How to make screen sharing using WebRTC in Android

Implementing Screen Sharing on Android with WebRTC

WebRTC (Web Real-Time Communication) is an open-source project enabling real-time voice calls, video calls, and data sharing directly within web browsers. Although initially designed for web environments, WebRTC can also be effectively utilized in mobile applications, including Android platforms.

Implementing screen sharing on Android involves the following key steps:

1. Obtain Screen Capture Permission

First, secure user permission for screen recording. This is typically done by creating a screen capture intent.

java
MediaProjectionManager projectionManager =
    (MediaProjectionManager) getSystemService(Context.MEDIA_PROJECTION_SERVICE);

Intent intent = projectionManager.createScreenCaptureIntent();
startActivityForResult(intent, REQUEST_CODE);

In the onActivityResult() method, verify user permission and retrieve the MediaProjection object.

java
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_CODE) {
        if (resultCode == RESULT_OK) {
            MediaProjection mediaProjection = projectionManager.getMediaProjection(resultCode, data);
            // Proceed with media projection
        }
    }
}

2. Capture Screen Data

Once the MediaProjection object is obtained, it can be used to capture screen content. This process commonly involves the VirtualDisplay class.

java
DisplayMetrics metrics = getResources().getDisplayMetrics();
int density = metrics.densityDpi;

mediaProjection.createVirtualDisplay("ScreenSharingDemo",
    DISPLAY_WIDTH, DISPLAY_HEIGHT, density,
    DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR,
    surface, null /*Callbacks*/, null /*Handler*/);

3. Send Captured Data to the Remote End

To transmit data via WebRTC, the captured screen content (typically within a Surface object) must first be converted into a WebRTC-compatible format. The VideoCapturer interface facilitates this conversion.

java
VideoCapturer videoCapturer = new ScreenCapturerAndroid(
    mediaProjection, new VideoCapturer.CapturerObserver() {
        @Override
        public void onByteBufferFrameCaptured(byte[] data, int width, int height, int rotation, long timestamp) {
            // Handle captured frame
        }

        @Override
        public void onTextureFrameCaptured(int width, int height, int oesTextureId, float[] transformMatrix, int rotation, long timestamp) {
            // Handle texture frame
        }
    });

4. Integrate into WebRTC Session

Finally, create a PeerConnection and add the previously created videoCapturer to this connection.

java
PeerConnectionFactory factory = ...;
VideoSource videoSource = factory.createVideoSource(false);
VideoTrack videoTrack = factory.createVideoTrack("videoTrackID", videoSource);
videoTrack.addSink(remoteView); // remoteView is your remote video view

// Add track to PeerConnection
PeerConnection peerConnection = ...;
peerConnection.addTrack(videoTrack, Collections.singletonList("streamId"));

By following these steps, screen sharing functionality can be implemented using WebRTC and Android APIs. However, practical deployment requires careful consideration of factors such as network conditions, security, and error handling. Additionally, WebRTC services like signaling servers can be leveraged to manage and coordinate user connections.