How to correctly start activity from PostExecute in Android?

Question

I have an AsyncTask, that fills a custom List with parsed data from Internet.

In PostExecute I fill that List and get it ready to transfer it to a new Activity.

I do it this way:

@Override protected void onPostExecute(List<VideoDataDescription> result)  {     super.onPostExecute(result);     MainActivity.progressDialog.dismiss();      context.startActivity(new Intent(context, ResultsQueryActivity.class));   } 

where context

    private Context context; 

In LogCat after executing this code I get a Java.lang.NullPointerException. Is this possible and correct to start an Activity as I do it?

UPD I have added

    private Context mContext;   public YoutubeAndYahooParser(Context context)  {     super();     this.mContext = context; } 

to initialize context and call

YoutubeAndYahooParser youtubeAndYahooParser = new YoutubeAndYahooParser(ResultsQueryActivity.this);                     youtubeAndYahooParser.execute("my string to pass in asynctak"); 

After this in PostExecute

Intent intent = new Intent(mContext, ResultsQueryActivity.class);  intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);  mContext.startActivity(intent);     

I added new flag because of I have got in LogCat the next:

*Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?*

Am I right?

Answer 1

You should pass in the application context rather than a context from the local activity. I.e. use context.getApplicationContext() and save that in a local variable in your AsyncTask subsclass.

The code might looks something like this:

public class MyAsyncTask extends AsyncTask {      Context context;     private MyAsyncTask(Context context) {         this.context = context.getApplicationContext();     }      @Override     protected Object doInBackground(Object... params) {         ...     }      @Override     protected void onPostExecute(List<VideoDataDescription> result) {         super.onPostExecute(result);         MainActivity.progressDialog.dismiss();          context.startActivity(new Intent(context, ResultsQueryActivity.class));     } } 

you'd call it like this:

   new MyAsyncTask(context).execute();