How to create custom BaseAdapter for AutoCompleteTextView

Question

I've been having difficulty creating a custom ArrayAdapter for AutoCompleteTextView such errors that would come up despite following code found on the internet would be:

• Dropdown would not appear.
• Custom Objects and their details would not appear.

So for those who are having or had the same problem as me, I recommend using BaseAdapter for AutoCompleteTextView instead.

Solution 1

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!

Solution 2

Custom BaseAdapter Class

public class ObjectAdapter extends BaseAdapter implements Filterable {

    private Context context;
    private ArrayList<Object> originalList;
    private ArrayList<Object> suggestions = new ArrayList<>();
    private Filter filter = new CustomFilter();

    /**
     * @param context      Context
     * @param originalList Original list used to compare in constraints.
     */
    public ObjectAdapter(Context context, ArrayList<Object> originalList) {
        this.context = context;
        this.originalList = originalList;
    }

    @Override
    public int getCount() {
        return suggestions.size(); // Return the size of the suggestions list.
    }

    @Override
    public Object getItem(int position) {
        return suggestions.get(position).getCountryName();
    }


    @Override
    public long getItemId(int position) {
        return 0;
    }

    /**
     * This is where you inflate the layout and also where you set what you want to display.
     * Here we also implement a View Holder in order to recycle the views.
     */
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater inflater = LayoutInflater.from(context);

        ViewHolder holder;

        if (convertView == null) {
            convertView = inflater.inflate(R.layout.adapter_autotext,
                    parent,
                    false);
            holder = new ViewHolder();
            holder.autoText = (TextView) convertView.findViewById(R.id.autoText);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.autoText.setText(suggestions.get(position).getCountryName());

        return convertView;
    }


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

    private static class ViewHolder {
        TextView autoText;
    }

    /**
     * Our Custom Filter Class.
     */
    private class CustomFilter extends Filter {
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            suggestions.clear();

            if (originalList != null && constraint != null) { // Check if the Original List and Constraint aren't null.
                for (int i = 0; i < originalList.size(); i++) {
                    if (originalList.get(i).getCountryName().toLowerCase().contains(constraint)) { // Compare item in original list if it contains constraints.
                        suggestions.add(originalList.get(i)); // If TRUE add item in Suggestions.
                    }
                }
            }
            FilterResults results = new FilterResults(); // Create new Filter Results and return this to publishResults;
            results.values = suggestions;
            results.count = suggestions.size();

            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            if (results.count > 0) {
                notifyDataSetChanged();
            } else {
                notifyDataSetInvalidated();
            }
        }
    }
}

Main Activity Class

public class MainActivity extends AppCompatActivity{

    private SGetCountryListAdapter countryAdapter;
    private ArrayList<SGetCountryList> countryList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        country = (AutoCompleteTextView) findViewById(R.id.country);
        countryAdapter = new SGetCountryListAdapter(getApplicationContext(),
                    ConnectionParser.SGetCountryList);

        country.setAdapter(countryAdapter);
        country.setThreshold(1);

    }

}

Drop down layout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/autoText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginStart="16dp"
        android:layout_marginTop="8dp"
        android:textColor="@color/black" />

</LinearLayout>

My Original List has data taken from web service so let's just assume that it already has data. Of course you can customize the dropdown even more by adding more views, just don't forget to update the adapter in order to incorporate the new views.