AutoCompleteTextView: 就是一个带自动提示的EditText,当输入字符时,会出现提示.
android:completionThreshold 
输入几个字符时提示
android:completionHint/setCompletionHint(CharSequence)
设置出现下拉列表的提示标题
android:dropDownHeight/setDropHeight(int)
设置下拉列表的高度
android:dropDownWidth/setDropWidth(int)
设置下拉列表的宽度
android:popupBackground/setDropDownbackgroundResource(int)
设置下拉列表的背景
在Android程序中,为了展示数据,通常会用到一个Adapter的接口
setAdapter()设置提示内容的Adapter.

MultiAutoCompleteTextView是多选选项
使用MultiAutoCompleteTextView必须实现MultiAutoCompleteTextView.Tokenizer接口
用于声明用于选项与选项之间分隔的符号,一般如不特殊指定,可以使用Android为我们提供的实现类MultiAutoCompleteTextView.CommaTokenizer,它设定使用英文逗号","进行分隔选项.

例子：

<LinearLayout 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"

    android:orientation="vertical"

    tools:context=".MainActivity" >

    <LinearLayout android:layout_width="match_parent"

                  android:layout_height="wrap_content"

                  android:orientation="horizontal">

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="单选搜索"

        tools:ignore="HardcodedText" />

    <AutoCompleteTextView android:id="@+id/autoText"

                          android:layout_width="match_parent"

                          android:layout_height="wrap_content"

                          />

   </LinearLayout>

   <LinearLayout android:layout_width="match_parent"

                  android:layout_height="wrap_content">

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="多选搜索"

        tools:ignore="HardcodedText" />

   <MultiAutoCompleteTextView android:id="@+id/autoMultiText"

                              android:layout_width="match_parent"

                              android:layout_height="wrap_content"

                              />

  </LinearLayout>

</LinearLayout>

package com.light.android.study;

import android.app.Activity;

import android.os.Bundle;

import android.view.Gravity;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.ArrayAdapter;

import android.widget.AutoCompleteTextView;

import android.widget.CheckBox;

import android.widget.CompoundButton;

import android.widget.MultiAutoCompleteTextView;

import android.widget.MultiAutoCompleteTextView.CommaTokenizer;

import android.widget.RadioGroup;

import android.widget.RadioGroup.OnCheckedChangeListener;

import android.widget.Toast;

import android.widget.ToggleButton;

public class MainActivity extends Activity {

	private AutoCompleteTextView autoText;

	private MultiAutoCompleteTextView autoMultiText;

	private String[] keywords = {

			"ab","abc","abdfdf","abnsd","abdfff"

	};

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.activity_main);

		init();

		initAdapter();

	}

	private void init(){

		autoText = (AutoCompleteTextView) findViewById(R.id.autoText);

		autoMultiText = (MultiAutoCompleteTextView) findViewById(R.id.autoMultiText);

	}

	private void initAdapter(){

		ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, keywords);

		autoText.setAdapter(adapter);

		autoMultiText.setAdapter(adapter);

		autoMultiText.setTokenizer(new MultiAutoCompleteTextView.CommaTokenizer());

	}

}

效果：