Android - Using AutoCompleteTextView to detect a word next to `@`

Question

Firstly, I am really new in AutoCompleteTextView, and as can be inferred from the title, I want to use it to Tag people in the social media app I am currently developing.

First I've created a class named TagList to contain a list of model class named TagModel :

public class TagModel {
    public String user_avatar;
    public String user_name;

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

And here's the whole adapter class :

public class TagAdapter extends ArrayAdapter<TagModel> implements Filterable {

    private Context context;
    private int resource;
    private TagList mDataset;

    public TagAdapter(Context context, int resource) {
        super(context, resource);
        this.context = context;
        this.resource = resource;
        this.mDataset = new TagList();
    }

    public void changeItem(TagList tagList){
        this.mDataset.tagModelList.clear();
        notifyDataSetChanged();
        this.mDataset.tagModelList.addAll(tagList.tagModelList);
        notifyDataSetChanged();
    }

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

    @Override
    public TagModel getItem(int position) {
        return this.mDataset.tagModelList.get(position);
    }

    @Override
    public Filter getFilter() {
        Filter myFilter = new Filter() {
            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                FilterResults filterResults = new FilterResults();
                ArrayList<TagModel> tempTagModel = new ArrayList<TagModel>();
                if(constraint != null) {
                    int length = mDataset.tagModelList.size();
                    int i = 0;
                    while(i<length){
                        TagModel item = mDataset.tagModelList.get(i);
                        //do whatever you wanna do here
                        //adding result set output array

                        tempTagModel.add(item);

                        i++;
                    }
                    //following two lines is very important
                    //as publish result can only take FilterResults objects
                    filterResults.values = tempTagModel;
                    filterResults.count = tempTagModel.size();
                }
                return filterResults;
            }

            @Override
            protected void publishResults(CharSequence contraint, Filter.FilterResults results) {
                if(results != null && results.count > 0) {
                    notifyDataSetChanged();
                }
                else {
                    notifyDataSetInvalidated();
                }
            }
        };
        return myFilter;
    }

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

        try{
            if(convertView==null){
                // inflate the layout
                LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = inflater.inflate(resource, parent, false);
            }

            TagModel objectItem = mDataset.tagModelList.get(position);

            ImageView userAvatar = (ImageView) convertView.findViewById(R.id.popup_tag_avatar);

            OpenSansFont userName = (OpenSansFont) convertView.findViewById(R.id.popup_tag_name);
            userName.setText(objectItem.user_name);

        } catch (NullPointerException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }

        return convertView;

    }
}

I've added single dummy data to test whether the AutoComplete works, well, it works but now I'm at loss on filtering @(someone's name) because whatever I type, it'll display my dummy data in the list.

I actually need 2 things done here,

1. Getting filter to filter only @(someone's name) and put the query into API.

2. Stop autocomplete when user presses space.

Can anyone point me to the right direction on this? I'll gladly put up any code needed to explain my question..

Update : A buggy TextWatcher on an AutoCompleteTextView, trying to get whatever text after @ and before " ".

tagAutoComplete.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {

        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {

            if (count > 0) {
                if (before == 0) {
                    flag = false;
                    stringBuilder.replace(0, stringBuilder.length() - 1, "");
                }

                if (flag) {
                    stringBuilder.append(s.toString().charAt(count - 1));
                    FriendTagListShowAPI friendTagListShowAPI = new FriendTagListShowAPI();
                    friendTagListShowAPI.query.tag = stringBuilder.toString();
                    friendTagListShowAPI.query.user_id = userId;

                    FriendTagListShowAPIFunc friendTagListShowAPIFunc = new FriendTagListShowAPIFunc();
                    friendTagListShowAPIFunc.delegate = TestAutoComplete.this;
                    friendTagListShowAPIFunc.execute(friendTagListShowAPI);
                }

                if (before < s.length() && String.valueOf(s.charAt(before)).equals("@")) {
                    flag = true;
                }
            }
        }

        @Override
        public void afterTextChanged(Editable s) {

        }
    });

Answer 1

You have 2 things to do:

1. Detect the string that contains @someone.
2. Use the string without the character '@' as someone to do query.

So now, you can do as the link Multiautocompletetextview, Show autocomplete drop down only when user presses a key after '@' key (like mention in FB app)

Please scroll down to find @Phuong Sala answer. If you want to multi-tag with many people, let's use MultiAutoCompleteTextView.

Let me know if it helps

Answer 2

In the end, I used a Tokenizer as found in SO, but I forgot where I found it, sorry!

Here's the code :

    multiAutoCompleteTextView.setTokenizer(new MultiAutoCompleteTextView.Tokenizer() {

        @Override
        public CharSequence terminateToken(CharSequence text) {
            int i = text.length();

            while (i > 0 && text.charAt(i - 1) == ' ') {
                i--;
            }

            if (i > 0 && text.charAt(i - 1) == ' ') {
                return text;
            } else {
                if (text instanceof Spanned) {
                    SpannableString sp = new SpannableString(text + " ");
                    TextUtils.copySpansFrom((Spanned) text, 0, text.length(), Object.class, sp, 0);
                    return sp;
                } else {
                    return text + " ";
                }
            }
        }

        @Override
        public int findTokenStart(CharSequence text, int cursor) {
            int i = cursor;

            while (i > 0 && text.charAt(i - 1) != '@') {
                i--;
            }

            //Check if token really started with @, else we don't have a valid token
            if (i < 1 || text.charAt(i - 1) != '@') {
                return cursor;
            }

            return i;
        }

        @Override
        public int findTokenEnd(CharSequence text, int cursor) {
            int i = cursor;
            int len = text.length();

            while (i < len) {
                if (text.charAt(i) == ' ') {
                    return i;
                } else {
                    i++;
                }
            }

            return len;
        }
    });