why does my app crashes when I try to find a view that is in different xml files

Question

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TextView tv = (TextView)findViewById(R.id.text);
        tv.setText("hello world");

}

here the textview is present in a different xml file other than activity.main xml file.

Answer 1

To use views from XML you have to inflate them. setContentView(int id) is doing some background inflating for you on R.layout.activity_main but you can't get a handle to the TextView because it is not inflated. I can't imagine why you would want to do something with a view from a hierarchy that you are not displaying; in any case I doubt this is the way you want to go about it.

Answer 2

This simply won't work, as the current inflated view points to activity_main and the so the findViewById() method looks for TextView in the activity_main file.

For finding the TextView in other file, you will first have to inflate that view (in you case the another xml file).