Toast from implemented callback

Question

I have an activity that roughly follows this structure:

public class myActivity extends Activity implements myCallback{
   //Code

   @Override
   public void onCreate(Bundle savedInstaceState){
       super.onCreate(savedInstanceState);
       new myAsyncTask(myActivity.this).execute();
   }
   public void myCallback(Context context){
   //Code
   Toast.makeText(context,"Hello",Toast.LENGTH_SHORT).show();
   }
}

And myAsyncTask has the myCallback() interface defined and it calls it eventually. No matter what I do, whatever UI element I try to show, be it a Toast or a ProgressDialog, it won't show. Nor do I get any exceptions. The rest of the callback code gets perfectly executed. Why is this?

In which method of your asynctask are you calling myCallback()? doInBackground or onPostExecute()? And why are you passing the Activity to the constructor of the AsyncTask? — Dirk Jäckel, Aug 23 '12 at 19:01
Please consider starting Class and Interface names with an upper case character. — Dirk Jäckel, Aug 23 '12 at 19:03

score 0 · Answer 1 · answered Aug 23 '12 at 10:26

0

Try using:

public class myActivity extends Activity implements myCallback{
   //Code
   Context mContext;


   @Override
   public void onCreate(Bundle savedInstaceState){
       super.onCreate(savedInstanceState);
       mContext = this;
       new myAsyncTask(getApplicationContext()).execute();
   }
   public void myCallback(Context context){
   //Code
   Toast.makeText(mContext,"Hello",Toast.LENGTH_SHORT).show();
   }
}

answered Aug 23 '12 at 10:26

Raghav Sood

81,899
22
187
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Is the only difference the use of the mContext field? Didn't work. – Moises Jimenez Aug 23 '12 at 10:29
Nothing regarding this, as far as I can tell. – Moises Jimenez Aug 23 '12 at 10:33
If you move Toast.makeText() into the onCreate method, does it work? – Raghav Sood Aug 23 '12 at 10:36
It's working now. I just restarted the phone. Must have been some weird issue. – Moises Jimenez Aug 23 '12 at 10:40
Just one final question, when my AsyncTask calls the callback, is it being executed from within the main activity or within the AsyncTask? – Moises Jimenez Aug 23 '12 at 10:48
It'll be executed from the Activity. However, i think the problem was that you were creating a new instance of the Activity in the AsyncTask to call the method, which meant that your Context could be null or incorrect. – Raghav Sood Aug 23 '12 at 10:49
Run it in the debugger and see what "context" is being set as. and isnt the onPostExecute() method used for displaying changes to the UI? – shecodesthings May 15 '13 at 18:49

score 0 · Answer 2 · answered Aug 23 '12 at 11:11

0

Instead of using context , use getApplicationContext... i hope it will show toast... like this

   Toast.makeText(getApplicationContext(),"Hello",Toast.LENGTH_SHORT).show();

answered Aug 23 '12 at 11:11

G M Ramesh

3,420
9
37
53

Toast from implemented callback

2 Answers2