我必须在没有互联网连接的情况下将 UDP 数据包发送到 WiFi 模块(提供自己的 AP)，但是当我将手机连接到 AP 时，Android 会在移动数据接口(interface)上重定向我的数据包，因为它有互联网连接。

我已经使用下面的代码来完成我的工作，但它似乎无法在 Android M 上运行。

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private void setWifiInterfaceAsDefault() {
    ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

    NetworkRequest.Builder builder = new NetworkRequest.Builder();
    NetworkRequest networkRequest= builder.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED)
            .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
            .build();

    connectivityManager.requestNetwork(networkRequest, new ConnectivityManager.NetworkCallback());
}

我也添加了

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

在我的 AndroidManifest.xml 上，我确保 Settings.System.canWrite(this) 返回 true 但仍然没有。

提前致谢。

最佳答案

Stanislav的答案是正确的但不完整，因为只适用于 Lollipop。

我已经为 Lollipop 和 Marshmallow 编写了一个完整的解决方案，以便您在连接到您选择的特定网络时通过 WiFi 路由所有网络请求。

Kotlin

在您的 Activity 中，

@RequiresApi(Build.VERSION_CODES.LOLLIPOP)
class RoutingActivity : Activity() {

    private var mConnectivityManager: ConnectivityManager? = null
    private var mNetworkCallback: ConnectivityManager.NetworkCallback? = null
    //...

    override fun onCreate(savedInstanceState: Bundle?) {
        //...
        routeNetworkRequestsThroughWifi("Access-Point-SSID-You-Want-To-Route-Your-Requests")
    }

通过 WiFi 路由来自应用程序的 future 网络请求(即使给定的 WiFi 网络没有互联网并且移动数据有互联网连接)

/**
 * This method sets a network callback that is listening for network changes and once is
 * connected to the desired WiFi network with the given SSID it will bind to that network.
 *
 * Note: requires android.permission.INTERNET and android.permission.CHANGE_NETWORK_STATE in
 * the manifest.
 *
 * @param ssid The name of the WiFi network you want to route your requests
 */
private fun routeNetworkRequestsThroughWifi(ssid: String) {
    mConnectivityManager = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

    // ensure prior network callback is invalidated
    unregisterNetworkCallback(mNetworkCallback)

    // new NetworkRequest with WiFi transport type
    val request = NetworkRequest.Builder()
            .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
            .build()

    // network callback to listen for network changes
    mNetworkCallback = object : ConnectivityManager.NetworkCallback() {

        // on new network ready to use
        override fun onAvailable(network: Network) {

            if (getNetworkSsid(this@RoutingActivity).equals(ssid, ignoreCase = false)) {
                releaseNetworkRoute()
                createNetworkRoute(network)

            } else {
                releaseNetworkRoute()
            }
        }
    }
    mConnectivityManager?.requestNetwork(request, mNetworkCallback)
}

注销网络回调

private fun unregisterNetworkCallback(networkCallback: ConnectivityManager.NetworkCallback?) {
    if (networkCallback != null) {
        try {
            mConnectivityManager?.unregisterNetworkCallback(networkCallback)

        } catch (ignore: Exception) {
        } finally {
            mNetworkCallback = null
        }
    }
}

创建网络路由

private fun createNetworkRoute(network: Network): Boolean? {
    var processBoundToNetwork: Boolean? = false
    when {
    // 23 = Marshmallow
        Build.VERSION.SDK_INT >= 23 -> {
            processBoundToNetwork = mConnectivityManager?.bindProcessToNetwork(network)
        }

    // 21..22 = Lollipop
        Build.VERSION.SDK_INT in 21..22 -> {
            processBoundToNetwork = ConnectivityManager.setProcessDefaultNetwork(network)
        }
    }
    return processBoundToNetwork
}

释放网络路由

private fun releaseNetworkRoute(): Boolean? {
    var processBoundToNetwork: Boolean? = false
    when {
    // 23 = Marshmallow
        Build.VERSION.SDK_INT >= 23 -> {
            processBoundToNetwork = mConnectivityManager?.bindProcessToNetwork(null)
        }

    // 21..22 = Lollipop
        Build.VERSION.SDK_INT in 21..22 -> {
            processBoundToNetwork = ConnectivityManager.setProcessDefaultNetwork(null)
        }
    }
    return processBoundToNetwork
}

助手

private fun getNetworkSsid(context: Context?): String {
    // WiFiManager must use application context (not activity context) otherwise a memory leak can occur
    val mWifiManager = context?.applicationContext?.getSystemService(Context.WIFI_SERVICE) as WifiManager
    val wifiInfo: WifiInfo? = mWifiManager.connectionInfo
    if (wifiInfo?.supplicantState == SupplicantState.COMPLETED) {
        return wifiInfo.ssid.removeSurrounding("\"")
    }
    return ""
}

关于android - 即使在 Android M 上打开移动数据(有连接)，也可以通过 WiFi(无连接)发送请求，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/36653126/