how to access UI elements in parent activity from fragment

Question

parent activity layout

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".LockerCodeActivity" >

    <LinearLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </LinearLayout>

    <ProgressBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:id="@+id/ctrlActivityIndicator"
        android:indeterminateOnly="true"
        android:keepScreenOn="false"
     />

    <TextView
        android:id="@+id/tv_results"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="" />

</RelativeLayout>

Inflate the fragment in the parent activity onCreate function

FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    Fragment scannerFragment = new ScanFragment();
    fragmentTransaction.add(R.id.fragment_container, scannerFragment);
    fragmentTransaction.commit();

Working great so far... now how do I hide the progressbar? This is what I've tried

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_scan, container, false);

    ProgressBar progressBar = (ProgressBar) view.findViewById(R.id.ctrlActivityIndicator);
    progressBar.setVisibility(View.INVISIBLE);
    return view;
    }

I get a null pointer exception

score 64 · Accepted Answer · answered Jan 24 '13 at 03:59

64

Since you want the Activity's views, you're going to want to do this:

ProgressBar progressBar = (ProgressBar) getActivity().findViewById(R.id.ctrlActivityIndicator);

You call getActivity() to get the Activity instance then you use findViewById() as normal (provided that R.id.ctrlActivityIndicator is part of the Activity layout, you won't get NPEs).

answered Jan 24 '13 at 03:59

A--C

36,351
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Thanks, Found this after hours of searching. – LvN Sep 17 '14 at 10:57
What about a possible NPE from `getActivity()`? – Ed Lee Oct 27 '16 at 21:53
@EdLee we have to handle that case in code itself, checking for null before making relevant calls. – Divya Gupta Nov 04 '21 at 04:33

score 3 · Answer 2 · edited May 23 '17 at 11:55

3

This didn't work for me unitl i cast the result of getActivity to the parent activity. See link below: Call parent's activity from a fragment

edited May 23 '17 at 11:55

Community

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1

answered May 16 '15 at 22:22

m-j

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It is good practice to include the relevant information from the link in your answer. What if the link breaks in the future? – Theresa May 16 '15 at 22:36
As a thumb rule, you should always cast the getActivity() method call to the activity it supposedly returning per se the logic of your code. And to safely do that you make a check befor casting. Example below, to cast the activity returned by getActivity method inside fragment to MainActivity if (getActivity instanceof MainActivity){ MainActivity activity = (MainActivity) getActivity(); } – Khay May 17 '17 at 18:32

score 2 · Answer 3 · answered Dec 08 '19 at 17:28

2

You can use:

((ParentActivity)getActivity()).UI_COMPONENT_NAME

to access the ui component of the parent activity.

UI_COMPONENT_NAME is the name of the component as initialised in the ParentActivity.

answered Dec 08 '19 at 17:28

Anubhav

1,984
22
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how to access UI elements in parent activity from fragment

3 Answers3