@UnstableApi
public final class SntpClient

Static utility to retrieve the device time offset using SNTP.

Based on the Android framework SntpClient.

Summary

Nested types

Callback for calls to initialize.

Constants
static final String
DEFAULT_NTP_HOST = "time.android.com"

The default NTP host address used to retrieve getElapsedRealtimeOffsetMs.
static final int

The default maximum time, in milliseconds, to wait for the SNTP request to complete.

Public fields
static long
@GuardedBy(value = "valueLock")
elapsedRealtimeOffsetMs
static boolean
@GuardedBy(value = "valueLock")
isInitialized
static long
@GuardedBy(value = "valueLock")
maxElapsedTimeUntilUpdateMs
static String
@GuardedBy(value = "valueLock")
ntpHost
static int
@GuardedBy(value = "valueLock")
timeoutMs

Public methods
static long

Returns the offset between elapsedRealtime and the NTP server time in milliseconds, or TIME_UNSET if isInitialized returns false.
static long

Returns the maximum time to elapse until the client is re-initialized, in milliseconds.
static String

Returns the NTP host address used to retrieve getElapsedRealtimeOffsetMs.
static int

Returns the maximum time to wait for the SNTP request to complete, in milliseconds.
static void

Starts loading the device time offset.
static boolean

Returns whether the device time offset has already been loaded.
static void
setMaxElapsedTimeUntilUpdateMs(long maxElapsedTimeUntilUpdateMs)

Sets the maximum time to elapse until the client is re-initialized, in milliseconds.
static void
setNtpHost(String ntpHost)

Sets the NTP host address used to retrieve getElapsedRealtimeOffsetMs.
static void
setTimeoutMs(int timeoutMs)

Sets the maximum time to wait for the SNTP request to complete, in milliseconds.

Constants

DEFAULT_NTP_HOST

public static final String DEFAULT_NTP_HOST = "time.android.com"

The default NTP host address used to retrieve getElapsedRealtimeOffsetMs.

DEFAULT_TIMEOUT_MS

public static final int DEFAULT_TIMEOUT_MS = 1000

The default maximum time, in milliseconds, to wait for the SNTP request to complete.

Public fields

elapsedRealtimeOffsetMs

@GuardedBy(value = "valueLock")
public static long elapsedRealtimeOffsetMs

isInitialized

@GuardedBy(value = "valueLock")
public static boolean isInitialized

maxElapsedTimeUntilUpdateMs

@GuardedBy(value = "valueLock")
public static long maxElapsedTimeUntilUpdateMs

ntpHost

@GuardedBy(value = "valueLock")
public static String ntpHost

timeoutMs

@GuardedBy(value = "valueLock")
public static int timeoutMs

Public methods

getElapsedRealtimeOffsetMs

public static long getElapsedRealtimeOffsetMs()

Returns the offset between elapsedRealtime and the NTP server time in milliseconds, or TIME_UNSET if isInitialized returns false.

The offset is calculated as ntpServerTime - deviceElapsedRealTime.

getMaxElapsedTimeUntilUpdateMs

public static long getMaxElapsedTimeUntilUpdateMs()

Returns the maximum time to elapse until the client is re-initialized, in milliseconds.

getNtpHost

public static String getNtpHost()

Returns the NTP host address used to retrieve getElapsedRealtimeOffsetMs.

getTimeoutMs

public static int getTimeoutMs()

Returns the maximum time to wait for the SNTP request to complete, in milliseconds.

initialize

public static void initialize(
    @Nullable Loader loader,
    @Nullable SntpClient.InitializationCallback callback
)

Starts loading the device time offset.

Parameters
@Nullable Loader loader

A Loader to use for loading the time offset, or null to create a new one.
@Nullable SntpClient.InitializationCallback callback

An optional InitializationCallback to be notified when the time offset has been initialized or initialization failed.

isInitialized

public static boolean isInitialized()

Returns whether the device time offset has already been loaded.

If false, use initialize to start the initialization.

setMaxElapsedTimeUntilUpdateMs

public static void setMaxElapsedTimeUntilUpdateMs(long maxElapsedTimeUntilUpdateMs)

Sets the maximum time to elapse until the client is re-initialized, in milliseconds.

The default is TIME_UNSET to never re-initialize.

setNtpHost

public static void setNtpHost(String ntpHost)

Sets the NTP host address used to retrieve getElapsedRealtimeOffsetMs.

The default is DEFAULT_NTP_HOST.

If the new host address is different from the previous one, the NTP client will be isInitialized uninitialized} again.

Parameters
String ntpHost

The NTP host address.

setTimeoutMs

public static void setTimeoutMs(int timeoutMs)

Sets the maximum time to wait for the SNTP request to complete, in milliseconds.

The default is DEFAULT_TIMEOUT_MS.

If the new timeout is different from the previous one, the NTP client will be isInitialized uninitialized} again.