然而我还是没有看懂，这是为什么？我跟老师敲得代码一毛一样，一进去

很抱歉，Demo已停止运行

这个是MainActivity.java

package com.imooc.demo;

import android.app.Activity;

import android.os.Bundle;

import android.widget.ArrayAdapter;

import android.widget.AutoCompleteTextView;

import android.widget.MultiAutoCompleteTextView;

public class MainActivity extends Activity {

private AutoCompleteTextView acTextView;

private MultiAutoCompleteTextView macTextView;

private String[] res={"李浩","李浩1","李浩2","李浩3","李浩4"};

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        acTextView=(AutoCompleteTextView)findViewById(R.id.

        autoCompleteTextView1);

       ArrayAdapter<String> adapter=new ArrayAdapter<String>(this,

        android.R.layout.simple_list_item_1,res);

        acTextView.setAdapter(adapter);

        macTextView=(MultiAutoCompleteTextView)findViewById(R.

        id.multiAutoCompleteTextView1);

        macTextView.setAdapter(adapter);

        macTextView.setTokenizer(new 

        MultiAutoCompleteTextView.CommaTokenizer());

    }

}

这个是activity.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:orientation="vertical" >

    <AutoCompleteTextView

        android:id="@+id/autoCompleteTextView1"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:completionThreshold="2"

        android:hint="@string/hello_world" />

    <MultiAutoCompleteTextView

        android:id="@+id/multiAutoCompleteTextView1"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:completionThreshold="2"

        android:hint="@string/action_setting" />

</LinearLayout>

这个是String.xml  

<?xml version="1.0" encoding="utf-8"?>

<resources>

    <string name="app_name">Demo</string>

    <string name="hello_world">请输入你要搜索的关键字</string>

    <string name="action_setting">请输入你的联系人</string>

   </resources>

你能调试一下吗？

把log贴出来，不然谁知道