Reduce flickering on login failure

The flickering behavior is reduced by adding a short delay for all
states except the loading state.

2 files changed, 18 insertions, 1 deletions

diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/ui/LoginFragment.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/ui/LoginFragment.kt
index 07e7748935..c04f41ca1c 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/ui/LoginFragment.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/ui/LoginFragment.kt
@@ -12,7 +12,9 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.lifecycleScope
 import androidx.lifecycle.repeatOnLifecycle
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
 import net.mullvad.mullvadvpn.R
 import net.mullvad.mullvadvpn.ui.extension.requireMainActivity
@@ -127,7 +129,14 @@ class LoginFragment : BaseFragment(), NavigationBarPainter {
     }
 
     private fun CoroutineScope.launchUpdateUiOnViewModelStateChanges() = launch {
-        loginViewModel.uiState.collect { uiState -> updateUi(uiState) }
+        loginViewModel.uiState
+            .onEach {
+                // Adds a short delay to prevent loading spinner flickering.
+                if (it.isLoading().not()) {
+                    delay(MINIMUM_LOADING_SPINNER_TIME_MILLIS)
+                }
+            }
+            .collect { uiState -> updateUi(uiState) }
     }
 
     private fun updateUi(uiState: LoginViewModel.LoginUiState) {
@@ -269,4 +278,8 @@ class LoginFragment : BaseFragment(), NavigationBarPainter {
         val rectangle = Rect(0, 0, view.width, view.height)
         scrollArea.requestChildRectangleOnScreen(view, rectangle, false)
     }
+
+    companion object {
+        private const val MINIMUM_LOADING_SPINNER_TIME_MILLIS = 200L
+    }
 }
diff --git a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/LoginViewModel.kt b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/LoginViewModel.kt
index e73d42438a..cc653b0c73 100644
--- a/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/LoginViewModel.kt
+++ b/android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/LoginViewModel.kt
@@ -39,6 +39,10 @@ class LoginViewModel(
         data class TooManyDevicesError(val accountToken: String) : LoginUiState()
         object TooManyDevicesMissingListError : LoginUiState()
         data class OtherError(val errorMessage: String) : LoginUiState()
+
+        fun isLoading(): Boolean {
+            return this is Loading
+        }
     }
 
     fun clearAccountHistory() = accountRepository.clearAccountHistory()