recycler-fast-scroll issue 8 https://github.com/FutureMind/recycler-fast-scroll/issues/8

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    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:fitsSystemWindows="true"
    tools:context="com.talklittle.recyclerfastscrollgithubissue8.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay"/>

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

    <include layout="@layout/content_main"/>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        android:src="@android:drawable/ic_dialog_email"/>

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

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.talklittle.recyclerfastscrollgithubissue8.MainActivity"
    tools:showIn="@layout/activity_main">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>


    <com.futuremind.recyclerviewfastscroll.FastScroller
        android:id="@+id/fastscroller"
        android:orientation="vertical"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_alignParentRight="true"/>
</RelativeLayout>

MainActivity.java

package com.talklittle.recyclerfastscrollgithubissue8;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.futuremind.recyclerviewfastscroll.FastScroller;

public class MainActivity extends AppCompatActivity {

    private FastScroller mFastScroller;
    private RecyclerView mRecyclerView;

    private int mItemCount;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                toggleItemCount();
            }
        });

        mRecyclerView = (RecyclerView) findViewById(R.id.recyclerview);
        mFastScroller = (FastScroller) findViewById(R.id.fastscroller);

        mRecyclerView.setAdapter(new RecyclerView.Adapter() {
            @Override
            public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                TextView root = new TextView(MainActivity.this);
                root.setText("hi fast scroller");
                return new DummyViewHolder(root);
            }

            @Override
            public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
            }

            @Override
            public int getItemCount() {
                return mItemCount;
            }
        });
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        mRecyclerView.setItemAnimator(null);

        mFastScroller.setRecyclerView(mRecyclerView);
    }

    private void toggleItemCount() {
        final int maxCount = 40;
        mItemCount = mItemCount == 0 ? maxCount : 0;
        if (mItemCount == 0) {
            mRecyclerView.getAdapter().notifyItemRangeRemoved(0, maxCount);
            mRecyclerView.post(new Runnable() {
                @Override
                public void run() {
                    mRecyclerView.requestLayout();
                }
            });
        } else {
            mRecyclerView.getAdapter().notifyItemRangeInserted(0, maxCount);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onPostResume() {
        super.onPostResume();

        toggleItemCount();

    }

    private class DummyViewHolder extends RecyclerView.ViewHolder {
        public DummyViewHolder(View itemView) {
            super(itemView);
        }
    }
}