Android 获取dns的值

在做盒子开发过程中需要获取有线网络的dns，查阅好多资料，终于搞定，现在把代码分享一下

 /**
     * 获取dns
     *
     * @param context
     * @return
     */
    public String getDnsFromIp(Context context) {
        /**
         * 获取dns
         */
        String[] dnsServers = getDnsFromCmd();
        if (dnsServers == null || dnsServers.length == 0) {
            dnsServers = getDnsFromConnectionManager(context);
        }
        /**
         * 组装
         */
        StringBuffer sb = new StringBuffer();
        if (dnsServers != null) {
            for (int i = 0; i < dnsServers.length; i++) {
                sb.append(dnsServers[i]);
            }
        }
        //
        return sb.toString();
    }


    //通过 getprop 命令获取
    private String[] getDnsFromCmd() {
        LinkedList<String> dnsServers = new LinkedList<>();
        try {
            Process process = Runtime.getRuntime().exec("getprop");
            InputStream inputStream = process.getInputStream();
            LineNumberReader lnr = new LineNumberReader(new InputStreamReader(inputStream));
            String line = null;
            while ((line = lnr.readLine()) != null) {
                int split = line.indexOf("]: [");
                if (split == -1) continue;
                String property = line.substring(1, split);
                String value = line.substring(split + 4, line.length() - 1);
                if (property.endsWith(".dns")
                        || property.endsWith(".dns1")
                        || property.endsWith(".dns2")
                        || property.endsWith(".dns3")
                        || property.endsWith(".dns4")) {
                    InetAddress ip = InetAddress.getByName(value);
                    if (ip == null) continue;
                    value = ip.getHostAddress();
                    if (value == null) continue;
                    if (value.length() == 0) continue;
                    dnsServers.add(value);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return dnsServers.isEmpty() ? new String[0] : dnsServers.toArray(new String[dnsServers.size()]);
    }


    private String[] getDnsFromConnectionManager(Context context) {
        LinkedList<String> dnsServers = new LinkedList<>();
        if (Build.VERSION.SDK_INT >= 21 && context != null) {
            ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(context.CONNECTIVITY_SERVICE);
            if (connectivityManager != null) {
                NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
                if (activeNetworkInfo != null) {
                    for (Network network : connectivityManager.getAllNetworks()) {
                        NetworkInfo networkInfo = connectivityManager.getNetworkInfo(network);
                        if (networkInfo != null && networkInfo.getType() == activeNetworkInfo.getType()) {
                            LinkProperties lp = connectivityManager.getLinkProperties(network);
                            for (InetAddress addr : lp.getDnsServers()) {
                                dnsServers.add(addr.getHostAddress());
                            }
                        }
                    }
                }
            }
        }
        return dnsServers.isEmpty() ? new String[0] : dnsServers.toArray(new String[dnsServers.size()]);
    }

主要是通过getprop命令来获取信息，然后拼接成最终的dns.