QChronoTimer 類提供重復 (和單發) 計時器。 更多...
| 頭： |
#include <QChronoTimer>
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| CMake: |
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core)
|
| qmake: |
QT += core
|
| Since: | Qt 6.8 |
| 繼承： | QObject |
|
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| QChronoTimer (QObject * parent = nullptr) | |
| QChronoTimer (std::chrono::nanoseconds nsec , QObject * parent = nullptr) | |
| virtual | ~QChronoTimer () override |
| QBindable<bool> | bindableActive () |
| QBindable<std::chrono::nanoseconds> | bindableInterval () |
| QBindable<bool> | bindableSingleShot () |
| QBindable<Qt::TimerType> | bindableTimerType () |
| QMetaObject::Connection | callOnTimeout (const QObject * context , Functor && slot , Qt::ConnectionType connectionType = Qt::AutoConnection) |
| Qt::TimerId | id () const |
| std::chrono::nanoseconds | interval () const |
| bool | isActive () const |
| bool | isSingleShot () const |
| std::chrono::nanoseconds | remainingTime () const |
| void | setInterval (std::chrono::nanoseconds nsec ) |
| void | setSingleShot (bool singleShot ) |
| void | setTimerType (Qt::TimerType atype ) |
| Qt::TimerType | timerType () const |
| void | start () |
| void | stop () |
| void | timeout () |
| virtual void | timerEvent (QTimerEvent * e ) override |
The QChronoTimer class provides a high-level programming interface for timers. To use it, create a QChronoTimer, either passing the interval to the constructor, or setting it after construction using setInterval (), connect its timeout () 信號到適當槽，並調用 start ()。從那時起，它將發射 timeout () signal at constant intervals. For example:
auto *timer = new QChronoTimer(1s, this);
connect(timer, &QChronoTimer::timeout, this, &MyWidget::processOneThing);
timer->start();
QChronoTimer *timer = new QChronoTimer(this);
connect(timer, &QChronoTimer::timeout, this, &MyWidget::processOneThing);
timer->setInterval(1s);
timer->start();
可以將計時器設為僅超時一次，通過調用 setSingleShot (true)。
注意： QChronoTimer has no singleShot() static methods, as the ones on QTimer already work with chrono types and nanoseconds resolution.
In multithreaded applications, you can use QChronoTimer in any thread that has an event loop. To start an event loop from a non-GUI thread, use QThread::exec ()。Qt 使用計時器的 綫程親緣關係 確定哪個綫程將發射 timeout () 信號。因此這，必須在其綫程中啓動和停止計時器；從另一綫程啓動計時器，是不可能的。
As a special case, a QChronoTimer with a timeout of
0ns
will time out as soon as possible, though the ordering between zero timers and other sources of events is unspecified. Zero timers can be used to do some work while still providing a responsive user interface:
// The default interval is 0ns
QTimer *timer = new QTimer(this);
connect(timer, &QTimer::timeout, this, &MyWidget::processOneThing);
timer->start();
從那時起，
processOneThing()
will be called repeatedly. It should be written in such a way that it always returns quickly (for example, after processing one data item) so that Qt can deliver events to the user interface and stop the timer as soon as it has done all its work. This is the traditional way of implementing heavy work in GUI applications, but as multithreading is becoming available on more platforms, a modern alternative is doing the heavy work in a thread other than the GUI (main) thread. Qt has the
QThread
class, which can be used to achieve that.
The accuracy of timers depends on the underlying operating system and hardware. Most platforms support requesting nano-second precision for timers (for example, libc's
nanosleep
), though the accuracy of the timer will not equal this resolution in many real-world situations.
可以設置 計時器類型 to tell QChronoTimer which precision to request from the system.
For
Qt::PreciseTimer
, QChronoTimer will try to keep the precision at
1ns
. Precise timers will never time out earlier than expected.
For Qt::CoarseTimer and Qt::VeryCoarseTimer types, QChronoTimer may wake up earlier than expected, within the margins for those types:
500ms
for
Qt::VeryCoarseTimer
所有計時器類型的超時均可能晚於期望，若係統繁忙 (或無法提供要求的精度)。在這種超時超限情況下，Qt 會發射 timeout () 僅一次，即使有多個超時過期，然後再繼續原始間隔。
QChronoTimer provides nanosecond resolution and a ±292 years range (less chances of integer overflow if the interval is longer than
std::numeric_limits<int>::max()
). If you only need millisecond resolution and ±24 days range, you can continue to use the classical
QTimer
class
Another alternative is reimplementing the QObject::timerEvent () method in your class (which must be a sub-class of QObject ), and using one of the following approaches:
A disadvantage of using timerEvent () is that some high-level features, such as single-shot timers and signals, aren't supported.
Some operating systems limit the number of timers that may be used; Qt does its best to work around these limitations.
另請參閱 QBasicTimer , QTimerEvent , QObject::timerEvent (), 計時器 ，和 指針式時鍾 .
[bindable read-only]
active
:
bool
注意： 此特性支持 QProperty 綁定。
此布爾特性為
true
if the timer is running; otherwise
false
.
[bindable]
interval
:
std::chrono::nanoseconds
注意： 此特性支持 QProperty 綁定。
This property holds the timeout interval
此特性的默認值為
0ns
.
A
QChronoTimer
with a timeout of
0ns
will time out as soon as all the events in the window system's event queue have been processed.
Setting the interval of a running timer will change the interval, stop () and then start () the timer, and acquire a new id (). If the timer is not running, only the interval is changed.
另請參閱 singleShot .
[read-only]
remainingTime
: const
std::chrono::nanoseconds
This property holds the remaining time
Returns the remaining duration until the timeout.
If the timer is inactive, the returned duration will be negative.
If the timer is overdue, the returned duration will be
0ns
.
訪問函數：
| std::chrono::nanoseconds | remainingTime () const |
另請參閱 interval .
[bindable]
singleShot
:
bool
注意： 此特性支持 QProperty 綁定。
此特性保持計時器是否為單次計時器
單發計時器僅激發一次，非單發計時器被激發每隔 interval .
此特性的默認值為
false
.
另請參閱 interval .
[bindable]
timerType
:
Qt::TimerType
注意： 此特性支持 QProperty 綁定。
Controls the accuracy of the timer
此特性的默認值為
Qt::CoarseTimer
.
另請參閱 Qt::TimerType .
[explicit]
QChronoTimer::
QChronoTimer
(
QObject
*
parent
= nullptr)
構造計時器采用給定
parent
, using the default interval,
0ns
.
[explicit]
QChronoTimer::
QChronoTimer
(
std::chrono::nanoseconds
nsec
,
QObject
*
parent
= nullptr)
構造計時器采用給定 parent , using an interval of nsec .
[override virtual noexcept]
QChronoTimer::
~QChronoTimer
()
銷毀計時器。
此函數重載 callOnTimeout()。
創建連接從 timeout () 信號到 slot 以放置在特定事件循環 context , with connection type connectionType ，並返迴要連接的句柄。
This method is provided as a convenience. It's equivalent to calling:
QObject::connect(timer, &QChronoTimer::timeout, context, slot, connectionType);
另請參閱 QObject::connect () 和 timeout ().
返迴
Qt::TimerId
representing the timer ID if the timer is running; otherwise returns
Qt::TimerId::Invalid
.
另請參閱 Qt::TimerId .
返迴
true
if the timer is running; otherwise returns
false
.
注意： getter 函數對於特性 active .
[slot]
void
QChronoTimer::
start
()
此函數重載 start()。
啓動 (或重啓) 計時器采用指定超時在 interval .
若計時器已經在運行，它會被 stopped and restarted. This will also change its id ().
若 singleShot 為 true，將僅激活計時器一次。
[slot]
void
QChronoTimer::
stop
()
停止計時器。
另請參閱 start ().
[private signal]
void
QChronoTimer::
timeout
()
此信號被發射當計時器超時。
注意： 這是私有信號。它可以用於信號連接，但不能由用戶發射。
另請參閱 interval , start ()，和 stop ().
[override virtual protected]
void
QChronoTimer::
timerEvent
(
QTimerEvent
*
e
)
重實現： QObject::timerEvent (QTimerEvent *event).