java - Extending ArrayAdapter in android

Question

I need to override a getFilter() method from the class ArrayAdapter and i found the source code from here in the github

//package name

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import android.content.Context;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.Filter;
import android.widget.Filterable;

public class CustomAdapter<T> extends ArrayAdapter<T> implements Filterable{

    private ArrayList<T> mOriginalValues;
    private List<T> mObjects;
    private CustomFilter mFilter;
    private final Object mLock = new Object();
    public CustomAdapter(Context context, int textViewResourceId, T[] objects) {
        super(context, textViewResourceId, objects);

        mObjects = Arrays.asList(objects);
        // TODO Auto-generated constructor stub
    }

    @Override
    public Filter getFilter() {
        // TODO Auto-generated method stub
        if (mFilter == null) {
            mFilter = new CustomFilter();
        }
        return mFilter;
    }


    private class CustomFilter extends Filter {
        @Override
        protected FilterResults performFiltering(CharSequence prefix) {
            FilterResults results = new FilterResults();
            Log.d("bajji", "its ---> " + prefix);
            if (mOriginalValues == null) {
                synchronized (mLock) {
                    mOriginalValues = new ArrayList<T>(mObjects);
                }
            }

            if (prefix == null || prefix.length() == 0) {
                ArrayList<T> list;
                synchronized (mLock) {
                    list = new ArrayList<T>(mOriginalValues);
                }
                results.values = list;
                results.count = list.size();
            } else {
                String prefixString = prefix.toString().toLowerCase();

                ArrayList<T> values;
                synchronized (mLock) {
                    values = new ArrayList<T>(mOriginalValues);
                }

                final int count = values.size();
                final ArrayList<T> newValues = new ArrayList<T>();
                final ArrayList<T> approxValues = new ArrayList<T>();
                final ArrayList<T> secondApproxValues = new ArrayList<T>();


                for (int i = 0; i < count; i++) {
                    final T value = values.get(i);
                    final String valueText = value.toString().toLowerCase();
                    boolean flag = true;
                    // First match against the whole, non-splitted value
                    if (valueText.startsWith(prefixString)) {
                        newValues.add(value);
                        flag = false;
                    } else {
                        final String[] words = valueText.split(" ");
                        final int wordCount = words.length;

                        // Start at index 0, in case valueText starts with space(s)
                        for (int k = 0; k < wordCount; k++) {
                            if (words[k].startsWith(prefixString)) {
                                newValues.add(value);
                                flag = false;
                                break;
                            } 
                        }
                    }

                    if(flag) {
                        if(approxMatch(valueText, prefixString) <= 3) { //change the stuff and do a levi work
                            approxValues.add(value);
                        }
                        else {
                            final String[] words = valueText.split(" ");
                            final int wordCount = words.length;

                            // Start at index 0, in case valueText starts with space(s)
                            for (int k = 0; k < wordCount; k++) {
                                if(approxMatch(words[k], prefixString) <= 3) {
                                    //leve work
                                    secondApproxValues.add(value);
                                    break;
                                }
                            }
                        }
                    }
                }
                newValues.addAll(approxValues);
                newValues.addAll(secondApproxValues);
                results.values = newValues;
                results.count = newValues.size();
            }
            return results;
        }
        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            //noinspection unchecked
            mObjects = (List<T>) results.values;
            if (results.count > 0) {
                notifyDataSetChanged();
            } else {
                notifyDataSetInvalidated();
            }
        }
    }

    private int approxMatch (String s, String t) {
          // an approxmimate string matching algo
          return p;
    }
}

The problem is the getFilter method has a object of a private inner class ArrayFilter which has a method peformFiltering and i need to put a different code there so i have to overide the class. And i get an exception in the method.

In the derived class which extends ArrayAdapter i created a private inner class which is similar to ArrayFilter and called it MyFilter and i get the same exception again in the method performFiltering.

I found a solution to solve my problem. I copied all the code in ArrayAdapter class and created a new class called MyAdapter and i altered some code inside the inner class ArrayFilter and the app works the way i wanted it to. But i feel its not the best solution.

Android has various api levels so if the array adapter is changed in different api level then i have to add those changes in my codes to. So i feel the best way is to extend the class ArrayAdapter to create MyAdapter rather than just copying and pasting the code from the ArrayAdapter

How can i override the inner private class of a parent class..?

Edit: The exception i get..

Edit2: Now i added the full code in the question. and it works perfectly if i copy and edit the array adapter.. the problem is only when i extend..!! now the code and search is working perfectly. I checked it with Log.i.. but the drop down list for auto complete suggestion in UI is not working.. i only get for the first character i type the next character filtering takes place but UI update is not taking place.

Answer 1

After some help from stackoverflow community i removed the exception and later i found out that the suggestions that are returned doesn't really change because the mObjects was returned from the super class or base class. The problem was the there were two public methods getCount() and getItem(int position) which gets the count and fetches the list from mObjects from the base class. So i just have to add those two methods in my class..

public int getCount() {
    return mObjects.size();
}

public T getItem(int position) {
    return mObjects.get(position);
}

Now mObjects of the derived class will be returned. Which are the updated in the dropdown list in the UI.

I am not a java expert, but this solves my problem. If you have any suggestions to make the code better please add it in comments or feel free to edit the answer.!