我正在使用UTC时区和应用程序中的时间来获取数据。在应用程序中，用户可以获取UTC时间并用于获取数据。 我用这种方法来获取UTC时间。
String format = "yyyy-MM-dd HH:mm:ss";
final SimpleDateFormat sdf = new SimpleDateFormat(format);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
String utcTime = sdf.format(new Date());
该应用程序运行正常。但它正在将系统时间转换为UTC时间。问题是有时用户可以将时间更改为错误的时间。所以数据还没有到来。
上述问题的案例是：
例如，印度的当前日期时间是2012年7月26日星期四，14：27：56，加尔各答时区。那么太平洋时区的时间应该是2012年7月26日星期四，太平洋时间01:59:30。
但是用户将设备时间从14:27:56更改为13:27:56，因此转换的UTC时间将是2012年7月26日星期四，太平洋时间00:59:30。此时我的应用程序因为一小时的差异而无法获取日期。
我不想使用日期，Java日历类，我不想使用设备时间。如何在不涉及设备的时间和日期的情况下直接获取UTC时间。是否有任何开源API？
提前致谢。
答案 0 :(得分：5)
long dateInMillis = System.currentTimeMillis();
这将返回自1970年1月1日00:00:00 UTC以来的毫秒数。
然后只需将其解析为您想要的最合适的格式：
String format = "yyyy-MM-dd HH:mm:ss";
final SimpleDateFormat sdf = new SimpleDateFormat(format);
String dateString = sdf.format(new Date(dateInMillis)));
答案 1 :(得分：5)
如果Sytem时间改变，则上面的SntpClient上的UTC时间不起作用，例如手动8小时。因为它使用System.currentTimeMillis返回false值!!!
// get current time and write it to the request packet
long requestTime = System.currentTimeMillis();
long requestTicks = SystemClock.elapsedRealtime();
最好使用此类从NTP服务器获取正确的UTC时间：
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
class NTP_UTC_Time
{
private static final String TAG = "SntpClient";
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;
private long mNtpTime;
public boolean requestTime(String host, int timeout) {
try {
DatagramSocket 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);
buffer[0] = NTP_MODE_CLIENT | (NTP_VERSION << 3);
writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET);
socket.send(request);
// read the response
DatagramPacket response = new DatagramPacket(buffer, buffer.length);
socket.receive(response);
socket.close();
mNtpTime = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);
} catch (Exception e) {
// if (Config.LOGD) Log.d(TAG, "request time failed: " + e);
return false;
}
return true;
}
public long getNtpTime() {
return mNtpTime;
}
/**
* 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 0 as NTP starttime stamp in the buffer. --> Then NTP returns Time OFFSET since 1900
*/
private void writeTimeStamp(byte[] buffer, int offset) {
int ofs = offset++;
for (int i=ofs;i<(ofs+8);i++)
buffer[i] = (byte)(0);
}
}
并将其用于：
long now = 0;
NTP_UTC_Time client = new NTP_UTC_Time();
if (client.requestTime("pool.ntp.org", 2000)) {
now = client.getNtpTime();
}
如果您需要UTC时间“现在”作为DateTimeString使用函数：
private String get_UTC_Datetime_from_timestamp(long timeStamp){
try{
Calendar cal = Calendar.getInstance();
TimeZone tz = cal.getTimeZone();
int tzt = tz.getOffset(System.currentTimeMillis());
timeStamp -= tzt;
// DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss",Locale.getDefault());
DateFormat sdf = new SimpleDateFormat();
Date netDate = (new Date(timeStamp));
return sdf.format(netDate);
}
catch(Exception ex){
return "";
}
}
并将其用于：
String UTC_DateTime = get_UTC_Datetime_from_timestamp(now);
答案 2 :(得分：4)
我认为您必须实现Sntp客户端并访问NTP才能获得网络时间。 我的代码：
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Date;
public class GetTime {
public static void main(String[] args) {
SntpClient client = new SntpClient();
if (client.requestTime("pool.ntp.org", 30000)) {
long now = client.getNtpTime() + System.nanoTime() / 1000
- client.getNtpTimeReference();
Date current = new Date(now);
System.out.println(current.toString());
}
}
}
class SntpClient {
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) {
try {
DatagramSocket 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 = System.nanoTime() / 1000;
writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET, requestTime);
socket.send(request);
// read the response
DatagramPacket response = new DatagramPacket(buffer, buffer.length);
socket.receive(response);
long responseTicks = System.nanoTime() / 1000;
long responseTime = requestTime + (responseTicks - requestTicks);
socket.close();
// 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 (Config.LOGD) Log.d(TAG, "round trip: " + roundTripTime +
// " ms");
// if (Config.LOGD) 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) {
return false;
}
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);
}
}
希望能帮到你。
答案 3 :(得分：3)
使用http://www.worldweatheronline.com/上的免费API，您可以通过java执行HTTP GET以获取UTC的当前时间（http://www.worldweatheronline.com/time-zone-api.aspx)
答案 4 :(得分：0)
您可以使用Joda库来操作日期/时间数据
答案 5 :(得分：0)
对于android系统，如果您尝试从主线程连接到Internet，则该应用程序将崩溃，因此我将其编辑为可在android系统上正常工作的代码
import android.os.AsyncTask;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class NTPUTCTime {
private static final String TAG = "SntpClient";
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;
private long mNtpTime;
public boolean requestTime() {
try {
new AsyncTask<Void, Void, Boolean>() {
@Override
protected Boolean doInBackground(Void... voids) {
try {
DatagramSocket socket = new DatagramSocket();
socket.setSoTimeout(1000);
InetAddress address = InetAddress.getByName("pool.ntp.org");
byte[] buffer = new byte[NTP_PACKET_SIZE];
DatagramPacket request = new DatagramPacket(buffer, buffer.length, address, NTP_PORT);
buffer[0] = NTP_MODE_CLIENT | (NTP_VERSION << 3);
writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET);
socket.send(request);
// read the response
DatagramPacket response = new DatagramPacket(buffer, buffer.length);
socket.receive(response);
socket.close();
mNtpTime = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);
} catch (Exception e) {
// if (Config.LOGD) Log.d(TAG, "request time failed: " + e);
e.printStackTrace();
return false;
}
return true;
}
}.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR).get();
} catch (Exception e) {
// if (Config.LOGD) Log.d(TAG, "request time failed: " + e);
e.printStackTrace();
return false;
}
return true;
}
public long getNtpTime() {
return mNtpTime;
}
/**
* 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 0 as NTP starttime stamp in the buffer. --> Then NTP returns Time OFFSET since 1900
*/
private void writeTimeStamp(byte[] buffer, int offset) {
int ofs = offset++;
for (int i = ofs; i < (ofs + 8); i++)
buffer[i] = (byte) (0);
}
}
答案 6 :(得分：-1)
class GetUTCTime : AppCompatActivity() {
private val OUTPUT_DATE_FORMATE = "dd-MM-yyyy - hh:mm a"
internal lateinit var textView : TextView
val utcTime: String
get() {
LongOperation().execute("")
return ""
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_get_utctime)
// Log.d("UTC", "onCreate: "+ getUTCTime());
textView = findViewById(R.id.dateTime)
findViewById<View>(R.id.fetchButton).setOnClickListener {
utcTime
textView.text = "Fetching..."
}
}
private inner class LongOperation : AsyncTask<String, Void, Long>() {
override fun doInBackground(vararg params: String): Long? {
var nowAsPerDeviceTimeZone: Long = 0
try {
val sntpClient = SntpClient()
if (sntpClient.requestTime("ntp.ubuntu.com", 30000)) {
nowAsPerDeviceTimeZone = sntpClient.ntpTime
}
Thread.sleep(1000)
} catch (e: InterruptedException) {
Thread.interrupted()
}
return nowAsPerDeviceTimeZone
}
override fun onPostExecute(nowAsPerDeviceTimeZone: Long?) {
// might want to change "executed" for the returned string passed
// into onPostExecute() but that is upto you
Log.d("GMT", "getUTCTime:0 " + Date(nowAsPerDeviceTimeZone!!))
textView.text = Date(nowAsPerDeviceTimeZone).toString()
// Calendar cal = Calendar.getInstance();
// TimeZone timeZoneInDevice = cal.getTimeZone();
// int differentialOfTimeZones = timeZoneInDevice.getOffset(System.currentTimeMillis());
// nowAsPerDeviceTimeZone -= differentialOfTimeZones;
//
//
//
//
//
// Log.d("GMT", "getUTCTime:1 "+ new Date(nowAsPerDeviceTimeZone).toString());
}
override fun onPreExecute() {}
override fun onProgressUpdate(vararg values: Void) {}
}
}