Whatsapping a chosen contact, Android

Question

I've been looking at other answers in this forum but i didn't find a complete one. I wanna send a message through whatsapp to an specific number. Say this number is 123456789.

The two possibilities i've seen are these ones:

1. The problem here is that you have to choose to whom you wanna send the messsage:

   Intent whatsapp = new Intent(Intent.ACTION_SEND);
   whatsapp.setPackage("com.whatsapp");
   whatsapp.setType("text/plain");
   whatsapp.putExtra(Intent.EXTRA_TEXT, "Hello World");
   startActivity(whatsapp);
   

2. In this case, the user is selected correctly but the text isn't added:

   String whatsappid = "123456789@s.whatsapp.net";
   Cursor c = getContentResolver().query(ContactsContract.Data.CONTENT_URI,
           new String[] { ContactsContract.Contacts.Data._ID }, ContactsContract.Data.DATA1 + "=?",
           new String[] { whatsappid }, null);
   c.moveToFirst();
   
   Intent whatsapp = new Intent(Intent.ACTION_VIEW, Uri.parse("content://com.android.contacts/data/" + c.getString(0)));
   c.close();
   
   whatsapp.putExtra(Intent.EXTRA_TEXT, "Hello World");
   startActivity(whatsapp);
   

When I try to mix both solutions either the ActivityNotFoundException is thrown (if i set the whatsapp as the package to use) or the wrong application is launched (in case i don't use ACTION_SEND). I've tried with ACTION_SENDTO and it doesn't work either.

I know someone is gonna mark it as duplicated... Anyway, I'll take the risk.

May anyone help me?