如何在 Android 上同时连接到 MOBILE 时检查 Wi-Fi 连接 (SSID)

Question

当我想验证 Android 设备是否连接到特定的 Wi-Fi（由 SSID 识别）并且同时有一个活动的移动数据网络时，我遇到了一些奇怪的问题。 我的问题也可能与 Android 9 (SDK 28) 有关，因为我没有收到使用以前 Android 版本的用户的任何投诉。

这就是我所拥有的：

这是我的主要方法，它应该告诉我设备当前是否连接到它的目标 Wi-Fi：

public boolean isConnectedToTrackerHotSpot() {

        if (isConnectedToWiFi()) {
            final String ssid = getConnectedSSID();
            if (ssid.startsWith(TRACKER_WIFI_PREFIX)) {
                Log.i(TAG, "isConnectedToTrackerHotSpot() --> YEAH, connected to Tracker: " + ssid);
                return true;
            } else {
                Log.d(TAG, "isConnectedToTrackerHotSpot() --> NOT connected to Tracker, but: " + ssid);
                return false;
            }
        }

        Log.d(TAG, "isConnectedToTrackerHotSpot() --> NOT connected to any Wi-Fi!");
        return false;
    }

这里是辅助方法：

检查我们当前是否有 Wi-Fi 连接：

    public boolean isConnectedToWiFi() {
        if (!isWifiEnabled()) {
            Log.w(TAG, "isConnectedToWiFi(): Wi-Fi is DISABLED");
            return false;
        }

        final WifiInfo wifiInfo = getConnectionInfo();
        if (wifiInfo == null) {
            Log.w(TAG, "isConnectedToWiFi() --> wifiInfo is null!");
            return false;
        }

        final int networkId = wifiInfo.getNetworkId();
        if (networkId == -1) {
            Log.d(TAG, "isConnectedToWiFi() --> NOT connected to any Wi-Fi (networkId == -1)");
            return false;
        }

        Log.d(TAG, "isConnectedToWiFi() --> connected to Wi-Fi with networkId: " + networkId);
        return true;
    }

检查我们是否连接到任何网络：

    public boolean isConnected() {
        /*
           Returns details about the currently active default data network.
           When connected, this network is the default route for outgoing connections.
        */
        final NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();

        if (networkInfo == null) {
            Log.d(TAG, "isConnected() --> getActiveNetworkInfo() == NULL (no network connection)");
            return false;
        } else {
            Log.d(TAG, "isConnected() --> networkInfo.getTypeName() = " + networkInfo.getTypeName());
        }

        if (networkInfo.isConnectedOrConnecting()) {
            return true;
        }

        Log.w(TAG, "isConnected() --> !networkInfo.isConnectedOrConnecting()");
        return false;
    }

---

现在在我的广播接收器中，我想在连接到预期的设备后立即处理此案：

    private BroadcastReceiver connectivityBroadcastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            if (!Objects.equals(intent.getAction(), CONNECTIVITY_CHANGE)) {
                Log.d(TAG, "connectivityBroadcastReceiver.onReceive() --> not the intent we are interested in");
                return;
            }

            if (wiFiConnectionManager.isConnectedToTrackerHotSpot()) {
                Log.i(TAG, "connectivityBroadcastReceiver.onReceive() --> CONNECTED to Tracker --> fragment.updateUiConnectedToTracker()");
                fragment.updateUiConnectedToTracker();
                openTrackerSocketConnection();
            } else {
                // Make sure we only show 1 AlertDialog per CONNECT attempt (= button press)
                if (userAwaitsResponse) {
                    Log.d(TAG, "connectivityBroadcastReceiver.onReceive() --> fragment.updateUiFailedToConnect()");
                    fragment.updateUiFailedToConnect();
                    userAwaitsResponse = false;
                } else {
                    Log.d(TAG, "connectivityBroadcastReceiver.onReceive() --> SUPPRESSING UI update (since already done)");
                }
            }

        }
    };

但是，当我在装有 Android 9 的 Pixel 3 上进行测试并启用移动网络时，我收到了以下日志：

D/ConnectDeviceFragment: connectButton --> onClick()
I/WiFiConnectionManager: isWiFiEnabled(): true
I/WiFiConnectionManager: isWiFiEnabled(): true
D/ConnectDeviceFragmentPresenter: connectToTrackersWiFi() --> use existing WifiConfiguration SSID: "TRACKER-pat08" (networkId: 141)
D/ConnectDeviceFragmentPresenter: connectToTrackersWiFi() --> going to disconnect from current network...
I/WiFiConnectionManager: disconnect() success: true
D/ConnectDeviceFragmentPresenter: connectToTrackersWiFi() --> in order to enableNetwork for networkId: 141
I/WiFiConnectionManager: enableNetwork() --> netId: 141 | success: true
D/WiFiConnectionManager: isConnectedToWiFi() --> NOT connected to any Wi-Fi (networkId == -1)
D/WiFiConnectionManager: isConnectedToTrackerHotSpot() --> NOT connected to any Wi-Fi!
D/WiFiConnectionManager: isConnected() --> networkInfo.getTypeName() = MOBILE
I/MainFragmentPresenter: connectivityBroadcastReceiver.onReceive() --> Assuming we have internet...
D/WiFiConnectionManager: isConnectedToWiFi() --> NOT connected to any Wi-Fi (networkId == -1)
D/WiFiConnectionManager: isConnectedToTrackerHotSpot() --> NOT connected to any Wi-Fi!
D/ConnectDeviceFragmentPresenter: connectivityBroadcastReceiver.onReceive() --> fragment.updateUiFailedToConnect()
D/ConnectDeviceFragment: updateUiFailedToConnect() --> creating but not showing yet (status might still change)
D/WiFiConnectionManager: isConnectedToWiFi() --> NOT connected to any Wi-Fi (networkId == -1)
D/WiFiConnectionManager: isConnectedToTrackerHotSpot() --> NOT connected to any Wi-Fi!
D/WiFiConnectionManager: isConnected() --> networkInfo.getTypeName() = MOBILE
I/MainFragmentPresenter: connectivityBroadcastReceiver.onReceive() --> Assuming we have internet...
D/WiFiConnectionManager: isConnectedToWiFi() --> NOT connected to any Wi-Fi (networkId == -1)
D/WiFiConnectionManager: isConnectedToTrackerHotSpot() --> NOT connected to any Wi-Fi!
D/ConnectDeviceFragmentPresenter: connectivityBroadcastReceiver.onReceive() --> SUPPRESSING UI update (since already done)
I/ConnectDeviceFragment: updateUiFailedToConnect() --> run() delayed by: 5000

我做错了什么？我的代码在任何没有启用移动网络的设备上都能正常工作...

---

编辑：

我可能已经找到了根本原因：

    boolean openSocketConnection() {
        if (isSocketReady()) {
            Log.i(TAG, "openSocketConnection() --> isSocketReady() --> return true");
            return true;
        }

        //FIXME: Timeout if Wi-Fi AND mobile network are active --> force open socket on Wi-Fi
        try {
            socket = new Socket(InetAddress.getByName(SERVER_IP), SERVER_PORT);
            outputStream = new DataOutputStream(socket.getOutputStream());
            inputStream = new DataInputStream(socket.getInputStream());
            Log.i(TAG, "openSocketConnection() --> connection opened and input/output streams created!");
            return true;
        } catch (IOException e) {
            Log.e(TAG, "openSocketConnection() --> IOException!", e);
            return false;
        }
    }

所以新问题是：如何在 Wi-Fi 连接上打开套接字（尽管活动网络将是移动网络）。因为我的嵌入式设备的 Wi-Fi 连接永远不会有互联网，但我需要打开一个套接字进行通信......

非常感谢任何帮助！

Answer 1

我找到了一个我可以接受的解决方案。最后的根本问题是，如果您没有明确说明，Android 确实会在默认网络上打开一个套接字。而且默认网络显然总是有互联网的（我学得很辛苦）。

所以这是我的新解决方案的核心部分：

    private Socket getTrackerWiFiSocket() throws SocketException {
        final Socket socket;
        try {
            Log.i(TAG, "getTrackerWiFiSocket() --> TRY getSocketFactory().createSocket()");
            socket = getSocketFactory().createSocket(TRACKER_API_ADDRESS, TRACKER_API_PORT);
        } catch (IOException e) {
            Log.e(TAG, "getTrackerWiFiSocket() --> getSocketFactory().createSocket() produced IOException: ", e);
            throw new SocketException(TAG + ".getTrackerWiFiSocket() --> create socket failed!");
        }

        Log.d(TAG, "getTrackerWiFiSocket() --> socket: " + socket);
        return socket;
    }

    private SocketFactory getSocketFactory() throws SocketException {
        if (SDK_INT < 21) {
            Log.d(TAG, "getSocketFactory() --> SDK_INT is < 21 --> return SocketFactory.getDefault()");
            return SocketFactory.getDefault();
        }
        /*
            On API 21 and later, a socket that is NOT created with the Wi-Fi network's SocketFactory may try
            to connect via another network --> we have to make sure that always the Wi-Fi network is chosen
        */
        Network wifiNetwork = getWiFiNetwork();
        // FIXME: Find a nicer approach
        for (int i = 0; i < 10; i++) {
            Log.d(TAG, "getSocketFactory() --> getWiFiNetwork() loop: " + i);
            if (wifiNetwork == null) {

                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    Log.w(TAG, "getSocketFactory() --> getWiFiNetwork() --> error during Thread.sleep");
                }

                wifiNetwork = getWiFiNetwork();

            } else {
                Log.i(TAG, "getSocketFactory() --> found Wi-Fi network socket!");
                return wifiNetwork.getSocketFactory();
            }
        }

        Log.e(TAG, "getSocketFactory() -> Could not find a suitable SocketFactory --> return default");
        throw new SocketException(TAG + ".getSocketFactory() --> could not get a SocketFactory!");
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private Network getWiFiNetwork() {
        for (Network network : connectivityManager.getAllNetworks()) {
            NetworkInfo info = connectivityManager.getNetworkInfo(network);

            // FIXME: Use another (non-deprecated) way to determine whether type is Wi-Fi
            if (info != null && info.getType() == TYPE_WIFI) {
                Log.d(TAG, "getWiFiNetwork() --> found network with info: " + info);
                return network;
            }
        }

        Log.w(TAG, "getWiFiNetwork() --> Could not find the Wi-Fi network!");
        return null;
    }

如果有人有更好的方法来确保，有一个 Network 对象可用于创建一个 Socket，而不是我使用 Thread.sleep() 的丑陋循环，我正在听...