diff --git a/V2rayNG/app/build.gradle b/V2rayNG/app/build.gradle
index e025b84a..a1ff9805 100644
--- a/V2rayNG/app/build.gradle
+++ b/V2rayNG/app/build.gradle
@@ -91,6 +91,7 @@ dependencies {
     implementation "com.android.support:cardview-v7:$supportLibVersion"
     implementation "com.android.support:preference-v7:$supportLibVersion"
     implementation "com.android.support:recyclerview-v7:$supportLibVersion"
+    implementation "com.android.support:multidex:1.0.3"
     // DSL
     implementation "org.jetbrains.anko:anko-sdk15:$ankoVersion"
     implementation "org.jetbrains.anko:anko-support-v4:$ankoVersion"
diff --git a/V2rayNG/app/src/main/kotlin/com/v2ray/ang/AngApplication.kt b/V2rayNG/app/src/main/kotlin/com/v2ray/ang/AngApplication.kt
index 26d8c378..73f816d5 100644
--- a/V2rayNG/app/src/main/kotlin/com/v2ray/ang/AngApplication.kt
+++ b/V2rayNG/app/src/main/kotlin/com/v2ray/ang/AngApplication.kt
@@ -1,12 +1,12 @@
 package com.v2ray.ang
 
-import android.app.Application
 //import com.squareup.leakcanary.LeakCanary
+import android.support.multidex.MultiDexApplication
 import com.v2ray.ang.util.AngConfigManager
 import me.dozen.dpreference.DPreference
 import org.jetbrains.anko.defaultSharedPreferences
 
-class AngApplication : Application() {
+class AngApplication : MultiDexApplication() {
     companion object {
         const val PREF_LAST_VERSION = "pref_last_version"
     }
diff --git a/V2rayNG/app/src/main/kotlin/com/v2ray/ang/service/V2RayVpnService.kt b/V2rayNG/app/src/main/kotlin/com/v2ray/ang/service/V2RayVpnService.kt
index 3c27f7bb..89c1766c 100644
--- a/V2rayNG/app/src/main/kotlin/com/v2ray/ang/service/V2RayVpnService.kt
+++ b/V2rayNG/app/src/main/kotlin/com/v2ray/ang/service/V2RayVpnService.kt
@@ -28,14 +28,9 @@ import libv2ray.Libv2ray
 import libv2ray.V2RayVPNServiceSupportsSet
 import rx.Observable
 import rx.Subscription
-import java.net.InetAddress
-import java.io.IOException
 import java.io.File
-import java.io.FileDescriptor
-import java.io.FileInputStream
 import java.lang.ref.SoftReference
 import android.os.Build
-import android.annotation.TargetApi
 import android.util.Log
 import go.Seq
 import org.jetbrains.anko.doAsync
@@ -74,25 +69,36 @@ class V2RayVpnService : VpnService() {
         *
         * Source: https://android.googlesource.com/platform/frameworks/base/+/2df4c7d/services/core/java/com/android/server/ConnectivityService.java#887
         */
-    @TargetApi(28)
-    private val defaultNetworkRequest = NetworkRequest.Builder()
-            .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
-            .addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED)
-            .build()
+    private val defaultNetworkRequest by lazy {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+            NetworkRequest.Builder()
+                .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
+                .addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED)
+                .build()
+        } else {
+            null
+        }
+    }
 
 
     private val connectivity by lazy { getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager }
-    @TargetApi(28)
-    private val defaultNetworkCallback = object : ConnectivityManager.NetworkCallback() {
-        override fun onAvailable(network: Network) {
-            setUnderlyingNetworks(arrayOf(network))
-        }
-        override fun onCapabilitiesChanged(network: Network, networkCapabilities: NetworkCapabilities?) {
-            // it's a good idea to refresh capabilities
-            setUnderlyingNetworks(arrayOf(network))
-        }
-        override fun onLost(network: Network) {
-            setUnderlyingNetworks(null)
+
+    private val defaultNetworkCallback by lazy {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+            object : ConnectivityManager.NetworkCallback() {
+                override fun onAvailable(network: Network) {
+                    setUnderlyingNetworks(arrayOf(network))
+                }
+                override fun onCapabilitiesChanged(network: Network, networkCapabilities: NetworkCapabilities?) {
+                    // it's a good idea to refresh capabilities
+                    setUnderlyingNetworks(arrayOf(network))
+                }
+                override fun onLost(network: Network) {
+                    setUnderlyingNetworks(null)
+                }
+            }
+        } else {
+            null
         }
     }
     private var listeningForDefaultNetwork = false
@@ -176,7 +182,7 @@ class V2RayVpnService : VpnService() {
         }
 
 
-        if (Build.VERSION.SDK_INT >= 28) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
             connectivity.requestNetwork(defaultNetworkRequest, defaultNetworkCallback)
             listeningForDefaultNetwork = true
         }
@@ -260,7 +266,7 @@ class V2RayVpnService : VpnService() {
 //        val emptyInfo = VpnNetworkInfo()
 //        val info = loadVpnNetworkInfo(configName, emptyInfo)!! + (lastNetworkInfo ?: emptyInfo)
 //        saveVpnNetworkInfo(configName, info)
-        if (Build.VERSION.SDK_INT >= 28) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
             if (listeningForDefaultNetwork) {
                 connectivity.unregisterNetworkCallback(defaultNetworkCallback)
                 listeningForDefaultNetwork = false