diff --git a/src/main/AndroidManifest.xml b/src/main/AndroidManifest.xml
index 14c0bb78..dfb8ced2 100644
--- a/src/main/AndroidManifest.xml
+++ b/src/main/AndroidManifest.xml
@@ -66,7 +66,8 @@
                 android:name=".ProfileManagerActivity"
                 android:label="@string/profiles"
                 android:parentActivityName=".Shadowsocks"
-                android:exported="false">
+                android:exported="false"
+                android:launchMode="singleTask">
             <intent-filter>
                 <action android:name="com.github.shadowsocks.ProfileManagerActivity"/>
                 <category android:name="android.intent.category.DEFAULT"/>
@@ -76,7 +77,8 @@
         <activity
                 android:name=".AppManager"
                 android:label="@string/proxied_apps"
-                android:parentActivityName=".Shadowsocks"/>
+                android:parentActivityName=".Shadowsocks"
+                android:launchMode="singleTask"/>
 
         <service
                 android:name=".ShadowsocksRunnerService"
diff --git a/src/main/res/xml/pref_all.xml b/src/main/res/xml/pref_all.xml
index a3017ba1..637eebaa 100644
--- a/src/main/res/xml/pref_all.xml
+++ b/src/main/res/xml/pref_all.xml
@@ -14,23 +14,19 @@
             android:title="@string/proxy_cat">
 
         <com.github.shadowsocks.preferences.SummaryEditTextPreference
-                android:defaultValue="Default"
                 android:key="profileName"
                 android:title="@string/profile_name"/>
         <com.github.shadowsocks.preferences.SummaryEditTextPreference
-                android:defaultValue="198.199.101.152"
                 android:key="proxy"
                 android:summary="@string/proxy_summary"
                 android:title="@string/proxy"/>
         <com.github.shadowsocks.preferences.NumberPickerPreference
-                android:defaultValue="443"
                 app:min="1"
                 app:max="65535"
                 android:key="remotePort"
                 app:summary="@string/remote_port_summary"
                 android:title="@string/remote_port"/>
         <com.github.shadowsocks.preferences.NumberPickerPreference
-                android:defaultValue="1080"
                 app:min="1025"
                 app:max="65535"
                 android:key="port"
@@ -38,12 +34,10 @@
                 android:title="@string/port"/>
         <com.github.shadowsocks.preferences.PasswordEditTextPreference
                 android:inputType="textPassword"
-                android:defaultValue="u1rRWTssNv0p"
                 android:key="sitekey"
                 android:summary="@string/sitekey_summary"
                 android:title="@string/sitekey"/>
         <com.github.shadowsocks.preferences.DropDownPreference
-                android:defaultValue="rc4"
                 android:key="encMethod"
                 app:entries="@array/enc_method_entry"
                 app:entryValues="@array/enc_method_value"
@@ -51,7 +45,6 @@
                 android:title="@string/enc_method"/>
         <SwitchPreference
                 android:key="isAuth"
-                android:defaultValue="false"
                 android:summary="@string/onetime_auth_summary"
                 android:title="@string/onetime_auth"/>
 
@@ -61,7 +54,6 @@
             android:title="@string/feature_cat">
 
         <com.github.shadowsocks.preferences.DropDownPreference
-                android:defaultValue="all"
                 android:key="route"
                 app:entries="@array/route_entry"
                 app:entryValues="@array/route_value"
@@ -69,17 +61,14 @@
                 android:title="@string/route_list"/>
         <SwitchPreference
                 android:key="isIpv6"
-                android:defaultValue="false"
                 android:summary="@string/ipv6_summary"
                 android:title="@string/ipv6"/>
         <SwitchPreference
                 android:key="isProxyApps"
-                android:defaultValue="false"
                 android:summary="@string/proxied_apps_summary"
                 android:title="@string/proxied_apps"/>
         <SwitchPreference
                 android:key="isUdpDns"
-                android:defaultValue="false"
                 android:summary="@string/udp_dns_summary"
                 android:title="@string/udp_dns"/>
 
diff --git a/src/main/scala/com/github/shadowsocks/ParserActivity.scala b/src/main/scala/com/github/shadowsocks/ParserActivity.scala
index 1900a27f..6d24af45 100644
--- a/src/main/scala/com/github/shadowsocks/ParserActivity.scala
+++ b/src/main/scala/com/github/shadowsocks/ParserActivity.scala
@@ -44,33 +44,33 @@ import android.content.DialogInterface
 import android.graphics.Color
 import android.graphics.drawable.ColorDrawable
 import android.os.Bundle
-import android.preference.PreferenceManager
 import android.view.WindowManager
-import com.github.shadowsocks.database.{Profile, ProfileManager}
 import com.github.shadowsocks.utils.Parser
 
 class ParserActivity extends Activity {
   override def onCreate(savedInstanceState: Bundle) {
     super.onCreate(savedInstanceState)
-    showAsPopup(this)
     val data = getIntent.getData.toString
-    new AlertDialog.Builder(this)
+    val profile = Parser.parse(data)
+    if (profile.isEmpty) {  // ignore
+      finish()
+      return
+    }
+    showAsPopup(this)
+    val dialog = new AlertDialog.Builder(this)
       .setTitle(R.string.add_profile_dialog)
       .setCancelable(false)
       .setPositiveButton(android.R.string.yes, ((dialog: DialogInterface, id: Int) => {
-        Parser.parse(data) match {
-          case Some(profile) => addProfile(profile)
-          case _ => // ignore
-        }
+        ShadowsocksApplication.profileManager.createOrUpdateProfile(profile.get)
         dialog.dismiss()
       }): DialogInterface.OnClickListener)
       .setNegativeButton(android.R.string.no, ((dialog: DialogInterface, id: Int) => {
         dialog.dismiss()
-        finish()
       }): DialogInterface.OnClickListener)
       .setMessage(data)
       .create()
-      .show()
+    dialog.setOnDismissListener((dialog: DialogInterface) => finish())  // builder method was added in API 17
+    dialog.show()
   }
 
   def showAsPopup(activity: Activity) {
@@ -82,13 +82,4 @@ class ParserActivity extends Activity {
     activity.getWindow.setAttributes(params.asInstanceOf[android.view.WindowManager.LayoutParams])
     activity.getWindow.setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT))
   }
-
-  def addProfile(profile: Profile) {
-    val profileManager =
-      new ProfileManager(PreferenceManager.getDefaultSharedPreferences(getBaseContext),
-        ShadowsocksApplication.dbHelper)
-    profileManager.createOrUpdateProfile(profile)
-    profileManager.reload(profile.id)
-  }
-
 }
diff --git a/src/main/scala/com/github/shadowsocks/ProfileManagerActivity.scala b/src/main/scala/com/github/shadowsocks/ProfileManagerActivity.scala
index 1f2d9583..8bbebe0c 100644
--- a/src/main/scala/com/github/shadowsocks/ProfileManagerActivity.scala
+++ b/src/main/scala/com/github/shadowsocks/ProfileManagerActivity.scala
@@ -61,7 +61,7 @@ class ProfileManagerActivity extends AppCompatActivity with OnMenuItemClickListe
     }
 
     def onClick(v: View) = {
-      ShadowsocksApplication.profileId(item.id)
+      ShadowsocksApplication.switchProfile(item.id)
       finish
     }
   }
@@ -82,10 +82,8 @@ class ProfileManagerActivity extends AppCompatActivity with OnMenuItemClickListe
       removedSnackbar.dismiss
       commitRemoves
       val pos = getItemCount
-      if (ShadowsocksApplication.profileManager.createOrUpdateProfile(item)) {
-        profiles += item
-        notifyItemInserted(pos)
-      }
+      profiles += item
+      notifyItemInserted(pos)
     }
 
     def remove(pos: Int) {
@@ -126,6 +124,7 @@ class ProfileManagerActivity extends AppCompatActivity with OnMenuItemClickListe
     toolbar.inflateMenu(R.menu.add_profile_methods)
     toolbar.setOnMenuItemClickListener(this)
 
+    ShadowsocksApplication.profileManager.setProfileAddedListener(profilesAdapter.add)
     val profilesList = findViewById(R.id.profilesList).asInstanceOf[RecyclerView]
     profilesList.setLayoutManager(new LinearLayoutManager(this))
     profilesList.setItemAnimator(new DefaultItemAnimator)
@@ -147,13 +146,14 @@ class ProfileManagerActivity extends AppCompatActivity with OnMenuItemClickListe
 
   override def onDestroy {
     super.onDestroy
+    ShadowsocksApplication.profileManager.setProfileAddedListener(null)
     profilesAdapter.commitRemoves
   }
 
   override def onActivityResult(requestCode: Int, resultCode: Int, data: Intent) {
     val scanResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, data)
     if (scanResult != null) Parser.parse(scanResult.getContents) match {
-      case Some(profile) => profilesAdapter.add(profile)
+      case Some(profile) => ShadowsocksApplication.profileManager.createOrUpdateProfile(profile)
       case _ => // ignore
     }
   }
@@ -168,7 +168,7 @@ class ProfileManagerActivity extends AppCompatActivity with OnMenuItemClickListe
       true
     case R.id.manual_settings =>
       ShadowsocksApplication.profileManager.reload(-1)
-      ShadowsocksApplication.profileId(ShadowsocksApplication.profileManager.save.id)
+      ShadowsocksApplication.switchProfile(ShadowsocksApplication.profileManager.save.id)
       finish
       true
     case _ => false
diff --git a/src/main/scala/com/github/shadowsocks/Shadowsocks.scala b/src/main/scala/com/github/shadowsocks/Shadowsocks.scala
index 853cef0f..1aa91273 100644
--- a/src/main/scala/com/github/shadowsocks/Shadowsocks.scala
+++ b/src/main/scala/com/github/shadowsocks/Shadowsocks.scala
@@ -55,12 +55,12 @@ import android.support.v4.content.ContextCompat
 import android.support.v7.app.AppCompatActivity
 import android.support.v7.widget.Toolbar
 import android.util.Log
-import android.view.{View, ViewGroup, ViewParent}
+import android.view.{ViewGroup, View, ViewParent}
 import android.widget._
 import com.github.jorgecastilloprz.FABProgressCircle
 import com.github.shadowsocks.aidl.{IShadowsocksService, IShadowsocksServiceCallback}
 import com.github.shadowsocks.database._
-import com.github.shadowsocks.preferences.{NumberPickerPreference, DropDownPreference, PasswordEditTextPreference, SummaryEditTextPreference}
+import com.github.shadowsocks.preferences.{DropDownPreference, NumberPickerPreference, PasswordEditTextPreference, SummaryEditTextPreference}
 import com.github.shadowsocks.utils._
 import com.google.android.gms.ads.{AdRequest, AdSize, AdView}
 
@@ -197,6 +197,7 @@ class Shadowsocks
 
   private lazy val preferences =
     getFragmentManager.findFragmentById(android.R.id.content).asInstanceOf[ShadowsocksSettings]
+  private var adView: AdView = _
   private lazy val greyTint = ContextCompat.getColorStateList(this, R.color.material_blue_grey_700)
   private lazy val greenTint = ContextCompat.getColorStateList(this, R.color.material_green_700)
 
@@ -349,22 +350,7 @@ class Shadowsocks
   override def onCreate(savedInstanceState: Bundle) {
 
     super.onCreate(savedInstanceState)
-
-    // Initialize the profile
-    currentProfile = {
-      ShadowsocksApplication.currentProfile getOrElse currentProfile
-    }
-    ShadowsocksApplication.profileManager.load(currentProfile.id)
-
     setContentView(R.layout.layout_main)
-    if (ShadowsocksApplication.proxy == "198.199.101.152") {
-      val adView = new AdView(this)
-      adView.setAdUnitId("ca-app-pub-9097031975646651/7760346322")
-      adView.setAdSize(AdSize.SMART_BANNER)
-      preferences.getView.asInstanceOf[ViewGroup].addView(adView, 0)
-      adView.loadAd(new AdRequest.Builder().build())
-    }
-
     // Initialize action bar
     val toolbar = findViewById(R.id.toolbar).asInstanceOf[Toolbar]
     toolbar.setTitle(getString(R.string.screen_name))
@@ -429,7 +415,8 @@ class Shadowsocks
       case Some(profile) => profile // updated
       case None =>                  // removed
         val profiles = ShadowsocksApplication.profileManager.getAllProfiles.getOrElse(List[Profile]())
-        ShadowsocksApplication.profileId(if (profiles.isEmpty) -1 else profiles.head.id)
+        if (profiles.isEmpty) ShadowsocksApplication.profileManager.createDefault()
+        else ShadowsocksApplication.switchProfile(profiles.head.id)
     }
 
     updatePreferenceScreen()
@@ -437,14 +424,6 @@ class Shadowsocks
     serviceStop()
   }
 
-  def addProfile(profile: Profile) {
-    currentProfile = profile
-    ShadowsocksApplication.profileManager.createOrUpdateProfile(currentProfile)
-    ShadowsocksApplication.profileManager.reload(currentProfile.id)
-
-    updatePreferenceScreen()
-  }
-
   protected override def onPause() {
     super.onPause()
     ShadowsocksApplication.profileManager.save
@@ -509,6 +488,14 @@ class Shadowsocks
   }
 
   private def updatePreferenceScreen() {
+    if (ShadowsocksApplication.proxy == "198.199.101.152" && adView == null) {
+      adView = new AdView(this)
+      adView.setAdUnitId("ca-app-pub-9097031975646651/7760346322")
+      adView.setAdSize(AdSize.SMART_BANNER)
+      preferences.getView.asInstanceOf[ViewGroup].addView(adView, 0)
+      adView.loadAd(new AdRequest.Builder().build())
+    }
+
     val profile = currentProfile
     for (name <- Shadowsocks.PROXY_PREFS) {
       val pref = preferences.findPreference(name)
diff --git a/src/main/scala/com/github/shadowsocks/ShadowsocksApplication.scala b/src/main/scala/com/github/shadowsocks/ShadowsocksApplication.scala
index f63114e0..a267eb1b 100644
--- a/src/main/scala/com/github/shadowsocks/ShadowsocksApplication.scala
+++ b/src/main/scala/com/github/shadowsocks/ShadowsocksApplication.scala
@@ -77,12 +77,14 @@ object ShadowsocksApplication {
     .build())
 
   def profileId = settings.getInt(Key.profileId, -1)
-  def profileId(i: Int) = {
-    settings.edit.putInt(Key.profileId, i).apply
-    profileManager.load(i)
-  }
+  def profileId(i: Int) = settings.edit.putInt(Key.profileId, i).apply
   def proxy = settings.getString(Key.proxy, "")
   def currentProfile = profileManager.getProfile(profileId)
+
+  def switchProfile(id: Int) = {
+    profileId(id)
+    profileManager.load(id)
+  }
 }
 
 class ShadowsocksApplication extends Application {
diff --git a/src/main/scala/com/github/shadowsocks/database/ProfileManager.scala b/src/main/scala/com/github/shadowsocks/database/ProfileManager.scala
index 2370153f..fd2cda35 100644
--- a/src/main/scala/com/github/shadowsocks/database/ProfileManager.scala
+++ b/src/main/scala/com/github/shadowsocks/database/ProfileManager.scala
@@ -46,9 +46,13 @@ import com.github.shadowsocks.utils.Key
 
 class ProfileManager(settings: SharedPreferences, dbHelper: DBHelper) {
 
+  var profileAddedListener: Profile => Any = _
+  def setProfileAddedListener(listener: Profile => Any) = this.profileAddedListener = listener
+
   def createOrUpdateProfile(profile: Profile): Boolean = {
     try {
       dbHelper.profileDao.createOrUpdate(profile)
+      if (profileAddedListener != null) profileAddedListener(profile)
       true
     } catch {
       case ex: Exception =>
@@ -163,4 +167,15 @@ class ProfileManager(settings: SharedPreferences, dbHelper: DBHelper) {
     updateProfile(profile)
     profile
   }
+
+  def createDefault(): Profile = {
+    val profile = new Profile {
+      name = "Default"
+      host = "198.199.101.152"
+      remotePort = 443
+      password = "u1rRWTssNv0p"
+    }
+    createOrUpdateProfile(profile)
+    profile
+  }
 }
diff --git a/src/main/scala/com/github/shadowsocks/preferences/NatSwitchPreference.scala b/src/main/scala/com/github/shadowsocks/preferences/NatSwitchPreference.scala
index 0d9e34ba..4471c329 100644
--- a/src/main/scala/com/github/shadowsocks/preferences/NatSwitchPreference.scala
+++ b/src/main/scala/com/github/shadowsocks/preferences/NatSwitchPreference.scala
@@ -22,5 +22,6 @@ final class NatSwitchPreference(context: Context, attrs: AttributeSet) extends S
     setSummary(R.string.nat_summary_no_root)
   }
 
-  override def onGetDefaultValue(a: TypedArray, index: Int) = ShadowsocksApplication.isVpnEnabled.asInstanceOf[AnyRef]
+  override def onGetDefaultValue(a: TypedArray, index: Int) =
+    (!ShadowsocksApplication.isVpnEnabled).asInstanceOf[AnyRef]
 }