diff --git a/app/src/main/java/io/legado/app/service/DownloadService.kt b/app/src/main/java/io/legado/app/service/DownloadService.kt
index d386aef2d..446e7ae06 100644
--- a/app/src/main/java/io/legado/app/service/DownloadService.kt
+++ b/app/src/main/java/io/legado/app/service/DownloadService.kt
@@ -275,7 +275,6 @@ class DownloadService : BaseService() {
         startForeground(AppConst.notificationIdDownload, notification)
     }
 
-
     class DownloadCount {
         @Volatile
         var downloadFinishedCount = 0 // 下载完成的条目数量
diff --git a/app/src/main/java/io/legado/app/ui/book/download/DownloadActivity.kt b/app/src/main/java/io/legado/app/ui/book/download/DownloadActivity.kt
index 0d3de4895..ecb9c6b67 100644
--- a/app/src/main/java/io/legado/app/ui/book/download/DownloadActivity.kt
+++ b/app/src/main/java/io/legado/app/ui/book/download/DownloadActivity.kt
@@ -30,6 +30,8 @@ import kotlinx.coroutines.Dispatchers.IO
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import org.jetbrains.anko.toast
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.CopyOnWriteArraySet
 
 
 class DownloadActivity : VMBaseActivity<DownloadViewModel>(R.layout.activity_download),
@@ -172,7 +174,7 @@ class DownloadActivity : VMBaseActivity<DownloadViewModel>(R.layout.activity_dow
     }
 
     override fun observeLiveBus() {
-        observeEvent<HashMap<String, LinkedHashSet<BookChapter>>>(EventBus.UP_DOWNLOAD) {
+        observeEvent<ConcurrentHashMap<String, CopyOnWriteArraySet<BookChapter>>>(EventBus.UP_DOWNLOAD) {
             if (it.isEmpty()) {
                 menu?.findItem(R.id.menu_download)?.setIcon(R.drawable.ic_play_24dp)
                 menu?.applyTint(this)
diff --git a/app/src/main/java/io/legado/app/ui/book/download/DownloadAdapter.kt b/app/src/main/java/io/legado/app/ui/book/download/DownloadAdapter.kt
index 082e5aecc..3da043450 100644
--- a/app/src/main/java/io/legado/app/ui/book/download/DownloadAdapter.kt
+++ b/app/src/main/java/io/legado/app/ui/book/download/DownloadAdapter.kt
@@ -10,13 +10,15 @@ import io.legado.app.data.entities.BookChapter
 import io.legado.app.service.help.Download
 import kotlinx.android.synthetic.main.item_download.view.*
 import org.jetbrains.anko.sdk27.listeners.onClick
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.CopyOnWriteArraySet
 
 
 class DownloadAdapter(context: Context, private val callBack: CallBack) :
     SimpleRecyclerAdapter<Book>(context, R.layout.item_download) {
 
     val cacheChapters = hashMapOf<String, HashSet<String>>()
-    var downloadMap: HashMap<String, LinkedHashSet<BookChapter>>? = null
+    var downloadMap: ConcurrentHashMap<String, CopyOnWriteArraySet<BookChapter>>? = null
 
     override fun convert(holder: ItemViewHolder, item: Book, payloads: MutableList<Any>) {
         with(holder.itemView) {