diff --git a/app/src/main/java/io/legado/app/ui/book/read/ReadBookActivity.kt b/app/src/main/java/io/legado/app/ui/book/read/ReadBookActivity.kt
index 3125f70d0..8bd8c8d0c 100644
--- a/app/src/main/java/io/legado/app/ui/book/read/ReadBookActivity.kt
+++ b/app/src/main/java/io/legado/app/ui/book/read/ReadBookActivity.kt
@@ -6,6 +6,7 @@ import android.content.Intent
 import android.net.Uri
 import android.os.AsyncTask.execute
 import android.os.Bundle
+import android.os.Handler
 import android.text.SpannableStringBuilder
 import android.view.KeyEvent
 import android.view.Menu
@@ -63,20 +64,26 @@ class ReadBookActivity : VMBaseActivity<ReadBookViewModel>(R.layout.activity_boo
     ChangeSourceDialog.CallBack,
     ReadBook.CallBack,
     ColorPickerDialogListener {
+    private val requestCodeChapterList = 568
+    private val requestCodeEditSource = 111
+    private val requestCodeReplace = 31242
+
     override val viewModel: ReadBookViewModel
         get() = getViewModel(ReadBookViewModel::class.java)
 
     override val isInitFinish: Boolean
         get() = viewModel.isInitFinish
 
-    private val requestCodeChapterList = 568
-    private val requestCodeEditSource = 111
-    private val requestCodeReplace = 31242
+    private val mHandler = Handler()
+    private val keepScreenRunnable: Runnable = Runnable { Help.keepScreenOn(window, false) }
+
+    private var screenTimeOut: Long = 0
     private var timeElectricityReceiver: TimeElectricityReceiver? = null
 
     override fun onActivityCreated(savedInstanceState: Bundle?) {
         Help.upLayoutInDisplayCutoutMode(window)
         initView()
+        upScreenTimeOut()
         ReadBook.callBack = this
         ReadBook.titleDate.observe(this, Observer { title_bar.title = it })
         viewModel.initData(intent)
@@ -179,11 +186,11 @@ class ReadBookActivity : VMBaseActivity<ReadBookViewModel>(R.layout.activity_boo
                 }.show().applyTint()
             }
             R.id.menu_add_bookmark -> {
-                val book = ReadBook.book
+                val book = ReadBook.book ?: return true
                 val textChapter = ReadBook.curTextChapter
                 alert(title = getString(R.string.bookmark_add)) {
                     var editText: EditText? = null
-                    message = book?.name + " • " + textChapter?.title
+                    message = book.name + " • " + textChapter?.title
                     customView {
                         layoutInflater.inflate(R.layout.dialog_edit_text, null).apply {
                             editText = edit_view.apply {
@@ -195,9 +202,9 @@ class ReadBookActivity : VMBaseActivity<ReadBookViewModel>(R.layout.activity_boo
                         editText?.text?.toString()?.let { editContent ->
                             execute {
                                 val bookmark = Bookmark(
-                                    book!!.durChapterTime,
-                                    book!!.bookUrl,
-                                    book!!.name,
+                                    book.durChapterTime,
+                                    book.bookUrl,
+                                    book.name,
                                     ReadBook.durChapterIndex,
                                     ReadBook.durPageIndex,
                                     textChapter!!.title,
@@ -548,4 +555,27 @@ class ReadBookActivity : VMBaseActivity<ReadBookViewModel>(R.layout.activity_boo
         }
     }
 
+    private fun upScreenTimeOut() {
+        getPrefString("keep_light")?.let {
+            screenTimeOut = it.toLong() * 1000
+        }
+    }
+
+    /**
+     * 重置黑屏时间
+     */
+    fun screenOffTimerStart() {
+        if (screenTimeOut < 0) {
+            Help.keepScreenOn(window, true)
+            return
+        }
+        val t = screenTimeOut - getScreenOffTime()
+        if (t > 0) {
+            mHandler.removeCallbacks(keepScreenRunnable)
+            Help.keepScreenOn(window, true)
+            mHandler.postDelayed(keepScreenRunnable, screenTimeOut)
+        } else {
+            Help.keepScreenOn(window, false)
+        }
+    }
 }
\ No newline at end of file
diff --git a/app/src/main/java/io/legado/app/utils/ContextExtensions.kt b/app/src/main/java/io/legado/app/utils/ContextExtensions.kt
index 7f4be23c0..7b920dfa7 100644
--- a/app/src/main/java/io/legado/app/utils/ContextExtensions.kt
+++ b/app/src/main/java/io/legado/app/utils/ContextExtensions.kt
@@ -6,6 +6,7 @@ import android.content.Intent
 import android.content.res.ColorStateList
 import android.graphics.Bitmap
 import android.graphics.drawable.Drawable
+import android.provider.Settings
 import androidx.annotation.ColorRes
 import androidx.annotation.DrawableRes
 import androidx.core.content.ContextCompat
@@ -63,6 +64,16 @@ fun Context.getCompatDrawable(@DrawableRes id: Int): Drawable? = ContextCompat.g
 fun Context.getCompatColorStateList(@ColorRes id: Int): ColorStateList? =
     ContextCompat.getColorStateList(this, id)
 
+fun Context.getScreenOffTime(): Int {
+    var screenOffTime = 0
+    try {
+        screenOffTime = Settings.System.getInt(contentResolver, Settings.System.SCREEN_OFF_TIMEOUT)
+    } catch (e: Exception) {
+        e.printStackTrace()
+    }
+    return screenOffTime
+}
+
 fun Context.getStatusBarHeight(): Int {
     val resourceId = resources.getIdentifier("status_bar_height", "dimen", "android")
     return resources.getDimensionPixelSize(resourceId)