AutoCompleteTextView

To create a text entry widget that provides auto-complete suggestions, use the AutoCompleteTextView widget. Suggestions are received from a collection of strings associated with the widget through an ArrayAdapter.
For this Explanation we using two xml files:
list_item.xml:

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/ res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dp"
    android:textSize="16sp"
    android:textColor="#000">
</TextView>
  main.xml:
 <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/
                                    res/android" 
    android:orientation="horizontal"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:padding="5dp">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Country" />
    <AutoCompleteTextView android:id="@+id/autocomplete_country"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"/>
</LinearLayout>
Add below lines to your java class,
static String[] COUNTRIES = new String[] {
  "Afghanistan", "Albania", "Algeria", "American Samoa", 
 "Andorra",  "Angola", "Anguilla", "Antarctica", "Antigua
 and Barbuda", "Argentina",  "Armenia", "Aruba", "Australia", 
 "Austria", "Azerbaijan",  "Bahrain", "Bangladesh", "Barbados",
  "Belarus", "Belgium",  "Belize", "Benin", "Bermuda", "Bhutan",
  "Bolivia",  "Bosnia and Herzegovina", "Botswana", "Bouvet Island",
  "Brazil", "British Indian Ocean Territory","British Virgin Islands",
  "Brunei", "Bulgaria", "Burkina Faso", "Burundi","Cote d'Ivoire",
  "Cambodia", "Cameroon"}; 
    AutoCompleteTextView textView = (AutoCompleteTextView) 
                     findViewById(R.id.autocomplete_country);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>
                    (this, R.layout.list_item, COUNTRIES);
    textView.setAdapter(adapter);
 AutoCompleteTextView widget is captured from the layout with  
findViewById(int). A new ArrayAdapter is then initialized to 
bind the list_item.xml layoutto each list item in the COUNTRIES 
 string array (defined in the next step).Finally, setAdapter() 
is called to associate the ArrayAdapter with the AutoCompleteTextView
widget so that the string array will populate the list of suggestions. 
Here is the ScreenShot: