android: add explanatory dialog for taildrop directory selection (#657)

fixes tailscale/corp#29067

Adds an interstitial explaining that the user needs to select/create
a taildrop target directory on startup.

Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>
(cherry picked from commit a14d4c7184)

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

@@ -32,6 +32,7 @@ import androidx.compose.material.icons.outlined.Close
 import androidx.compose.material.icons.outlined.Lock
 import androidx.compose.material.icons.outlined.Search
 import androidx.compose.material.icons.outlined.Settings
+import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Button
 import androidx.compose.material3.DropdownMenu
 import androidx.compose.material3.DropdownMenuItem
@@ -61,12 +62,14 @@ import androidx.compose.ui.focus.onFocusChanged
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.LocalClipboardManager
 import androidx.compose.ui.platform.LocalFocusManager
+import androidx.compose.ui.platform.LocalUriHandler
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.SpanStyle
 import androidx.compose.ui.text.buildAnnotatedString
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.text.style.TextDecoration
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
@@ -78,11 +81,13 @@ import com.tailscale.ipn.App
 import com.tailscale.ipn.R
 import com.tailscale.ipn.mdm.MDMSettings
 import com.tailscale.ipn.mdm.ShowHide
+import com.tailscale.ipn.ui.Links
 import com.tailscale.ipn.ui.model.Ipn
 import com.tailscale.ipn.ui.model.IpnLocal
 import com.tailscale.ipn.ui.model.Netmap
 import com.tailscale.ipn.ui.model.Permissions
 import com.tailscale.ipn.ui.model.Tailcfg
+import com.tailscale.ipn.ui.theme.AppTheme
 import com.tailscale.ipn.ui.theme.customErrorContainer
 import com.tailscale.ipn.ui.theme.disabled
 import com.tailscale.ipn.ui.theme.errorButton
@@ -97,7 +102,6 @@ import com.tailscale.ipn.ui.theme.short
 import com.tailscale.ipn.ui.theme.surfaceContainerListItem
 import com.tailscale.ipn.ui.theme.warningButton
 import com.tailscale.ipn.ui.theme.warningListItem
-import com.tailscale.ipn.ui.util.AndroidTVUtil
 import com.tailscale.ipn.ui.util.AndroidTVUtil.isAndroidTV
 import com.tailscale.ipn.ui.util.AutoResizingText
 import com.tailscale.ipn.ui.util.Lists
@@ -124,7 +128,7 @@ data class MainViewNavigation(
 fun MainView(
     loginAtUrl: (String) -> Unit,
     navigation: MainViewNavigation,
-    viewModel: MainViewModel
+    viewModel: MainViewModel,
 ) {
   val currentPingDevice by viewModel.pingViewModel.peer.collectAsState()
   val healthIcon by viewModel.healthIcon.collectAsState()
@@ -147,6 +151,8 @@ fun MainView(
             val showExitNodePicker by MDMSettings.exitNodesPicker.flow.collectAsState()
             val disableToggle by MDMSettings.forceEnabled.flow.collectAsState()
             val showKeyExpiry by viewModel.showExpiry.collectAsState(initial = false)
+            val showDirectoryPickerInterstitial by
+                viewModel.showDirectoryPickerInterstitial.collectAsState()
 
             // Hide the header only on Android TV when the user needs to login
             val hideHeader = (isAndroidTV() && state == Ipn.State.NeedsLogin)
@@ -214,8 +220,8 @@ fun MainView(
                 viewModel.maybeRequestVpnPermission()
                 LaunchVpnPermissionIfNeeded(viewModel)
                 LaunchedEffect(state) {
-                  if (state == Ipn.State.Running && !AndroidTVUtil.isAndroidTV()) {
+                  if (state == Ipn.State.Running && !isAndroidTV()) {
-                    viewModel.showDirectoryPickerLauncher()
+                    viewModel.checkIfTaildropDirectorySelected()
                   }
                 }
 
@@ -248,13 +254,29 @@ fun MainView(
                     { viewModel.login() },
                     loginAtUrl,
                     netmap?.SelfNode,
-                    {
+                    { viewModel.showVPNPermissionLauncherIfUnauthorized() })
-                      viewModel.showVPNPermissionLauncherIfUnauthorized()
-                    })
               }
             }
-          }
 
+            showDirectoryPickerInterstitial.let { show ->
+              if (show) {
+                AppTheme {
+                  AlertDialog(
+                      onDismissRequest = { viewModel.showDirectoryPickerLauncher() },
+                      title = {
+                        Text(text = stringResource(id = R.string.taildrop_directory_picker_title))
+                      },
+                      text = { TaildropDirectoryPickerPrompt() },
+                      confirmButton = {
+                        PrimaryActionButton(onClick = { viewModel.showDirectoryPickerLauncher() }) {
+                          Text(
+                              text = stringResource(id = R.string.taildrop_directory_picker_button))
+                        }
+                      })
+                }
+              }
+            }
+          }
       currentPingDevice?.let { _ ->
         ModalBottomSheet(onDismissRequest = { viewModel.onPingDismissal() }) {
           PingView(model = viewModel.pingViewModel)
@@ -264,6 +286,20 @@ fun MainView(
   }
 }
 
+@Composable
+fun TaildropDirectoryPickerPrompt() {
+  val uriHandler = LocalUriHandler.current
+
+  Column(verticalArrangement = Arrangement.spacedBy(8.dp), horizontalAlignment = Alignment.Start) {
+    Text(text = stringResource(id = R.string.taildrop_directory_picker_body))
+    Text(
+        text = stringResource(id = R.string.taildrop_directory_picker_info),
+        modifier = Modifier.clickable { uriHandler.openUri(Links.TAILDROP_KB_URL) },
+        color = MaterialTheme.colorScheme.primary,
+        textDecoration = TextDecoration.Underline)
+  }
+}
+
 @Composable
 fun LaunchVpnPermissionIfNeeded(viewModel: MainViewModel) {
   val lifecycleOwner = LocalLifecycleOwner.current
@@ -441,7 +477,7 @@ fun ConnectView(
     loginAction: () -> Unit,
     loginAtUrlAction: (String) -> Unit,
     selfNode: Tailcfg.Node?,
-    showVPNPermissionLauncher: () -> Unit
+    showVPNPermissionLauncher: () -> Unit,
 ) {
   LaunchedEffect(isPrepared) {
     if (!isPrepared && shouldStartAutomatically) {
@@ -553,7 +589,7 @@ fun PeerList(
     viewModel: MainViewModel,
     onNavigateToPeerDetails: (Tailcfg.Node) -> Unit,
     onSearchBarClick: () -> Unit,
-    onSearch: (String) -> Unit
+    onSearch: (String) -> Unit,
 ) {
   val peerList by viewModel.peers.collectAsState(initial = emptyList<PeerSet>())
   val searchTermStr by viewModel.searchTerm.collectAsState(initial = "")
@@ -774,7 +810,7 @@ fun PromptPermissionsIfNecessary() {
 @Composable
 fun Search(
     onSearchBarClick: () -> Unit, // Callback for navigating to SearchView
-    backgroundColor: Color = MaterialTheme.colorScheme.background // Default background color
+    backgroundColor: Color = MaterialTheme.colorScheme.background, // Default background color
 ) {
   // Prevent multiple taps
   var isNavigating by remember { mutableStateOf(false) }

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

@@ -68,6 +68,8 @@ class MainViewModel(private val vpnViewModel: VpnViewModel) : IpnViewModel() {
 
   // Select Taildrop directory
   private var directoryPickerLauncher: ActivityResultLauncher<Uri?>? = null
+  private val _showDirectoryPickerInterstitial = MutableStateFlow(false)
+  val showDirectoryPickerInterstitial: StateFlow<Boolean> = _showDirectoryPickerInterstitial
 
   // The list of peers
   private val _peers = MutableStateFlow<List<PeerSet>>(emptyList())
@@ -211,11 +213,16 @@ class MainViewModel(private val vpnViewModel: VpnViewModel) : IpnViewModel() {
   }
 
   fun showDirectoryPickerLauncher() {
+    _showDirectoryPickerInterstitial.set(false)
+    directoryPickerLauncher?.launch(null)
+  }
+
+  fun checkIfTaildropDirectorySelected() {
     val app = App.get()
     val storedUri = app.getStoredDirectoryUri()
     if (storedUri == null) {
       // No stored URI, so launch the directory picker.
-      directoryPickerLauncher?.launch(null)
+      _showDirectoryPickerInterstitial.set(true)
       return
     }
 
@@ -224,7 +231,7 @@ class MainViewModel(private val vpnViewModel: VpnViewModel) : IpnViewModel() {
       TSLog.d(
           "MainViewModel",
           "Stored directory URI is invalid or inaccessible; launching directory picker.")
-      directoryPickerLauncher?.launch(null)
+      _showDirectoryPickerInterstitial.set(true)
     } else {
       TSLog.d("MainViewModel", "Using stored directory URI: $storedUri")
     }
@@ -237,7 +244,7 @@ class MainViewModel(private val vpnViewModel: VpnViewModel) : IpnViewModel() {
     }
 
     viewModelScope.launch {
-      showDirectoryPickerLauncher()
+      checkIfTaildropDirectorySelected()
       isToggleInProgress.value = true
       try {
         val currentState = Notifier.state.value

android/src/main/res/values/strings.xml

@@ -324,4 +324,10 @@
     <string name="hostname">Hostname</string>
     <string name="failed_to_save">Failed to save</string>
 
+    <!-- Strings for the taildrop directory picker interstitial -->
+    <string name="taildrop_directory_picker_title">Taildrop Directory</string>
+    <string name="taildrop_directory_picker_body">You have not selected a directory for incoming taildrop transfers. Please select or create a target directory.</string>
+    <string name="taildrop_directory_picker_info">What is taildrop?</string>
+    <string name="taildrop_directory_picker_button">Open Directory Picker</string>
+
 </resources>