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Add multi-model download: Gemma 3n E4B (recommended), E2B, Gemma 2B

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- ModelSpec enum with 3 downloadable options from MediaPipe CDN
- Gemma 3n E4B set as recommended default (best coding/reasoning via MoE)
- Gemma 3n E2B as faster/smaller alternative
- Gemma 2B kept as lightest option
- UI shows all 3 download buttons, hides all once any model is installed
- Installed model name shown in status (e.g. "✓ Gemma 3n E4B ready")
- Custom models (DeepSeek Coder, Qwen2.5-Coder) can be manually placed in files dir

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
alexpolo1
2026-02-28 22:25:49 +01:00
parent 95b7c02fd0
commit e4a8fd805a
4 changed files with 120 additions and 34 deletions
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79
app/src/main/java/com/pixel10/ai/inference/ModelDownloader.kt
View File

@@ -10,23 +10,60 @@ import java.net.HttpURLConnection
import java.net.URL
/**
* Downloads a MediaPipe-compatible Gemma model for background-safe inference.
* Downloads a MediaPipe-compatible model for background-safe inference.
*
* Gemini Nano (ML Kit) blocks inference when the app is backgrounded (ErrorCode 30).
* MediaPipe with a local model file has no such restriction — it runs entirely in
* the app process using the Tensor G5 GPU via OpenCL/Vulkan.
*
* The downloaded model is stored in the app's private files directory and
* survives app restarts. Only needs to be downloaded once (~1.3 GB).
* Three model options (all from Google's MediaPipe CDN):
* - [ModelSpec.GEMMA_3N_E4B_CODING] — best coding/reasoning, ~2.5 GB (recommended)
* - [ModelSpec.GEMMA_3N_E2B_CODING] — good balance, ~1.5 GB
* - [ModelSpec.GEMMA_2B_GENERAL] — lightest, ~1.3 GB
*
* Custom models (DeepSeek Coder, Qwen2.5-Coder, etc.) can be placed manually in
* the app's files directory after converting with ai-edge-torch.
*/
object ModelDownloader {
private const val TAG = "ModelDownloader"
const val MODEL_FILENAME = "gemma-2b-it-gpu-int4.bin"
private const val MODEL_URL =
"https://storage.googleapis.com/mediapipe-models/llm_inference/" +
"gemma-2b-it-gpu-int4/float16/1/gemma-2b-it-gpu-int4.bin"
/** Available model specs that can be downloaded from Google's MediaPipe CDN. */
enum class ModelSpec(
val displayName: String,
val filename: String,
val url: String,
val sizeMb: Int,
val description: String
) {
/** Recommended: best coding & reasoning quality via MoE architecture. */
GEMMA_3N_E4B_CODING(
displayName = "Gemma 3n E4B",
filename = "gemma-3n-E4B-it-int4.task",
url = "https://storage.googleapis.com/mediapipe-models/llm_inference/" +
"gemma-3n-E4B-it-int4/float16/1/gemma-3n-E4B-it-int4.task",
sizeMb = 2500,
description = "Best coding & reasoning (~2.5 GB)"
),
/** Good balance between quality and speed. */
GEMMA_3N_E2B_CODING(
displayName = "Gemma 3n E2B",
filename = "gemma-3n-E2B-it-int4.task",
url = "https://storage.googleapis.com/mediapipe-models/llm_inference/" +
"gemma-3n-E2B-it-int4/float16/1/gemma-3n-E2B-it-int4.task",
sizeMb = 1500,
description = "Good balance, faster (~1.5 GB)"
),
/** Lightest option — general-purpose, not optimised for code. */
GEMMA_2B_GENERAL(
displayName = "Gemma 2B",
filename = "gemma-2b-it-gpu-int4.bin",
url = "https://storage.googleapis.com/mediapipe-models/llm_inference/" +
"gemma-2b-it-gpu-int4/float16/1/gemma-2b-it-gpu-int4.bin",
sizeMb = 1300,
description = "Lightest, general-purpose (~1.3 GB)"
)
}
data class Progress(
val downloadedBytes: Long,
@@ -34,25 +71,37 @@ object ModelDownloader {
val percent: Int = if (totalBytes > 0) (downloadedBytes * 100 / totalBytes).toInt() else 0
)
/** Returns true if any supported model is present in the app's files directory. */
fun isModelPresent(context: Context): Boolean =
modelFile(context).let { it.exists() && it.length() > 1_000_000L }
ModelSpec.values().any { modelFile(context, it).let { f -> f.exists() && f.length() > 1_000_000L } }
fun modelFile(context: Context): File = File(context.filesDir, MODEL_FILENAME)
/** Returns the installed [ModelSpec], or null if no model is present. */
fun installedSpec(context: Context): ModelSpec? =
ModelSpec.values().firstOrNull { modelFile(context, it).let { f -> f.exists() && f.length() > 1_000_000L } }
fun modelFile(context: Context, spec: ModelSpec): File =
File(context.filesDir, spec.filename)
/** Legacy compat — returns the file of the installed model, or Gemma 3n E4B path as default. */
fun modelFile(context: Context): File =
installedSpec(context)?.let { modelFile(context, it) }
?: modelFile(context, ModelSpec.GEMMA_3N_E4B_CODING)
/**
* Download the model, reporting progress via [onProgress].
* Download [spec], reporting progress via [onProgress].
* Supports resume — if a partial file exists, continues from where it left off.
*/
suspend fun download(
context: Context,
spec: ModelSpec = ModelSpec.GEMMA_3N_E4B_CODING,
onProgress: (Progress) -> Unit
) = withContext(Dispatchers.IO) {
val dest = modelFile(context)
val dest = modelFile(context, spec)
val alreadyDownloaded = if (dest.exists()) dest.length() else 0L
Log.i(TAG, "Download starting (already have $alreadyDownloaded bytes)")
Log.i(TAG, "Download starting ${spec.displayName} (already have $alreadyDownloaded bytes)")
val conn = URL(MODEL_URL).openConnection() as HttpURLConnection
val conn = URL(spec.url).openConnection() as HttpURLConnection
try {
conn.connectTimeout = 30_000
conn.readTimeout = 60_000
@@ -90,7 +139,7 @@ object ModelDownloader {
}
fun deleteModel(context: Context) {
modelFile(context).delete()
Log.i(TAG, "Model deleted")
ModelSpec.values().forEach { modelFile(context, it).delete() }
Log.i(TAG, "All models deleted")
}
}

45
app/src/main/java/com/pixel10/ai/ui/MainActivity.kt
View File

@@ -19,6 +19,7 @@ import androidx.lifecycle.lifecycleScope
import com.pixel10.ai.R
import com.pixel10.ai.databinding.ActivityMainBinding
import com.pixel10.ai.inference.ModelDownloader
import com.pixel10.ai.inference.ModelDownloader.ModelSpec
import com.pixel10.ai.server.ApiServerService
import kotlinx.coroutines.launch
import java.text.SimpleDateFormat
@@ -73,8 +74,14 @@ class MainActivity : AppCompatActivity() {
if (service?.isRunning == true) stopServer() else startServer()
}
binding.btnDownloadGemma3nE4b.setOnClickListener {
startModelDownload(ModelSpec.GEMMA_3N_E4B_CODING)
}
binding.btnDownloadGemma3nE2b.setOnClickListener {
startModelDownload(ModelSpec.GEMMA_3N_E2B_CODING)
}
binding.btnDownloadModel.setOnClickListener {
startModelDownload()
startModelDownload(ModelSpec.GEMMA_2B_GENERAL)
}
updateModelCard()
@@ -121,34 +128,33 @@ class MainActivity : AppCompatActivity() {
}
}
private fun startModelDownload() {
private fun startModelDownload(spec: ModelSpec) {
if (downloading) return
downloading = true
binding.btnDownloadModel.isEnabled = false
binding.btnDownloadModel.text = "Downloading…"
setDownloadButtonsEnabled(false)
binding.progressDownload.visibility = View.VISIBLE
binding.tvModelDownloadStatus.text = "Starting download…"
binding.tvModelDownloadStatus.text = "Starting download: ${spec.displayName}…"
lifecycleScope.launch {
try {
ModelDownloader.download(this@MainActivity) { progress ->
ModelDownloader.download(this@MainActivity, spec) { progress ->
runOnUiThread {
binding.progressDownload.progress = progress.percent
val mb = progress.downloadedBytes / 1_048_576
val total = progress.totalBytes / 1_048_576
binding.tvModelDownloadStatus.text = "Downloading… ${mb}MB / ${total}MB (${progress.percent}%)"
binding.tvModelDownloadStatus.text =
"${spec.displayName}: ${mb}MB / ${total}MB (${progress.percent}%)"
}
}
runOnUiThread {
downloading = false
updateModelCard()
appendLog("Model downloaded — background inference enabled")
appendLog("${spec.displayName} downloaded — background inference enabled")
}
} catch (e: Exception) {
runOnUiThread {
downloading = false
binding.btnDownloadModel.isEnabled = true
binding.btnDownloadModel.text = getString(R.string.btn_download_model)
setDownloadButtonsEnabled(true)
binding.progressDownload.visibility = View.GONE
binding.tvModelDownloadStatus.text = "Download failed: ${e.message}"
appendLog("Download error: ${e.message}")
@@ -157,17 +163,26 @@ class MainActivity : AppCompatActivity() {
}
}
private fun setDownloadButtonsEnabled(enabled: Boolean) {
binding.btnDownloadGemma3nE4b.isEnabled = enabled
binding.btnDownloadGemma3nE2b.isEnabled = enabled
binding.btnDownloadModel.isEnabled = enabled
}
private fun updateModelCard() {
val present = ModelDownloader.isModelPresent(this)
if (present) {
binding.tvModelDownloadStatus.text = getString(R.string.model_downloaded)
val spec = ModelDownloader.installedSpec(this)
if (spec != null) {
binding.tvModelDownloadStatus.text = getString(R.string.model_downloaded, spec.displayName)
binding.btnDownloadGemma3nE4b.visibility = View.GONE
binding.btnDownloadGemma3nE2b.visibility = View.GONE
binding.btnDownloadModel.visibility = View.GONE
binding.progressDownload.visibility = View.GONE
} else {
binding.tvModelDownloadStatus.text = getString(R.string.model_not_downloaded)
binding.btnDownloadGemma3nE4b.visibility = View.VISIBLE
binding.btnDownloadGemma3nE2b.visibility = View.VISIBLE
binding.btnDownloadModel.visibility = View.VISIBLE
binding.btnDownloadModel.isEnabled = true
binding.btnDownloadModel.text = getString(R.string.btn_download_model)
setDownloadButtonsEnabled(true)
binding.progressDownload.visibility = View.GONE
}
}

22
app/src/main/res/layout/activity_main.xml
View File

@@ -142,11 +142,31 @@
android:visibility="gone" />
<com.google.android.material.button.MaterialButton
android:id="@+id/btnDownloadModel"
android:id="@+id/btnDownloadGemma3nE4b"
style="@style/Widget.MaterialComponents.Button.OutlinedButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:text="@string/btn_download_gemma3n_e4b"
android:textSize="13sp"
app:cornerRadius="8dp" />
<com.google.android.material.button.MaterialButton
android:id="@+id/btnDownloadGemma3nE2b"
style="@style/Widget.MaterialComponents.Button.OutlinedButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:text="@string/btn_download_gemma3n_e2b"
android:textSize="13sp"
app:cornerRadius="8dp" />
<com.google.android.material.button.MaterialButton
android:id="@+id/btnDownloadModel"
style="@style/Widget.MaterialComponents.Button.OutlinedButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
android:text="@string/btn_download_model"
android:textSize="13sp"
app:cornerRadius="8dp" />

8
app/src/main/res/values/strings.xml
View File

@@ -18,9 +18,11 @@
<string name="model_not_loaded">Model: not loaded</string>
<!-- Controls -->
<string name="btn_download_model">Download Model (~1.3 GB)</string>
<string name="model_downloaded">✓ Gemma 2B ready — background inference enabled</string>
<string name="model_not_downloaded">No local model. Download to enable background inference.</string>
<string name="btn_download_gemma3n_e4b">⭐ Gemma 3n E4B — Best coding (~2.5 GB)</string>
<string name="btn_download_gemma3n_e2b">Gemma 3n E2B — Faster (~1.5 GB)</string>
<string name="btn_download_model">Gemma 2B — Lightest (~1.3 GB)</string>
<string name="model_downloaded">✓ %s ready — background inference enabled</string>
<string name="model_not_downloaded">No local model. Download one to enable background inference.</string>
<string name="btn_start">Start Server</string>
<string name="btn_stop">Stop Server</string>
<string name="port_label">Port:</string>