feat: 优化代码

app/src/main/res/drawable/ic_cursor_left.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+
+    <path
+        android:fillColor="#595757"
+        android:pathData="M12,4h8v8c0,4.418-3.582,8-8,8s-8-3.582-8-8S7.582,4,12,4z" />
+</vector>

app/src/main/res/drawable/ic_cursor_right.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+
+    <path
+        android:fillColor="#595757"
+        android:pathData="M12,4.208H4v8c0,4.418,3.582,8,8,8s8-3.582,8-8S16.418,4.208,12,4.208z" />
+</vector>

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

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical">
@@ -9,10 +9,26 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent" />
 
+    <ImageView
+        android:id="@+id/cursor_left"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:contentDescription="@null"
+        android:src="@drawable/ic_cursor_left"
+        android:visibility="invisible" />
+
+    <ImageView
+        android:id="@+id/cursor_right"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:contentDescription="@null"
+        android:src="@drawable/ic_cursor_right"
+        android:visibility="invisible" />
+
     <io.legado.app.ui.book.read.ReadMenu
         android:id="@+id/read_menu"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:visibility="gone" />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+</FrameLayout>