Android (Java) Learning note 164:relativelayout relative layout case

Let's take a look at the case code and take the hint:

<?XML version= "1.0" encoding= "Utf-8"?><Relativelayoutxmlns:android= "Http://schemas.android.com/apk/res/android"Android:layout_width= "Match_parent"Android:layout_height= "Match_parent" >    <ButtonAndroid:id= "@+id/bt_middle"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"android:layout_centerinparent= "true"Android:text= "Middle" />    <ButtonAndroid:id= "@+id/button1"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"Android:layout_above= "@id/bt_middle"Android:layout_centerhorizontal= "true"Android:text= "↑" />    <ButtonAndroid:id= "@+id/bt_down"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"Android:layout_below= "@id/bt_middle"Android:layout_centerhorizontal= "true"Android:text= "↓" />    <ButtonAndroid:id= "@+id/bt_left"Android:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"android:layout_centervertical= "true"Android:layout_toleftof= "@id/bt_middle"Android:text= "←" />    <ButtonAndroid:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"android:layout_centervertical= "true"Android:layout_torightof= "@id/bt_middle"Android:text= "→" />    <ButtonAndroid:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"Android:layout_below= "@id/bt_left"Android:layout_toleftof= "@id/bt_down"Android:text="" />    <ButtonAndroid:layout_width= "Wrap_content"Android:layout_height= "Wrap_content"Android:layout_alignbaseline= "@+id/button1"Android:layout_alignbottom= "@+id/button1"Android:layout_torightof= "@+id/button1"Android:text="" /></Relativelayout>

Layout:

Android (Java) Learning note 164:relativelayout relative layout case