In the Android docs on AlertDialog, it gives the following instruction and example for setting a custom view in an AlertDialog:
If you want to display a
You are correct, it's because you didn't manually inflate it. It appears that you're trying to "extract" the "body" id from your Activity's layout, and that won't work.
You probably want something like this:
LayoutInflater inflater = getLayoutInflater();
FrameLayout f1 = (FrameLayout)alert.findViewById(android.R.id.body);
f1.addView(inflater.inflate(R.layout.dialog_view, f1, false));