diff --git a/installer/src/main/java/com/oasisfeng/island/installer/AppInfoForwarderActivity.kt b/installer/src/main/java/com/oasisfeng/island/installer/AppInfoForwarderActivity.kt
index d12e2c07..f85742f8 100644
--- a/installer/src/main/java/com/oasisfeng/island/installer/AppInfoForwarderActivity.kt
+++ b/installer/src/main/java/com/oasisfeng/island/installer/AppInfoForwarderActivity.kt
@@ -21,6 +21,7 @@ import com.oasisfeng.island.shuttle.ActivityShuttle
 import com.oasisfeng.island.shuttle.Shuttle
 import com.oasisfeng.island.util.CallerAwareActivity
 import com.oasisfeng.island.util.Users
+import com.oasisfeng.island.util.Users.Companion.isParentProfile
 
 /**
  * Created by Oasis on 2018-11-16.
@@ -70,7 +71,7 @@ class AppInfoForwarderActivity : CallerAwareActivity() {
 		if (SDK_INT >= O) chooser.putExtra(IntentCompat.EXTRA_AUTO_LAUNCH_SINGLE_CHOICE, isCallerNotSettings)
 		val initialIntents: MutableList<Intent> = ArrayList()
 		if (isCallerNotSettings && detailsActivity != null) {
-			if (user != null && ! Users.isParentProfile(user) && Users.isProfileManagedByIsland(this, user)) {    // Use mainland resolve to replace the misleading forwarding-resolved "Switch to work profile".
+			if (user != null && ! user.isParentProfile() && Users.isProfileManagedByIsland(this, user)) {    // Use mainland resolve to replace the misleading forwarding-resolved "Switch to work profile".
 				val labelRes = detailsActivity.run { if (labelRes != 0) labelRes else applicationInfo.labelRes }
 				initialIntents.add(LabeledIntent(details, detailsActivity.packageName, labelRes, detailsActivity.iconResource))
 			} else initialIntents.add(details) }
diff --git a/mobile/src/main/java/com/oasisfeng/island/controller/IslandAppClones.kt b/mobile/src/main/java/com/oasisfeng/island/controller/IslandAppClones.kt
index 5b404b4e..717e0460 100644
--- a/mobile/src/main/java/com/oasisfeng/island/controller/IslandAppClones.kt
+++ b/mobile/src/main/java/com/oasisfeng/island/controller/IslandAppClones.kt
@@ -54,6 +54,7 @@ import com.oasisfeng.island.model.interactive
 import com.oasisfeng.island.shuttle.Shuttle
 import com.oasisfeng.island.ui.ModelBottomSheetFragment
 import com.oasisfeng.island.util.*
+import com.oasisfeng.island.util.Users.Companion.isParentProfile
 import com.oasisfeng.island.util.Users.Companion.toId
 import eu.chainfire.libsuperuser.Shell
 import kotlinx.coroutines.Dispatchers
@@ -86,7 +87,7 @@ class IslandAppClones(val activity: FragmentActivity, val vm: AndroidViewModel,
 		val shouldShowBadge: Boolean = targets.size > 2
 		val icons: Map<UserHandle, Drawable> = targets.entries.stream().collect(Collectors.toMap({ obj: Map.Entry<UserHandle, String> -> obj.key }) { e: Map.Entry<UserHandle, String> ->
 			val user = e.key
-			val res = if (Users.isParentProfile(user)) R.drawable.ic_portrait_24dp else R.drawable.ic_island_black_24dp
+			val res = if (user.isParentProfile()) R.drawable.ic_portrait_24dp else R.drawable.ic_island_black_24dp
 			val drawable: Drawable = context.getDrawable(res)!!
 			val dark = (context.resources.configuration.uiMode and UI_MODE_NIGHT_MASK) == UI_MODE_NIGHT_YES
 			drawable.setTint(context.getColor(if (dark) android.R.color.white else android.R.color.black))		// TODO: Decouple
@@ -138,7 +139,7 @@ class IslandAppClones(val activity: FragmentActivity, val vm: AndroidViewModel,
 	}
 
 	private suspend fun cloneApp(source: IslandAppInfo, target: UserHandle, mode: @AppCloneMode Int) {
-		if (Users.isParentProfile(target) && isInstallerUsable()) @Suppress("DEPRECATION") // Only works in parent profile due to a bug in AOSP.
+		if (target.isParentProfile() && isInstallerUsable()) @Suppress("DEPRECATION") // Only works in parent profile due to a bug in AOSP.
 			return activity.startActivityForResult(Intent(Intent.ACTION_INSTALL_PACKAGE, Uri.fromParts("package", pkg, null)), 1)   // startActivityForResult() is required on Android U+ due to a bug in AOSP.
 
 		val context = source.context(); val pkg = source.packageName
diff --git a/mobile/src/main/java/com/oasisfeng/island/data/IslandAppListProvider.kt b/mobile/src/main/java/com/oasisfeng/island/data/IslandAppListProvider.kt
index 718184e5..bb97ab2f 100644
--- a/mobile/src/main/java/com/oasisfeng/island/data/IslandAppListProvider.kt
+++ b/mobile/src/main/java/com/oasisfeng/island/data/IslandAppListProvider.kt
@@ -24,6 +24,7 @@ import com.oasisfeng.island.shuttle.Shuttle
 import com.oasisfeng.island.util.DPM
 import com.oasisfeng.island.util.DevicePolicies
 import com.oasisfeng.island.util.Users
+import com.oasisfeng.island.util.Users.Companion.isParentProfile
 import com.oasisfeng.island.util.Users.Companion.toId
 import java.util.function.Predicate
 import java.util.stream.Stream
@@ -37,7 +38,7 @@ import kotlin.streams.asSequence
 class IslandAppListProvider : AppListProvider<IslandAppInfo>() {
 
 	operator fun get(pkg: String, profile: UserHandle): IslandAppInfo? {
-		return if (Users.isParentProfile(profile)) super.get(pkg) else loadAppsInProfileIfNotYet(profile)[pkg]
+		return if (profile.isParentProfile()) super.get(pkg) else loadAppsInProfileIfNotYet(profile)[pkg]
 	}
 
 	fun addPlaceholder(pkg: String, profile: UserHandle) {
@@ -62,7 +63,7 @@ class IslandAppListProvider : AppListProvider<IslandAppInfo>() {
 	fun isInstalled(pkg: String, profile: UserHandle) = get(pkg, profile)?.run { installed && shouldShowAsEnabled() } == true
 
 	fun isExclusive(app: IslandAppInfo): Boolean {
-		if (Users.isParentProfile(app.user) && ! Users.hasProfile()) return true
+		if (app.user.isParentProfile() && ! Users.hasProfile()) return true
 		return Users.getProfilesManagedByIsland().asSequence().plus(Users.parentProfile).minus(app.user).all { profile ->
 			! isInstalled(app.packageName, profile) }
 	}
@@ -84,7 +85,7 @@ class IslandAppListProvider : AppListProvider<IslandAppInfo>() {
 	}
 
 	fun installedApps(profile: UserHandle): Stream<IslandAppInfo> {
-		return if (Users.isParentProfile(profile)) installedAppsInOwnerUser() else loadAppsInProfileIfNotYet(profile).values.stream()
+		return if (profile.isParentProfile()) installedAppsInOwnerUser() else loadAppsInProfileIfNotYet(profile).values.stream()
 	}
 
 	private fun loadAppsInProfileIfNotYet(profile: UserHandle): Map<String, IslandAppInfo>
diff --git a/mobile/src/main/java/com/oasisfeng/island/model/MainViewModel.kt b/mobile/src/main/java/com/oasisfeng/island/model/MainViewModel.kt
index 040218e0..de6252d9 100644
--- a/mobile/src/main/java/com/oasisfeng/island/model/MainViewModel.kt
+++ b/mobile/src/main/java/com/oasisfeng/island/model/MainViewModel.kt
@@ -18,6 +18,7 @@ import com.oasisfeng.island.data.LiveProfileStates.ProfileState
 import com.oasisfeng.island.mobile.R
 import com.oasisfeng.island.util.Users
 import com.oasisfeng.island.util.Users.Companion.ACTION_USER_INFO_CHANGED
+import com.oasisfeng.island.util.Users.Companion.isParentProfile
 import com.oasisfeng.island.util.Users.Companion.toId
 
 class MainViewModel(app: Application, state: SavedStateHandle): AppListViewModel(app, state) {
@@ -33,10 +34,9 @@ class MainViewModel(app: Application, state: SavedStateHandle): AppListViewModel
 			override fun onTabReselected(tab: TabLayout.Tab) {}})
 
 		// Tab "Discovery" and "Mainland" are always present
-		tabs.addTab(tabs.newTab().setText(R.string.tab_discovery),/* setSelected = */false)
+		tabs.addTab(tabs.newTab().setText(R.string.tab_discovery), /* setSelected */false)
 		val currentProfile = currentProfile
-		tabs.addTab(tabs.newTab().setText(com.oasisfeng.island.shared.R.string.mainland_name),
-			/* setSelected */currentProfile?.let { Users.isParentProfile(it) } == true)
+		tabs.addTab(tabs.newTab().setText(com.oasisfeng.island.shared.R.string.mainland_name), /* setSelected */currentProfile.isParentProfile())
 
 		for ((profile, name) in IslandNameManager.getAllNames(activity)) {
 			val tab = tabs.newTab().setTag(profile).setText(name)
diff --git a/mobile/src/main/java/com/oasisfeng/island/settings/SettingsActivity.kt b/mobile/src/main/java/com/oasisfeng/island/settings/SettingsActivity.kt
index f707b9a1..013c22ce 100644
--- a/mobile/src/main/java/com/oasisfeng/island/settings/SettingsActivity.kt
+++ b/mobile/src/main/java/com/oasisfeng/island/settings/SettingsActivity.kt
@@ -27,6 +27,7 @@ import com.oasisfeng.island.mobile.R
 import com.oasisfeng.island.util.DevicePolicies
 import com.oasisfeng.island.util.Modules
 import com.oasisfeng.island.util.Users
+import com.oasisfeng.island.util.Users.Companion.isParentProfile
 
 @Suppress("DEPRECATION") class SettingsActivity : android.preference.PreferenceActivity() {
 	override fun onCreate(savedInstanceState: Bundle?) {
@@ -67,7 +68,7 @@ import com.oasisfeng.island.util.Users
 
 		val names = IslandNameManager.getAllNames(this)
 		val labels = users.map { user ->
-			if (Users.isParentProfile(user)) getText(com.oasisfeng.island.shared.R.string.mainland_name) else names[user]
+			if (user.isParentProfile()) getText(com.oasisfeng.island.shared.R.string.mainland_name) else names[user]
 		}.toTypedArray()
 		Dialogs.buildList(this, null, labels) { _, which ->
 			if (which == 0) super.onHeaderClick(header, position)
diff --git a/shared/src/main/java/com/oasisfeng/island/IslandNameManager.kt b/shared/src/main/java/com/oasisfeng/island/IslandNameManager.kt
index 9b7966ac..276110f6 100644
--- a/shared/src/main/java/com/oasisfeng/island/IslandNameManager.kt
+++ b/shared/src/main/java/com/oasisfeng/island/IslandNameManager.kt
@@ -14,6 +14,7 @@ import com.oasisfeng.island.util.ProfileUser
 import com.oasisfeng.island.util.Users
 import com.oasisfeng.island.util.Users.Companion.ACTION_USER_INFO_CHANGED
 import com.oasisfeng.island.util.Users.Companion.EXTRA_USER_HANDLE
+import com.oasisfeng.island.util.Users.Companion.isParentProfile
 import com.oasisfeng.island.util.Users.Companion.toId
 
 object IslandNameManager {
@@ -31,7 +32,7 @@ object IslandNameManager {
 		getStore(context).getString(buildIslandNameKey(context), null) ?: getDefaultName(context)
 
 	private fun getDefaultName(context: Context, profile: UserHandle = Users.current()): String {
-		if (Users.isParentProfile(profile)) return context.getString(R.string.mainland_name)
+		if (profile.isParentProfile()) return context.getString(R.string.mainland_name)
 		val islandCount = Users.run { if (isParentProfile()) getProfilesManagedByIsland().size else getProfileCount() - 1 }
 		return if (islandCount > 1) getDefaultSpecificName(context, profile) else context.getString(R.string.default_island_name)
 	}
diff --git a/shared/src/main/java/com/oasisfeng/island/util/Users.kt b/shared/src/main/java/com/oasisfeng/island/util/Users.kt
index ec9d1f56..9ace8413 100644
--- a/shared/src/main/java/com/oasisfeng/island/util/Users.kt
+++ b/shared/src/main/java/com/oasisfeng/island/util/Users.kt
@@ -104,12 +104,12 @@ class Users : PseudoContentProvider() {
 
 		@JvmStatic fun isSystemUser() = CURRENT_ID == 0
 		@JvmStatic fun isParentProfile() = CURRENT_ID == parentProfile.toId()
-		@JvmStatic fun isParentProfile(user: UserHandle) = user == parentProfile
-		@JvmStatic fun isParentProfile(user_id: Int) = user_id == parentProfile.toId()
+		@JvmStatic fun UserHandle?.isParentProfile() = this == parentProfile
+		@JvmStatic fun isParentProfile(userId: Int) = userId == parentProfile.toId()
 
 		@OwnerUser @JvmStatic fun isProfileManagedByIsland(context: Context, user: UserHandle): Boolean {
 			ensureParentProfile()
-			if (isParentProfile(user)) {
+			if (user.isParentProfile()) {
 				if (isParentProfile()) return DevicePolicies(context).isProfileOwner
 				throw IllegalArgumentException("Not working for profile parent user") }
 			return sProfilesManagedByIsland.contains(user)