diff --git a/app/src/main/java/io/legado/app/ui/book/read/page/ContentView.kt b/app/src/main/java/io/legado/app/ui/book/read/page/ContentView.kt
index bcc375a69..95b7ae318 100644
--- a/app/src/main/java/io/legado/app/ui/book/read/page/ContentView.kt
+++ b/app/src/main/java/io/legado/app/ui/book/read/page/ContentView.kt
@@ -51,6 +51,11 @@ class ContentView(context: Context) : FrameLayout(context) {
         }
     }
 
+    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
+        super.onSizeChanged(w, h, oldw, oldh)
+        upStyle()
+    }
+
     fun upStyle() {
         ReadBookConfig.apply {
             bv_header_left.typeface = ChapterProvider.typeface
diff --git a/app/src/main/java/io/legado/app/utils/ActivityExtensions.kt b/app/src/main/java/io/legado/app/utils/ActivityExtensions.kt
index c8a0531ec..df4bae769 100644
--- a/app/src/main/java/io/legado/app/utils/ActivityExtensions.kt
+++ b/app/src/main/java/io/legado/app/utils/ActivityExtensions.kt
@@ -22,6 +22,10 @@ fun Activity.getSize(): DisplayMetrics {
     return displayMetrics
 }
 
+/**
+ * 该方法需要在View完全被绘制出来之后调用，否则判断不了
+ * 在比如 onWindowFocusChanged（）方法中可以得到正确的结果
+ */
 val Activity.navigationBarHeight: Int
     get() {
         if (SystemUtils.isNavigationBarExist(this)) {