Filter Specific Apps In Android

I have to filter the android application using intent.action_send.If in my device having twitter app means go to twitter application.otherwise have to display the toast message.

In my device twitter application is available.But am getting the toast message and also its going to twitter application.In these situation my app going to twitter application.but don't display the toast message.

final CharSequence[] items = { "Twitter", "Facebook", "Gmail" };
AlertDialog.Builder builder = new AlertDialog.Builder( HomePage.this);
builder.setTitle("Share Via:");
builder.setItems(items, new DialogInterface.OnClickListener() {
[code]...