android : How to initialize/inflate a RelativeLayout using id defined in XML?

Question

I need to set a RelativeLayout block in an activity to VISIBLE. But I can't seem to assign the RelativeLayout to a variable like so :

Relative Layout alarmSetBlock = (RelativeLayout) findViewById(R.id.sleep_text_block);

alarmSetBlock is assigned null instead.

I think I am supposed to use something like inflater.inflate but don't know how to use it outside of fragments.

Please tell me the easiest/best way to resolve this.

layout xml :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="0dp">
        <Button
            android:id="@+id/alarm_set_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:paddingLeft="20dp"
            android:paddingRight="20dp"
            android:paddingBottom="10dp"
            android:paddingTop="10dp"
            android:background="@color/mediumGray"
            android:text="SET ALARM"
            android:onClick="showTimePickerDialog"/>
    </RelativeLayout>


    <RelativeLayout
        android:id="@+id/sleep_text_block"
        android:layout_weight="1"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:visibility="gone">
        <TextView
            android:id="@+id/sleep_text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="50dp"
            android:layout_centerHorizontal="true"
            android:textSize="20sp"
            android:text="Alarm set to :"/>

        <TextView
            android:id="@+id/alarm_time"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:layout_centerHorizontal="true"
            android:layout_below="@id/sleep_text"
            android:textColor="@color/colorAccent"
            android:textSize="36sp" />
    </RelativeLayout>

</LinearLayout>

The RelativeLayout I am trying to initialize is the second one in the layout.

Here is the fragment file for the above layout. I am trying to initialize the RelativeLayout inside the activity java file that holds this fragment.

public class SleepSetFragment extends Fragment {

    public static SleepSetFragment newInstance()
    {
        SleepSetFragment fragment = new SleepSetFragment();
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState)
    {
        return inflater.inflate(R.layout.fragment_sleep_set, container, false);
    }
}

That should work, are you using multiple layout folders? Make sure also the IDs are also set in each XML. — Lawrence Gimenez, Apr 03 '16 at 07:39
All my layouts are in my res/layout folder. How do I set IDs in each XML? If you mean define ID using `android:id` I've already done it here. — Flame of udun, Apr 03 '16 at 07:40
Can you try using android:visibility="invisible" instead, and see if it works. — Lawrence Gimenez, Apr 03 '16 at 07:42
I am wondering if something is wrong with my Android studio. It has been throwing this sort of "Attempt to invoke virtual method on a null object reference" for a number of things. And using the `Log.d` for this `RelativeLayout` shows that id fetch is not working properly — Flame of udun, Apr 03 '16 at 07:49
Funny, works fine on my end. I copied your XML and didn't return any null. — Lawrence Gimenez, Apr 03 '16 at 07:51
Well I have fragments in this activity so I am using `FragmentActivity` — Flame of udun, Apr 03 '16 at 08:00

score 1 · Answer 1 · edited May 23 '17 at 11:59

1

You are trying to get a view inside a fragment from the Activity. You can't use findViewById() for such cases. Instead, you should expose a public method from your fragment to use get that specific view. But make sure that your fragment is inflated and added to the activity before calling it.

Here's an example: https://stackoverflow.com/a/17023533/1395437

edited May 23 '17 at 11:59

Community

1
1

answered Apr 03 '16 at 08:01

Daniel Zolnai

16,487
7
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`RelativeLayout` is in a fragment file which has onCreateView() – Flame of udun Apr 03 '16 at 08:03
Are you trying to get a view inside the activity from the fragment, or a view of a fragment from your activity? – Daniel Zolnai Apr 03 '16 at 08:04
Trying to get a view of a fragment inside the activity. – Flame of udun Apr 03 '16 at 08:05

Lawrence Gimenez · Accepted Answer · 2016-04-03T09:08:42.177

1

You forgot to inflate the XML layout on onCreateView() like this

    @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

            View view = inflater.inflate(R.layout.your_layout, container, false);

            RelativeLayout alarmSetBlock = (RelativeLayout) view.findViewById(R.id.sleep_text_block);
alarmSetBlock.setVisibility(Visibility.VISIBLE);

            return view;
        }

edited Apr 03 '16 at 09:08

answered Apr 03 '16 at 08:08

Lawrence Gimenez

2,662
4
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Where do I set the visibility of my `RelativeLayout`? Should I do it in the fragment `onCreateView()` method itself along with the `SharedPreference` logic that it is connected to? – Flame of udun Apr 03 '16 at 08:17
Just below the RelativeLayout alarmSetBlock line – Lawrence Gimenez Apr 03 '16 at 09:06
You can review, because Fragment and Activity has different lifecycles. – Lawrence Gimenez Apr 03 '16 at 09:07

android : How to initialize/inflate a RelativeLayout using id defined in XML?

2 Answers2