An unexpected bottom border in floatingSearchView...

[8Q757]

This view will have a bottom border about 30px ,do I make a mistake?

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context=".MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <com.arlib.floatingsearchview.FloatingSearchView
            android:id="@+id/search_bar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:floatingSearch_close_search_on_keyboard_dismiss="true"
            app:floatingSearch_dimBackground="false"
            app:floatingSearch_dismissOnOutsideTouch="true"
            app:floatingSearch_leftActionMode="showHamburger"
            app:floatingSearch_searchHint="Search..."
            app:layout_scrollFlags="scroll">

        </com.arlib.floatingsearchview.FloatingSearchView>

    </android.support.design.widget.AppBarLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:elevation="5dp"
        app:srcCompat="@drawable/ic_add_black_24dp" />

    <ListView
        android:id="@+id/list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:dividerHeight="7.5dp"
        android:paddingTop="10dp"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"></ListView>

</android.support.design.widget.CoordinatorLayout>