Chromecast streaming from mobile app

Implementing Chromecast Streaming from a Mobile Application

Chromecast works through Google Cast SDK: the phone (Sender) controls a playback device (Receiver — Chromecast, Android TV, Google Nest). The phone doesn't stream media data through itself — it sends a URL, and the Receiver fetches the stream directly from the server.

Connecting Google Cast SDK

Android. com.google.android.gms:play-services-cast-framework:latest in build.gradle. Initialization in Application:

class App : Application() {
    override fun onCreate() {
        super.onCreate()
        val options = CastOptions.Builder()
            .setReceiverApplicationId(CastMediaControlIntent.DEFAULT_MEDIA_RECEIVER_APPLICATION_ID)
            .build()
        CastContext.getSharedInstance(this, executor).addOnSuccessListener { castContext ->
            // Cast context is ready
        }
    }
}

DEFAULT_MEDIA_RECEIVER_APPLICATION_ID is the standard Default Media Receiver that plays HLS, DASH, MP4, MP3. For a custom Receiver (your own web application on Chromecast) — register in Google Cast Developer Console and use your own App ID.

iOS. pod 'google-cast-sdk' (CocoaPods) or GoogleCast via SPM (unofficial). API is similar to Android.

Cast Button in UI

Google Cast SDK automatically provides UICastButton (iOS) / MediaRouteButton (Android) — standard Cast icon that displays the list of available devices and changes appearance when connected:

// In menu toolbar
override fun onCreateOptionsMenu(menu: Menu): Boolean {
    menuInflater.inflate(R.menu.menu_player, menu)
    CastButtonFactory.setUpMediaRouteButton(this, menu, R.id.media_route_menu_item)
    return true
}

For Jetpack Compose — AndroidView with MediaRouteButton.

Starting Playback on Receiver

val castSession = CastContext.getSharedInstance(context).sessionManager.currentCastSession
val remoteClient = castSession?.remoteMediaClient ?: return

val mediaMetadata = MediaMetadata(MediaMetadata.MEDIA_TYPE_MOVIE).apply {
    putString(MediaMetadata.KEY_TITLE, "Movie Title")
    putString(MediaMetadata.KEY_SUBTITLE, "Description")
    addImage(WebImage(Uri.parse(thumbnailUrl)))
}

val mediaInfo = MediaInfo.Builder(streamUrl)
    .setStreamType(MediaInfo.STREAM_TYPE_BUFFERED)
    .setContentType("application/x-mpegURL") // HLS, or video/mp4 for MP4
    .setMetadata(mediaMetadata)
    .build()

val loadOptions = MediaLoadRequestData.Builder()
    .setMediaInfo(mediaInfo)
    .setAutoplay(true)
    .setCurrentTime(startPositionMs.toLong())
    .build()

remoteClient.load(loadOptions)

Playback Control

RemoteMediaClient is the central object for all commands: play(), pause(), seek(position), setStreamVolume(volume). State is accessed through RemoteMediaClient.Callback:

remoteClient.registerCallback(object : RemoteMediaClient.Callback() {
    override fun onStatusUpdated() {
        val status = remoteClient.mediaStatus ?: return
        val position = status.streamPosition
        val isPlaying = status.playerState == MediaStatus.PLAYER_STATE_PLAYING
        updateUI(isPlaying, position)
    }
})

Mini Controller and Expanded Controller

Google Cast SDK provides ready-made UI components: MiniControllerFragment — a control bar at the bottom of the screen (similar to a mini-player), ExpandedControllerActivity — a fullscreen Cast player. Connected declaratively — minimal code required.

Cast Session and Reconnection

When Wi-Fi connection is lost, CastSession transitions to TEMPORARILY_DISCONNECTED state. After 3 minutes — DISCONNECTED. SessionManagerListener.onSessionSuspended / onSessionResumed — handle reconnection, resume playback from saved position.

If the user closed the application and returned — Cast SDK automatically restores the session through CastContext.sessionManager.currentCastSession. Check on app startup and show the Cast mini-controller if a session is active.

Chromecast on React Native and Flutter

React Native: react-native-google-cast (github.com/react-native-google-cast) — unofficial wrapper. Stable for basic scenarios (starting video, pause, seeking), but extended functionality (queue, custom data) requires native code through bridge.

Flutter: no official package. flutter_google_cast (pub.dev) — community package with unstable support. For production, we recommend native implementation through MethodChannel.

Timeline

Basic Chromecast streaming with Cast button, playback launch and mini-controller — 2–3 days. Custom Receiver (web application) — a separate task, plus 2–3 days.