Ndtyjky

I have a top-level Fetch class that extends AsyncTask and I have a MainActivity. I can't get the Fetch class to make a toast due to not having an instance of the MainActivity or its context. I have tried to pass the MainActivity to the Fetch class but it potentially leaks memory. I have tried setting a WeakReference instance of the context, but I can't make a toast from that.

I have read many other posts about this and most seem to have a static inner-class but mine is top-level and I would prefer to keep it that way.

The MainActivity creates an instance of Fetch and then executes it.

public class Fetch extends AsyncTask<Void, Integer, List<List<String>>>

    {

    @Override

    protected void onPreExecute()

        {

        super.onPreExecute();

        }

    @Override

    protected List<List<String>> doInBackground(Context... params)

        {

        // run tasks

        }

    @Override

    protected void onProgressUpdate(Integer... progress)

        {

        }

    @Override

    protected void onPostExecute(List<List<String>> result)

        {

        super.onPostExecute(result);

        }

    }

One way, in doInBackground:

runOnUiThread(new Runnable() {

public void run() {

        Toast.makeText(<your class name>.this, "hello", Toast.LENGTH_SHORT).show();

    }

});

Or in onPostExecute(which invoked on the UI thread after the background computation finishes)

Toast.makeText(<your class name>.this, "hello", Toast.LENGTH_SHORT).show();

Edited: if you want to pass context to AsyncTask，you could do like:

public class MyAsyncTask extends AsyncTask<Void, Integer, List<List<String>>>



    private final Context mContext;



    public MyAsyncTask(final Context context) {

         mContext = context;

    }

}

And in MainActivity ：

final MyAsyncTask task = new MyAsyncTask(getApplicationContext());

task.execute();

Edited again:
I tested WeakReference successfully.

public class ExampleAsyncTask extends AsyncTask {

    private WeakReference<Context> contextRef;



    public ExampleAsyncTask(Context context) {

        contextRef = new WeakReference<>(context);

    }





    @Override

    protected void onPostExecute(Object result) {

        Context context = contextRef.get();

        if (context != null) {

            Toast.makeText(context, "hello", Toast.LENGTH_SHORT).show();

        }

    }

}

In MainActivity:

  new ExampleAsyncTask(MainActivity.this).execute();

yeah,Don't be worry ，you can use the application context.may be as follow:

implement your App.getContext() in your Application.

and use it in your "Fetch" class and execute it in MainThread.