Чтобы настроить Android на использование Cloudflare DNS, вы можете воспользоваться несколькими способами. Вот несколько примеров с фрагментами кода:

Метод 1: использование настроек Android

// Open Android Settings
Intent intent = new Intent(android.provider.Settings.ACTION_SETTINGS);
startActivity(intent);
// Navigate to Wi-Fi settings
Intent intent = new Intent(android.provider.Settings.ACTION_WIFI_SETTINGS);
startActivity(intent);
// Select the Wi-Fi network you are connected to
// Tap on the network name and go to Advanced settings
// Change the IP settings to Static
// Set the DNS 1 and DNS 2 fields to Cloudflare DNS addresses:
// DNS 1: 1.1.1.1
// DNS 2: 1.0.0.1

Метод 2: использование ConnectivityManager

// Get the ConnectivityManager instance
ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
// Create a NetworkRequest builder
NetworkRequest.Builder builder = new NetworkRequest.Builder();
// Set the DNS servers to Cloudflare DNS addresses
InetAddress[] dnsServers = {
    InetAddress.parseNumericAddress("1.1.1.1"),
    InetAddress.parseNumericAddress("1.0.0.1")
};
builder.setDnsServers(Arrays.asList(dnsServers));
// Build the NetworkRequest
NetworkRequest networkRequest = builder.build();
// Set the NetworkRequest for the default network
connectivityManager.registerDefaultNetworkCallback(new ConnectivityManager.NetworkCallback() {
    @Override
    public void onAvailable(Network network) {
        connectivityManager.bindProcessToNetwork(network);
    }
});

Метод 3. Использование службы VPN

// Create a new class extending VpnService
public class CloudflareVpnService extends VpnService {
    @Override
    public void onCreate() {
        super.onCreate();
        // ...
    }
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // ...
        return START_STICKY;
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        // ...
    }
    @Override
    public synchronized void onRevoke() {
        super.onRevoke();
        // ...
    }
    @Override
    public synchronized ParcelFileDescriptor establishVpnTunnel() {
        // Set up the VPN tunnel and configure DNS to Cloudflare DNS addresses
        // ...
        return null;
    }
}
// Start the VPN service
Intent intent = VpnService.prepare(getApplicationContext());
if (intent != null) {
    startActivityForResult(intent, VPN_REQUEST_CODE);
} else {
    startVpnService();
}