PreferenceFragmentCompat custom layout

Question

I need a custom layout for my PreferenceFragmentCompat. In the docs for PreferenceFragmentCompat it seems that you can possibly inflate and return a view in onCreateView().

However a NPE results:-

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)' on a null object reference
                                                                       at android.support.v7.preference.PreferenceFragmentCompat.bindPreferences(PreferenceFragmentCompat.java:511)
                                                                       at android.support.v7.preference.PreferenceFragmentCompat.onActivityCreated(PreferenceFragmentCompat.java:316)
                                                                       at com.cls.example.MyPrefFrag.onActivityCreated(MyPrefFrag.java:42) 

After I checked the source of PreferenceFragmentCompat:onCreateView I found the following piece of code :-

 RecyclerView listView = this.onCreateRecyclerView(themedInflater, listContainer, savedInstanceState);
 if(listView == null) {
    throw new RuntimeException("Could not create RecyclerView");
 } else {
    this.mList = listView;   //problem
    ...
    return view;
 }

So if you override onCreateView() and return a custom layout the onCreateRecyclerView() is not called plus the RecyclerView private field mList will not be set. So the NPE on setAdapter() results.

Should I assume that having a custom layout is not feasible for PreferenceFragmentCompat ?

Answer 1

You can specify a custom layout in your theme.

For example:

styles.xml

<style name="YourTheme" parent="Theme.AppCompat">
    <!-- ... -->
    <item name="preferenceTheme">@style/YourTheme.PreferenceThemeOverlay</item>
</style>

<style name="YourTheme.PreferenceThemeOverlay" parent="@style/PreferenceThemeOverlay">
    <item name="android:layout">@layout/fragment_your_preferences</item>
</style>

fragment_your_preferences.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">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.v7.widget.Toolbar
            android:id="@+id/custom_toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

    </android.support.design.widget.AppBarLayout>

    <!-- Required ViewGroup for PreferenceFragmentCompat -->
    <FrameLayout
        android:id="@android:id/list_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </FrameLayout>

</LinearLayout>

And then in onViewCreated() of your fragment class you can start using the views:

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState)
{
    super.onViewCreated(view, savedInstanceState);

    Toolbar toolbar = (Toolbar)view.findViewById(R.id.custom_toolbar);

    if (toolbar != null)
    {
        getMainActivity().setSupportActionBar(toolbar);
    }
}

Answer 2

I had the same problem, however my requirements were a bit different, I just needed to show a layout above the settings list, so I did this

<NestedScrollView>
  <ConstrainLayout>
    <CustomView>
    <SettingsFragmentHolder/>
  </ConstraintLayout>
</NestedScrollView>

Then later in code I just do this

FragmentManager.beginTransaction().replace(holder, PreferencesFragment()).commit()

One thing to note is that, preferences fragment has its own scrollview or a list, that will cause the NestedScrollView to scroll to the beginning of PreferencesFragment layout, to fix that add this to the parent layout of the PreferencesFragment, in this case it is ConstraintLayout

android:descendantFocusability="beforeDescendants"
android:focusableInTouchMode="true"

That will stop the default scrolling behavior

Answer 3

You can. In my example I specified custom layout:

preferences_fragment.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">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:text="Custom Layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"/>

    <FrameLayout
        android:id="@+id/settings_container_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent" />

    <TextView
        android:text="End of Layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"/>

</LinearLayout>

I created class it extends PreferenceFragmentCompat. You must override methods:

onCreatePreferences

@Override
public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
    setPreferencesFromResource(R.xml.app_main_preferences, rootKey);
}

This method sets your preferences. In my Example I use app_main_preferences.xml

app_main_preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:app="http://schemas.android.com/apk/res-auto">

    <Preference
        app:key="logout"
        app:title="Logout"
        app:summary="Logout From The Application Account"/>

</PreferenceScreen>

onCreateView

@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View layout = inflater.inflate(R.layout.preferences_fragment, container, false);
        ViewGroup settingsContainerView = layout.findViewById(R.id.settings_container_view);

        Toolbar toolbar = layout.findViewById(R.id.toolbar);

        MainActivity mainActivity = (MainActivity) requireActivity();
        mainActivity.setSupportActionBar(toolbar);

        View settingsView = super.onCreateView(inflater, settingsContainerView, savedInstanceState);
        settingsContainerView.addView(settingsView);
        return layout;
}

Congratulations!

enter image description here

How it works:

In our custom layout we create FrameLayout it's our container for settings, Toolbar and TextView widgets.

Then we create class it extends PreferenceFragmentCompat class. We override methods. In onCreatePreferences method we set our setting's layout using setPreferencesFromResource.

And our "Main" method is onCreateView method.

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

We inflate our custom layout using our inflater and it inflate method, we pass our custom layout and other parameters such container and savedInstanceBundle.

ViewGroup settingsContainerView = layout.findViewById(R.id.settings_container_view);

Toolbar toolbar = layout.findViewById(R.id.toolbar);

MainActivity mainActivity = (MainActivity) requireActivity();

We get our FrameLayout (it's container for our settings), toolbar and MainActivity of our application.

mainActivity.setSupportActionBar(toolbar);

We set our toolbar using setSupportActionBar method.

View settingsView = super.onCreateView(inflater, settingsContainerView, savedInstanceState);
settingsContainerView.addView(settingsView);
return layout;

Finally we call super.onCreateView method which populate settings and returns populated view. We must add our populated view as child to our settingsContainerView using addView method and return layout variable.