QDeadlineTimer ¶

函数 ¶

静态函数 ¶

参考时钟 ¶

QDeadlineTimer will use the same clock as QElapsedTimer (见 clockType() and isMonotonic() ).

计时器类型 ¶

像 QTimer , QDeadlineTimer can select among different levels of coarseness on the timers. You can select precise timing by passing PreciseTimer to the functions that set of change the timer, or you can select coarse timing by passing CoarseTimer . VeryCoarseTimer is currently interpreted the same way as 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 PreciseTimer was passed.

QDeadlineTimer 默认为 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 is compatible with the 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() and deadline() that can be used to return std::chrono 对象。

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);
												

另请参阅

QTime QTimer QDeadlineTimer TimerType

class QDeadlineTimer ( arg__1 [ , type_=Qt.CoarseTimer ] ) ¶

QDeadlineTimer([type_=Qt.CoarseTimer])

QDeadlineTimer(QDeadlineTimer)

QDeadlineTimer(msecs[, type=Qt.CoarseTimer])

param type

TimerType

param arg__1

ForeverConstant

param msecs

qint64

param type_

TimerType

param QDeadlineTimer

QDeadlineTimer

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.

另请参阅

ForeverConstant hasExpired() isForever() remainingTime() 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 current() .

另请参阅

hasExpired() remainingTime() TimerType current()

构造 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 object will be constructed with the specified timer 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 current() and add time to it.

另请参阅

hasExpired() isForever() remainingTime() setRemainingTime()

PySide2.QtCore.QDeadlineTimer. ForeverConstant ¶

常量	描述
QDeadlineTimer.Forever	使用当创建 QDeadlineTimer 以指示截止日期不应该过期

PySide2.QtCore.QDeadlineTimer. _q_data ( ) ¶

返回类型

static PySide2.QtCore.QDeadlineTimer. addNSecs ( dt , nsecs ) ¶

参数

• dt – QDeadlineTimer

• nsecs – qint64

返回类型

QDeadlineTimer

返回 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 PySide2.QtCore.QDeadlineTimer. current ( [ timerType=Qt.CoarseTimer ] ) ¶

参数

timerType – TimerType

返回类型

QDeadlineTimer

返回 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() 函数。

QDeadlineTimer object will be constructed with the specified timerType .

PySide2.QtCore.QDeadlineTimer. deadline ( ) ¶

返回类型

qint64

Returns the absolute time point for the deadline stored in QDeadlineTimer object, calculated in milliseconds relative to the reference clock, the same as 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 current() or 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.

另请参阅

remainingTime() deadlineNSecs() setDeadline()

PySide2.QtCore.QDeadlineTimer. deadlineNSecs ( ) ¶

返回类型

qint64

Returns the absolute time point for the deadline stored in QDeadlineTimer object, calculated in nanoseconds relative to the reference clock, the same as 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 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.

另请参阅

remainingTime() deadlineNSecs()

PySide2.QtCore.QDeadlineTimer. hasExpired ( ) ¶

返回类型

bool

返回 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.

另请参阅

isForever() remainingTime()

PySide2.QtCore.QDeadlineTimer. isForever ( ) ¶

返回类型

bool

返回 true，若此 QDeadlineTimer object never expires, false otherwise. For timers that never expire, remainingTime() always returns -1 and deadline() returns the maximum value.

另请参阅

ForeverConstant hasExpired() remainingTime()

PySide2.QtCore.QDeadlineTimer. __iadd__ ( msecs ) ¶

参数

msecs – qint64

返回类型

QDeadlineTimer

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() .

PySide2.QtCore.QDeadlineTimer. __isub__ ( msecs ) ¶

参数

msecs – qint64

返回类型

QDeadlineTimer

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() .

PySide2.QtCore.QDeadlineTimer. remainingTime ( ) ¶

返回类型

qint64

返回剩余时间在此 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());
												

另请参阅

setRemainingTime() remainingTimeNSecs() isForever() hasExpired()

PySide2.QtCore.QDeadlineTimer. remainingTimeNSecs ( ) ¶

返回类型

qint64

返回剩余时间在此 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.

另请参阅

remainingTime() isForever() hasExpired()

PySide2.QtCore.QDeadlineTimer. setDeadline ( msecs [ , timerType=Qt.CoarseTimer ] ) ¶

参数

• msecs – qint64

• timerType – TimerType

设置截止日期为此 QDeadlineTimer object to be the msecs absolute time point, counted in milliseconds since the reference clock (the same as 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.

另请参阅

setPreciseDeadline() deadline() deadlineNSecs() setRemainingTime()

PySide2.QtCore.QDeadlineTimer. setPreciseDeadline ( secs [ , nsecs=0 [ , type=Qt.CoarseTimer ] ] ) ¶

参数

• secs – qint64

• nsecs – qint64

• type – TimerType

设置截止日期为此 QDeadlineTimer object to be secs seconds and nsecs nanoseconds since the reference clock epoch (the same as 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.

另请参阅

setDeadline() deadline() deadlineNSecs() setRemainingTime()

PySide2.QtCore.QDeadlineTimer. setPreciseRemainingTime ( secs [ , nsecs=0 [ , type=Qt.CoarseTimer ] ] ) ¶

参数

• secs – qint64

• nsecs – qint64

• type – TimerType

设置剩余时间为此 QDeadlineTimer 对象到 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 .

另请参阅

setRemainingTime() hasExpired() isForever() remainingTime()

PySide2.QtCore.QDeadlineTimer. setRemainingTime ( msecs [ , type=Qt.CoarseTimer ] ) ¶

参数

• msecs – qint64

• type – TimerType

设置剩余时间为此 QDeadlineTimer 对象到 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 .

另请参阅

setPreciseRemainingTime() hasExpired() isForever() remainingTime()

PySide2.QtCore.QDeadlineTimer. setTimerType ( type ) ¶

参数

type – TimerType

Changes the timer type for this object to timerType .

The behavior for each possible value of timerType is operating-system dependent. 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 CoarseTimer and VeryCoarseTimer .

另请参阅

timerType() TimerType

PySide2.QtCore.QDeadlineTimer. swap ( other ) ¶

参数

other – QDeadlineTimer

Swaps this deadline timer with the other deadline timer.

PySide2.QtCore.QDeadlineTimer. timerType ( ) ¶

返回类型

TimerType

Returns the timer type is active for this object.

另请参阅

setTimerType()