fragment_b.xml

<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:background="@color/colorPrimary"    android:orientation="vertical">        <com.handmark.pulltorefresh.library.PullToRefreshListView            android:id="@+id/plv"            android:layout_width="match_parent"            android:layout_height="match_parent"/></LinearLayout>