android脚步---自动完成文本框

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

    <AutoCompleteTextView
        android:id="@+id/auto"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:completionHint="请选择您喜欢的图书"
        android:dropDownHorizontalOffset="20dp"
        android:completionThreshold="1"
        />

</LinearLayout>

package com.example.autocompletetextview;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;

public class MainActivity extends Activity {
	//定义字符串数组，作为提示文本
	String[]  books = new String[]{
			"aaa",
			"abbb",
			"accc",
			"addd",
	};
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		//创建一个ArrayAdapter,封装数组
		ArrayAdapter<String> aa = new ArrayAdapter<String>(
				this,
				android.R.layout.simple_dropdown_item_1line,
				books);
		AutoCompleteTextView actv = (AutoCompleteTextView)
				findViewById(R.id.auto);
		//设置adapter
		actv.setAdapter(aa);
	}
}