How to add AsyncTask to a public class with no activity?

Issue

I have a class which has function of getJSON from an url. There is no problem with the code, I think. But it gives me android.os.NetworkOnMainThreadException . I should use AsyncTask but I can not do that with myself. Can we add AsyncTask to any class like my JsonCreator class? My class definition is;

public class JsonCreator{
private String Url = Constants.url;
JSONObject result = null;
JSONArray json = null;
Connect connect = new Connect();

public JSONArray getJson(String command, String[] parameter, int connectionMode){
    String urlParameter = null;

    //Creating parameter which will be added to the end of the URL
    for(int i=0 ; i<parameter.length-1 ; i=i+2){
        if(i == 0)
            urlParameter = "?" + parameter[i] + "=" + parameter[i+1];
        else
            urlParameter = urlParameter + "&" + parameter[i] + "=" + parameter[i+1];
    }

    //First Scenario
    if(connectionMode == 1){

        //Control host availability and take Json Array
        try {
            result = connect.connect(Url+command+urlParameter);
            Constants.hostReachability = Constants.isHostRechable(Url+command+urlParameter);
            json = result.getJSONArray("d");
        } catch (Exception e) {
            e.printStackTrace();
        }

        //Save JsonArray to SharedPrefs
        Constants.saveJSONArray(Constants.context, "Json", command, json);
    }

    //Second Scenario
    else if(connectionMode == 2){

        //Control host availability and take Json Array
        try {
            result = connect.connect(Url+command+urlParameter);
            Constants.hostReachability = Constants.isHostRechable(Url+command+urlParameter);
            json = result.getJSONArray("d");
        } catch (Exception e) {
            e.printStackTrace();
        }

        //If json can not be taken from URL, Search for data from SharedPrefs
        if(json == null || !Constants.hostReachability){
            try {
                json = Constants.loadJSONArray(Constants.context, "Json", command);
            } catch (JSONException e) {
                Constants.connectionProblem = "No Data";
                e.printStackTrace();
            }
        }
    }
    //Third Scenario
    else if(connectionMode == 3){

        //Take data from SharedPrefs
        try {
            json = Constants.loadJSONArray(Constants.context, "Json", command);
        } catch (JSONException e) {
            Constants.connectionProblem = "No Data";
            e.printStackTrace();
        }

        //If the data from SharedPref can not be found, Take json from URL
        if(json == null){
            //Control host availability and take Json Array
            try {
                result = connect.connect(Url+command+urlParameter);
                Constants.hostReachability = Constants.isHostRechable(Url+command+urlParameter);
                json = result.getJSONArray("d");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    return json;
}

public JSONArray getJson(String command, String[] parameter){
    String urlParameter = null;
    //Creating parameter which will be added to the end of the URL
    for(int i=0 ; i<parameter.length ; i=i+2){
        if(i == 0)
            urlParameter = "?" + parameter[i] + "=" + parameter[i+1];
        else
            urlParameter = urlParameter + "&" + parameter[i] + "=" + parameter[i+1]; 
    }
    //Take json from server
    try {
        result = connect.connect(Url+command+urlParameter);
        Constants.hostReachability = Constants.isHostRechable(Url+command+urlParameter);
        json = result.getJSONArray("d");
    } catch (Exception e) {
        e.printStackTrace();
    }
    return json;
}

}

Solution

You getandroid.os.NetworkOnMainThreadException because you are running network related operation on the ui thread. Use AsyncTask or Thread.

http://developer.android.com/reference/android/os/AsyncTask.html

Check the topic under threading rules in the above link

Invoke asynctask like

  new TheTask().execute(); // you can pass values to asynctask doinbackground

Then

public class TheTask extends AsyncTask <Void,Void,Void>
{

@Override
protected void onPreExecute() {
    super.onPreExecute();
            // display progress dialog

}
@Override
protected Void doInBackground(Void... params) {
        // your background computation. do not update ui here
        // your getjson method code here
    return null; //return result of doinbackground computation 
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
         //dismiss progress dialog
         // recieve result and update ui
    }
}

As codemagic suggested your class can extend asynctask and call appropriate methods in doInbackground.

To return result back to the activity use a interface. Check the example below

Can't post response from AsyncTask to MainActivity

Answered By - Raghunandan