优化

app/src/main/res/layout/activity_book_search.xml

@@ -48,6 +48,15 @@
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintTop_toBottomOf="@id/title_bar">
 
+        <TextView
+            android:id="@+id/tv_searchScope"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:padding="6dp"
+            android:text="@string/all_source"
+            android:singleLine="true"
+            android:gravity="center" />
+
         <TextView
             android:id="@+id/tv_book_show"
             android:layout_width="match_parent"