Search cyrillics in custom listview does not work

Question

I am trying to develop search application with cyrillics. I have one edittext and listview. I would like to search the listview with the content of edittext. I am having custom list view. Here is my code:

Here is the main activity:

package com.searchapplication;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.ListView;

import java.util.ArrayList;


public class MainActivity extends ActionBarActivity {

    private LinearLayout llContainer;
    private EditText etSearch;
    private ListView lvProducts;

    private ArrayList<Municipality> mProductArrayList = new ArrayList<Municipality>();
    private MyAdapter adapter1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initialize();
        mProductArrayList.add(new Municipality("1", getResources().getString(R.string.skopje)));
        mProductArrayList.add(new Municipality("2", getResources().getString(R.string.skopska_crna_gora)));
        mProductArrayList.add(new Municipality("3", getResources().getString(R.string.saraj)));
        mProductArrayList.add(new Municipality("4", getResources().getString(R.string.kumanovo)));
        mProductArrayList.add(new Municipality("5", getResources().getString(R.string.kratovo)));

        adapter1 = new MyAdapter(MainActivity.this, mProductArrayList);
        lvProducts.setAdapter(adapter1);

        etSearch.addTextChangedListener(new TextWatcher() {

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                // Call back the Adapter with current character to Filter

            }

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void afterTextChanged(Editable s) {
                adapter1.getFilter().filter(s);
            }
        });
    }

    private void initialize() {
        etSearch = (EditText) findViewById(R.id.etSearch);
        lvProducts = (ListView)findViewById(R.id.lvProducts);
    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
    }

    @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);
    }
}

Here is the code of the model:

package com.searchapplication;
public class Municipality {

    private String id;
    private String name;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Municipality(String id, String name) {
        this.id = id;
        this.name = name;
    }

    @Override
    public String toString() {
        return name;
    }
}

Here is my custom adapter:

package com.searchapplication;

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

import java.util.ArrayList;


public class MyAdapter extends BaseAdapter implements Filterable{

    private ArrayList<Municipality> mOriginalValues; // Original Values
    private ArrayList<Municipality> mDisplayedValues;    // Values to be displayed
    LayoutInflater inflater;
    Context context;

    public MyAdapter(Context context, ArrayList<Municipality> mProductArrayList) {
        this.mOriginalValues = mProductArrayList;
        this.mDisplayedValues = mProductArrayList;
        inflater = LayoutInflater.from(context);
        this.context=context;
    }

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

    @Override
    public Object getItem(int position) {
        return position;
    }

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

    private class ViewHolder {
        LinearLayout llContainer;
        TextView tvName, tvPrice;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {

        ViewHolder holder = null;

        if (convertView == null) {

            holder = new ViewHolder();
            convertView = inflater.inflate(R.layout.row, null);
            holder.llContainer = (LinearLayout) convertView.findViewById(R.id.llContainer);
            holder.tvName = (TextView) convertView.findViewById(R.id.tvName);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        holder.tvName.setText(mDisplayedValues.get(position).getName());


        holder.llContainer.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {


            }
        });

        return convertView;
    }

    @Override
    public Filter getFilter() {
        Filter filter = new Filter() {

            @SuppressWarnings("unchecked")
            @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {

                mDisplayedValues = (ArrayList<Municipality>) results.values; // has the filtered values
                notifyDataSetChanged();  // notifies the data with new filtered values
            }

            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                FilterResults results = new FilterResults();        // Holds the results of a filtering operation in values
                ArrayList<Municipality> FilteredArrList = new ArrayList<Municipality>();

                if (mOriginalValues == null) {
                    mOriginalValues = new ArrayList<Municipality>(mDisplayedValues); // saves the original data in mOriginalValues
                }

                /********
                 *
                 *  If constraint(CharSequence that is received) is null returns the mOriginalValues(Original) values
                 *  else does the Filtering and returns FilteredArrList(Filtered)
                 *
                 ********/
                if (constraint == null || constraint.length() == 0) {

                    // set the Original result to return
                    results.count = mOriginalValues.size();
                    results.values = mOriginalValues;
                } else {
                    constraint = constraint.toString().toLowerCase();
                    for (int i = 0; i < mOriginalValues.size(); i++) {
                        String data = mOriginalValues.get(i).getName();
                        if (data.toString().toLowerCase().contains(constraint)) {
                            FilteredArrList.add(new Municipality(mOriginalValues.get(i).getId(), mOriginalValues.get(i).getName()));
                        }


                    }
                    // set the Filtered result to return
                    results.count = FilteredArrList.size();
                    results.values = FilteredArrList;
                }
                return results;
            }
        };
        return filter;
    }

}

And here is the layout:

<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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/etSearch"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <ListView
        android:id="@+id/lvProducts"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
    ></ListView>

</RelativeLayout>

Here is the layout of the row:

<?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:id="@+id/llContainer">

    <TextView
        android:id="@+id/tvName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:singleLine="true"
        android:layout_weight="1"
    />

</LinearLayout>

Here is string resource file:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">SearchApplication</string>

    <string name="hello_world">Hello world!</string>
    <string name="action_settings">Settings</string>
    <string name="skopje">Скопје</string>
    <string name="skopska_crna_gora">Скопска</string>
    <string name="saraj">Сарај</string>
    <string name="kumanovo">Куманово</string>
    <string name="kratovo">Кратово</string>
    <string name="kriva_palanka">Крива Паланка</string>
    <string name="kicevo">Кичево</string>
    <string name="kamenica">Каменица</string>
    <string name="makedonska_kamenica">Македонска Каменица</string>
    <string name="makedonski_brod">Македонски Брод</string>
    <string name="struga">Струга</string>
    <string name="tetovo">Тетово</string>
    <string name="prefix">скоп</string>
</resources>

The problem is when I type с or ск it is everything ok, but when I type ско there is no result

This piece of code does not return true:

if (data.toString().toLowerCase().contains(constraint))

I am using Macedonian keyboard.