Android WebRTC实现屏幕共享

一、WebRTC实现简单的屏幕共享

　　屏幕共享原理：其实就还是利用系统提供的录屏服务，把录制好的屏幕内容通通过P2P发送给对等端，让对等端能够看到分享者的屏幕。其实对于分享者来说是推流，对于观看分享的端来说就是拉取视频流

二、代码演示

　　1.初始化截屏服务

//屏幕截取服务
    private MediaProjectionManager mediaProjectionManager = null;

    private DeviceManager(Context context) {
        this.context = context;
        audioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (Build.VERSION.SDK_INT >= 21) {
            mediaProjectionManager = (MediaProjectionManager) context.getSystemService(Context.MEDIA_PROJECTION_SERVICE);
        } else {
            Toast.makeText(context, "您的设备不支持屏幕共享", Toast.LENGTH_SHORT).show();
        }
    }

　　2.启动Android系统的屏幕共享　　

 /**
     * 开启屏幕截屏，调用此方法后会弹框提示用户开始截屏
     * @param activity
     */
    public void startScreenCapture(Activity activity) {
        if(mediaProjectionManager == null){
            Toast.makeText(context, "截屏服务不可用", Toast.LENGTH_SHORT).show();
            return;
        }
        Intent intent = null;
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
            intent = mediaProjectionManager.createScreenCaptureIntent();
            activity.startActivityForResult(intent, SCREEN_CAPTURE_REQUEST_CODE);
        }

    }

　　3.启动系统的屏幕共享后会再当前Activity的onActivityResult中收到回调

 @Override
    public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == DeviceManager.SCREEN_CAPTURE_REQUEST_CODE) {
            rtcClient.startShareScreen(data);
        }
    }

　　rtcClient.startShareScreen(data)　　

/**
     * 开始分享屏幕
     *
     * @param intent 分享屏幕创建的intent，用于创建ScreenCaptureAndroid
     */
    public void startShareScreen(Intent intent) {
        Log.e(TAG, "startShareScreen----->start");
        //创建屏幕捕获
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            if (shareScreenCapture == null) {
                shareScreenCapture = new ScreenCapturerAndroid(intent, new MediaProjection.Callback() {
                    @Override
                    public void onStop() {
                        super.onStop();
                    }
                });
            }
        }
        if (videoSource == null) {
            Log.e(TAG, "startShareScreen----->createVideoSource");
            videoSource = createVideoSource(shareScreenCapture);
        }
        Log.e(TAG, "startShareScreen----->startCapture");
        shareScreenCapture.initialize(surfaceTextureHelper, context, videoSource.getCapturerObserver());
        shareScreenCapture.startCapture(480, 640, 30);
        if (videoTrack == null) {
            Log.e(TAG, "startShareScreen----->createVideoTrack");
            videoTrack = createVideoTrack(videoSource);
        }
        //将视频加入媒体流
        Log.e(TAG, "startShareScreen----->createMediaStream");
        mediaStream = createMediaStream();
        mediaStream.addTrack(videoTrack);
        Log.e(TAG, "startShareScreen----->end");
    }

　　其实除了前几步和P2P通信不一样外，后几步都是一样的：都是先创建一个VideoCapture，然后调用其startCapture方法--->创建VideoTrack--->创建mediaStrea--->然后将videoTrack加入mediaStream。