使用NTP服务器同步Android设备时间

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一、概述

最近在搞机器人项目,Pad在断电后时间会被恢复到出厂时间,开启了从网络中获取时间,有时有效,有时无效。所以需要利用NTP服务器来同步Pad的时间。在Android中已经存在一个SntpClient用于获取NTP服务器时间的类,只不过是hide类,直接拷出来为我所用。

二、代码实现

private final int NTP_TIME_OUT_MILLISECOND = 30000;
    private final String LOG_TAG = TimeCalibrateHelper.class.getSimpleName();

    private boolean isStopCalibrate = false;
    /**
     * ntp服务器地址集
     */
    private String[] ntpServerHost = new String[]{
            "dns1.synet.edu.cn",
            "news.neu.edu.cn",
            "dns.sjtu.edu.cn",
            "dns2.synet.edu.cn",
            "ntp.glnet.edu.cn",
            "ntp-sz.chl.la",
            "ntp.gwadar.cn",
            "cn.pool.ntp.org"
    };

    /**
     * 开始校准时间
     */
    public void startCalibrateTime() {
        new Thread() {
            @Override
            public void run() {
                while (!isStopCalibrate) {
                    for (int i = 0; i < ntpServerHost.length; i++) {
                        long time = getTimeFromNtpServer(ntpServerHost[i]);
                        if (time != -1) {
                            int tryCount = 3;
                            while (tryCount > 0) {
                                tryCount--;
                                boolean isSetTimeSuccessful = setCurrentTimeMillis(time);
                                if (isSetTimeSuccessful) {
                                    tryCount = 0;
                                    isStopCalibrate = true;
                                    Log.i(LOG_TAG, "set time successful");
                                } else {
                                    Log.i(LOG_TAG, "set time failure");
                                }
                            }
                            break;
                        }
                    }
                }
            }
        }.start();
    }

    /**
     * 停止校准时间
     */
    public void stopCalibrateTime() {
        isStopCalibrate = true;
    }

    /**
     * 从ntp服务器中获取时间
     *
     * @param ntpHost ntp服务器域名地址
     * @return 如果失败返回-1,否则返回当前的毫秒数
     */
    private long getTimeFromNtpServer(String ntpHost) {
        Log.i(LOG_TAG, "get time from " + ntpHost);
        SntpClient client = new SntpClient();
        boolean isSuccessful = client.requestTime(ntpHost, NTP_TIME_OUT_MILLISECOND);
        if (isSuccessful) {
            return client.getNtpTime();
        }
        return -1;
    }


    /**
     * 设置当前的系统时间
     *
     * @param time
     * @return true表示设置成功, false表示设置失败
     */
    public boolean setCurrentTimeMillis(long time) {
        try {
            if (ShellUtils.checkRootPermission()) {
                TimeZone.setDefault(TimeZone.getTimeZone("GMT+8"));
                Date current = new Date(time);
                SimpleDateFormat df = new SimpleDateFormat("yyyyMMdd.HHmmss");
                String datetime = df.format(current);
                Process process = Runtime.getRuntime().exec("su");
                DataOutputStream os = new DataOutputStream(process.getOutputStream());
                //os.writeBytes("setprop persist.sys.timezone GMT\n");
                os.writeBytes("/system/bin/date -s " + datetime + "\n");
                os.writeBytes("clock -w\n");
                os.writeBytes("exit\n");
                os.flush();
                return true;
            } else {
                return false;
            }
        } catch (Exception e) {
            return false;
        }
    }

    public static class SntpClient {
        private static final String TAG = "SntpClient";

        private static final int REFERENCE_TIME_OFFSET = 16;
        private static final int ORIGINATE_TIME_OFFSET = 24;
        private static final int RECEIVE_TIME_OFFSET = 32;
        private static final int TRANSMIT_TIME_OFFSET = 40;
        private static final int NTP_PACKET_SIZE = 48;

        private static final int NTP_PORT = 123;
        private static final int NTP_MODE_CLIENT = 3;
        private static final int NTP_VERSION = 3;

        // Number of seconds between Jan 1, 1900 and Jan 1, 1970
        // 70 years plus 17 leap days
        private static final long OFFSET_1900_TO_1970 = ((365L * 70L) + 17L) * 24L * 60L * 60L;

        // system time computed from NTP server response
        private long mNtpTime;

        // value of SystemClock.elapsedRealtime() corresponding to mNtpTime
        private long mNtpTimeReference;

        // round trip time in milliseconds
        private long mRoundTripTime;

        /**
         * Sends an SNTP request to the given host and processes the response.
         *
         * @param host    host name of the server.
         * @param timeout network timeout in milliseconds.
         * @return true if the transaction was successful.
         */
        public boolean requestTime(String host, int timeout) {
            DatagramSocket socket = null;
            try {
                socket = new DatagramSocket();
                socket.setSoTimeout(timeout);
                InetAddress address = InetAddress.getByName(host);
                byte[] buffer = new byte[NTP_PACKET_SIZE];
                DatagramPacket request = new DatagramPacket(buffer, buffer.length, address, NTP_PORT);

                // set mode = 3 (client) and version = 3
                // mode is in low 3 bits of first byte
                // version is in bits 3-5 of first byte
                buffer[0] = NTP_MODE_CLIENT | (NTP_VERSION << 3);

                // get current time and write it to the request packet
                long requestTime = System.currentTimeMillis();
                long requestTicks = SystemClock.elapsedRealtime();
                writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET, requestTime);

                socket.send(request);

                // read the response
                DatagramPacket response = new DatagramPacket(buffer, buffer.length);
                socket.receive(response);
                long responseTicks = SystemClock.elapsedRealtime();
                long responseTime = requestTime + (responseTicks - requestTicks);

                // extract the results
                long originateTime = readTimeStamp(buffer, ORIGINATE_TIME_OFFSET);
                long receiveTime = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);
                long transmitTime = readTimeStamp(buffer, TRANSMIT_TIME_OFFSET);
                long roundTripTime = responseTicks - requestTicks - (transmitTime - receiveTime);
                // receiveTime = originateTime + transit + skew
                // responseTime = transmitTime + transit - skew
                // clockOffset = ((receiveTime - originateTime) + (transmitTime - responseTime))/2
                //             = ((originateTime + transit + skew - originateTime) +
                //                (transmitTime - (transmitTime + transit - skew)))/2
                //             = ((transit + skew) + (transmitTime - transmitTime - transit + skew))/2
                //             = (transit + skew - transit + skew)/2
                //             = (2 * skew)/2 = skew
                long clockOffset = ((receiveTime - originateTime) + (transmitTime - responseTime)) / 2;
                // if (false) Log.d(TAG, "round trip: " + roundTripTime + " ms");
                // if (false) Log.d(TAG, "clock offset: " + clockOffset + " ms");

                // save our results - use the times on this side of the network latency
                // (response rather than request time)
                mNtpTime = responseTime + clockOffset;
                mNtpTimeReference = responseTicks;
                mRoundTripTime = roundTripTime;
            } catch (Exception e) {
                if (false) Log.d(TAG, "request time failed: " + e);
                return false;
            } finally {
                if (socket != null) {
                    socket.close();
                }
            }

            return true;
        }

        /**
         * Returns the time computed from the NTP transaction.
         *
         * @return time value computed from NTP server response.
         */
        public long getNtpTime() {
            return mNtpTime;
        }

        /**
         * Returns the reference clock value (value of SystemClock.elapsedRealtime())
         * corresponding to the NTP time.
         *
         * @return reference clock corresponding to the NTP time.
         */
        public long getNtpTimeReference() {
            return mNtpTimeReference;
        }

        /**
         * Returns the round trip time of the NTP transaction
         *
         * @return round trip time in milliseconds.
         */
        public long getRoundTripTime() {
            return mRoundTripTime;
        }

        /**
         * Reads an unsigned 32 bit big endian number from the given offset in the buffer.
         */
        private long read32(byte[] buffer, int offset) {
            byte b0 = buffer[offset];
            byte b1 = buffer[offset + 1];
            byte b2 = buffer[offset + 2];
            byte b3 = buffer[offset + 3];

            // convert signed bytes to unsigned values
            int i0 = ((b0 & 0x80) == 0x80 ? (b0 & 0x7F) + 0x80 : b0);
            int i1 = ((b1 & 0x80) == 0x80 ? (b1 & 0x7F) + 0x80 : b1);
            int i2 = ((b2 & 0x80) == 0x80 ? (b2 & 0x7F) + 0x80 : b2);
            int i3 = ((b3 & 0x80) == 0x80 ? (b3 & 0x7F) + 0x80 : b3);

            return ((long) i0 << 24) + ((long) i1 << 16) + ((long) i2 << 8) + (long) i3;
        }

        /**
         * Reads the NTP time stamp at the given offset in the buffer and returns
         * it as a system time (milliseconds since January 1, 1970).
         */
        private long readTimeStamp(byte[] buffer, int offset) {
            long seconds = read32(buffer, offset);
            long fraction = read32(buffer, offset + 4);
            return ((seconds - OFFSET_1900_TO_1970) * 1000) + ((fraction * 1000L) / 0x100000000L);
        }

        /**
         * Writes system time (milliseconds since January 1, 1970) as an NTP time stamp
         * at the given offset in the buffer.
         */
        private void writeTimeStamp(byte[] buffer, int offset, long time) {
            long seconds = time / 1000L;
            long milliseconds = time - seconds * 1000L;
            seconds += OFFSET_1900_TO_1970;

            // write seconds in big endian format
            buffer[offset++] = (byte) (seconds >> 24);
            buffer[offset++] = (byte) (seconds >> 16);
            buffer[offset++] = (byte) (seconds >> 8);
            buffer[offset++] = (byte) (seconds >> 0);

            long fraction = milliseconds * 0x100000000L / 1000L;
            // write fraction in big endian format
            buffer[offset++] = (byte) (fraction >> 24);
            buffer[offset++] = (byte) (fraction >> 16);
            buffer[offset++] = (byte) (fraction >> 8);
            // low order bits should be random data
            buffer[offset++] = (byte) (Math.random() * 255.0);
        }
    }

}

修改系统时间需要Root权限,所以必须要为应用授予Root权限,上面代码中的ShellUtils代码如下

/**
 * ShellUtils
 * <ul>
 * <strong>Check root</strong>
 * <li>{@link ShellUtils#checkRootPermission()}</li>
 * </ul>
 * <ul>
 * <strong>Execte command</strong>
 * <li>{@link ShellUtils#execCommand(String, boolean)}</li>
 * <li>{@link ShellUtils#execCommand(String, boolean, boolean)}</li>
 * <li>{@link ShellUtils#execCommand(List, boolean)}</li>
 * <li>{@link ShellUtils#execCommand(List, boolean, boolean)}</li>
 * <li>{@link ShellUtils#execCommand(String[], boolean)}</li>
 * <li>{@link ShellUtils#execCommand(String[], boolean, boolean)}</li>
 * </ul>
 * 
 * @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2013-5-16
 */
public class ShellUtils {

    public static final String COMMAND_SU       = "su";
    public static final String COMMAND_SH       = "sh";
    public static final String COMMAND_EXIT     = "exit\n";
    public static final String COMMAND_LINE_END = "\n";

    private ShellUtils() {
        throw new AssertionError();
    }

    /**
     * check whether has root permission
     * 
     * @return
     */
    public static boolean checkRootPermission() {
        return execCommand("echo root", true, false).result == 0;
    }

    /**
     * execute shell command, default return result msg
     * 
     * @param command command
     * @param isRoot whether need to run with root
     * @return
     * @see ShellUtils#execCommand(String[], boolean, boolean)
     */
    public static CommandResult execCommand(String command, boolean isRoot) {
        return execCommand(new String[] {command}, isRoot, true);
    }

    /**
     * execute shell commands, default return result msg
     * 
     * @param commands command list
     * @param isRoot whether need to run with root
     * @return
     * @see ShellUtils#execCommand(String[], boolean, boolean)
     */
    public static CommandResult execCommand(List<String> commands, boolean isRoot) {
        return execCommand(commands == null ? null : commands.toArray(new String[] {}), isRoot, true);
    }

    /**
     * execute shell commands, default return result msg
     * 
     * @param commands command array
     * @param isRoot whether need to run with root
     * @return
     * @see ShellUtils#execCommand(String[], boolean, boolean)
     */
    public static CommandResult execCommand(String[] commands, boolean isRoot) {
        return execCommand(commands, isRoot, true);
    }

    /**
     * execute shell command
     * 
     * @param command command
     * @param isRoot whether need to run with root
     * @param isNeedResultMsg whether need result msg
     * @return
     * @see ShellUtils#execCommand(String[], boolean, boolean)
     */
    public static CommandResult execCommand(String command, boolean isRoot, boolean isNeedResultMsg) {
        return execCommand(new String[] {command}, isRoot, isNeedResultMsg);
    }

    /**
     * execute shell commands
     * 
     * @param commands command list
     * @param isRoot whether need to run with root
     * @param isNeedResultMsg whether need result msg
     * @return
     * @see ShellUtils#execCommand(String[], boolean, boolean)
     */
    public static CommandResult execCommand(List<String> commands, boolean isRoot, boolean isNeedResultMsg) {
        return execCommand(commands == null ? null : commands.toArray(new String[] {}), isRoot, isNeedResultMsg);
    }

    /**
     * execute shell commands
     * 
     * @param commands command array
     * @param isRoot whether need to run with root
     * @param isNeedResultMsg whether need result msg
     * @return <ul>
     *         <li>if isNeedResultMsg is false, {@link CommandResult#successMsg} is null and
     *         {@link CommandResult#errorMsg} is null.</li>
     *         <li>if {@link CommandResult#result} is -1, there maybe some excepiton.</li>
     *         </ul>
     */
    public static CommandResult execCommand(String[] commands, boolean isRoot, boolean isNeedResultMsg) {
        int result = -1;
        if (commands == null || commands.length == 0) {
            return new CommandResult(result, null, null);
        }

        Process process = null;
        BufferedReader successResult = null;
        BufferedReader errorResult = null;
        StringBuilder successMsg = null;
        StringBuilder errorMsg = null;

        DataOutputStream os = null;
        try {
            process = Runtime.getRuntime().exec(isRoot ? COMMAND_SU : COMMAND_SH);
            os = new DataOutputStream(process.getOutputStream());
            for (String command : commands) {
                if (command == null) {
                    continue;
                }

                // donnot use os.writeBytes(commmand), avoid chinese charset error
                os.write(command.getBytes());
                os.writeBytes(COMMAND_LINE_END);
                os.flush();
            }
            os.writeBytes(COMMAND_EXIT);
            os.flush();

            result = process.waitFor();
            // get command result
            if (isNeedResultMsg) {
                successMsg = new StringBuilder();
                errorMsg = new StringBuilder();
                successResult = new BufferedReader(new InputStreamReader(process.getInputStream()));
                errorResult = new BufferedReader(new InputStreamReader(process.getErrorStream()));
                String s;
                while ((s = successResult.readLine()) != null) {
                    successMsg.append(s);
                }
                while ((s = errorResult.readLine()) != null) {
                    errorMsg.append(s);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (os != null) {
                    os.close();
                }
                if (successResult != null) {
                    successResult.close();
                }
                if (errorResult != null) {
                    errorResult.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

            if (process != null) {
                process.destroy();
            }
        }
        return new CommandResult(result, successMsg == null ? null : successMsg.toString(), errorMsg == null ? null
                : errorMsg.toString());
    }

    /**
     * result of command
     * <ul>
     * <li>{@link CommandResult#result} means result of command, 0 means normal, else means error, same to excute in
     * linux shell</li>
     * <li>{@link CommandResult#successMsg} means success message of command result</li>
     * <li>{@link CommandResult#errorMsg} means error message of command result</li>
     * </ul>
     * 
     * @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2013-5-16
     */
    public static class CommandResult {

        /** result of command **/
        public int    result;
        /** success message of command result **/
        public String successMsg;
        /** error message of command result **/
        public String errorMsg;

        public CommandResult(int result) {
            this.result = result;
        }

        public CommandResult(int result, String successMsg, String errorMsg) {
            this.result = result;
            this.successMsg = successMsg;
            this.errorMsg = errorMsg;
        }
    }
}

点这里可以跳转到人工智能网站

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