So this is related to a question I asked earlier. I am trying to display an alert using a specified layout. My layout is:

And the code to call and show the alert dialog is:

Context mContext = getApplicationContext();

    AlertDialog.Builder builder = new AlertDialog.Builder(mContext);
    // use a custom View defined in xml
    View view = LayoutInflater.from(mContext).inflate(R.layout.sell_dialog,      (ViewGroup) findViewById(R.id.layout_root));
    builder.setView(view);
    builder.setPositiveButton(android.R.string.ok, new OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {

            // do whatever you want with the input
        }
    });
    AlertDialog alertDialog = builder.create();

    alertDialog.show();

When I run it I get an error saying:

Uncaught handler: thread main exiting due to uncaught exception android.view.WindowManager$NadTokenException: Unable to add window -- token null is not for an application

I've looked through the android development site and can't figure it out. I think I'm just missing something obvious but the fix isn't jumping out at me. How can I get this alert dialog to display?