How to speed up AutocompleteTextView in Android?

Hi everyone, I have an adapter that extends the ArrayAdapter class and overrides some Filterable methods. I am using this adapter to do some filtering when the user types inside the AutocompleteTextView. But I have seen that if you type a bit quickly, updating the filtered items becomes very slow. This is the adapter class:

public class MunicipalitySearchAdapter extends ArrayAdapter<Municipality> {

private ArrayList<Municipality> municipalities;
private ArrayList<Municipality> allMunicipalities;
private ArrayList<Municipality> suggestedMunicipalities;
private int viewResourceId;

@SuppressWarnings("unchecked")
public MunicipalitySearchAdapter(Context context, int viewResourceId, ArrayList<Municipality> municipalities) {
    super(context, viewResourceId, municipalities);
    this.municipalities = municipalities;
    this.allMunicipalities = (ArrayList<Municipality>) this.municipalities.clone();
    this.suggestedMunicipalities = new ArrayList<Municipality>();
    this.viewResourceId = viewResourceId;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View v = convertView;
    if (v == null) {
        LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = inflater.inflate(this.viewResourceId, null);
    }
    Municipality municipality = municipalities.get(position);
    if (municipality != null) {
        TextView munNameTxtView = (TextView) v.findViewById(R.id.name);
        TextView proSignTxtView = (TextView) v.findViewById(R.id.sign);
        if (munNameTxtView != null) {
            munNameTxtView.setText(municipality.getName());
        }
        if (proSignTxtView != null) {
            proSignTxtView.setText(municipality.getProvinceSign());
        }
 }
    return v;
}


@Override 
public Filter getFilter() {
    return municipalityFilter;
}

Filter municipalityFilter = new Filter() {

    @Override
    public String convertResultToString(Object resultValue) {
        String str = ((Municipality) (resultValue)).getName();
        return str;
    }

    @Override
    protected FilterResults performFiltering(CharSequence constraint) {
        if (constraint != null) {
            suggestedMunicipalities.clear();
            for (Municipality municipality : allMunicipalities) {
                if (municipality.getName().toLowerCase(Locale.getDefault()).startsWith(constraint.toString().toLowerCase(Locale.getDefault()))) {
                    suggestedMunicipalities.add(municipality);
                }
            }
            FilterResults filterRes = new FilterResults();
            filterRes.values = suggestedMunicipalities;
            filterRes.count = suggestedMunicipalities.size();
            return filterRes;
        }
        else {
            return new FilterResults();
        }
    }

    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
        if (results != null && results.count > 0) {
            @SuppressWarnings("unchecked")
            ArrayList<Municipality> filteredMunicipalities = (ArrayList<Municipality>) results.values;
            ArrayList<Municipality> supportMunicipalitiesList = new ArrayList<Municipality>();

            clear();
            for (Municipality mun : filteredMunicipalities) {
                supportMunicipalitiesList.add(mun);
            }
            Iterator<Municipality> municipalityIterator = supportMunicipalitiesList.iterator();
            while (municipalityIterator.hasNext()) {
                Municipality municipality = municipalityIterator.next();
                add(municipality);
            }
            notifyDataSetChanged();
        }           
    }
};
 }

      

        
        
        
      

    

I would like to ask if anyone knows how to increase the performance of this type of AutocompleteTextView and make the update faster. What should I do? Thank!

EDIT: I created these classes: Vertex: public Vertex class {

private HashMap<Character, Vertex> vertexSons;
private List<Integer> wordsIndexList;
private List<Integer> prefixesIndexList;
private int wordsNumber;
private int prefixesNumber;

public Vertex() {
    vertexSons = new HashMap<Character, Vertex>();
    wordsIndexList = new ArrayList<Integer>();
    prefixesIndexList = new ArrayList<Integer>();
    wordsNumber = 0;
    prefixesNumber = 0;
}

public boolean hasWords() {
    if (wordsNumber > 0) {
        return true;
    }
    return false;
}

public boolean hasPrefixes() {
    if (prefixesNumber > 0) {
        return true;
    }
    return false;
}

public void addVertexSon(Character character) {
    vertexSons.put(character, new Vertex());
}

public void addIndexToWordsIndexList(int index) {
    wordsIndexList.add(index);
}

public void addIndexToPrefixesIndexList(int index) {
    prefixesIndexList.add(index);
}

public HashMap<Character, Vertex> getVertexSons() {
    return vertexSons;
}

public List<Integer> getWordsIndexList() {
    return wordsIndexList;
}

public List<Integer> getPrefixesIndexList() {
    return prefixesIndexList;
}

public int getWordsNumber() {
    return wordsNumber;
}

public int getPrefixesNumber() {
    return prefixesNumber;
}

public void increaseWordsNumber() {
    wordsNumber++;
}

public void increasePrefixesNumber() {
    prefixesNumber++;
}
}

      

        
        
        
      

    

And Trie:

public class Trie {

private Vertex rootVertex;

public Trie(List<Trieable> objectList, Locale locale) {
    rootVertex = new Vertex();

    for (int i = 0; i<objectList.size(); i++) {
        String word = objectList.get(i).toString().toLowerCase(locale);
        addWord(rootVertex, word, i);
    }
}

public Vertex getRootVertex() {
    return rootVertex;
}

public void addWord(Vertex vertex, String word, int index) {
    if (word.isEmpty()) { 
        vertex.addIndexToWordsIndexList(index);
        vertex.increaseWordsNumber();
    }
    else {
        vertex.addIndexToPrefixesIndexList(index);
        vertex.increasePrefixesNumber();
        Character fChar = word.charAt(0);
        HashMap<Character, Vertex> vertexSons = vertex.getVertexSons();

        if (!vertexSons.containsKey(fChar)) {
            vertex.addVertexSon(fChar);
        }

        word = (word.length() == 1) ? "" : word.substring(1);
        addWord(vertexSons.get(fChar), word, index);
    }
}

public List<Integer> getWordsIndexes(Vertex vertex, String word) {
    if (word.isEmpty()) {
        return vertex.getWordsIndexList();
    }
    else {
        Character fChar = word.charAt(0);
        if (!(vertex.getVertexSons().containsKey(fChar))) {
            return null;
        }
        else {
            word = (word.length() == 1) ? "" : word.substring(1);
            return getWordsIndexes(vertex.getVertexSons().get(fChar), word);
        }
    }
}

public List<Integer> getPrefixesIndexes(Vertex vertex, String prefix) {
    if (prefix.isEmpty()) {
        return vertex.getWordsIndexList();
    }
    else {
        Character fChar = prefix.charAt(0);
        if (!(vertex.getVertexSons().containsKey(fChar))) {
            return null;
        }
        else {
            prefix = (prefix.length() == 1) ? "" : prefix.substring(1);
            return getWordsIndexes(vertex.getVertexSons().get(fChar), prefix);
        }
    }
}

}

      

        
        
        
      

    

And edited my filter like this:

Filter municipalityFilter = new Filter() {



    @Override
    public String convertResultToString(Object resultValue) {
        String str = ((Municipality) (resultValue)).getName();
        return str;
    }

    @Override
    protected FilterResults performFiltering(CharSequence constraint) {

        if (constraint != null) {
            String constraintString = constraint.toString().trim();
            suggestedMunicipalities.clear();

            List<Integer> wordsIndexesList = municipalityTrie.getWordsIndexes(municipalityTrie.getRootVertex(), constraintString);
            for (int index : wordsIndexesList) {
                suggestedMunicipalities.add(allMunicipalities.get(index));
            }

            List<Integer> prefixesIndexesList = municipalityTrie.getPrefixesIndexes(municipalityTrie.getRootVertex(), constraintString);
            for (int index : prefixesIndexesList) {
                suggestedMunicipalities.add(allMunicipalities.get(index));
            }

            FilterResults filterRes = new FilterResults();
            filterRes.values = suggestedMunicipalities;
            filterRes.count = suggestedMunicipalities.size();
            return filterRes;
        }
        else {
            return new FilterResults();
        }
    }

    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
        if (results != null && results.count > 0) {
            @SuppressWarnings("unchecked")
            ArrayList<Municipality> filteredMunicipalities = (ArrayList<Municipality>) results.values;
            ArrayList<Municipality> supportMunicipalitiesList = new ArrayList<Municipality>();

            clear();
            for (Municipality mun : filteredMunicipalities) {
                supportMunicipalitiesList.add(mun);
            }
            Iterator<Municipality> municipalityIterator = supportMunicipalitiesList.iterator();
            while (municipalityIterator.hasNext()) {
                Municipality municipality = municipalityIterator.next();
                add(municipality);
            }
            notifyDataSetChanged();
        }           
    }
};

      

        
        
        
      

    

Now I am getting a null pointer warning when typing into AutoCompleteTextView on this line:

List<Integer> wordsIndexesList = municipalityTrie.getWordsIndexes(municipalityTrie.getRootVertex(), constraintString);
            for (int index : wordsIndexesList) {
                suggestedMunicipalities.add(allMunicipalities.get(index));
            }

      

        
        
        
      

    

In the for statement (int index: wordsIndexesList) . What should I do? Thank!