QDeadlineTimer 類標記未來最後期限。 更多...
| 頭： | #include <QDeadlineTimer> |
| qmake: | QT += core |
| Since: | Qt 5.8 |
該類在 Qt 5.8 引入。
注意： 此類的所有函數 可重入 .
| enum | ForeverConstant { Forever } |
| QDeadlineTimer (std::chrono::duration<Rep, Period> remaining , Qt::TimerType type = Qt::CoarseTimer) | |
| QDeadlineTimer (std::chrono::time_point<Clock, Duration> deadline , Qt::TimerType type = Qt::CoarseTimer) | |
| QDeadlineTimer (qint64 msecs , Qt::TimerType type = Qt::CoarseTimer) | |
| QDeadlineTimer ( QDeadlineTimer::ForeverConstant , Qt::TimerType timerType = Qt::CoarseTimer) | |
| QDeadlineTimer (Qt::TimerType timerType = Qt::CoarseTimer) | |
| qint64 | deadline () const |
| qint64 | deadlineNSecs () const |
| bool | hasExpired () const |
| bool | isForever () const |
| qint64 | remainingTime () const |
| std::chrono::nanoseconds | remainingTimeAsDuration () const |
| qint64 | remainingTimeNSecs () const |
| void | setDeadline (qint64 msecs , Qt::TimerType timerType = Qt::CoarseTimer) |
| void | setDeadline (std::chrono::time_point<Clock, Duration> deadline , Qt::TimerType type = Qt::CoarseTimer) |
| void | setPreciseDeadline (qint64 secs , qint64 nsecs = 0, Qt::TimerType timerType = Qt::CoarseTimer) |
| void | setPreciseRemainingTime (qint64 secs , qint64 nsecs = 0, Qt::TimerType timerType = Qt::CoarseTimer) |
| void | setRemainingTime (qint64 msecs , Qt::TimerType timerType = Qt::CoarseTimer) |
| void | setRemainingTime (std::chrono::duration<Rep, Period> remaining , Qt::TimerType type = Qt::CoarseTimer) |
| void | setTimerType (Qt::TimerType timerType ) |
| void | swap (QDeadlineTimer & other ) |
| Qt::TimerType | timerType () const |
| QDeadlineTimer & | operator+= (qint64 msecs ) |
| QDeadlineTimer & | operator-= (qint64 msecs ) |
| QDeadlineTimer & | operator= (std::chrono::time_point<Clock, Duration> deadline_ ) |
| QDeadlineTimer & | operator= (std::chrono::duration<Rep, Period> remaining ) |
| QDeadlineTimer | addNSecs (QDeadlineTimer dt , qint64 nsecs ) |
| QDeadlineTimer | current (Qt::TimerType timerType = Qt::CoarseTimer) |
| bool | operator!= (QDeadlineTimer d1 , QDeadlineTimer d2 ) |
| QDeadlineTimer | operator+ (QDeadlineTimer dt , qint64 msecs ) |
| QDeadlineTimer | operator+ (qint64 msecs , QDeadlineTimer dt ) |
| QDeadlineTimer | operator- (QDeadlineTimer dt , qint64 msecs ) |
| bool | operator< (QDeadlineTimer d1 , QDeadlineTimer d2 ) |
| bool | operator<= (QDeadlineTimer d1 , QDeadlineTimer d2 ) |
| bool | operator== (QDeadlineTimer d1 , QDeadlineTimer d2 ) |
| bool | operator> (QDeadlineTimer d1 , QDeadlineTimer d2 ) |
| bool | operator>= (QDeadlineTimer d1 , QDeadlineTimer d2 ) |
QDeadlineTimer 類通常用於計算未來截止日期並驗證截止日期是否已過期。QDeadlineTimer 也可以用於沒有過期 forever 的截止日期。它搭檔 QElapsedTimer ，計算已消耗多少時間從 QElapsedTimer::start () 被調用。
QDeadlineTimer 提供更方便 API 相比 QElapsedTimer::hasExpired ().
類的典型用例是在有問題操作開始之前創建 QDeadlineTimer，然後使用 remainingTime () 或 hasExpired () 以確定是否繼續試著操作。可以把 QDeadlineTimer 對象傳遞給執行此操作的調用函數，以便它們知道仍要運轉多久。
void executeOperation(int msecs)
{
QDeadlineTimer deadline(msecs);
do {
if (readFromDevice(deadline.remainingTime())
break;
waitForReadyRead(deadline);
} while (!deadline.hasExpired());
}
許多 QDeadlineTimer 函數處理超時值，均以毫秒為單位度量。有 2 個特殊值，如同許多其它 Qt 函數
waitFor
或類似：
QDeadlineTimer 將使用相同時鍾如 QElapsedTimer (見 QElapsedTimer::clockType () 和 QElapsedTimer::isMonotonic ()).
像 QTimer , QDeadlineTimer can select among different levels of coarseness on the timers. You can select precise timing by passing Qt::PreciseTimer to the functions that set of change the timer, or you can select coarse timing by passing Qt::CoarseTimer . Qt::VeryCoarseTimer is currently interpreted the same way as Qt::CoarseTimer .
This feature is dependent on support from the operating system: if the OS does not support a coarse timer functionality, then QDeadlineTimer will behave like Qt::PreciseTimer was passed.
QDeadlineTimer defaults to Qt::CoarseTimer because on operating systems that do support coarse timing, making timing calls to that clock source is often much more efficient. The level of coarseness depends on the operating system, but should be in the order of a couple of milliseconds.
std::chrono
兼容性
QDeadlineTimer 兼容
std::chrono
API from C++11 and can be constructed from or compared to both
std::chrono::duration
and
std::chrono::time_point
objects. In addition, it is fully compatible with the time literals from C++14, which allow one to write code as:
using namespace std::chrono;
using namespace std::chrono_literals;
QDeadlineTimer deadline(30s);
device->waitForReadyRead(deadline);
if (deadline.remainingTime<nanoseconds>() > 300ms)
cleanup();
As can be seen in the example above, QDeadlineTimer offers a templated version of
remainingTime
() 和
deadline
() that can be used to return
std::chrono
對象。
Note that comparing to
time_point
is not as efficient as comparing to
duration
, since QDeadlineTimer may need to convert from its own internal clock source to the clock source used by the
time_point
object. Also note that, due to this conversion, the deadlines will not be precise, so the following code is not expected to compare equally:
using namespace std::chrono;
using namespace std::chrono_literals;
auto now = steady_clock::now();
QDeadlineTimer deadline(now + 1s);
Q_ASSERT(deadline == now + 1s);
另請參閱 QTime , QTimer , QDeadlineTimer ，和 Qt::TimerType .
| 常量 | 值 | 描述 |
|---|---|---|
QDeadlineTimer::Forever
|
0
|
使用當創建 QDeadlineTimer 以指示截止日期不應該過期 |
構造 QDeadlineTimer 對象采用剩餘時間
remaining
。若
remaining
is zero or negative, this QDeadlineTimer object will be mark as expired, whereas if
remaining
等於
duration::max()
, the object will be set to never expire.
QDeadlineTimer 對象將被構造采用指定計時器 type .
此構造函數可以用於 C++ 14 的用戶定義時間文字，譬如在：
using namespace std::chrono_literals;
QDeadlineTimer deadline(250ms);
For optimization purposes, if remaining is zero or negative, this function may skip obtaining the current time and may instead use a value known to be in the past. If that happens, deadline () may return an unexpected value and this object cannot be used in calculation of how long it is overdue. If that functionality is required, use QDeadlineTimer::current () and add time to it.
另請參閱 hasExpired (), isForever (), remainingTime ()，和 setRemainingTime ().
Constructs a QDeadlineTimer object with a deadline at
deadline
time point, converting from the clock source
Clock
to Qt's internal clock source (see
QElapsedTimer::clockType
()).
若
deadline
is in the past, this QDeadlineTimer object is set to expired, whereas if
deadline
等於
Duration::max()
, then this object is set to never expire.
QDeadlineTimer 對象將被構造采用指定計時器 type .
另請參閱 hasExpired (), isForever (), remainingTime ()，和 setDeadline ().
Constructs a QDeadlineTimer object with an expiry time of msecs msecs from the moment of the creation of this object, if msecs is positive. If msecs is zero, this QDeadlineTimer will be marked as expired, causing remainingTime () to return zero and deadline () to return an indeterminate time point in the past. If msecs is -1, the timer will be set to never expire, causing remainingTime () to return -1 and deadline () to return the maximum value.
QDeadlineTimer 對象將被構造采用指定計時器 type .
For optimization purposes, if msecs is zero, this function may skip obtaining the current time and may instead use a value known to be in the past. If that happens, deadline () may return an unexpected value and this object cannot be used in calculation of how long it is overdue. If that functionality is required, use QDeadlineTimer::current () and add time to it.
另請參閱 hasExpired (), isForever (), remainingTime ()，和 setRemainingTime ().
QDeadlineTimer objects created with ForeverConstant never expire. For such objects, remainingTime () will return -1, deadline () will return the maximum value, and isForever () will return true.
The timer type timerType may be ignored, since the timer will never expire.
另請參閱 ForeverConstant , hasExpired (), isForever (), remainingTime ()，和 timerType ().
Constructs an expired QDeadlineTimer object. For this object, remainingTime () will return 0.
The timer type timerType may be ignored, since the timer is already expired. Similarly, for optimization purposes, this function will not attempt to obtain the current time and will use a value known to be in the past. Therefore, deadline () may return an unexpected value and this object cannot be used in calculation of how long it is overdue. If that functionality is required, use QDeadlineTimer::current ().
另請參閱 hasExpired (), remainingTime (), Qt::TimerType ，和 current ().
[static]
QDeadlineTimer
QDeadlineTimer::
addNSecs
(
QDeadlineTimer
dt
,
qint64
nsecs
)
返迴 QDeadlineTimer object whose deadline is extended from dt 's deadline by nsecs nanoseconds. If dt was set to never expire, this function returns a QDeadlineTimer that will not expire either.
注意： if dt was created as expired, its deadline is indeterminate and adding an amount of time may or may not cause it to become unexpired.
[static]
QDeadlineTimer
QDeadlineTimer::
current
(
Qt::TimerType
timerType
= Qt::CoarseTimer)
返迴 QDeadlineTimer that is expired but is guaranteed to contain the current time. Objects created by this function can participate in the calculation of how long a timer is overdue, using the deadline () 函數。
The QDeadlineTimer object will be constructed with the specified timerType .
Returns the absolute time point for the deadline stored in QDeadlineTimer object, calculated in milliseconds relative to the reference clock, the same as QElapsedTimer::msecsSinceReference (). The value will be in the past if this QDeadlineTimer has expired.
若此
QDeadlineTimer
never expires, this function returns
std::numeric_limits<qint64>::max()
.
This function can be used to calculate the amount of time a timer is overdue, by subtracting QDeadlineTimer::current () 或 QElapsedTimer::msecsSinceReference (), as in the following example:
qint64 realTimeLeft = deadline.deadline();
if (realTimeLeft != (std::numeric_limits<qint64>::max)()) {
realTimeLeft -= QDeadlineTimer::current().deadline();
// or:
//QElapsedTimer timer;
//timer.start();
//realTimeLeft -= timer.msecsSinceReference();
}
注意： Timers that were created as expired have an indetermine time point in the past as their deadline, so the above calculation may not work.
另請參閱 remainingTime (), deadlineNSecs ()，和 setDeadline ().
Returns the absolute time point for the deadline stored in QDeadlineTimer object, calculated in nanoseconds relative to the reference clock, the same as QElapsedTimer::msecsSinceReference (). The value will be in the past if this QDeadlineTimer has expired.
若此
QDeadlineTimer
never expires or the number of nanoseconds until the deadline can't be accommodated in the return type, this function returns
std::numeric_limits<qint64>::max()
.
This function can be used to calculate the amount of time a timer is overdue, by subtracting QDeadlineTimer::current (), as in the following example:
qint64 realTimeLeft = deadline.deadlineNSecs();
if (realTimeLeft != std::numeric_limits<qint64>::max())
realTimeLeft -= QDeadlineTimer::current().deadlineNSecs();
注意： Timers that were created as expired have an indetermine time point in the past as their deadline, so the above calculation may not work.
另請參閱 remainingTime () and deadlineNSecs().
返迴 true，若此 QDeadlineTimer object has expired, false if there remains time left. For objects that have expired, remainingTime () will return zero and deadline () will return a time point in the past.
QDeadlineTimer objects created with the ForeverConstant never expire and this function always returns false for them.
另請參閱 isForever () 和 remainingTime ().
返迴 true，若此 QDeadlineTimer object never expires, false otherwise. For timers that never expire, remainingTime () always returns -1 and deadline () returns the maximum value.
另請參閱 ForeverConstant , hasExpired ()，和 remainingTime ().
返迴剩餘時間在此 QDeadlineTimer object in milliseconds. If the timer has already expired, this function will return zero and it is not possible to obtain the amount of time overdue with this function (to do that, see deadline ()). If the timer was set to never expire, this function returns -1.
This function is suitable for use in Qt APIs that take a millisecond timeout, such as the many
QIODevice
waitFor
functions or the timed lock functions in
QMutex
,
QWaitCondition
,
QSemaphore
，或
QReadWriteLock
。例如：
mutex.tryLock(deadline.remainingTime());
另請參閱 setRemainingTime (), remainingTimeNSecs (), isForever ()，和 hasExpired ().
返迴截止日期之前的剩餘時間。
返迴剩餘時間在此 QDeadlineTimer object in nanoseconds. If the timer has already expired, this function will return zero and it is not possible to obtain the amount of time overdue with this function. If the timer was set to never expire, this function returns -1.
另請參閱 remainingTime (), isForever ()，和 hasExpired ().
設置截止日期為此 QDeadlineTimer object to be the msecs absolute time point, counted in milliseconds since the reference clock (the same as QElapsedTimer::msecsSinceReference ()), and the timer type to timerType . If the value is in the past, this QDeadlineTimer will be marked as expired.
若
msecs
is
std::numeric_limits<qint64>::max()
or the deadline is beyond a representable point in the future, this
QDeadlineTimer
will be set to never expire.
另請參閱 setPreciseDeadline (), deadline (), deadlineNSecs ()，和 setRemainingTime ().
設置此
QDeadlineTimer
to the deadline marked by
deadline
time point, converting from the clock source
Clock
to Qt's internal clock source (see
QElapsedTimer::clockType
()).
若
deadline
is in the past, this
QDeadlineTimer
object is set to expired, whereas if
deadline
等於
Duration::max()
, then this object is set to never expire.
The timer type for this QDeadlineTimer object will be set to the specified type .
另請參閱 hasExpired (), isForever ()，和 remainingTime ().
設置截止日期為此 QDeadlineTimer object to be secs seconds and nsecs nanoseconds since the reference clock epoch (the same as QElapsedTimer::msecsSinceReference ()), and the timer type to timerType . If the value is in the past, this QDeadlineTimer will be marked as expired.
若
secs
or
nsecs
is
std::numeric_limits<qint64>::max()
, this
QDeadlineTimer
will be set to never expire. If
nsecs
is more than 1 billion nanoseconds (1 second), then
secs
will be adjusted accordingly.
另請參閱 setDeadline (), deadline (), deadlineNSecs ()，和 setRemainingTime ().
設置剩餘時間為此 QDeadlineTimer 對象到 secs seconds plus nsecs nanoseconds from now, if secs has a positive value. If secs is -1, this QDeadlineTimer will be set it to never expire. If both parameters are zero, this QDeadlineTimer will be marked as expired.
The timer type for this QDeadlineTimer object will be set to the specified timerType .
另請參閱 setRemainingTime (), hasExpired (), isForever ()，和 remainingTime ().
設置剩餘時間為此 QDeadlineTimer 對象到 msecs milliseconds from now, if msecs has a positive value. If msecs is zero, this QDeadlineTimer object will be marked as expired, whereas a value of -1 will set it to never expire.
The timer type for this QDeadlineTimer object will be set to the specified timerType .
另請參閱 setPreciseRemainingTime (), hasExpired (), isForever ()，和 remainingTime ().
這是重載函數。
設置剩餘時間為此
QDeadlineTimer
對象到
remaining
。若
remaining
is zero or negative, this
QDeadlineTimer
object will be mark as expired, whereas if
remaining
等於
duration::max()
, the object will be set to never expire.
The timer type for this QDeadlineTimer object will be set to the specified type .
This function can be used with C++14's user-defined literals for time, such as in:
using namespace std::chrono_literals;
deadline.setRemainingTime(250ms);
注意： Qt 檢測必要 C++ 14 編譯器支持，通過特徵測試推薦從 C++ 委員會標準文檔 6 .
另請參閱 setDeadline (), remainingTime (), hasExpired ()，和 isForever ().
Changes the timer type for this object to timerType .
The behavior for each possible value of timerType is operating-system dependent. Qt::PreciseTimer will use the most precise timer that Qt can find, with resolution of 1 millisecond or better, whereas QDeadlineTimer will try to use a more coarse timer for Qt::CoarseTimer and Qt::VeryCoarseTimer .
另請參閱 timerType () 和 Qt::TimerType .
Swaps this deadline timer with the other deadline timer.
Returns the timer type is active for this object.
另請參閱 setTimerType ().
Extends this QDeadlineTimer object by msecs milliseconds and returns itself. If this object is set to never expire, this function does nothing.
To add times of precision greater than 1 millisecond, use addNSecs ().
Shortens this QDeadlineTimer object by msecs milliseconds and returns itself. If this object is set to never expire, this function does nothing.
To subtract times of precision greater than 1 millisecond, use addNSecs ().
賦值 deadline_ 到此截止日期計時器。
Sets this deadline timer to the remaining time.
Returns true if the deadline on d1 and the deadline in d2 are different, false otherwise. The timer type used to create the two deadlines is ignored. This function is equivalent to:
return d1.deadlineNSecs() != d2.deadlineNSecs();
注意： 比較 QDeadlineTimer objects with different timer types is not supported and may result in unpredictable behavior.
返迴 QDeadlineTimer object whose deadline is msecs later than the deadline stored in dt 。若 dt is set to never expire, this function returns a QDeadlineTimer that does not expire either.
To add times of precision greater than 1 millisecond, use addNSecs ().
返迴 QDeadlineTimer object whose deadline is msecs later than the deadline stored in dt 。若 dt is set to never expire, this function returns a QDeadlineTimer that does not expire either.
To add times of precision greater than 1 millisecond, use addNSecs ().
返迴 QDeadlineTimer object whose deadline is msecs before the deadline stored in dt 。若 dt is set to never expire, this function returns a QDeadlineTimer that does not expire either.
To subtract times of precision greater than 1 millisecond, use addNSecs ().
Returns true if the deadline on d1 is earlier than the deadline in d2 , false otherwise. The timer type used to create the two deadlines is ignored. This function is equivalent to:
return d1.deadlineNSecs() < d2.deadlineNSecs();
注意： 比較 QDeadlineTimer objects with different timer types is not supported and may result in unpredictable behavior.
Returns true if the deadline on d1 is earlier than or the same as the deadline in d2 , false otherwise. The timer type used to create the two deadlines is ignored. This function is equivalent to:
return d1.deadlineNSecs() <= d2.deadlineNSecs();
注意： 比較 QDeadlineTimer objects with different timer types is not supported and may result in unpredictable behavior.
Returns true if the deadline on d1 and the deadline in d2 are the same, false otherwise. The timer type used to create the two deadlines is ignored. This function is equivalent to:
return d1.deadlineNSecs() == d2.deadlineNSecs();
注意： 比較 QDeadlineTimer objects with different timer types is not supported and may result in unpredictable behavior.
Returns true if the deadline on d1 is later than the deadline in d2 , false otherwise. The timer type used to create the two deadlines is ignored. This function is equivalent to:
return d1.deadlineNSecs() > d2.deadlineNSecs();
注意： 比較 QDeadlineTimer objects with different timer types is not supported and may result in unpredictable behavior.
Returns true if the deadline on d1 is later than or the same as the deadline in d2 , false otherwise. The timer type used to create the two deadlines is ignored. This function is equivalent to:
return d1.deadlineNSecs() >= d2.deadlineNSecs();
注意： 比較 QDeadlineTimer objects with different timer types is not supported and may result in unpredictable behavior.