Android WebRTC實現屏幕共享

一、WebRTC實現簡單的屏幕共享

　　屏幕共享原理：其實就還是利用系統提供的錄屏服務，把錄制好的屏幕內容通通過P2P發送給對等端，讓對等端能夠看到分享者的屏幕。其實對於分享者來說是推流，對於觀看分享的端來說就是拉取視頻流

二、代碼演示

　　1.初始化截屏服務

//屏幕截取服務
    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, "您的設備不支持屏幕共享", Toast.LENGTH_SHORT).show();
        }
    }

　　2.啟動Android系統的屏幕共享　　

 /**
     * 開啟屏幕截屏，調用此方法后會彈框提示用戶開始截屏
     * @param activity
     */
    public void startScreenCapture(Activity activity) {
        if(mediaProjectionManager == null){
            Toast.makeText(context, "截屏服務不可用", 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.啟動系統的屏幕共享后會再當前Activity的onActivityResult中收到回調

 @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)　　

/**
     * 開始分享屏幕
     *
     * @param intent 分享屏幕創建的intent，用於創建ScreenCaptureAndroid
     */
    public void startShareScreen(Intent intent) {
        Log.e(TAG, "startShareScreen----->start");
        //創建屏幕捕獲
        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);
        }
        //將視頻加入媒體流
        Log.e(TAG, "startShareScreen----->createMediaStream");
        mediaStream = createMediaStream();
        mediaStream.addTrack(videoTrack);
        Log.e(TAG, "startShareScreen----->end");
    }

　　其實除了前幾步和P2P通信不一樣外，后幾步都是一樣的：都是先創建一個VideoCapture，然后調用其startCapture方法--->創建VideoTrack--->創建mediaStrea--->然后將videoTrack加入mediaStream。