如何在安卓手机修改以太网（IPv4）属性？开发以太网数据接收应用求助

Hey there! Let's break down your two questions step by step, since you're migrating from a Windows tool to an Android app for your car device communication.

The steps vary slightly depending on whether you're using stock Android or a custom UI (like Xiaomi, Huawei, Samsung). Here's how to do it:

Stock Android #

• Open Settings, navigate to Network & Internet (or "Connections" on some devices).
• Select Ethernet — this option only appears if you have an active USB Ethernet adapter connected to your phone.
• Tap the connected Ethernet network name to open its details.
• Find the IP settings dropdown (default is "DHCP") and switch it to Static.
• Manually enter your desired IP address, Subnet mask, Gateway (if required), and DNS servers.
• Tap Save to apply the changes.

Custom Android UIs (Example: Xiaomi) #

• Open Settings → WLAN & Internet → Ethernet.
• Tap the current Ethernet connection, then select Static IP.
• Fill in the IP address, subnet mask, and other required details, then save.

To replicate your Windows tool's functionality on Android, you'll need to handle two core tasks: configuring the Ethernet network statically, and capturing data transmitted over the connection.

Part 1: Static IP Configuration (Code Implementation) #

First, add the necessary permissions to your AndroidManifest.xml:

<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<!-- Required for Android 10+ to access network details -->
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

Next, use the ConnectivityManager to target the Ethernet network and apply static IP settings:

import android.content.Context
import android.net.ConnectivityManager
import android.net.LinkAddress
import android.net.LinkProperties
import android.net.Network
import android.net.NetworkCapabilities
import android.net.NetworkRequest
import android.net.RouteInfo
import java.net.InetAddress

// Get the ConnectivityManager instance
val connectivityManager = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager

// Create a NetworkRequest to target Ethernet networks
val ethernetNetworkRequest = NetworkRequest.Builder()
    .addTransportType(NetworkCapabilities.TRANSPORT_ETHERNET)
    .build()

// Register a callback to get the active Ethernet Network object
connectivityManager.registerNetworkCallback(ethernetNetworkRequest, object : ConnectivityManager.NetworkCallback() {
    override fun onAvailable(network: Network) {
        super.onAvailable(network)
        // Configure static IP with your car device's required settings
        configureStaticEthernetIp(
            network = network,
            ipAddress = "192.168.1.100", // Replace with your target IP
            subnetMask = "255.255.255.0", // Replace with your subnet mask
            gateway = "192.168.1.1", // Optional, if needed
            dnsServer = "8.8.8.8" // Optional, if needed
        )
        // Unregister the callback once configuration is done
        connectivityManager.unregisterNetworkCallback(this)
    }
})

// Helper method to apply static IP settings
private fun configureStaticEthernetIp(
    network: Network,
    ipAddress: String,
    subnetMask: String,
    gateway: String?,
    dnsServer: String?
) {
    val linkProperties = connectivityManager.getLinkProperties(network) ?: return

    // Clear existing DHCP settings
    linkProperties.linkAddresses.clear()
    linkProperties.routes.clear()
    linkProperties.dnsServers.clear()

    // Add static IP address (convert subnet mask to prefix length)
    val prefixLength = subnetMaskToPrefixLength(subnetMask)
    val staticLinkAddress = LinkAddress(
        InetAddress.getByName(ipAddress),
        prefixLength
    )
    linkProperties.linkAddresses.add(staticLinkAddress)

    // Add gateway if provided
    gateway?.let {
        val gatewayAddress = InetAddress.getByName(it)
        linkProperties.routes.add(RouteInfo(gatewayAddress))
    }

    // Add DNS server if provided
    dnsServer?.let {
        linkProperties.dnsServers.add(InetAddress.getByName(it))
    }

    // Apply the new configuration
    connectivityManager.setLinkProperties(network, linkProperties)
}

// Helper to convert subnet mask (e.g., 255.255.255.0) to CIDR prefix length (e.g., 24)
private fun subnetMaskToPrefixLength(subnetMask: String): Int {
    return subnetMask.split(".")
        .map { it.toInt() }
        .sumOf { Integer.bitCount(it) }
}

Part 2: Capturing Ethernet Data #

You have a few options depending on whether you need basic traffic stats or raw packet data:

Option 1: Basic Traffic Statistics (Easy)

Use TrafficStats to get total sent/received bytes over Ethernet:

import android.net.TrafficStats

val ethernetReceivedBytes = TrafficStats.getRxBytes(TrafficStats.TAG_ETHERNET)
val ethernetSentBytes = TrafficStats.getTxBytes(TrafficStats.TAG_ETHERNET)

Option 2: Raw Packet Capture (Android 14+)

Android 14 introduced the PacketCapture API for direct packet capturing. Add this permission to your manifest:

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

Then implement the capture logic:

import android.net.PacketCapture
import android.net.PacketCaptureManager

val packetCaptureManager = getSystemService(Context.PACKET_CAPTURE_SERVICE) as PacketCaptureManager

// Build a capture request targeting your Ethernet network
val captureRequest = PacketCaptureRequest.Builder()
    .addNetwork(network) // Use the Ethernet Network object from earlier
    .addFilter("tcp port 8080") // Filter for your car device's port/protocol
    .build()

// Callback to handle captured packets
val packetCallback = object : PacketCapture.Callback() {
    override fun onPacketCaptured(packet: PacketCapture.Packet) {
        val rawData = packet.data
        // Parse rawData according to your car device's communication protocol
        // (e.g., decode custom binary formats or ASCII messages)
    }
}

// Start capturing packets
packetCaptureManager.startCapture(
    captureRequest,
    packetCallback,
    Handler(Looper.getMainLooper())
)

Option 3: VPN Service (Compatible with Older Android Versions)

If you need support for Android versions before 14, use a VPNService to intercept Ethernet traffic. First, register the service in your manifest:

<service
    android:name=".EthernetCaptureVpnService"
    android:permission="android.permission.BIND_VPN_SERVICE">
    <intent-filter>
        <action android:name="android.net.VpnService" />
    </intent-filter>
</service>

Then implement the VPN service:

import android.net.VpnService
import android.os.ParcelFileDescriptor
import java.io.FileInputStream
import java.io.FileOutputStream

class EthernetCaptureVpnService : VPNService() {
    private var vpnInterface: ParcelFileDescriptor? = null

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        val vpnBuilder = Builder()
            .addAddress("10.0.0.2", 32)
            .addRoute("0.0.0.0", 0)
            .setSession("Car Ethernet Capture")
            .addTransportType(NetworkCapabilities.TRANSPORT_ETHERNET) // Target only Ethernet traffic

        vpnInterface = vpnBuilder.establish() ?: return START_NOT_STICKY

        // Start a thread to process captured packets
        val inputStream = FileInputStream(vpnInterface?.fileDescriptor)
        val outputStream = FileOutputStream(vpnInterface?.fileDescriptor)
        Thread { processCapturedPackets(inputStream, outputStream) }.start()

        return START_STICKY
    }

    private fun processCapturedPackets(inputStream: FileInputStream, outputStream: FileOutputStream) {
        val buffer = ByteArray(1500) // Standard MTU size
        while (true) {
            val bytesRead = inputStream.read(buffer)
            if (bytesRead > 0) {
                // Process the raw packet data in 'buffer'
                // Forward the packet if needed (write to outputStream)
                outputStream.write(buffer, 0, bytesRead)
                outputStream.flush()
            }
        }
    }

    override fun onDestroy() {
        super.onDestroy()
        vpnInterface?.close()
    }
}

To use the VPN service, you need to request user authorization first:

private const val REQUEST_VPN_PERMISSION = 1001

// Trigger VPN permission request
val vpnIntent = VpnService.prepare(this)
if (vpnIntent != null) {
    startActivityForResult(vpnIntent, REQUEST_VPN_PERMISSION)
} else {
    // Permission already granted, start the service
    startService(Intent(this, EthernetCaptureVpnService::class.java))
}

内容的提问来源于stack exchange，提问作者jjulianf