JSONArray jArray = null;
    JSONObject json_data = new JSONObject();
    String result = "";

    String strTemp = "";
    String strWindSpeed = "";
    String strWindDir = "";
    String strVisibility = "";

    String strPosition = "";

    public static final Uri KEY_121 = Uri.parse("http://api.worldweatheronline.com/free/v1/weather.ashx");
    String strWeatherApiKey = "REMOVED";

    public GetWeather(String Location) {
        strPosition = Location;
    }

    public void returnWeather() {
        try {
            HttpClient httpclient = new DefaultHttpClient();

            HttpPost httppost = new HttpPost(KEY_121 + "?key="
                    + strWeatherApiKey + "&q=" + strPosition + "&format=json");

            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();

        } catch (Exception e) {
            Log.e("log_tag", "Error in http connection " + e.toString());
        }

        // convert response to string
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            result = sb.toString();

        } catch (Exception e) {
            Log.e("log_tag", "Error converting result " + e.toString());
        }
        // parse json data
        try {
            JSONObject object = new JSONObject(result);
            JSONObject weather = object.getJSONObject("data");
            JSONArray current_conditions = weather
                    .getJSONArray("current_condition");
            for (int i = 0; i < current_conditions.length(); i++) {
                JSONObject object1 = (JSONObject) current_conditions.get(i);
                strTemp = object1.getString("temp_C");
                strWindSpeed = object1.getString("windspeedMiles");
                strWindDir = object1.getString("winddir16Point");
                strVisibility = object1.getString("visibility");

                // Testing output
                System.out.println(strTemp);
                System.out.println(strWindSpeed);
                System.out.println(strWindDir);
                System.out.println(strVisibility);
            }
        } catch (JSONException e) {
            Log.e("log_tag", "Error parsing data " + e.toString());
        }
    }
}

Here is the relevant code from the main activity:

Runnable updateConsoleRunnable = new Runnable() {
    public void run() {
        tvConsole.setMovementMethod(new ScrollingMovementMethod());
        tvConsole.setSelected(true);

        handler.postDelayed(this, TIME_DELAY);

        // Only display weather data while service is enabled
        if (isServiceRunning()) {
            GetWeather weather = new GetWeather(strPosition);
            weather.returnWeather();

            // Weather package
            tvConsole
                    .append("Weather Update\n-------------------\n\nCurrent Temp (C): "
                            + weather.strTemp
                            + "C\n"
                            + "Wind is out of the "
                            + weather.strWindDir
                            + " at "
                            + weather.strWindSpeed
                            + " MPH\n"
                            + "Visibility is "
                            + weather.strVisibility
                            + " miles\n\n");

            // Auto-scroll textview
            // Does not function on Android 4.0+
            final Layout layout = tvConsole.getLayout();
            if (layout != null) {
                int scrollDelta = layout.getLineBottom(tvConsole
                        .getLineCount() - 1)
                        - tvConsole.getScrollY()
                        - tvConsole.getHeight();
                if (scrollDelta > 0)
                    tvConsole.scrollBy(0, scrollDelta);
            }

        }

    }
};

As I mentioned previously, this works as expected in Gingerbread and FroYo , but ICS and JellyBean OS fail to see the variables set by GetWeather. I think, I read somewhere this has something to do with needing an AsyncTask, but I am not able to make-out heads or tails of it.

Advance Thanks

Answer 1

you cannot touch anything in the ui thread from a background thread, to do that use Handlers, initialize your background thread passing it a Handler object. When data arrives use the handler to send a message to the ui. In the ui when the message from the background thread comes, just update the Views.

Answer 2

Try to use async task like this,

In your main activity,

public class GetWeather extends AsyncTask<Void, Integer, Void> {



    public GetWeather(Activity activity) {
        this.activity = activity;


        context = activity;
        dialog = new ProgressDialog(context);


    }

    /** progress dialog to show user that the backup is processing. */
    private ProgressDialog dialog;
    /** application context. */
    private Activity activity;
    private Context context;



    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();






    }

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub


        GetWeather weather = new GetWeather(strPosition);
        weather.returnWeather();


        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);



                     tvConsole
                .append("Weather Update\n-------------------\n\nCurrent Temp (C): "
                        + weather.strTemp
                        + "C\n"
                        + "Wind is out of the "
                        + weather.strWindDir
                        + " at "
                        + weather.strWindSpeed
                        + " MPH\n"
                        + "Visibility is "
                        + weather.strVisibility
                        + " miles\n\n");

        // Auto-scroll textview
        // Does not function on Android 4.0+
        final Layout layout = tvConsole.getLayout();
        if (layout != null) {
            int scrollDelta = layout.getLineBottom(tvConsole
                    .getLineCount() - 1)
                    - tvConsole.getScrollY()
                    - tvConsole.getHeight();
            if (scrollDelta > 0)
                tvConsole.scrollBy(0, scrollDelta);
        }




                     }



  }

And call it like,

new GetWeather(Mainactivity.this).execute();