如何在设备处于睡眠状态时保持 ChromeCast 会话处于活动状态？

Question

我有一个可以将本地媒体内容流式传输到 Chromecast 接收器的应用。这主要是可行的，除了当设备处于睡眠状态并且没有使用外部电源时，会话将在大约 5 分钟后终止/断开连接（从屏幕变黑时开始测量）。

我已经在这里看过这个问题了：

How do I keep a ChromeCast route alive when my app is in the background on battery power?

...并实施了两个建议的答案。

具体来说，在我的应用清单中，我有：

<uses-permission android:name="android.permission.WAKE_LOCK" />

然后在我用来将媒体内容流式传输到 Chromecast 接收器的嵌入式 HTTP 服务器中，我正在做：

PowerManager powerManager = (PowerManager)Environment.getApplicationContext().getSystemService(Context.POWER_SERVICE);
wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "cast-server-cpu");
wakeLock.acquire();

WifiManager wifiManager = (WifiManager)Environment.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
wifiLock = wifiManager.createWifiLock(WifiManager.WIFI_MODE_FULL_HIGH_PERF, "cast-server-net");
wifiLock.acquire();

该代码在服务器线程启动时执行（在选择 Chromecast 路由时发生），并且在服务器停止之前不会释放锁。这发生在我的MediaRouter.Callback 实现中，它（结合上述问题中接受的答案）如下所示：

this.mediaRouterCallback = new MediaRouter.Callback() {
    private MediaRouter.RouteInfo autoconnectRoute = null;

    @Override
    public void onRouteSelected(MediaRouter mediaRouter, MediaRouter.RouteInfo routeInfo) {
        if (autoconnectRoute == null) {
            if (isPlaying()) {
                stop();
                playButton.setImageResource(R.drawable.icon_play);
            }

            castDevice = CastDevice.getFromBundle(routeInfo.getExtras());
            if (castServer != null) {
                castServer.stop();
            }

            //start the Chromecast file server
            castServer = new CastHttpFileServer();
            new Thread(castServer).start();
        }

        initCastClientListener();
        initRemoteMediaPlayer();
        launchReceiver();
    }

    @Override
    public void onRouteUnselected(MediaRouter mediaRouter, MediaRouter.RouteInfo routeInfo) {
        if (! doesRouterContainRoute(mediaRouter, routeInfo)) {
            //XXX:  do not disconnect in this case (the unselect was not initiated by a user action); see https://stackoverflow.com/questions/18967879/how-do-i-keep-a-chromecast-route-alive-when-my-app-is-in-the-background-on-batte
            autoconnectRoute = routeInfo;
            return;
        }

        //user disconnected, teardown and stop playback
        if (isPlaying()) {
            stop();
            playButton.setImageResource(R.drawable.icon_play);
        }
        if (castServer != null) {
            castServer.stop();
            castServer = null;
        }

        teardown();
        castDevice = null;
    }

    @Override
    public void onRouteAdded(MediaRouter router, MediaRouter.RouteInfo route) {
        super.onRouteAdded(router, route);
        if (autoconnectRoute != null && route.getId().equals(autoconnectRoute.getId())) {
            this.onRouteSelected(router, route);
        }
    }

    private boolean doesRouterContainRoute(MediaRouter router, MediaRouter.RouteInfo route) {
        if (router == null || route == null) {
            return false;
        }

        for (MediaRouter.RouteInfo info : router.getRoutes()) {
            if (info.getId().equals(route.getId())) {
                return true;
            }
        }

        return false;
    }
};

为了在设备处于睡眠状态且未连接到外部电源时保持 Chromecast 会话处于活动状态，还需要做些什么？

另外，考虑到这个问题只有在设备没有连接到 USB 时才会重现，在这种情况下，什么是调试的有效方法？

编辑

以下是会话终止时报告的堆栈跟踪（来自嵌入式 HTTP 服务器）：

java.net.SocketException: Software caused connection abort
 at java.net.SocketOutputStream.socketWrite0(Native Method)
 at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:112)
 at java.net.SocketOutputStream.write(SocketOutputStream.java:157)
 at com.myapp.CastHttpFileServer.writeResponse(CastHttpFileServer.java:124)
 at com.myapp.CastHttpFileServer.run(CastHttpFileServer.java:180)

我还注意到，我可以在我的 RemoteMediaPlayer.OnStatusUpdatedListener 实现中捕获此事件，例如：

if (lastStatus == MediaStatus.PLAYER_STATE_PLAYING && mediaStatus.getPlayerState() == MediaStatus.PLAYER_STATE_BUFFERING) {
    //buffer underrun/receiver went away because the wifi died; how do we fix this?
}

Answer 1

CommonsWare 有权在他的评论中使用它。我在运行 Android 7.1.2 的设备上进行了测试，Doze mode was causing the network to drop 在闲置了大约 5 分钟后，无论我的应用持有什么唤醒锁。

解决方法是在清单中添加以下权限：

<uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />

然后更新我的 onRouteSelected() 回调实现，以请求在选择 ChromeCast 路由时禁用打盹模式：

if (Build.VERSION.SDK_INT >= 23) {
    String packageName = context.getPackageName();
    PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
    if (! pm.isIgnoringBatteryOptimizations(packageName)) {
        //reguest that Doze mode be disabled
        Intent intent = new Intent();
        intent.setAction(
            Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS);
        intent.setData(Uri.parse("package:" + packageName));

        context.startActivity(intent);
    }

}

只要用户在出现提示时选择“是”，应用的唤醒锁就会受到尊重，即使设备未充电，ChromeCast 会话也会保持活动状态。