feat(ai-logic): add hybrid on-device inference sample

firebase-ai/app/build.gradle.kts

@@ -12,7 +12,7 @@ android {
 
     defaultConfig {
         applicationId = "com.google.firebase.quickstart.ai"
-        minSdk = 23
+        minSdk = 26
         targetSdk = 36
         versionCode = 1
         versionName = "1.0"
@@ -73,6 +73,7 @@ dependencies {
     // Firebase
     implementation(platform(libs.firebase.bom))
     implementation(libs.firebase.ai)
+    implementation(libs.firebase.ai.ondevice)
 
     // Image loading
     implementation(libs.coil.compose)

firebase-ai/app/src/main/java/com/google/firebase/quickstart/ai/MainActivity.kt

@@ -27,6 +27,7 @@ import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.rememberNavController
 import com.google.firebase.quickstart.ai.feature.live.BidiViewModel
+import com.google.firebase.quickstart.ai.feature.hybrid.HybridInferenceViewModel
 import com.google.firebase.quickstart.ai.feature.media.imagen.ImagenViewModel
 import com.google.firebase.quickstart.ai.feature.text.ChatViewModel
 import com.google.firebase.quickstart.ai.feature.text.ServerPromptTemplateViewModel
@@ -36,6 +37,7 @@ import com.google.firebase.quickstart.ai.ui.ImagenScreen
 import com.google.firebase.quickstart.ai.ui.ServerPromptScreen
 import com.google.firebase.quickstart.ai.ui.StreamRealtimeScreen
 import com.google.firebase.quickstart.ai.ui.StreamRealtimeVideoScreen
+import com.google.firebase.quickstart.ai.ui.HybridInferenceScreen
 import com.google.firebase.quickstart.ai.ui.SvgScreen
 import com.google.firebase.quickstart.ai.ui.navigation.FIREBASE_AI_SAMPLES
 import com.google.firebase.quickstart.ai.ui.navigation.MainMenuScreen
@@ -123,6 +125,10 @@ class MainActivity : ComponentActivity() {
                                             StreamRealtimeVideoScreen(it)
                                         }
                                     }
+
+                                    ScreenType.HYBRID -> {
+                                        (vm as? HybridInferenceViewModel)?.let { HybridInferenceScreen(it) }
+                                    }
                                 }
                             }
                         }

firebase-ai/app/src/main/java/com/google/firebase/quickstart/ai/feature/hybrid/Expense.kt

@@ -0,0 +1,10 @@
+package com.google.firebase.quickstart.ai.feature.hybrid
+
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class Expense(
+    val name: String,
+    val price: Double,
+    val inferenceMode: String = ""
+)

firebase-ai/app/src/main/java/com/google/firebase/quickstart/ai/feature/hybrid/HybridInferenceViewModel.kt

@@ -0,0 +1,153 @@
+package com.google.firebase.quickstart.ai.feature.hybrid
+
+import android.graphics.Bitmap
+import android.util.Log
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.google.firebase.Firebase
+import com.google.firebase.ai.InferenceMode
+import com.google.firebase.ai.InferenceSource
+import com.google.firebase.ai.OnDeviceConfig
+import com.google.firebase.ai.ai
+import com.google.firebase.ai.ondevice.DownloadStatus
+import com.google.firebase.ai.ondevice.FirebaseAIOnDevice
+import com.google.firebase.ai.ondevice.OnDeviceModelStatus
+import com.google.firebase.ai.type.GenerativeBackend
+import com.google.firebase.ai.type.PublicPreviewAPI
+import com.google.firebase.ai.type.content
+import com.google.firebase.quickstart.ai.ui.HybridInferenceUiState
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import java.util.UUID
+
+@Serializable
+object HybridInferenceRoute
+
+@OptIn(PublicPreviewAPI::class)
+class HybridInferenceViewModel : ViewModel() {
+    private val _uiState = MutableStateFlow(
+        HybridInferenceUiState(
+            expenses = listOf(
+                Expense("Lunch", 15.50, "Example data"),
+                Expense("Coffee", 4.75, "Example data")
+            )
+        )
+    )
+    val uiState: StateFlow<HybridInferenceUiState> = _uiState.asStateFlow()
+
+    private val model = Firebase.ai(backend = GenerativeBackend.googleAI()).generativeModel(
+        modelName = "gemini-3.1-flash-lite-preview",
+        onDeviceConfig = OnDeviceConfig(mode = InferenceMode.PREFER_ON_DEVICE)
+    )
+
+    init {
+        checkAndDownloadModel()
+    }
+
+    private fun checkAndDownloadModel() {
+        viewModelScope.launch {
+            try {
+                val status = FirebaseAIOnDevice.checkStatus()
+                updateStatus(status)
+
+                if (status == OnDeviceModelStatus.DOWNLOADABLE) {
+                    FirebaseAIOnDevice.download().collect { downloadStatus ->
+                        when (downloadStatus) {
+                            is DownloadStatus.DownloadStarted -> {
+                                _uiState.update { it.copy(modelStatus = "Downloading model...") }
+                            }
+
+                            is DownloadStatus.DownloadInProgress -> {
+                                val progress = downloadStatus.totalBytesDownloaded
+                                _uiState.update { it.copy(modelStatus = "Downloading: $progress bytes downloaded") }
+                            }
+
+                            is DownloadStatus.DownloadCompleted -> {
+                                _uiState.update { it.copy(modelStatus = "Model ready") }
+                            }
+
+                            is DownloadStatus.DownloadFailed -> {
+                                _uiState.update {
+                                    it.copy(
+                                        modelStatus = "Download failed", errorMessage = "Model download failed"
+                                    )
+                                }
+                            }
+                        }
+                    }
+                }
+            } catch (e: Exception) {
+                _uiState.update { it.copy(modelStatus = "Error checking status", errorMessage = e.message) }
+            }
+        }
+    }
+
+    private fun updateStatus(status: OnDeviceModelStatus) {
+        val statusText = when (status) {
+            OnDeviceModelStatus.AVAILABLE -> "Model available"
+            OnDeviceModelStatus.DOWNLOADABLE -> "Model downloadable"
+            OnDeviceModelStatus.DOWNLOADING -> "Model downloading..."
+            OnDeviceModelStatus.UNAVAILABLE -> "On-device model unavailable"
+            else -> "Unknown"
+        }
+        _uiState.update { it.copy(modelStatus = statusText) }
+    }
+
+    fun scanReceipt(bitmap: Bitmap) {
+        viewModelScope.launch {
+            _uiState.update { it.copy(isScanning = true, errorMessage = null) }
+            try {
+                val prompt = content {
+                    image(bitmap)
+                    text(
+                        """
+                        Extract the store name and the total price from this receipt.
+                        Output only in JSON format containg 2 fields '{name,price}'.
+                        Do not include any currency signs or backticks or any text around it.
+                        Use dots for decimals.
+                        Examples:
+                        - {"name": "FakeStore", "price": "2.0"}
+                        - {"name": "SomeMarket", "price": "3.5"}
+                        """.trimIndent()
+                    )
+                }
+
+                val response = model.generateContent(prompt)
+                val text = response.text
+                val inferenceMode = if (response.inferenceSource == InferenceSource.ON_DEVICE) {
+                    "On-device"
+                } else {
+                    "Cloud"
+                }
+                Log.d("HybridVM", "$inferenceMode response: $text")
+                if (text != null) {
+                    parseAndAddExpense(text, inferenceMode)
+                } else {
+                    _uiState.update { it.copy(errorMessage = "Could not extract data") }
+                }
+            } catch (e: Exception) {
+                _uiState.update { it.copy(errorMessage = "Error: ${e.message}") }
+            } finally {
+                _uiState.update { it.copy(isScanning = false) }
+            }
+        }
+    }
+
+    private fun parseAndAddExpense(text: String, inferenceMode: String) {
+        val json = text
+            // The on-device model sometimes outputs backticks, so we remove those
+            .replace("```json", "")
+            .replace("```", "")
+        try {
+            val newExpense = Json.decodeFromString<Expense>(json).copy(inferenceMode = inferenceMode)
+            _uiState.update { it.copy(expenses = it.expenses + newExpense) }
+        } catch (e: Exception) {
+            _uiState.update { it.copy(errorMessage = e.localizedMessage) }
+        }
+    }
+}