Use of Android and listview

package com.example.atest25;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.widget.ArrayAdapter;import android.widget.ListView;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);String[] str1 = {"aaa","bbb","ccc","ddd","eee","fff","ggg","hhh","iii","jjj","kkk","lll","mmm","nnn","ooo"};ListView list1 = (ListView)findViewById(R.id.listView1);ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1,str1);list1.setAdapter(arrayAdapter);}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}}

<Linearlayout xmlns: Android = "http://schemas.android.com/apk/res/android" xmlns: Tools = "http://schemas.android.com/tools" Android: Id = "@ + ID/linearlayout1" Android: layout_width = "match_parent" Android: layout_height = "match_parent" Android: Orientation = "vertical" Android: paddingbottom = "@ dimen/activity_vertical_margin" Android: paddingleft = "@ dimen/login" Android: paddingright = "@ dimen/activity_horizontal_margin" Android: paddingtop = "@ dimen/activity_vertical_margin" tools: context = ". mainactivity "> <linearlayout Android: layout_width =" match_parent "Android: layout_height =" wrap_content "> <textview Android: layout_width =" wrap_content "Android: layout_height =" wrap_content "Android: TEXT = "query by type"/> <spinner Android: Id = "@ + ID/spinner1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: layout_weight = "1"/> <button Android: Id = "@ + ID/button1" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content" Android: TEXT = "button"/> </linearlayout> <listview Android: Id = "@ + ID/listview1" Android: layout_width = "match_parent" Android: layout_height = "wrap_content"> </listview> </linearlayout>