Android alphabetical fast scrollview in RecyclerView with Collapsing toolbar

we want some Knowledge of SectionIndexer. Here is Doc of SectionIndexer.

We have to set TRUE setFastScrollEnabled(true) method, which is used with the LISTVIEW…….You can use recyclerview instead of listView in the below example….

this is activity

public class FastScoll extends ListActivity {

    ListView fruitView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fast_scoll);

        fruitView = (ListView) findViewById(android.R.id.list);

        fruitView.setFastScrollEnabled(true);
        String[] fruits = getResources().getStringArray(R.array.fruits_array);

        final List<String> fruitList = Arrays.asList(fruits);
        Collections.sort(fruitList);
        setListAdapter(new ListAdapter(this, fruitList));

        fruitView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            public void onItemClick(AdapterView<?> parent, View arg1,
                                    int position, long arg3) {
                Log.e("sushildlh",fruitList.get(position));
            }
        });

    }
}

this is the activity_fast_scoll.xml file

<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"
    android:padding="5dp" >

    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:scrollbarStyle="outsideOverlay" />

</RelativeLayout>

and this is my custom adapter with SectionIndexer….

public class ListAdapter extends ArrayAdapter<String> implements SectionIndexer {

    String[] sections;
    List<String> fruits;
    List<String> sectionLetters=new ArrayList<String>();

    public ListAdapter(Context context, List<String> fruitList) {
        super(context, android.R.layout.simple_list_item_1, fruitList);
        this.fruits = fruitList;

        for (int x = 0; x < fruits.size(); x++) {
            String fruit = fruits.get(x);
            String ch = fruit.charAt(0)+"";
            ch = ch.toUpperCase(Locale.US);

            sectionLetters.add(ch);
        }

        ArrayList<String> sectionList = new ArrayList<String>(sectionLetters);

        sections = new String[sectionList.size()];

        sectionList.toArray(sections);
    }

    public int getPositionForSection(int section) {

        Log.e("sushildlh", "" + section);
        return section;
    }

    public int getSectionForPosition(int position) {

        Log.d("sushildlh", "" + position);
        return position;
    }

    public Object[] getSections() {
        return sections;
    }
}

this is fruits array in string.xml file.

 <string-array name="fruits_array">
            <item>Apples</item>
            <item>Apricots</item>
            <item>Avocado</item>
            <item>Annona</item>
            <item>Banana</item>
            <item>Bilberry</item>
            <item>Blackberry</item>
            <item>Custard Apple</item>
            <item>Clementine</item>
            <item>Cantalope</item>
            <item>Coconut</item>
            <item>Currant</item>
            <item>Cherry</item>
            <item>Cherimoya</item>
            <item>Date</item>
            <item>Damson</item>
            <item>Durian</item>
            <item>Elderberry</item>
            <item>Fig</item>
            <item>Feijoa</item>
            <item>Grapefruit</item>
            <item>Grape</item>
            <item>Gooseberry</item>
            <item>Guava</item>
            <item>Honeydew melon</item>
            <item>Huckleberry</item>
            <item>Jackfruit</item>
            <item>Juniper Berry</item>
            <item>Jambul</item>
            <item>Jujube</item>
            <item>Kiwi</item>
            <item>Kumquat</item>
            <item>Lemons</item>
            <item>Limes</item>
            <item>Lychee</item>
            <item>Mango</item>
            <item>Mandarin</item>
            <item>Mangostine</item>
            <item>Nectaraine</item>
            <item>Orange</item>
            <item>Olive</item>
            <item>Prunes</item>
            <item>Pears</item>
            <item>Plum</item>
            <item>Pineapple</item>
            <item>Peach</item>
            <item>Papaya</item>
            <item>Passionfruit</item>
            <item>Pomegranate</item>
            <item>Pomelo</item>
            <item>Raspberries</item>
            <item>Rock melon</item>
            <item>Rambutan</item>
            <item>Strawberries</item>
            <item>Sweety</item>
            <item>Salmonberry</item>
            <item>Satsuma</item>
            <item>Tangerines</item>
            <item>Tomato</item>
            <item>Ugli</item>
            <item>Watermelon</item>
            <item>Woodapple</item>
        </string-array>

and finally this is the output of the these code….

Feel free to ask if you stuck anywhere in between code ….

Note:- FastScroll image will be differ in different version of android (eg:-lollipop,marshmallow,etc) below output is for lollipop

For Custom Alphabetical Fast scrollView just add these 2 line in your style.xml file in AppTheme.

<item name="android:fastScrollTextColor">@color/apptheme_color</item>         //this is used for the color of the Alphabetical Fast scrollView
<item name="android:fastScrollPreviewBackgroundRight">@drawable/bg_default_focused_holo_light</item>          //this is the image or and drawable file you want to set on Alphabetical Fast scrollView

Custom Fast Scorll Output :-