Android之获取DNS，优先返回本地网络DNS（插网线），其次选择Wifi网络的DNS

code 参考：https://www.cnblogs.com/alex-zhao/p/5254624.html

/**
     * 获取DNS，优先返回本地网络DNS（插网线），其次选择Wifi网络的DNS
     * */
    public static String getLocalDNS(Context context) {
        String TAG = "WiFiUtil_getLocalDNS";
        Process cmdProcess = null;
        BufferedReader reader = null;
        String dnsIP = "";
        try {
            cmdProcess = Runtime.getRuntime().exec("getprop net.dns1");
            reader = new BufferedReader(new InputStreamReader(cmdProcess.getInputStream()));
            dnsIP = reader.readLine();
        } catch (Exception ex) {
            slog.e(TAG, "获取Local网络DNS异常", ex);
            return null;
        } finally {
            try {
                reader.close();
            } catch (IOException ex) {
                slog.e(TAG, "获取Local网络DNS，关闭BufferedReader异常", ex);
            }
            cmdProcess.destroy();
        }
        if (Func.IsNullOrEmpty(dnsIP)) {
            try {
                WifiManager wifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
                if (wifiManager != null) {
                    // 获取WIFI的DHCP数据
                    DhcpInfo dhcpInfo = wifiManager.getDhcpInfo();
                    if (dhcpInfo != null) {
                        String dns1 = intToIp(dhcpInfo.dns1);
                        String dns2 = intToIp(dhcpInfo.dns2);
                        String dnsDef = "0.0.0.0";
                        if (dnsDef.equals(dns1)) {
                            dns1 = "";
                        }
                        if (dnsDef.equals(dns2)) {
                            dns2 = "";
                        }
                        if (!Func.IsNullOrEmpty(dns1) && !Func.IsNullOrEmpty(dns2)) {
                            dnsIP = dns1 + ";" + dns2;
                        } else {
                            dnsIP = dns1 + dns2;
                        }
                    }
                }
            } catch (Exception ex) {
                slog.e(TAG, "获取Wifi网络DNS异常", ex);
            }
        }
        return dnsIP;
    }