WifiDisplay(Miracast)技术原理及实现

void SurfaceFlinger::doComposition() {
    ATRACE_CALL();
    const bool repaintEverything = android_atomic_and(0, &mRepaintEverything);
    for (size_t dpy=0 ; dpy<mDisplays.size() ; dpy++) {
        const sp<DisplayDevice>& hw(mDisplays[dpy]);
        if (hw->isDisplayOn() && (hw->getDisplayType() != DisplayDevice::DISPLAY_EXTERNAL)) {
            // transform the dirty region into this screen's coordinate space
            const Region dirtyRegion(hw->getDirtyRegion(repaintEverything));
            // repaint the framebuffer (if needed)
            doDisplayComposition(hw, dirtyRegion);
            hw->dirtyRegion.clear();
            hw->flip(hw->swapRegion);
            hw->swapRegion.clear();
        }
        // inform the h/w that we're done compositing
        hw->compositionComplete();
    }
    postFramebuffer();
}

<bool name="config_enableWifiDisplay">true</bool>

private void update(int changes) {
    boolean invalidateOptions = false;
    // Update settings.
    if ((changes & CHANGE_SETTINGS) != 0) {
        mWifiDisplayOnSetting = Settings.Global.getInt(getContentResolver(),
                Settings.Global.WIFI_DISPLAY_ON, 0) != 0;
        mWifiDisplayCertificationOn = Settings.Global.getInt(getContentResolver(),
                Settings.Global.WIFI_DISPLAY_CERTIFICATION_ON, 0) != 0;
        mWpsConfig = Settings.Global.getInt(getContentResolver(),
            Settings.Global.WIFI_DISPLAY_WPS_CONFIG, WpsInfo.INVALID);
        // The wifi display enabled setting may have changed.
        invalidateOptions = true;
    }
    // Update wifi display state.
    if ((changes & CHANGE_WIFI_DISPLAY_STATUS) != 0) {
        mWifiDisplayStatus = mDisplayManager.getWifiDisplayStatus();
        // The wifi display feature state may have changed.
        invalidateOptions = true;
    }
    // Rebuild the routes.
    final PreferenceScreen preferenceScreen = getPreferenceScreen();
    preferenceScreen.removeAll();
    // Add all known remote display routes.
    final int routeCount = mRouter.getRouteCount();
    for (int i = 0; i < routeCount; i++) {
        MediaRouter.RouteInfo route = mRouter.getRouteAt(i);
        if (route.matchesTypes(MediaRouter.ROUTE_TYPE_REMOTE_DISPLAY)) {
            preferenceScreen.addPreference(createRoutePreference(route));
        }
    }
    // Additional features for wifi display routes.
    if (mWifiDisplayStatus != null
            && mWifiDisplayStatus.getFeatureState() == WifiDisplayStatus.FEATURE_STATE_ON) {
        // Add all unpaired wifi displays.
        for (WifiDisplay display : mWifiDisplayStatus.getDisplays()) {
            if (!display.isRemembered() && display.isAvailable()
                    && !display.equals(mWifiDisplayStatus.getActiveDisplay())) {
                preferenceScreen.addPreference(new UnpairedWifiDisplayPreference(
                        getActivity(), display));
            }
        }
        // Add the certification menu if enabled in developer options.
        if (mWifiDisplayCertificationOn) {
            buildCertificationMenu(preferenceScreen);
        }
    }
    // Invalidate menu options if needed.
    if (invalidateOptions) {
        getActivity().invalidateOptionsMenu();
    }
}

mP2pManager = (WifiP2pManager) context.getSystemService(Context.WIFI_P2P_SERVICE);
Looper looper = mHandlerThread.getLooper();
if (mP2pManager == null || looper == null) {
    throw new NullPointerException("Failed to get P2P_SERVICE or widi_receiver thread looper");
}
mChannel = mP2pManager.initialize(context, looper, mChannelListener);

WifiP2pWfdInfo wfdInfo = new WifiP2pWfdInfo();
wfdInfo.setWfdEnabled(true);
wfdInfo.setDeviceType(WifiP2pWfdInfo.PRIMARY_SINK);
wfdInfo.setSessionAvailable(true);
wfdInfo.setControlPort(7236);
wfdInfo.setMaxThroughput(50);
Log.d(TAG,"advertise sink");
mP2pManager.setWFDInfo(mChannel, wfdInfo, mActionListener);
mHandler.post(mDiscoverPeers);
mCallbackHandler.post(mSendEnabled);
discover peers

    public void run() {
        mP2pManager.discoverPeers(mChannel, mActionListener);
        mHandler.postDelayed(this, DISCOVER_INTERVAL_MS);
    }

else if (netInfo.getState() == NetworkInfo.State.CONNECTED) {
    if (mRtsp != null) {
        Log.i(TAG, "Ignoring extra CONNECTED event");
        return;
    }
    WifiP2pInfo p2pInfo = intent.getParcelableExtra(WifiP2pManager.EXTRA_WIFI_P2P_INFO);
    if (p2pInfo == null) {
        Log.i(TAG, "WIFI_P2P_INFO is not available");
        return;
    }
    if (p2pInfo.groupFormed) {
        mHandler.removeCallbacks(mDiscoverPeers);
        WifiP2pGroup group = intent.getParcelableExtra(WifiP2pManager.EXTRA_WIFI_P2P_GROUP);
        if (group == null) {
            Log.i(TAG, "WIFI_P2P_GROUP is not availble");
            return;
        }
        mP2pInterface = group.getInterface();
        mSourceRtspPort = 7236;
        if (p2pInfo.isGroupOwner) {
            Collection<WifiP2pDevice> devices = group.getClientList();
            if (devices != null) {
                if (devices.isEmpty())
                    Log.i(TAG, "Device list empty!");
                else {
                    for (WifiP2pDevice device : devices) {
                        if (sReflectionInited) {
                            // use reflection instead of:
                            // mSourceMacAddress = device.interfaceAddress;
                            try {
                                mSourceMacAddress = (String) sIfAddr.get(device);
                            } catch (Exception e) {
                                Log.e(TAG, "Failed to get interfaceAddress field"
                                        + " by reflection: " + e);
                            }
                        } else
                            Log.e(TAG, "Reflection not initialiazed,"
                                    + "can't get interfaceAddress content");
                        if (device.wfdInfo != null) {
                            mSourceRtspPort = device.wfdInfo.getControlPort();
                            Log.i(TAG, "mSourceRtspPort obtained is " + mSourceRtspPort);
                        }
                        else
                            Log.i(TAG, "Using default RTSP Port=" + mSourceRtspPort);
                    }
                }
            }
 }
        else {
            mSourceIp = p2pInfo.groupOwnerAddress.getHostAddress();
            if (group.getOwner().wfdInfo != null) {
                mSourceRtspPort = group.getOwner().wfdInfo.getControlPort();
                Log.i(TAG, "mSourceRtspPort obtained is " + mSourceRtspPort);
            }
            else
                Log.i(TAG, "Using default RTSP Port=" + mSourceRtspPort);
        }
        if (mSourceIp != null && mSourceRtspPort > 0 && mSourceRtspPort <= 65535) {
            mHandler.post(new ConnectRtsp(mSourceIp, mSourceRtspPort));
        }
    }
}
 }

public void run() {
        Log.i(TAG, "Connect RTSP " + sourceIp + "/" + sourceRtspPort);
        mConnectorTypeRequested = false;
        mDisplayManager.registerDisplayListener(mDisplayListener, null);
        try {
            Log.d(TAG,"media reset begin");
            mMediaPlayer.reset();
            Log.d(TAG,"media reset over");
            mMediaPlayer.setDataSource("intel_rtp://" + mP2pInterface + ":" + RTP_LISTEN_PORT);
            mMediaPlayer.prepare();
        } catch (Exception e) {
            Log.e(TAG, "Exception trying to play media", e);
        }
        mSourceIp = sourceIp;
        mRtsp = new WidiSinkRtsp();
        if (mRtsp.init(sourceIp + ":" + sourceRtspPort, mSinkListener) == 0)
            mRtsp.start();
    }
}