android: prepare VPN when quick tile is clicked (#473)

Currently, the VPN is prepared when MainActivity is launched. If Tailscale is enabled by a quick tile, the VPN is not prepared.
This change creates an application scoped view model and moves the VPN prep to the application class so that it is not dependent on MainActivity.

Fixes tailscale/tailscale#12489

Signed-off-by: kari-ts <kari@tailscale.com>

android/src/main/java/com/tailscale/ipn/App.kt

@@ -22,6 +22,9 @@ import android.util.Log
 import androidx.core.app.ActivityCompat
 import androidx.core.app.NotificationCompat
 import androidx.core.app.NotificationManagerCompat
+import androidx.lifecycle.ViewModelProvider
+import androidx.lifecycle.ViewModelStore
+import androidx.lifecycle.ViewModelStoreOwner
 import androidx.security.crypto.EncryptedSharedPreferences
 import androidx.security.crypto.MasterKey
 import com.tailscale.ipn.mdm.MDMSettings
@@ -30,6 +33,8 @@ import com.tailscale.ipn.ui.localapi.Request
 import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.ui.notifier.HealthNotifier
 import com.tailscale.ipn.ui.notifier.Notifier
+import com.tailscale.ipn.ui.viewModel.VpnViewModel
+import com.tailscale.ipn.ui.viewModel.VpnViewModelFactory
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
@@ -45,7 +50,7 @@ import java.net.NetworkInterface
 import java.security.GeneralSecurityException
 import java.util.Locale
 
-class App : UninitializedApp(), libtailscale.AppContext {
+class App : UninitializedApp(), libtailscale.AppContext, ViewModelStoreOwner {
   val applicationScope = CoroutineScope(SupervisorJob() + Dispatchers.Default)
 
   companion object {
@@ -72,6 +77,15 @@ class App : UninitializedApp(), libtailscale.AppContext {
   val dns = DnsConfig()
   private lateinit var connectivityManager: ConnectivityManager
   private lateinit var app: libtailscale.Application
+
+  override val viewModelStore: ViewModelStore
+    get() = appViewModelStore
+
+  lateinit var vpnViewModel: VpnViewModel
+    private set
+
+  private val appViewModelStore: ViewModelStore by lazy { ViewModelStore() }
+
   var healthNotifier: HealthNotifier? = null
 
   override fun getPlatformDNSConfig(): String = dns.dnsConfigAsString
@@ -108,6 +122,7 @@ class App : UninitializedApp(), libtailscale.AppContext {
     Notifier.stop()
     notificationManager.cancelAll()
     applicationScope.cancel()
+    viewModelStore.clear()
   }
 
   private var isInitialized = false
@@ -146,6 +161,11 @@ class App : UninitializedApp(), libtailscale.AppContext {
         QuickToggleService.setVPNRunning(vpnRunning)
       }
     }
+    initViewModels()
+  }
+
+  private fun initViewModels() {
+    vpnViewModel = ViewModelProvider(this, VpnViewModelFactory(this)).get(VpnViewModel::class.java)
   }
 
   fun setWantRunning(wantRunning: Boolean) {
@@ -518,7 +538,8 @@ open class UninitializedApp : Application() {
   }
 
   fun disallowedPackageNames(): List<String> {
-    val mdmDisallowed = MDMSettings.excludedPackages.flow.value.value?.split(",")?.map { it.trim() } ?: emptyList()
+    val mdmDisallowed =
+        MDMSettings.excludedPackages.flow.value.value?.split(",")?.map { it.trim() } ?: emptyList()
     if (mdmDisallowed.isNotEmpty()) {
       Log.d(TAG, "Excluded application packages were set via MDM: $mdmDisallowed")
       return builtInDisallowedPackageNames + mdmDisallowed

android/src/main/java/com/tailscale/ipn/MainActivity.kt

@@ -18,7 +18,6 @@ import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.result.ActivityResultLauncher
 import androidx.activity.result.contract.ActivityResultContract
-import androidx.activity.viewModels
 import androidx.browser.customtabs.CustomTabsIntent
 import androidx.compose.animation.core.tween
 import androidx.compose.animation.fadeIn
@@ -31,6 +30,7 @@ import androidx.compose.runtime.collectAsState
 import androidx.compose.ui.Modifier
 import androidx.core.net.toUri
 import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
+import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.lifecycleScope
 import androidx.navigation.NavHostController
 import androidx.navigation.NavType
@@ -71,8 +71,10 @@ import com.tailscale.ipn.ui.view.UserSwitcherNav
 import com.tailscale.ipn.ui.view.UserSwitcherView
 import com.tailscale.ipn.ui.viewModel.ExitNodePickerNav
 import com.tailscale.ipn.ui.viewModel.MainViewModel
+import com.tailscale.ipn.ui.viewModel.MainViewModelFactory
 import com.tailscale.ipn.ui.viewModel.PingViewModel
 import com.tailscale.ipn.ui.viewModel.SettingsNav
+import com.tailscale.ipn.ui.viewModel.VpnViewModel
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.cancel
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -82,7 +84,12 @@ import kotlinx.coroutines.launch
 class MainActivity : ComponentActivity() {
   private lateinit var navController: NavHostController
   private lateinit var vpnPermissionLauncher: ActivityResultLauncher<Intent>
-  private val viewModel: MainViewModel by viewModels()
+  private val viewModel: MainViewModel by lazy {
+    val app = App.get()
+    vpnViewModel = app.vpnViewModel
+    ViewModelProvider(this, MainViewModelFactory(vpnViewModel)).get(MainViewModel::class.java)
+  }
+  private lateinit var vpnViewModel: VpnViewModel
 
   companion object {
     private const val TAG = "Main Activity"
@@ -105,6 +112,7 @@ class MainActivity : ComponentActivity() {
 
     // grab app to make sure it initializes
     App.get()
+    vpnViewModel = ViewModelProvider(App.get()).get(VpnViewModel::class.java)
 
     // (jonathan) TODO: Force the app to be portrait on small screens until we have
     // proper landscape layout support
@@ -118,11 +126,11 @@ class MainActivity : ComponentActivity() {
         registerForActivityResult(VpnPermissionContract()) { granted ->
           if (granted) {
             Log.d("VpnPermission", "VPN permission granted")
-            viewModel.setVpnPrepared(true)
+            vpnViewModel.setVpnPrepared(true)
             App.get().startVPN()
           } else {
             Log.d("VpnPermission", "VPN permission denied")
-            viewModel.setVpnPrepared(false)
+            vpnViewModel.setVpnPrepared(false)
           }
         }
     viewModel.setVpnPermissionLauncher(vpnPermissionLauncher)

android/src/main/java/com/tailscale/ipn/ui/view/MainView.kt

@@ -70,6 +70,7 @@ import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import com.google.accompanist.permissions.ExperimentalPermissionsApi
+import com.tailscale.ipn.App
 import com.tailscale.ipn.R
 import com.tailscale.ipn.mdm.MDMSettings
 import com.tailscale.ipn.mdm.ShowHide
@@ -101,6 +102,7 @@ import com.tailscale.ipn.ui.util.itemsWithDividers
 import com.tailscale.ipn.ui.util.set
 import com.tailscale.ipn.ui.viewModel.IpnViewModel.NodeState
 import com.tailscale.ipn.ui.viewModel.MainViewModel
+import com.tailscale.ipn.ui.viewModel.VpnViewModel
 
 // Navigation actions for the MainView
 data class MainViewNavigation(
@@ -128,7 +130,7 @@ fun MainView(
             // Assume VPN has been prepared for optimistic UI. Whether or not it has been prepared
             // cannot be known
             // until permission has been granted to prepare the VPN.
-            val isPrepared by viewModel.vpnPrepared.collectAsState(initial = true)
+            val isPrepared by viewModel.isVpnPrepared.collectAsState(initial = true)
             val isOn by viewModel.vpnToggleState.collectAsState(initial = false)
             val state by viewModel.ipnState.collectAsState(initial = Ipn.State.NoState)
             val user by viewModel.loggedInUser.collectAsState(initial = null)
@@ -735,7 +737,9 @@ fun PromptPermissionsIfNecessary() {
 @Preview
 @Composable
 fun MainViewPreview() {
-  val vm = MainViewModel()
+  val vpnViewModel = VpnViewModel(App.get())
+  val vm = MainViewModel(vpnViewModel)
+
   MainView(
       {},
       MainViewNavigation(

android/src/main/java/com/tailscale/ipn/ui/view/SettingsView.kt

@@ -37,9 +37,11 @@ import com.tailscale.ipn.ui.util.Lists
 import com.tailscale.ipn.ui.util.set
 import com.tailscale.ipn.ui.viewModel.SettingsNav
 import com.tailscale.ipn.ui.viewModel.SettingsViewModel
+import com.tailscale.ipn.ui.viewModel.VpnViewModel
+import com.tailscale.ipn.ui.notifier.Notifier
 
 @Composable
-fun SettingsView(settingsNav: SettingsNav, viewModel: SettingsViewModel = viewModel()) {
+fun SettingsView(settingsNav: SettingsNav, viewModel: SettingsViewModel = viewModel(), vpnViewModel: VpnViewModel = viewModel()) {
   val handler = LocalUriHandler.current
 
   val user by viewModel.loggedInUser.collectAsState()
@@ -47,7 +49,7 @@ fun SettingsView(settingsNav: SettingsNav, viewModel: SettingsViewModel = viewMo
   val managedByOrganization by viewModel.managedByOrganization.collectAsState()
   val tailnetLockEnabled by viewModel.tailNetLockEnabled.collectAsState()
   val corpDNSEnabled by viewModel.corpDNSEnabled.collectAsState()
-  val isVPNPrepared by viewModel.vpnPrepared.collectAsState()
+  val isVPNPrepared by vpnViewModel.vpnPrepared.collectAsState()
   val showTailnetLock by MDMSettings.manageTailnetLock.flow.collectAsState()
 
   Scaffold(

android/src/main/java/com/tailscale/ipn/ui/viewModel/IpnViewModel.kt

@@ -3,11 +3,9 @@
 
 package com.tailscale.ipn.ui.viewModel
 
-import android.net.VpnService
 import android.util.Log
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
-import com.tailscale.ipn.App
 import com.tailscale.ipn.UninitializedApp
 import com.tailscale.ipn.mdm.MDMSettings
 import com.tailscale.ipn.ui.localapi.Client
@@ -64,16 +62,6 @@ open class IpnViewModel : ViewModel() {
   }
 
   init {
-    // Check if the user has granted permission yet.
-    if (!vpnPrepared.value) {
-      val vpnIntent = VpnService.prepare(App.get())
-      if (vpnIntent != null) {
-        setVpnPrepared(false)
-      } else {
-        setVpnPrepared(true)
-      }
-    }
-
     viewModelScope.launch {
       Notifier.state.collect {
         // Reload the user profiles on all state transitions to ensure loggedInUser is correct

android/src/main/java/com/tailscale/ipn/ui/viewModel/MainViewModel.kt

@@ -8,6 +8,8 @@ import android.net.VpnService
 import androidx.activity.result.ActivityResultLauncher
 import androidx.compose.ui.platform.ClipboardManager
 import androidx.compose.ui.text.AnnotatedString
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.viewModelScope
 import com.tailscale.ipn.App
 import com.tailscale.ipn.R
@@ -27,7 +29,16 @@ import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.launch
 import java.time.Duration
 
-class MainViewModel : IpnViewModel() {
+class MainViewModelFactory(private val vpnViewModel: VpnViewModel) : ViewModelProvider.Factory {
+  override fun <T : ViewModel> create(modelClass: Class<T>): T {
+    if (modelClass.isAssignableFrom(MainViewModel::class.java)) {
+      return MainViewModel(vpnViewModel) as T
+    }
+    throw IllegalArgumentException("Unknown ViewModel class")
+  }
+}
+
+class MainViewModel(private val vpnViewModel: VpnViewModel) : IpnViewModel() {
 
   // The user readable state of the system
   val stateRes: StateFlow<Int> = MutableStateFlow(userStringRes(State.NoState, State.NoState, true))
@@ -56,6 +67,8 @@ class MainViewModel : IpnViewModel() {
 
   var pingViewModel: PingViewModel = PingViewModel()
 
+  val isVpnPrepared: StateFlow<Boolean> = vpnViewModel.vpnPrepared
+
   // Icon displayed in the button to present the health view
   val healthIcon: StateFlow<Int?> = MutableStateFlow(null)
 
@@ -81,7 +94,7 @@ class MainViewModel : IpnViewModel() {
     viewModelScope.launch {
       var previousState: State? = null
 
-      combine(Notifier.state, vpnPrepared) { state, prepared -> state to prepared }
+      combine(Notifier.state, isVpnPrepared) { state, prepared -> state to prepared }
           .collect { (currentState, prepared) ->
             stateRes.set(userStringRes(currentState, previousState, prepared))
 
@@ -116,7 +129,6 @@ class MainViewModel : IpnViewModel() {
           }
         }
       }
-    }
 
       viewModelScope.launch {
         searchTerm.collect { term -> peers.set(peerCategorizer.groupedAndFilteredPeers(term)) }
@@ -126,20 +138,21 @@ class MainViewModel : IpnViewModel() {
         App.get().healthNotifier?.currentIcon?.collect { icon -> healthIcon.set(icon) }
       }
     }
+  }
 
   fun showVPNPermissionLauncherIfUnauthorized() {
     val vpnIntent = VpnService.prepare(App.get())
     if (vpnIntent != null) {
       vpnPermissionLauncher?.launch(vpnIntent)
     } else {
-      setVpnPrepared(true)
+      vpnViewModel.setVpnPrepared(true)
       startVPN()
     }
   }
 
   fun toggleVpn() {
     val state = Notifier.state.value
-    val isPrepared = vpnPrepared.value
+    val isPrepared = vpnViewModel.vpnPrepared.value
 
     when {
       !isPrepared -> showVPNPermissionLauncherIfUnauthorized()

android/src/main/java/com/tailscale/ipn/ui/viewModel/SettingsViewModel.kt

@@ -47,11 +47,7 @@ class SettingsViewModel : IpnViewModel() {
 
     viewModelScope.launch {
       Notifier.prefs.collect {
-        it?.let {
-          corpDNSEnabled.set(it.CorpDNS)
-        } ?: run {
-          corpDNSEnabled.set(null)
-        }
+        it?.let { corpDNSEnabled.set(it.CorpDNS) } ?: run { corpDNSEnabled.set(null) }
       }
     }
   }

android/src/main/java/com/tailscale/ipn/ui/viewModel/VpnViewModel.kt

@@ -0,0 +1,55 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package com.tailscale.ipn.ui.viewModel
+
+import android.app.Application
+import android.net.VpnService
+import android.util.Log
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+
+class VpnViewModelFactory(private val application: Application) : ViewModelProvider.Factory {
+  @Suppress("UNCHECKED_CAST")
+  override fun <T : ViewModel> create(modelClass: Class<T>): T {
+    if (modelClass.isAssignableFrom(VpnViewModel::class.java)) {
+      return VpnViewModel(application) as T
+    }
+    throw IllegalArgumentException("Unknown ViewModel class")
+  }
+}
+
+// Application context aware view model that tracks whether the VPN has been prepared. This must be
+// application scoped because Tailscale might be toggled on and off outside of the activity
+// lifecycle.
+class VpnViewModel(application: Application) : AndroidViewModel(application) {
+  // Whether the VPN is prepared
+  val _vpnPrepared = MutableStateFlow(false)
+  val vpnPrepared: StateFlow<Boolean> = _vpnPrepared
+  val TAG = "VpnViewModel"
+
+  init {
+    prepareVpn()
+  }
+
+  private fun prepareVpn() {
+    // Check if the user has granted permission yet.
+    if (!vpnPrepared.value) {
+      val vpnIntent = VpnService.prepare(getApplication())
+      if (vpnIntent != null) {
+        setVpnPrepared(false)
+        Log.d(TAG, "VpnService.prepare returned non-null intent")
+      } else {
+        setVpnPrepared(true)
+        Log.d(TAG, "VpnService.prepare returned null intent, VPN is already prepared")
+      }
+    }
+  }
+
+  fun setVpnPrepared(prepared: Boolean) {
+    _vpnPrepared.value = prepared
+  }
+}