Alphabetical Scroll in ListView

Step 1:
Create a Project named as Alphabetical Scroll
Step 2:
Copy Below code in to main activity
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.regex.Pattern;

import uk.co.brightec.alphabetscroller.AlphabetListAdapter.Item;
import uk.co.brightec.alphabetscroller.AlphabetListAdapter.Row;
import uk.co.brightec.alphabetscroller.AlphabetListAdapter.Section;
import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.GestureDetector;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends ListActivity {

    private AlphabetListAdapter adapter = new AlphabetListAdapter();
    private GestureDetector mGestureDetector;
    private List < Object[] > alphabet = new ArrayList < Object[] > ();
    private HashMap < String, Integer > sections = new HashMap < String, Integer > ();
    private int sideIndexHeight;
    private static float sideIndexX;
    private static float sideIndexY;
    private int indexListSize;

    class SideIndexGestureListener extends GestureDetector.SimpleOnGestureListener {@
        Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            sideIndexX = sideIndexX - distanceX;
            sideIndexY = sideIndexY - distanceY;

            if (sideIndexX >= 0 && sideIndexY >= 0) {
                displayListItem();
            }

            return super.onScroll(e1, e2, distanceX, distanceY);
        }
    }

    @
    Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.list_alphabet);

        mGestureDetector = new GestureDetector(this, new SideIndexGestureListener());

        List < String > countries = populateCountries();
        Collections.sort(countries);

        List < Row > rows = new ArrayList < Row > ();
        int start = 0;
        int end = 0;
        String previousLetter = null;
        Object[] tmpIndexItem = null;
        Pattern numberPattern = Pattern.compile("[0-9]");

        for (String country: countries) {
            String firstLetter = country.substring(0, 1);

            // Group numbers together in the scroller
            if (numberPattern.matcher(firstLetter).matches()) {
                firstLetter = "#";
            }

            // If we've changed to a new letter, add the previous letter to the alphabet scroller
            if (previousLetter != null && !firstLetter.equals(previousLetter)) {
                end = rows.size() - 1;
                tmpIndexItem = new Object[3];
                tmpIndexItem[0] = previousLetter.toUpperCase(Locale.UK);
                tmpIndexItem[1] = start;
                tmpIndexItem[2] = end;
                alphabet.add(tmpIndexItem);

                start = end + 1;
            }

            // Check if we need to add a header row
            if (!firstLetter.equals(previousLetter)) {
                rows.add(new Section(firstLetter));
                sections.put(firstLetter, start);
            }

            // Add the country to the list
            rows.add(new Item(country));
            previousLetter = firstLetter;
        }

        if (previousLetter != null) {
            // Save the last letter
            tmpIndexItem = new Object[3];
            tmpIndexItem[0] = previousLetter.toUpperCase(Locale.UK);
            tmpIndexItem[1] = start;
            tmpIndexItem[2] = rows.size() - 1;
            alphabet.add(tmpIndexItem);
        }

        adapter.setRows(rows);
        setListAdapter(adapter);

        updateList();
    }

    @
    Override
    public boolean onTouchEvent(MotionEvent event) {
        if (mGestureDetector.onTouchEvent(event)) {
            return true;
        } else {
            return false;
        }
    }

    public void updateList() {
        LinearLayout sideIndex = (LinearLayout) findViewById(R.id.sideIndex);
        sideIndex.removeAllViews();
        indexListSize = alphabet.size();
        if (indexListSize < 1) {
            return;
        }

        int indexMaxSize = (int) Math.floor(sideIndex.getHeight() / 20);
        int tmpIndexListSize = indexListSize;
        while (tmpIndexListSize > indexMaxSize) {
            tmpIndexListSize = tmpIndexListSize / 2;
        }
        double delta;
        if (tmpIndexListSize > 0) {
            delta = indexListSize / tmpIndexListSize;
        } else {
            delta = 1;
        }

        TextView tmpTV;
        for (double i = 1; i <= indexListSize; i = i + delta) {
            Object[] tmpIndexItem = alphabet.get((int) i - 1);
            String tmpLetter = tmpIndexItem[0].toString();

            tmpTV = new TextView(this);
            tmpTV.setText(tmpLetter);
            tmpTV.setGravity(Gravity.CENTER);
            tmpTV.setTextSize(15);
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT, 1);
            tmpTV.setLayoutParams(params);
            sideIndex.addView(tmpTV);
        }

        sideIndexHeight = sideIndex.getHeight();

        sideIndex.setOnTouchListener(new OnTouchListener() {@
            Override
            public boolean onTouch(View v, MotionEvent event) {
                // now you know coordinates of touch
                sideIndexX = event.getX();
                sideIndexY = event.getY();

                // and can display a proper item it country list
                displayListItem();

                return false;
            }
        });
    }

    public void displayListItem() {
        LinearLayout sideIndex = (LinearLayout) findViewById(R.id.sideIndex);
        sideIndexHeight = sideIndex.getHeight();
        // compute number of pixels for every side index item
        double pixelPerIndexItem = (double) sideIndexHeight / indexListSize;

        // compute the item index for given event position belongs to
        int itemPosition = (int)(sideIndexY / pixelPerIndexItem);

        // get the item (we can do it since we know item index)
        if (itemPosition < alphabet.size()) {
            Object[] indexItem = alphabet.get(itemPosition);
            int subitemPosition = sections.get(indexItem[0]);

            //ListView listView = (ListView) findViewById(android.R.id.list);
            getListView().setSelection(subitemPosition);
        }
    }

    private List < String > populateCountries() {
        List < String > countries = new ArrayList < String > ();
        countries.add("Afghanistan");
        countries.add("Albania");
        countries.add("Bahrain");
        countries.add("Bangladesh");
        countries.add("Cambodia");
        countries.add("Cameroon");
        countries.add("Denmark");
        countries.add("Djibouti");
        countries.add("East Timor");
        countries.add("Ecuador");
        countries.add("Fiji");
        countries.add("Finland");
        countries.add("Gabon");
        countries.add("Georgia");
        countries.add("Haiti");
        countries.add("Holy See");
        countries.add("Iceland");
        countries.add("India");
        countries.add("Jamaica");
        countries.add("Japan");
        countries.add("Kazakhstan");
        countries.add("Kenya");
        countries.add("Laos");
        countries.add("Latvia");
        countries.add("Macau");
        countries.add("Macedonia");
        countries.add("Namibia");
        countries.add("Nauru");
        countries.add("Oman");
        countries.add("Pakistan");
        countries.add("Palau");
        countries.add("Qatar");
        countries.add("Romania");
        countries.add("Russia");
        countries.add("Saint Kitts and Nevis");
        countries.add("Saint Lucia");
        countries.add("Taiwan");
        countries.add("Tajikistan");
        countries.add("Uganda");
        countries.add("Ukraine");
        countries.add("Vanuatu");
        countries.add("Venezuela");
        countries.add("Yemen");
        countries.add("Zambia");
        countries.add("Zimbabwe");
        countries.add("0");
        countries.add("2");
        countries.add("9");
        return countries;
    }
}

Step 2: Create a class named as AlphabetListAdapter paste below code into it

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.TextView;

public class AlphabetListAdapter extends BaseAdapter {

public static abstract class Row {}

public static final class Section extends Row {
public final String text;

public Section(String text) {
this.text = text;
}
}

public static final class Item extends Row {
public final String text;

public Item(String text) {
this.text = text;
}
}

private List < Row > rows;

public void setRows(List < Row > rows) {
this.rows = rows;
}

@Override
public int getCount() {
return rows.size();
}

@Override
public Row getItem(int position) {
return rows.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public int getViewTypeCount() {
return 2;
}

@Override
public int getItemViewType(int position) {
if (getItem(position) instanceof Section) {
return 1;
} else {
return 0;
}
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
View view = convertView;

if (getItemViewType(position) == 0) { // Item
if (view == null) {
LayoutInflater inflater = (LayoutInflater) parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = (LinearLayout) inflater.inflate(R.layout.row_item, parent, false);
}

Item item = (Item) getItem(position);
TextView textView = (TextView) view.findViewById(R.id.textView1);
textView.setText(item.text);
} else { // Section
if (view == null) {
LayoutInflater inflater = (LayoutInflater) parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = (LinearLayout) inflater.inflate(R.layout.row_section, parent, false);
}

Section section = (Section) getItem(position);
TextView textView = (TextView) view.findViewById(R.id.textView1);
textView.setText(section.text);
}

return view;
}

}
Step 3: paste following code into activity_main.xml\

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

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

    <LinearLayout
        android:id="@+id/sideIndex"
        android:layout_width="40dip"
        android:layout_height="fill_parent"
        android:background="#FFF"
        android:gravity="center_horizontal"
        android:orientation="vertical" >
    </LinearLayout>

</LinearLayout>
Step 4: Create an xml file named as row item paste following code into it
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:padding="10dp" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

</LinearLayout>

Step 5: Create an xml file named as row section  paste following code into it
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/darker_gray"
    android:orientation="horizontal"
    android:paddingBottom="2dp"
    android:paddingLeft="10dp"
    android:paddingTop="2dp" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        android:textColor="@android:color/white"
        android:textStyle="bold" />

</LinearLayout>
Done:)