android layout allignment issue -

i want put "type 1" , "type 2" in same line , make on center. means everything. working on api level 23. trued android:layout_centerhorizontal="true" in inner linearlayout doesn't work

<?xml version="1.0" encoding="utf-8"?> <relativelayout 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:paddingbottom="@dimen/activity_vertical_margin" android:paddingleft="@dimen/activity_horizontal_margin" android:paddingright="@dimen/activity_horizontal_margin" android:paddingtop="@dimen/activity_vertical_margin" tools:context="com.example.sid.roommanager.btrancol">    <linearlayout     android:id="@+id/linearlayout02"     android:layout_height="wrap_content"     android:layout_width="fill_parent"     android:layout_alignparenttop="true"      >  <textview     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="milliseconds"      android:id="@+id/tv_milli"     />  <edittext     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:id="@+id/edittext"     android:inputtype="number"      android:text="1000"     /> </linearlayout>  <button     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="type 1"     android:id="@+id/bt_led1"     android:layout_below="@+id/linearlayout02"             android:layout_marginend="134dp"      android:layout_centerhorizontal="true"     />  <button     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="type 2"     android:id="@+id/bt_led2"     android:layout_below="@+id/bt_led1"     android:layout_centerhorizontal="true"     />      </relativelayout> 

there many solutions problem. 1 of them given below. use nested <linearlayout> elements gravity set center_horizontal:

<?xml version="1.0" encoding="utf-8"?> <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:gravity="center_horizontal"               android:orientation="vertical"               android:paddingbottom="@dimen/activity_vertical_margin"               android:paddingleft="@dimen/activity_horizontal_margin"               android:paddingright="@dimen/activity_horizontal_margin"               android:paddingtop="@dimen/activity_vertical_margin"               tools:context="com.example.sid.roommanager.btrancol">       <linearlayout         android:id="@+id/linearlayout02"         android:layout_width="fill_parent"         android:layout_height="wrap_content"         android:gravity="center_horizontal">          <textview             android:id="@+id/tv_milli"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="milliseconds"             />          <edittext             android:id="@+id/edittext"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:inputtype="number"             android:text="1000"             />     </linearlayout>      <linearlayout         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:gravity="center_horizontal">          <button             android:id="@+id/bt_led1"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="type 1"             />          <button             android:id="@+id/bt_led2"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="type 2"             />      </linearlayout>   </linearlayout>