WebRTCAndroid：实现视频和音频实时通信的Android开源库

一、简介

WebRTCAndroid是一个开源的Android应用程序开发库，支持视频和音频实时通话。它由Google开发并维护，以简化实时通信应用程序的开发。

在WebRTCAndroid中，我们可以使用许多官方提供的API来实现实时通信，并且可以很容易地与其他平台（如Web、iOS等）进行交互。这些API包括MediaStream、RTCPeerConnection和RTCDataChannel等，所有这些API都是Java接口，易于开发和集成。

二、使用WebRTCAndroid实现实时视频通话

以下是使用WebRTCAndroid实现实时视频通话的示例代码：

private PeerConnectionFactory peerConnectionFactory;
private PeerConnection peerConnection;
private localMediaStream localStream;
private VideoCapturer videoCapturer;
private VideoSource videoSource;
private VideoTrack localVideoTrack;
private SurfaceTextureHelper surfaceTextureHelper;
 
public void start() {
    // 初始化PeerConnectionFactory
    PeerConnectionFactory.initialize(PeerConnectionFactory.InitializationOptions.builder(context).createInitializationOptions());
    PeerConnectionFactory.Options options = new PeerConnectionFactory.Options();
    options.disableEncryption = true;
    options.disableNetworkMonitor = true;
    peerConnectionFactory = new PeerConnectionFactory(options);
 
    // 创建本地视频流
    surfaceTextureHelper = SurfaceTextureHelper.create("CaptureThread", null);
    videoCapturer = createCameraCapturer(new Camera1Enumerator(false));
    videoSource = peerConnectionFactory.createVideoSource(false);
    videoCapturer.initialize(surfaceTextureHelper, context, videoSource.getCapturerObserver());
    videoCapturer.startCapture(640, 480, 30);
    localVideoTrack = peerConnectionFactory.createVideoTrack("100", videoSource);
    localVideoTrack.addSink(localView); // localView是本地的SurfaceView
 
    // 创建PeerConnection
    peerConnection = peerConnectionFactory.createPeerConnection(null, new CustomPeerConnectionObserver(TAG), new CustomSdpObserver(TAG))；
    MediaStreamManager localMediaStreamManager = new MediaStreamManager(peerConnection);
    localMediaStreamManager.addTrack(localVideoTrack); // 添加本地视频轨道到媒体流中
    peerConnection.createOffer(new CustomSdpObserver(TAG) {
        @Override
        public void onCreateSuccess(SessionDescription sessionDescription) {
            super.onCreateSuccess(sessionDescription);
            peerConnection.setLocalDescription(new CustomSdpObserver(TAG), sessionDescription);
            remoteDescription(sessionDescription); // 发送SDP offer到远程连接
        }
    }, new MediaConstraints());
}

三、使用WebRTCAndroid实现实时音频通话

以下是使用WebRTCAndroid实现实时音频通话的示例代码：

private PeerConnectionFactory peerConnectionFactory;
private PeerConnection peerConnection;
private localMediaStream localStream;
private AudioTrack localAudioTrack;
private AudioSource audioSource;
 
public void start() {
    // 初始化PeerConnectionFactory
    PeerConnectionFactory.initialize(PeerConnectionFactory.InitializationOptions.builder(context).createInitializationOptions());
    PeerConnectionFactory.Options options = new PeerConnectionFactory.Options();
    options.disableEncryption = true;
    options.disableNetworkMonitor = true;
    peerConnectionFactory = new PeerConnectionFactory(options);
 
    // 创建音频轨道
    audioSource = peerConnectionFactory.createAudioSource(new MediaConstraints());
    localAudioTrack = peerConnectionFactory.createAudioTrack("101", audioSource);
 
    // 创建PeerConnection
    peerConnection = peerConnectionFactory.createPeerConnection(null, new CustomPeerConnectionObserver(TAG), new CustomSdpObserver(TAG))；
    MediaStreamManager localMediaStreamManager = new MediaStreamManager(peerConnection);
    localMediaStreamManager.addTrack(localAudioTrack); // 添加本地音频轨道到媒体流中
    peerConnection.createOffer(new CustomSdpObserver(TAG) {
        @Override
        public void onCreateSuccess(SessionDescription sessionDescription) {
            super.onCreateSuccess(sessionDescription);
            peerConnection.setLocalDescription(new CustomSdpObserver(TAG), sessionDescription);
            remoteDescription(sessionDescription); // 发送SDP offer到远程连接
        }
    }, new MediaConstraints());
}

四、WebRTCAndroid的使用示例

在WebRTCAndroid中，我们可以使用许多官方提供的API来实现实时通信。下面是一个使用WebRTCAndroid实现实时视频通话的示例：

public class CallActivity extends Activity {
    private View hangupButton;
    private VideoRenderer remoteVideoView;
    private VideoRenderer localVideoView;
 
    private VideoCapturerAndroid videoCapturer;
    private PeerConnectionFactory factory;
    private PeerConnection peerConnection;
    private MediaStream localStream;
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_call);
        hangupButton = findViewById(R.id.hangup_button);
        remoteVideoView = (VideoRendererGui.ScalingType scalingType, boolean mirror) ->
            VideoRendererGui.create(remoteVideoView, 0, 0, 100, 100, scalingType, mirror);
        localVideoView = (VideoRendererGui.ScalingType scalingType, boolean mirror) ->
            VideoRendererGui.create(localVideoView, 0, 0, 100, 100, scalingType, mirror);
 
        PeerConnectionFactory.initializeAndroidGlobals(this);
        factory = new PeerConnectionFactory();
 
        // 创建本地视频流
        videoCapturer = new VideoCapturerAndroid(CameraEnumerationAndroid.getNameOfFrontFacingDevice(), null);
        VideoSource localVideoSource = factory.createVideoSource(videoCapturer, new MediaConstraints());
        VideoTrack localVideoTrack = factory.createVideoTrack("video", localVideoSource);
        localVideoTrack.addRenderer(new VideoRenderer(localVideoView));
        localStream = factory.createLocalMediaStream("stream");
        localStream.addTrack(localVideoTrack);
 
        // 设置远程和本地视频视图
        VideoRendererGui.setView(remoteVideoView, null);
        VideoRendererGui.setView(localVideoView, null);
 
        // 创建peerConnection，添加本地媒体流
        peerConnection = factory.createPeerConnection(getIceServerList(), getMediaConstraints(), new CustomPeerConnectionObserver(TAG));
        if (peerConnection != null) {
            peerConnection.addStream(localStream, new MediaConstraints());
        }
 
        // 建立SDP offer
        peerConnection.createOffer(new CustomSdpObserver(TAG) {
            @Override
            public void onCreateSuccess(SessionDescription sessionDescription) {
                super.onCreateSuccess(sessionDescription);
                peerConnection.setLocalDescription(new CustomSdpObserver(TAG), sessionDescription);
                sendOfferToRemote(peerConnection, sessionDescription.description);
            }
        }, new MediaConstraints());
 
        hangupButton.setOnClickListener(v -> {
            disconnectPeerConnection(peerConnection);
        });
    }
 
    private List getIceServerList() {
        List iceServers = new ArrayList();
        iceServers.add(new PeerConnection.IceServer("stun:stun.l.google.com:19302"));
        iceServers.add(new PeerConnection.IceServer("turn:192.158.29.39:3478?transport=udp",
                "username",
                "password"));
        return iceServers;
    }
 
    private MediaConstraints getMediaConstraints() {
        MediaConstraints mediaConstraints = new MediaConstraints();
        mediaConstraints.mandatory.add(new MediaConstraints.KeyValuePair("OfferToReceiveAudio", "true"));
        mediaConstraints.mandatory.add(new MediaConstraints.KeyValuePair("OfferToReceiveVideo", "true"));
        mediaConstraints.optional.add(new MediaConstraints.KeyValuePair("DtlsSrtpKeyAgreement", "true"));
        return mediaConstraints;
    }
 
    private void sendOfferToRemote(PeerConnection peerConnection, String sdp){
        // 发送SDP offer到远程连接
    }
 
    private void disconnectPeerConnection(PeerConnection peerConnection) {
        if (peerConnection != null) {
            peerConnection.dispose();
            peerConnection = null;
        }
        if (videoCapturer != null) {
            try {
                videoCapturer.stopCapture();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            videoCapturer.dispose();
            videoCapturer = null;
        }
        if (localStream != null) {
            localStream.dispose();
            localStream = null;
        }
        VideoRendererGui.remove(remoteVideoView);
        VideoRendererGui.remove(localVideoView);
    }
}

五、总结

WebRTCAndroid是一个非常有用的开源库，提供了许多API和示例代码，可以让开发人员轻松地实现实时通信应用程序。在使用WebRTCAndroid时，需要注意实时通信的性能和稳定性，以便提供更好的用户体验。