AlertDialog.Builder builder = new AlertDialog.Builder(Config.this);

            builder.setMessage("Hola");
            builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    Toast toast = Toast.makeText(Config.this,"hola",Toast.LENGTH_SHORT);
                    toast.show();
                }
            });
            builder.setNegativeButton("cancela", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    Toast toast = Toast.makeText(Config.this,"adios",Toast.LENGTH_SHORT);
                    toast.show();
                }
            });
            AlertDialog dialog = builder.create();
            dialog.show();