如何在Android中利用ScrollView实现一个顶部悬停效果

<&#63;xml version="1.0" encoding="utf-8"&#63;><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"        android:layout_width="match_parent"        android:layout_height="match_parent">  <com.lanmai.ObservableScrollView    xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/scrollview"    android:layout_width="match_parent"    android:layout_height="match_parent"    >    <RelativeLayout      android:layout_width="match_parent"      android:layout_height="match_parent"      android:orientation="vertical">      <LinearLayout        android:layout_width="match_parent"        android:layout_height="match_parent"        android:orientation="vertical">          <!-- 中间就是填充的view就不写了-->          <!--指定要置顶的view-->        <TextView          android:id="@+id/specific_text_view"          android:layout_width="match_parent"          android:layout_height="wrap_content"          android:background="@android:color/holo_red_dark"          android:gravity="center"          android:text="text"          android:textSize="40sp"/>        <TextView          android:layout_width="match_parent"          android:layout_height="200dp"          android:background="@android:color/darker_gray"          android:gravity="center"          android:text="text"          android:textSize="40sp"/>      </LinearLayout>    </RelativeLayout>  </com.lanmai.ObservableScrollView>  <!--指定要置顶的相同的view visibility设置为gone -->  <TextView    android:id="@+id/specific_text_view_gone"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:background="@android:color/holo_red_dark"    android:gravity="center"    android:text="text"    android:textSize="40sp"    android:visibility="gone"/></RelativeLayout>