diff --git a/BeanCovertor.kt b/BeanCovertor.kt
index 7001164c8..5c35c0da1 100644
--- a/BeanCovertor.kt
+++ b/BeanCovertor.kt
@@ -1,6 +1,7 @@
 package io.agora.rtc.base
 
 import android.graphics.Color
+import io.agora.rtc.RtcEngineConfig
 import io.agora.rtc.internal.EncryptionConfig
 import io.agora.rtc.internal.LastmileProbeConfig
 import io.agora.rtc.live.LiveInjectStreamConfig
@@ -172,6 +173,13 @@ fun mapToChannelMediaOptions(map: Map<*, *>): ChannelMediaOptions {
   }
 }
 
+fun mapToRtcEngineConfig(map: Map<*, *>): RtcEngineConfig {
+  return RtcEngineConfig().apply {
+    mAppId = map["appId"] as String
+    (map["areaCode"] as? Number)?.toInt()?.let { mAreaCode = it }
+  }
+}
+
 fun mapToEncryptionConfig(map: Map<*, *>): EncryptionConfig {
   return EncryptionConfig().apply {
     (map["encryptionMode"] as? Number)?.let { encryptionMode = intToEncryptionMode(it.toInt()) }
diff --git a/MediaObserver.kt b/MediaObserver.kt
index fef7214f1..21f3b20c3 100644
--- a/MediaObserver.kt
+++ b/MediaObserver.kt
@@ -8,7 +8,7 @@ import java.util.concurrent.atomic.AtomicInteger
 class MediaObserver(
   private val emit: (data: Map<String, Any?>?) -> Unit
 ) : IMetadataObserver {
-  private var maxMetadataSize = AtomicInteger(0)
+  private var maxMetadataSize = AtomicInteger(1024)
   private var metadataList = Collections.synchronizedList<String>(mutableListOf())
 
   fun addMetadata(metadata: String) {
diff --git a/RtcChannel.kt b/RtcChannel.kt
index 4734add1c..cce3f51fe 100644
--- a/RtcChannel.kt
+++ b/RtcChannel.kt
@@ -141,11 +141,7 @@ class RtcChannelManager(
   }
 
   override fun destroy(params: Map<String, *>, callback: Callback) {
-    var code: Int? = -Constants.ERR_NOT_INITIALIZED
-    this[params["channelId"] as String]?.let {
-      code = rtcChannelMap.remove(it.channelId())?.destroy()
-    }
-    callback.code(code)
+    callback.code(rtcChannelMap.remove(params["channelId"] as String)?.destroy())
   }
 
   override fun setClientRole(params: Map<String, *>, callback: Callback) {
@@ -258,24 +254,22 @@ class RtcChannelManager(
   }
 
   override fun registerMediaMetadataObserver(params: Map<String, *>, callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    this[params["channelId"] as String]?.let {
-      val mediaObserver = MediaObserver { data ->
-        emit(RtcChannelEvents.MetadataReceived, data?.toMutableMap()?.apply { put("channelId", it.channelId()) })
-      }
-      code = it.registerMediaMetadataObserver(mediaObserver, IMetadataObserver.VIDEO_METADATA)
-      if (code == 0) mediaObserverMap[it.channelId()] = mediaObserver
+    val channelId = params["channelId"] as String
+    val mediaObserver = MediaObserver { data ->
+      emit(RtcChannelEvents.MetadataReceived, data?.toMutableMap()?.apply { put("channelId", channelId) })
+    }
+    callback.code(this[channelId]?.registerMediaMetadataObserver(mediaObserver, IMetadataObserver.VIDEO_METADATA)) {
+      mediaObserverMap[channelId] = mediaObserver
+      Unit
     }
-    callback.code(code)
   }
 
   override fun unregisterMediaMetadataObserver(params: Map<String, *>, callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    this[params["channelId"] as String]?.let {
-      code = it.registerMediaMetadataObserver(null, IMetadataObserver.VIDEO_METADATA)
-      if (code == 0) mediaObserverMap.remove(it.channelId())
+    val channelId = params["channelId"] as String
+    callback.code(this[channelId]?.registerMediaMetadataObserver(null, IMetadataObserver.VIDEO_METADATA)) {
+      mediaObserverMap.remove(channelId)
+      Unit
     }
-    callback.code(code)
   }
 
   override fun setMaxMetadataSize(params: Map<String, *>, callback: Callback) {
@@ -318,18 +312,11 @@ class RtcChannelManager(
   }
 
   override fun createDataStream(params: Map<String, *>, callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    this[params["channelId"] as String]?.let {
-      code = it.createDataStream(params["reliable"] as Boolean, params["ordered"] as Boolean)
-    }
-    callback.code(code) { it }
+    val channel = this[params["channelId"] as String]
+    callback.code(channel?.createDataStream(params["reliable"] as Boolean, params["ordered"] as Boolean)) { it }
   }
 
   override fun sendStreamMessage(params: Map<String, *>, callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    this[params["channelId"] as String]?.let {
-      code = it.sendStreamMessage((params["streamId"] as Number).toInt(), (params["message"] as String).toByteArray())
-    }
-    callback.code(code)
+    callback.code(this[params["channelId"] as String]?.sendStreamMessage((params["streamId"] as Number).toInt(), (params["message"] as String).toByteArray()))
   }
 }
diff --git a/RtcEngine.kt b/RtcEngine.kt
index 90d9a7343..9ffba110a 100644
--- a/RtcEngine.kt
+++ b/RtcEngine.kt
@@ -344,10 +344,8 @@ class RtcEngineManager(
   }
 
   override fun create(params: Map<String, *>, callback: Callback) {
-    engine = RtcEngineEx.create(RtcEngineConfig().apply {
+    engine = RtcEngineEx.create(mapToRtcEngineConfig(params["config"] as Map<*, *>).apply {
       mContext = params["context"] as Context
-      mAppId = params["appId"] as String
-      mAreaCode = (params["areaCode"] as Number).toInt()
       mEventHandler = RtcEngineEventHandler { methodName, data ->
         emit(methodName, data)
       }
@@ -373,11 +371,17 @@ class RtcEngineManager(
   }
 
   override fun joinChannel(params: Map<String, *>, callback: Callback) {
-    callback.code(engine?.joinChannel(params["token"] as? String, params["channelName"] as String, params["optionalInfo"] as? String, (params["optionalUid"] as Number).toInt()))
+    val token = params["token"] as? String
+    val channelName = params["channelName"] as String
+    val optionalInfo = params["optionalInfo"] as? String
+    val optionalUid = (params["optionalUid"] as Number).toInt()
+    callback.code(engine?.joinChannel(token, channelName, optionalInfo, optionalUid))
   }
 
   override fun switchChannel(params: Map<String, *>, callback: Callback) {
-    callback.code(engine?.switchChannel(params["token"] as? String, params["channelName"] as String))
+    val token = params["token"] as? String
+    val channelName = params["channelName"] as String
+    callback.code(engine?.switchChannel(token, channelName))
   }
 
   override fun leaveChannel(callback: Callback) {
@@ -437,7 +441,10 @@ class RtcEngineManager(
   }
 
   override fun joinChannelWithUserAccount(params: Map<String, *>, callback: Callback) {
-    callback.code(engine?.joinChannelWithUserAccount(params["token"] as? String, params["channelName"] as String, params["userAccount"] as String))
+    val token = params["token"] as? String
+    val channelName = params["channelName"] as String
+    val userAccount = params["userAccount"] as String
+    callback.code(engine?.joinChannelWithUserAccount(token, channelName, userAccount))
   }
 
   override fun getUserInfoByUserAccount(params: Map<String, *>, callback: Callback) {
@@ -785,24 +792,20 @@ class RtcEngineManager(
   }
 
   override fun registerMediaMetadataObserver(callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    engine?.let {
-      val mediaObserver = MediaObserver { data ->
-        emit(RtcEngineEvents.MetadataReceived, data)
-      }
-      code = it.registerMediaMetadataObserver(mediaObserver, IMetadataObserver.VIDEO_METADATA)
-      if (code == 0) this.mediaObserver = mediaObserver
+    val mediaObserver = MediaObserver { data ->
+      emit(RtcEngineEvents.MetadataReceived, data)
+    }
+    callback.code(engine?.registerMediaMetadataObserver(mediaObserver, IMetadataObserver.VIDEO_METADATA)) {
+      this.mediaObserver = mediaObserver
+      Unit
     }
-    callback.code(code)
   }
 
   override fun unregisterMediaMetadataObserver(callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    engine?.let {
-      code = it.registerMediaMetadataObserver(null, IMetadataObserver.VIDEO_METADATA)
-      if (code == 0) mediaObserver = null
+    callback.code(engine?.registerMediaMetadataObserver(null, IMetadataObserver.VIDEO_METADATA)) {
+      mediaObserver = null
+      Unit
     }
-    callback.code(code)
   }
 
   override fun setMaxMetadataSize(params: Map<String, *>, callback: Callback) {
@@ -916,18 +919,10 @@ class RtcEngineManager(
   }
 
   override fun createDataStream(params: Map<String, *>, callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    engine?.let {
-      code = it.createDataStream(params["reliable"] as Boolean, params["ordered"] as Boolean)
-    }
-    callback.code(code) { it }
+    callback.code(engine?.createDataStream(params["reliable"] as Boolean, params["ordered"] as Boolean)) { it }
   }
 
   override fun sendStreamMessage(params: Map<String, *>, callback: Callback) {
-    var code = -Constants.ERR_NOT_INITIALIZED
-    engine?.let {
-      code = it.sendStreamMessage((params["streamId"] as Number).toInt(), (params["message"] as String).toByteArray())
-    }
-    callback.code(code)
+    callback.code(engine?.sendStreamMessage((params["streamId"] as Number).toInt(), (params["message"] as String).toByteArray()))
   }
 }