Modification de l'ancrage du bouton d'action flottant lors de la création d'une vue

Question

J'ai un problème avec le FAB qui est ancré dans un listview ( Voir l'exemple vidéo ), il semble vaciller au tirage au sort en changeant la position de l'ancre. Le problème apparaît dans l'émulateur, ainsi que sur tous les appareils que j'ai testés après le niveau 19 de l'API.

J'ai l'activité principale :

<LinearLayout
    android:id="@+id/main_layout"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <!-- our toolbar -->
    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        android:elevation="4dp"/>

    <!-- our tablayout to display tabs  -->
    <android.support.design.widget.TabLayout
        android:id="@+id/tabLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        android:elevation="4dp"/>

    <!-- View pager to swipe views -->
    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="fill_parent" />

</LinearLayout>

Qui tient alors la nav du bas

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#fff">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:id="@+id/svBody"
        android:background="#fff">
    </FrameLayout>
    <android.support.design.widget.BottomNavigationView
        android:id="@+id/bottomNavigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        app:itemBackground="@color/colorPrimary"
        android:background="@color/colorPrimary"
        app:itemIconTint="@color/cardview_light_background"
        app:itemTextColor="@color/cardview_light_background"
        app:menu="@menu/bottom_navigation_main">
    </android.support.design.widget.BottomNavigationView>
</LinearLayout>

Qui contient le fragment :

<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/lvWords"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:background="#fff">

        <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:orientation="horizontal"
            android:background="#fff"
            android:elevation="4dp">

        <TextView
            android:text="Lipshapes"
            android:layout_width="wrap_content"
            android:layout_height="50dp"
            android:id="@+id/lipshapes_titlestrip"
            android:background="#33b5e5"
            android:textColor="#fff"
            android:textSize="32sp"
            android:paddingTop="4dp"
            android:paddingBottom="4dp"
            android:elevation="6dp"
            android:paddingLeft="@dimen/margin_medium"
            android:paddingRight="@dimen/margin_medium"/>

            <TextView
                android:id="@+id/words_titlestrip"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_gravity="bottom|right"
                android:layout_weight="1"
                android:background="#059FD8"
                android:elevation="10dp"
                android:paddingBottom="4dp"
                android:paddingLeft="@dimen/margin_medium"
                android:paddingRight="@dimen/margin_medium"
                android:paddingTop="4dp"
                android:text="Words"
                android:textColor="#fff"
                android:textSize="32sp" />

        </LinearLayout>

        <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:orientation="vertical"
        android:layout_weight="1"
        android:elevation="0dp"
        android:background="#fff">

        <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="0dp"
            android:layout_weight="1"
            />

        <View
            android:id="@+id/view"
            android:layout_width="match_parent"
            android:layout_height="4dp"
            android:background="@drawable/shadow" />

    </LinearLayout>
    </LinearLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_margin="16dp"
        android:src="@drawable/plus_white_48"
        app:layout_anchor="@android:id/list"
        app:layout_anchorGravity="bottom|right|end"
        app:fabSize="normal" />

Et voici le code des fragments :

public static class WordListSectionFragment extends ListFragment implements AdapterView.OnItemClickListener, AdapterView.OnItemLongClickListener, View.OnClickListener, LoaderManager.LoaderCallbacks<Cursor> {

        public SimpleCursorAdapter wordAdapter;
        final static int LIST_VIEW = 0;
        private FloatingActionButton fab;
        String lipshape = null;
        int lipshape_id = 0;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_wordlist, container, false);
            fab = (FloatingActionButton) rootView.findViewById(R.id.fab);

            Bundle args = getArguments();

            lipshape = args.getString("lipshape_selected_desc");

            lipshape_id = Integer.valueOf(args.getString("lipshape_selected_id"));

            ((TextView) rootView.findViewById(R.id.words_titlestrip)).setText(
                    lipshape
            );

            TextView lipshapesTV = (TextView) rootView.findViewById(R.id.lipshapes_titlestrip);
            lipshapesTV.setOnClickListener(this);

            return rootView;
        }

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

            //  if you only want one column do it like this
            // String[] projection = new String[]{BaseColumns._ID, VideoFilesContract.videoFiles.FILENAME};
            wordAdapter =
                    new SimpleCursorAdapter(
                            getContext(),
                            R.layout.item_word,
                            null,
                            new String[] {WordContract.wordItems.DESCRIPTION, "number_of_videos"},
                            new int[] {R.id.tvWord, R.id.tvVideoCount},
                            LIST_VIEW);

            // Setup cursor adapter using cursor from last step

            setListAdapter(wordAdapter);
            //getListView().setOnItemClickListener(this);

            getLoaderManager().initLoader(LIST_VIEW, null, this);

        }

        @Override
        public void onViewCreated(View view, Bundle savedInstanceState) {
            super.onViewCreated(view, savedInstanceState);
            getListView().setOnItemClickListener(this);
            getListView().setOnItemLongClickListener(this);

            fab.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    // Click action
                    //Toast.makeText(getActivity(), "Button Clicked!", Toast.LENGTH_SHORT).show();

                    Intent intent = new Intent(getActivity(), AddWord.class);
                    intent.putExtra("lipshape_selected_id", lipshape_id);
                    intent.putExtra("lipshape_selected_desc", lipshape);

                    startActivityForResult(intent, 1);
                }
            });
        }

        public void restartLoader()
        {
            wordAdapter.swapCursor(null);
            getLoaderManager().restartLoader(LIST_VIEW, null, this);
        }

        @Override
        public void onActivityResult(int requestCode, int resultCode, Intent data) {
            super.onActivityResult(requestCode, resultCode, data);
            switch(requestCode) {
                case (1) : {
                    if (resultCode == Activity.RESULT_OK) {

                        Boolean returnValue = data.getBooleanExtra("added_word", false);

                        if (returnValue)
                        {
                            restartLoader();
                            Snackbar.make(getView().getRootView().findViewById(R.id.lvWords), "Word Added Successfully!", Snackbar.LENGTH_LONG)
                                    .setAction("Action", null).show();
                        }
                    }
                    break;
                }
            }
        }

        @Override
        public void onClick(View v)
        {
            if (v.getId() == R.id.lipshapes_titlestrip)
            {
                LipshapeSectionFragment fragment = new LipshapeSectionFragment();

                FragmentManager fragmentManager = getFragmentManager();
                fragmentManager.beginTransaction().replace(R.id.svBody, fragment).commit();
            }
        }

        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int position,long id)
        {
            Cursor _cursor  = ((Cursor) getListView().getItemAtPosition(position));
            Cursor cursor;
            int count =0;

            //do a count for videos if 0

            int word_id = _cursor.getInt(_cursor.getColumnIndex("_id"));
            String word  = _cursor.getString(_cursor.getColumnIndex(WordContract.wordItems.DESCRIPTION));

            ContentResolver resolver = getContext().getContentResolver();

            if (word_id!=0) {
                cursor =
                        resolver.query(VideoFilesContract.videoFiles.CONTENT_URI,
                                VideoFilesContract.videoFiles.PROJECTION_ALL,
                                "word_id=?",
                                new String[]{Integer.toString(word_id)},
                                null,
                                null);

                count = cursor.getCount();
            }

            switch(count)
            {
                case 0:

                    Snackbar.make(view, "There are no videos recorded with this word.", Snackbar.LENGTH_LONG)
                            .setAction("Action", null).show();

                    break;
                default:
                    Intent intent = new Intent(getActivity(), CollectionDemoActivity.class);
                    intent.putExtra("word_id", word_id);
                    intent.putExtra("word", word);
                    startActivity(intent);

            }

            //Toast.makeText(getActivity(), "Item: " + test, Toast.LENGTH_SHORT).show();
        }

        @Override
        public Loader<Cursor> onCreateLoader(int id, Bundle bundle) {
            CursorLoader loader = null;

            Bundle args = getArguments();

            switch (id) {

                case LIST_VIEW:
                    loader = new CursorLoader(
                            this.getActivity(),
                            WordContract.wordItems.CONTENT_TEST,
                            new String[]{WordContract.wordItems._ID, WordContract.wordItems.DESCRIPTION, "number_of_videos"},
                            null,
                            new String[]{args.getString("lipshape_selected_id")},
                            null);

                    return loader;
                default:
                    return loader;

            }
        }

            @Override
            public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
            ((SimpleCursorAdapter)this.getListAdapter()).
                    swapCursor(cursor);
        }

            @Override
            public void onLoaderReset(Loader<Cursor> loader) {
            ((SimpleCursorAdapter)this.getListAdapter()).
                    swapCursor(null);
        }

        public void showDialog(final int word_id, String word_clicked) {
            AlertDialog.Builder builder = new AlertDialog.Builder(getContext());
            builder.setTitle("Delete Word: "+ word_clicked + "?");
            builder.setMessage("Deleting this word will also delete all videos tagged by this word.");

            String positiveText = "Delete";
            builder.setPositiveButton(positiveText,
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {

                           deleteWord(word_id);
                            //reload

                        }
                    });

            String negativeText = getString(android.R.string.cancel);
            builder.setNegativeButton(negativeText,
                    new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            // negative button logic
                        }
                    });

            AlertDialog dialog = builder.create();
            // display dialog
            dialog.show();
        }

        public boolean deleteWord(int word_id)
        {
            ContentResolver resolver = getContext().getContentResolver();

            Uri delUri = ContentUris.withAppendedId(WordContract.wordItems.CONTENT_URI, word_id);

            //resolver.delete(VideoFilesContract.videoFiles.CONTENT_URI, "_id=?", selectionArgs);

            long resultCount = resolver.delete(delUri, null, null);

            if (resultCount == 0)
            {
                //couldn't delete word with that id
                return false;
            }
            else
            {
                restartLoader();
                Snackbar.make(getListView(), "Word deleted successfully.", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
                return true;
            }
        }

        @Override
        public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l)
        {

            //Snackbar.make(view, "Item has been long clicked!", Snackbar.LENGTH_LONG)
              //      .setAction("Action", null).show();
            Cursor _cursor  = ((Cursor) getListView().getItemAtPosition(i));
            Cursor cursor;
            int count =0;

            //do a count for videos if 0

            int word_id = _cursor.getInt(_cursor.getColumnIndex("_id"));
            String word  = _cursor.getString(_cursor.getColumnIndex(WordContract.wordItems.DESCRIPTION));

            showDialog(word_id, word);

            return true;
        }
    }