Android: ArrayList - filtering

For example: You have a model - FriendItem

public class FriendItem {

    private String firstName;
    private String lastName;

    //.....

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }
}

and have an adapter - FriendAllAdapter. In this adapter you should implement Filterable interface. You"ll need to Override getFilter() method and return new object of Filter class (android.widget.Filter).

• In performFiltering() method your need return FilterResults object with count of filtered elements and value - list of elements. Also in this method you need to realize the algorithm comparison of the search query to values in your FriendItem (list item). In my example I search FriendItem(s) which fields (firstName or lastName) contains text in my editText. Input parameter is a CharSequence object which you set in onTextChanged() method on added textChangeListener to your EditText.

  myFilter.addTextChangedListener(new TextWatcher() {
  
      public void onTextChanged(CharSequence s, int start, int before, int count) {
  
          adapter.getFilter().filter(s); 
  
      }
  });
  

• In publishResults() method your get filtering result your need cast results.values to List and replace your list to filtering result.

  public class FriendAllAdapter extends BaseAdapter implements Filterable {       
  
      private List<FriendItem> list;
      private final List<FriendItem> fullList = new ArrayList<>();
  
      public FriendAllAdapter(Context context, List<FriendItem> list) {
  
          //...... your code
  
          this.list = list;
          fullList.addAll(list);
      }
  
  
      //...... your code
  
      @Override
      public View getView(int position, View convertView, ViewGroup parent) {
          //... your code
      }
  
      @Override
      public Filter getFilter() {
          Filter filter = new Filter() {
              @Override
              protected FilterResults performFiltering(CharSequence constraint) {
                  FilterResults results = new FilterResults();
  
                      if (constraint == null || constraint.length() == 0) { // if your editText field is empty, return full list of FriendItem
                          results.count = fullList.size();
                          results.values = fullList;
                      } else {
                          List<FriendItem> filteredList = new ArrayList<>();
  
                          constraint = constraint.toString().toLowerCase(); // if we ignore case
                          for (FriendItem item : fullList) {
                              String firstName = item.getFirstName().toLowerCase(); // if we ignore case
                              String lastName = item.getLastName().toLowerCase(); // if we ignore case
                              if (firstName.contains(constraint.toString()) || lastName.contains(constraint.toString())) {
                                  filteredList.add(item); // added item witch contains our text in EditText
                              }
                          }
  
                          results.count = filteredList.size(); // set count of filtered list
                          results.values = filteredList; // set filtered list
                      }
                  return results; // return our filtered list
              }
  
              @Override
              protected void publishResults(CharSequence constraint, FilterResults results) {
  
                      list = (List<FriendItem>) results.values; // replace list to filtered list 
                      notifyDataSetChanged(); // refresh adapter
              }
          };
          return filter;
      }
  }
  

I think you`ll understand it. P.S. sorry for my English.