Question

Content view is a LinearLayout. We’ll call it llOne and we’ll say it’s in the file llOne.xml.

The view I’m trying to add is also a LinearLayout but they’re in separate files. We’ll call it llTwo and we’ll say it’s in the file llTwo.xml.

 setContentView(R.layout.llOne);

 LinearLayout llOne = (LinearLayout) findViewById(R.id.llOne);
 LinearLayout llTwo = (LinearLayout) findViewById(R.id.llTwo);

 llOne.addView(llTwo); //NullPointerException

Answer 1

you need to inflate the second layout, as setContentView only inflate your llOne

LayoutInflater inflater = (LayoutInflater) mContext
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View otherView = inflater.inflate(R.layout.yourSecondLayoutFileName, null);

and then

LinearLayout llTwo = (LinearLayout) otherView .findViewById(R.id.llTwo);
llOne.addView(llTwo);