public class MainActivity extends Activity {    //[0]声明AutoCompleteTextView要显示的数据      private static final String[] COUNTRIES = new String[] {             "laofang", "laozhang", "laoli", "laobi","laoli","laowang","aab","abb","cc"         };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //[1]找到控件        AutoCompleteTextView actv = (AutoCompleteTextView) findViewById(R.id.actv);                //[2]创建数据适配器        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,                android.R.layout.simple_dropdown_item_1line, COUNTRIES);        //[3]设置数据适配器        actv.setAdapter(adapter);    }}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".MainActivity" >    <AutoCompleteTextView        android:id="@+id/actv"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:completionThreshold="1"                 /></RelativeLayout>