How to create custom BaseAdapter for AutoCompleteTextView

The following is my working code using ArrayAdapter.

Let’s assume the reponse data from web service looks like the following:

[
    {
        "id": "1",
        "name": "Information Technology"
    },
    {
        "id": "2",
        "name": "Human Resources"
    },
    {
        "id": "3",
        "name": "Marketing and PR"
    },
    {
        "id": "4",
        "name": "Research and Developement"
    }
]

---

Then in your Android client:

Department class:

public class Department {
    public int id;
    public String name;
}

Custom Adapter class:

public class DepartmentArrayAdapter extends ArrayAdapter<Department> {
    private final Context mContext;
    private final List<Department> mDepartments;
    private final List<Department> mDepartmentsAll;
    private final int mLayoutResourceId;

    public DepartmentArrayAdapter(Context context, int resource, List<Department> departments) {
        super(context, resource, departments);
        this.mContext = context;
        this.mLayoutResourceId = resource;
        this.mDepartments = new ArrayList<>(departments);
        this.mDepartmentsAll = new ArrayList<>(departments);
    }

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

    public Department getItem(int position) {
        return mDepartments.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        try {
            if (convertView == null) {                    
                LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
                convertView = inflater.inflate(mLayoutResourceId, parent, false);
            }
            Department department = getItem(position);
            TextView name = (TextView) convertView.findViewById(R.id.textView);
            name.setText(department.name);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return convertView;
    }

    @Override
    public Filter getFilter() {
        return new Filter() {
            @Override
            public String convertResultToString(Object resultValue) {
                return ((Department) resultValue).name;
            }

            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                FilterResults filterResults = new FilterResults();
                List<Department> departmentsSuggestion = new ArrayList<>();
                if (constraint != null) {
                    for (Department department : mDepartmentsAll) {
                        if (department.name.toLowerCase().startsWith(constraint.toString().toLowerCase())) {
                            departmentsSuggestion.add(department);
                        }
                    }
                    filterResults.values = departmentsSuggestion;
                    filterResults.count = departmentsSuggestion.size();
                }
                return filterResults;
            }

            @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {
                mDepartments.clear();
                if (results != null && results.count > 0) {
                    // avoids unchecked cast warning when using mDepartments.addAll((ArrayList<Department>) results.values);
                    for (Object object : (List<?>) results.values) {
                        if (object instanceof Department) {
                            mDepartments.add((Department) object);
                        }
                    }
                    notifyDataSetChanged();
                } else if (constraint == null) {
                    // no filter, add entire original list back in
                    mDepartments.addAll(mDepartmentsAll);
                    notifyDataSetInvalidated();
                }
            }
        };
    }
}

Main Activity:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mAutoCompleteTextView = (AutoCompleteTextView) findViewById(R.id.autoCompleteTextView);
    mAutoCompleteTextView.setThreshold(1);

    new DepartmentRequest().execute();
}

private class DepartmentRequest extends AsyncTask<Void, Void, JSONArray> {
        @Override
        protected JSONArray doInBackground(Void... voids) {
            OkHttpJsonArrayRequest request = new OkHttpJsonArrayRequest();
            try {
                return request.get("http://...");
            } catch (IOException | JSONException e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(JSONArray jsonArray) {
            super.onPostExecute(jsonArray);
            if (jsonArray != null && jsonArray.length() > 0) {
                Gson gson = new Gson();
                Department[] departments = gson.fromJson(jsonArray.toString(), Department[].class);
                mDepartmentList = Arrays.asList(departments);
                mDepartmentArrayAdapter = new DepartmentArrayAdapter(mContext, R.layout.simple_text_view, mDepartmentList);
                mAutoCompleteTextView.setAdapter(mDepartmentArrayAdapter);
            }
        }
    }

    private class OkHttpJsonArrayRequest {
        OkHttpClient client = new OkHttpClient();
        // HTTP GET REQUEST
        JSONArray get(String url) throws IOException, JSONException {
            Request request = new Request.Builder()
                    .url(url)
                    .build();
            Response response = client.newCall(request).execute();
            return new JSONArray(response.body().string());
        }
    }

Here’s the screenshot:

Hope this helps!