android: synchronize ipn state and UI

Pass in intended state to toggleVpn and keep track of progress to avoid redundant updates and ensure that the action taken reflects the user's intent. This fixes a possible recomposition loop caused by the ipn state and the vpn toggle state getting out of sync. Updates tailscale/tailscale#14125 Signed-off-by: kari-ts <[email protected]>
tailscale · Dec 9, 2024 · 675d57f · 675d57f
1 parent 45ddef1
commit 675d57f
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Showing 2 changed files with 37 additions and 17 deletions.
diff --git a/android/src/main/java/com/tailscale/ipn/ui/view/MainView.kt b/android/src/main/java/com/tailscale/ipn/ui/view/MainView.kt
@@ -145,13 +145,12 @@ fun MainView(
                 leadingContent = {
                   if (!hideHeader) {
                     TintedSwitch(
-                        onCheckedChange = {
-                          if (!disableToggle.value) {
-                            viewModel.toggleVpn()
-                          }
-                        },
-                        enabled = !disableToggle.value,
-                        checked = isOn)
+                        checked = isOn,
+                        enabled =
+                            !disableToggle.value &&
+                                !viewModel.isToggleInProgress
+                                    .value, // Disable switch if toggle is in progress
+                        onCheckedChange = { desiredState -> viewModel.toggleVpn(desiredState) })
                   }
                 },
                 headlineContent = {
@@ -228,7 +227,7 @@ fun MainView(
                     // action (eg, if the user connected to another VPN).
                     state != Ipn.State.Stopping,
                     user,
-                    { viewModel.toggleVpn() },
+                    { viewModel.toggleVpn(desiredState = !isOn) },
                     { viewModel.login() },
                     loginAtUrl,
                     netmap?.SelfNode,

diff --git a/android/src/main/java/com/tailscale/ipn/ui/viewModel/MainViewModel.kt b/android/src/main/java/com/tailscale/ipn/ui/viewModel/MainViewModel.kt
@@ -18,7 +18,6 @@ import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.ui.model.Ipn.State
 import com.tailscale.ipn.ui.model.Tailcfg
 import com.tailscale.ipn.ui.notifier.Notifier
-import com.tailscale.ipn.ui.util.AndroidTVUtil.isAndroidTV
 import com.tailscale.ipn.ui.util.PeerCategorizer
 import com.tailscale.ipn.ui.util.PeerSet
 import com.tailscale.ipn.ui.util.TimeUtil
@@ -53,6 +52,10 @@ class MainViewModel(private val vpnViewModel: VpnViewModel) : IpnViewModel() {
   private val _vpnToggleState = MutableStateFlow(false)
   val vpnToggleState: StateFlow<Boolean> = _vpnToggleState
 
+  // Keeps track of whether a toggle operation is in progress. This ensures that toggleVpn cannot be
+  // invoked until the current operation is complete.
+  var isToggleInProgress = MutableStateFlow(false)
+
   // Permission to prepare VPN
   private var vpnPermissionLauncher: ActivityResultLauncher<Intent>? = null
 
@@ -184,15 +187,33 @@ class MainViewModel(private val vpnViewModel: VpnViewModel) : IpnViewModel() {
     }
   }
 
-  fun toggleVpn() {
-    val state = Notifier.state.value
-    val isPrepared = vpnViewModel.vpnPrepared.value
+  fun toggleVpn(desiredState: Boolean) {
+    if (isToggleInProgress.value) {
+      // Prevent toggling while a previous toggle is in progress
+      return
+    }
 
-    when {
-      !isPrepared -> showVPNPermissionLauncherIfUnauthorized()
-      state == Ipn.State.Running -> stopVPN()
-      state == Ipn.State.NeedsLogin && isAndroidTV() -> login()
-      else -> startVPN()
+    viewModelScope.launch {
+      isToggleInProgress.value = true
+      try {
+        val currentState = Notifier.state.value
+        val isPrepared = vpnViewModel.vpnPrepared.value
+
+        if (desiredState) {
+          // User wants to turn ON the VPN
+          when {
+            !isPrepared -> showVPNPermissionLauncherIfUnauthorized()
+            currentState != Ipn.State.Running -> startVPN()
+          }
+        } else {
+          // User wants to turn OFF the VPN
+          if (currentState == Ipn.State.Running) {
+            stopVPN()
+          }
+        }
+      } finally {
+        isToggleInProgress.value = false
+      }
     }
   }