Can't cast library class to fragment

Question

I added Yahoo weather library to m project. Then I tried to implement YahooWeatherInfoListener to the main fragment.

There is a problem.

Inside AsyncTask I can't cast YahooWeatherInfoListener to the fragment.

I think there is sth I'm doin wrong inside AsncTask. Please take a look:

import zh.wang.android.apis.yweathergetter4a.WeatherInfo;
import zh.wang.android.apis.yweathergetter4a.YahooWeather;
import zh.wang.android.apis.yweathergetter4a.YahooWeather.SEARCH_MODE;
import zh.wang.android.apis.yweathergetter4a.YahooWeatherInfoListener;
import android.app.Fragment;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class HomeFragment extends Fragment implements YahooWeatherInfoListener {

public HomeFragment(){}
private TextView Temperature;
private YahooWeather mYahooWeather = YahooWeather.getInstance(5000, 5000, true);

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_home, container, false);
    Temperature = (TextView) rootView.findViewById(R.id.txtLabel);
    new searchByGPS().execute();
    return rootView;
}
private class searchByGPS extends AsyncTask<Void, Void, Void>{
    @Override
    protected void onPreExecute() {
    }

    @Override
    protected Void doInBackground(Void... unused) {
        mYahooWeather.setNeedDownloadIcons(true);
        mYahooWeather.setSearchMode(SEARCH_MODE.GPS);
        mYahooWeather.queryYahooWeatherByGPS(getActivity().getApplicationContext(), (YahooWeatherInfoListener) this);

        return null;
    }
    protected void onPostExecute(Void unused) {

    }
}
@Override
public void gotWeatherInfo(WeatherInfo weatherInfo) {
    // TODO Auto-generated method stub
    Temperature.setText(weatherInfo.getCurrentTempC());
}
}

Answer 1

protected Void doInBackground(Void... unused) {
        mYahooWeather.setNeedDownloadIcons(true);
        mYahooWeather.setSearchMode(SEARCH_MODE.GPS);
        mYahooWeather.queryYahooWeatherByGPS(getActivity().getApplicationContext(), (YahooWeatherInfoListener) HomeFragment.this);

        return null;
    }

You have to change your this to HomeFragment.this because this is directly connected to your AsyncTask.

Answer 2

That's because in

(YahooWeatherInfoListener) this

this refers to the AsyncTask. Instead, you need to use:

(YahooWeatherInfoListener) HomeFragment.this

The cleaner way to implement this would be:

private class SearchByGPSTask extends AsyncTask<Void, Void, Void>{

    private YahooWeatherInfoListener mListener;

    public SearchByGPSTask( YahooWeatherInfoListener listener ) {
        super();
        mListener = listener;
    }

    @Override
    protected void onPreExecute() {
    }

    @Override
    protected Void doInBackground(Void... unused) {
        mYahooWeather.setNeedDownloadIcons(true);
        mYahooWeather.setSearchMode(SEARCH_MODE.GPS);
        mYahooWeather.queryYahooWeatherByGPS(getActivity().getApplicationContext(), mListener );

        return null;
    }
    protected void onPostExecute(Void unused) {

    }
}

(note: Classes are generally uppercase, and better nouns -- "searchByGPS" sounds like a method, while "SearchByGPSTask" indicates that it's a class meant to do something.)

Answer 3

With this line mYahooWeather.queryYahooWeatherByGPS(getActivity().getApplicationContext(), (YahooWeatherInfoListener) this);, you are trying to cast the AsyncTask to a YahooWeatherInfoListener. Use HomeFragment.this instead