Android Screen sharing¶

Example of Android application to publish device screen¶

The example shows how to share device screen. Device microphone or (in Android 10 or above) system audio may also be captured.

Analyzing the example code¶

To analyze the code let's take the class ScreenSharingActivity.java of the screen-sharing example, which can be downloaded with build 1.1.0.64.

1. Initialization of the API¶

Flashphoner.init() code

Context object is passed to method init() for initialization.

Flashphoner.init(this);

2. Display or hide a system sound capture button depending on Android version¶

code

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
    mAudioRadioGroup.setVisibility(View.VISIBLE);
} else {
    mAudioRadioGroup.setVisibility(View.GONE);

}

3. Request the permission to capture audio¶

code

mUseAudioCheckBox.setOnClickListener(v -> {
    if (mUseAudioCheckBox.isChecked()) {
        ActivityCompat.requestPermissions(ScreenSharingActivity.this,
                new String[]{Manifest.permission.RECORD_AUDIO},
                PUBLISH_REQUEST_CODE);
    }
});

4. Choose the microphone¶

code

mMicSpinner = (Spinner) findViewById(R.id.spinner_mic);
ArrayAdapter<MediaDevice> arrayAdapter = new ArrayAdapter<MediaDevice>(this, android.R.layout.simple_spinner_item, Flashphoner.getMediaDevices().getAudioList());
arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
mMicSpinner.setAdapter(arrayAdapter);

5. Session creation¶

Flashphoner.createSession() code

SessionOptions object is passed to the method with the following parameters

WCS server URL
SurfaceViewRenderer localRender to display local video
SurfaceViewRenderer remoteRender to display video published

SessionOptions sessionOptions = new SessionOptions(url);
sessionOptions.setLocalRenderer(localRender);
sessionOptions.setRemoteRenderer(remoteRender);

/**
 * Session for connection to WCS server is created with method createSession().
 */
session = Flashphoner.createSession(sessionOptions);

6. Connection to the server¶

Session.connect() code

session.connect(new Connection());

7. Receiving the event confirming successful connection¶

Session.onConnected() code

@Override
public void onConnected(final Connection connection) {
    runOnUiThread(() -> {
        mStartButton.setText(R.string.action_stop);
        mStartButton.setTag(R.string.action_stop);
        mStatusView.setText(connection.getStatus());
    });
    ...
}

8. Video stream creation¶

Session.createStream() code

StreamOptions streamOptions = new StreamOptions(streamName);
VideoConstraints videoConstraints = new VideoConstraints();
DisplayMetrics metrics = getResources().getDisplayMetrics();
videoConstraints.setResolution(metrics.widthPixels, metrics.heightPixels);
videoConstraints.setVideoFps(metrics.densityDpi);
streamOptions.getConstraints().setVideoConstraints(videoConstraints);
streamOptions.getConstraints().updateAudio(mUseAudioCheckBox.isChecked());

/**
 * Stream is created with method Session.createStream().
 */
publishStream = session.createStream(streamOptions);
...
startScreenCapture();

9. Prepare to capture device screen¶

code

private void startScreenCapture() {
    mMediaProjectionManager = (MediaProjectionManager) getSystemService(
            Context.MEDIA_PROJECTION_SERVICE);
    Intent permissionIntent = mMediaProjectionManager.createScreenCaptureIntent();
    startActivityForResult(permissionIntent, REQUEST_CODE_CAPTURE_PERM);
}

10. Start foreground service¶

context.startForegroundService() code

protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (REQUEST_CODE_CAPTURE_PERM == requestCode && resultCode == RESULT_OK) {

        this.mediaProjectionData = data;

        Context context = getApplicationContext();
        this.serviceIntent = new Intent(context, ScreenSharingService.class);
        context.startForegroundService(serviceIntent);
    } else {
        runOnUiThread(() -> mStartButton.setEnabled(false));
        stop();
        Log.i(TAG, "Permission has been denied by user");
    }
}

11. Capture device screen and publish a stream¶

ScreenCapturerAndroid(), Stream.publish() code

private final BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent != null) {
            if (ScreenSharingService.ACTION_START.equals(intent.getAction())) {
                MediaProjection mediaProjection = null;
                if (mUseAudioCheckBox.isChecked() && !mUseMicRadioButton.isChecked() && Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                    mediaProjection = mediaProjectionManager.getMediaProjection(Activity.RESULT_OK, mediaProjectionData);
                }

                WebRTCMediaProvider.getInstance().setMediaProjection(mediaProjection);
                videoCapturer = new ScreenCapturerAndroid(mediaProjection, mediaProjectionData, new MediaProjection.Callback() {
                    @Override
                    public void onStop() {
                        super.onStop();
                        handler.post(ScreenSharingActivity.this::stop);
                    }
                });
                WebRTCMediaProvider.getInstance().setVideoCapturer(videoCapturer);

                publishStream.publish();
            } else if (ScreenSharingService.ACTION_STOP.equals(intent.getAction())) {
                handler.post(ScreenSharingActivity.this::stop);
            }
        }
    }
};

12. Receiving the event confirming the successful stream publishing¶

StreamStatusEvent.PUBLISHING code

On receiving this event preview stream is created with Session.createStream() and Stream.play() is invoked to play it.

publishStream.on(new StreamStatusEvent() {
    @Override
    public void onStreamStatus(final Stream stream, final StreamStatus streamStatus) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                if (StreamStatus.PUBLISHING.equals(streamStatus)) {

                    /**
                     * The options for the stream to play are set.
                     * The stream name is passed when StreamOptions object is created.
                     */
                    StreamOptions streamOptions = new StreamOptions(streamName);
                    streamOptions.getConstraints().updateAudio(mUseAudioCheckBox.isChecked());

                    /**
                     * Stream is created with method Session.createStream().
                     */
                    playStream = session.createStream(streamOptions);
                    ...
                    playStream.play();
                } else {
                    Log.e(TAG, "Can not publish stream " + stream.getName() + " " + streamStatus);
                }
                mStatusView.setText(streamStatus.toString());
            }
        });
    }
});

13. Session disconnection¶

Session.disconnect() code

private synchronized void stop() {
    if (session != null) {
        session.disconnect();
        session = null;
    }

    WebRTCMediaProvider.getInstance().releaseLocalMediaAccess();

    if (serviceIntent != null) {
        stopService(serviceIntent);
        this.serviceIntent = null;
    }

    ...
}

14. Foreground service creation¶

Service.onCreate(), startForeground() code

@Override
public void onCreate() {
    super.onCreate();

    NotificationChannel chan = new NotificationChannel(CHANNEL_ID, CHANNEL_NAME, NotificationManager.IMPORTANCE_NONE);
    chan.setImportance(NotificationManager.IMPORTANCE_MIN);

    NotificationManager manager =
            (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    chan.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
    manager.createNotificationChannel(chan);

    final int notificationId = (int) System.currentTimeMillis();
    Notification.Builder notificationBuilder = new Notification.Builder(this, CHANNEL_ID);
    Notification notification =
            notificationBuilder
                    .setSmallIcon(R.drawable.service_icon)
                    .setOngoing(true)
                    .setShowWhen(true)
                    .setContentTitle("ScreenSharingService is running in the foreground")
                    .setCategory(Notification.CATEGORY_SERVICE)
                    .addAction(createStopAction())
                    .build();

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
        startForeground(notificationId, notification, ServiceInfo.FOREGROUND_SERVICE_TYPE_MEDIA_PROJECTION);
    } else {
        startForeground(notificationId, notification);
    }
}

15. Stopping foreground service¶

Service.onDestroy(), stopForeground() code

@Override
public void onDestroy() {
    stopForeground(true);
    super.onDestroy();
}