Android: making layouts in the activity's fragment, if not using several fragments

Question

I am making an activity that contains a ListView and a Button . Being new to Android I didn't notice that I was writing it in the fragment xml document.

I noticed that the java code generated when making an activity ( Activity.java ) pertains to the activity xml, not the fragment, as getViewById() returns null when I try to get my ListView or Button .

My question is, should I move the layout from the fragment xml to the activity xml, or is there a way to call the fragment from the Activity.java file?

I read up a bit on the use of fragments and saw that they are mainly used while having several tabs, or "mini-activities" (sorta) in the same window/activity. I will not be needing that functionality though. Should I still be making the layout in the fragment xml?

Answer 1

setcontentview(R.layout.activity_main) 

to

setcontentview(R.layout.fragment_main)

and remove below code

if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
    }

from onCreate method thats it. now fragment remove from your activity.. also remove activity_main.xml no need to this xml...

Answer 2

/ You can add fragment in activity in java like this: Fragment manager is responsible to manage all fragments you will have. MyFragment is class that extends Fragment and myFragment is object of that class. ContainerId is optional /

FragmentManager manager=getFragmentManager();
    MyFragment myFragment=new MyFragment();
    FragmentTransaction transaction=manager.beginTransaction();
    transaction.add(R.id.container,myFragment,"Stringtag");
    transaction.commit();