Try out below code for your listitems:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center_horizontal"
android:gravity="center" >
<TextView
android:id="@+id/tvItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_marginLeft="10dp"
android:gravity="center_vertical"
android:layout_toLeftOf="@+id/bDelete"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
<Button
android:id="@+id/bDelete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_marginRight="5dp"
android:layout_alignBaseline="@+id/tvItem"
android:text="DONE"
android:gravity="center_vertical"
android:textSize="15dp" />
</RelativeLayout>