Design (layout XML):

<AutoCompleteTextView
   android:id="@+id/autoCompleteTextView1"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignParentTop="true"
   android:layout_centerHorizontal="true"
   android:layout_marginTop="65dp"
   android:ems="10" />

Find the view in code after setContentView() (or its fragment or custom view equivalent):

final AutoCompleteTextView myAutoCompleteTextView = 
    (AutoCompleteTextView) findViewById(R.id.autoCompleteTextView1);

Provide hard-coded data via an adapter:

String[] countries = getResources().getStringArray(R.array.list_of_countries);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,countries);
myAutoCompleteTextView.setAdapter(adapter);

Tip: Though the preferred way would be to provide data via a Loader of some kind instead of a hard-coded list like this.

Main layout : activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <AutoCompleteTextView
        android:id="@+id/auto_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:completionThreshold="2"
        android:hint="@string/hint_enter_name" />
</LinearLayout>

Row layout row.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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/lbl_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="16dp"
        android:paddingLeft="8dp"
        android:paddingRight="8dp"
        android:paddingTop="16dp"
        android:text="Medium Text"
        android:textAppearance="?android:attr/textAppearanceMedium" />
</RelativeLayout>

strings.xml

<resources>
    <string name="hint_enter_name">Enter Name</string>
</resources>

MainActivity.java

public class MainActivity extends AppCompatActivity {
    AutoCompleteTextView txtSearch;
    List<People> mList;
    PeopleAdapter adapter;
    private People selectedPerson;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mList = retrievePeople();
        txtSearch = (AutoCompleteTextView) findViewById(R.id.auto_name);
        adapter = new PeopleAdapter(this, R.layout.activity_main, R.id.lbl_name, mList);
        txtSearch.setAdapter(adapter);
        txtSearch.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int pos, long id) {
                //this is the way to find selected object/item
                selectedPerson = (People) adapterView.getItemAtPosition(pos);
            }
        });
    }

    private List<People> retrievePeople() {
        List<People> list = new ArrayList<People>();
        list.add(new People("James", "Bond", 1));
        list.add(new People("Jason", "Bourne", 2));
        list.add(new People("Ethan", "Hunt", 3));
        list.add(new People("Sherlock", "Holmes", 4));
        list.add(new People("David", "Beckham", 5));
        list.add(new People("Bryan", "Adams", 6));
        list.add(new People("Arjen", "Robben", 7));
        list.add(new People("Van", "Persie", 8));
        list.add(new People("Zinedine", "Zidane", 9));
        list.add(new People("Luis", "Figo", 10));
        list.add(new People("John", "Watson", 11));
        return list;
    }
}

Model class : People.java

public class People {

    private String name, lastName;
    private int id;

    public People(String name, String lastName, int id) {
        this.name = name;
        this.lastName = lastName;
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getlastName() {
        return lastName;
    }

    public void setlastName(String lastName) {
        this.lastName = lastName;
    }
}

Adapter class : PeopleAdapter.java

public class PeopleAdapter extends ArrayAdapter<People> {

    Context context;
    int resource, textViewResourceId;
    List<People> items, tempItems, suggestions;

    public PeopleAdapter(Context context, int resource, int textViewResourceId, List<People> items) {
        super(context, resource, textViewResourceId, items);
        this.context = context;
        this.resource = resource;
        this.textViewResourceId = textViewResourceId;
        this.items = items;
        tempItems = new ArrayList<People>(items); // this makes the difference.
        suggestions = new ArrayList<People>();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = convertView;
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflater.inflate(R.layout.row, parent, false);
        }
        People people = items.get(position);
        if (people != null) {
            TextView lblName = (TextView) view.findViewById(R.id.lbl_name);
            if (lblName != null)
                lblName.setText(people.getName());
        }
        return view;
    }

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

    /**
     * Custom Filter implementation for custom suggestions we provide.
     */
    Filter nameFilter = new Filter() {
        @Override
        public CharSequence convertResultToString(Object resultValue) {
            String str = ((People) resultValue).getName();
            return str;
        }

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            if (constraint != null) {
                suggestions.clear();
                for (People people : tempItems) {
                    if (people.getName().toLowerCase().contains(constraint.toString().toLowerCase())) {
                        suggestions.add(people);
                    }
                }
                FilterResults filterResults = new FilterResults();
                filterResults.values = suggestions;
                filterResults.count = suggestions.size();
                return filterResults;
            } else {
                return new FilterResults();
            }
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            List<People> filterList = (ArrayList<People>) results.values;
            if (results != null && results.count > 0) {
                clear();
                for (People people : filterList) {
                    add(people);
                    notifyDataSetChanged();
                }
            }
        }
    };
}