UI: locks user in alert dialog when model is unloading

examples/llama.android/app/src/main/java/com/example/llama/revamp/MainActivity.kt

@@ -293,21 +293,27 @@ fun AppContent() {
     }
 
     // Model unload confirmation dialog
-    // TODO-han.yin: show a progress indicator until the model success unloads?
+    var isUnloading by remember { mutableStateOf(false) }
+
     if (showUnloadDialog) {
         UnloadModelConfirmationDialog(
             onConfirm = {
-                showUnloadDialog = false
+                isUnloading = true
                 coroutineScope.launch {
                     viewModel.unloadModel()
+                    isUnloading = false
+                    showUnloadDialog = false
                     pendingNavigation?.invoke()
                     pendingNavigation = null
                 }
             },
             onDismiss = {
-                showUnloadDialog = false
-                pendingNavigation = null
-            }
+                if (!isUnloading) {
+                    showUnloadDialog = false
+                    pendingNavigation = null
+                }
+            },
+            isUnloading = isUnloading
         )
     }
 }

examples/llama.android/app/src/main/java/com/example/llama/revamp/ui/components/UnloadModelConfirmationDialog.kt

@@ -1,9 +1,21 @@
 package com.example.llama.revamp.ui.components
 
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
 import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
 
 /**
  * Confirmation dialog shown when the user attempts to navigate away from
@@ -12,27 +24,55 @@ import androidx.compose.runtime.Composable
 @Composable
 fun UnloadModelConfirmationDialog(
     onConfirm: () -> Unit,
-    onDismiss: () -> Unit
+    onDismiss: () -> Unit,
+    isUnloading: Boolean = false
 ) {
     AlertDialog(
-        onDismissRequest = onDismiss,
+        onDismissRequest = {
+            // Ignore dismiss requests while unloading the model
+            if (!isUnloading) onDismiss()
+        },
         title = {
             Text("Confirm Exit")
         },
         text = {
-            Text(
-                "Going back will unload the current model. " +
-                    "This operation cannot be undone. " +
-                    "Any unsaved conversation will be lost."
-            )
+            Column {
+                Text(
+                    "Going back will unload the current model. " +
+                        "This operation cannot be undone. " +
+                        "Any unsaved conversation will be lost."
+                )
+
+                if (isUnloading) {
+                    Spacer(modifier = Modifier.height(16.dp))
+                    Row(
+                        modifier = Modifier.fillMaxWidth(),
+                        horizontalArrangement = Arrangement.Center,
+                        verticalAlignment = Alignment.CenterVertically
+                    ) {
+                        CircularProgressIndicator(
+                            modifier = Modifier.size(24.dp),
+                            strokeWidth = 2.dp
+                        )
+                        Spacer(modifier = Modifier.width(8.dp))
+                        Text("Unloading model...")
+                    }
+                }
+            }
         },
         confirmButton = {
-            TextButton(onClick = onConfirm) {
+            TextButton(
+                onClick = onConfirm,
+                enabled = !isUnloading
+            ) {
                 Text("Yes, Exit")
             }
         },
         dismissButton = {
-            TextButton(onClick = onDismiss) {
+            TextButton(
+                onClick = onDismiss,
+                enabled = !isUnloading
+            ) {
                 Text("Cancel")
             }
         }