怎么就会崩溃了，求各位学友解答啊。

Question

package com.example.android_arrayadapter;import android.R.anim;import android.support.v7.app.ActionBarActivity;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.widget.ArrayAdapter;import android.widget.ListView;import android.widget.SimpleAdapter;public class MainActivity extends ActionBarActivity { private ListView listView; private ArrayAdapter<String>arrayAdapter; private SimpleAdapter simpleAdapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        listView=(ListView) findViewById(R.id.listView);        String[]arr_data={"慕课网1","慕课网2","慕课网3","慕课网4"};        arrayAdapter=new ArrayAdapter<String>(this, android.R.layout.simple_expandable_list_item_1, arr_data);        listView.setAdapter(arrayAdapter);    }}