QT qtimer class

Header:
#include
CMake:
find_package(Qt6 COMPONENTS Core REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Core) qmake: QT += core Inherits: QObject
qmake:
QT+=core
Inherited from ：QObject

Public function (Public Functions)

QTimer(QObject *parent = nullptr);

QTimer Class constructor .

virtual ~QTmer();

QTimer Destructor of class .

QMetaObject::Connection callOnTimeout(Functor slot, Qt::ConnectionType connectionType = Qt::AutoConnection)

This function is created from timeout() Signal to slot connectionType Type of connection , And return the handle of the connection . This method is provided for convenience , It's equivalent to calling QObject::connect(timer, &QTimer::timeout, timer, slot, connectionType).

QMetaObject::Connection callOnTimeout(const QObject *context, Functor slot, Qt::ConnectionType connectionType = Qt::AutoConnection)

It's equivalent to calling QObject::connect(timer, &QTimer::timeout, context, slot, connectionType).

QMetaObject::Connection callOnTimeout(const QObject *receiver, MemberFunction *slot, Qt::ConnectionType connectionType = Qt::AutoConnection)

It's equivalent to calling QObject::connect(timer, &QTimer::timeout, receiver, slot, connectionType).

int interval() const

Get the timer trigger interval .

std::chrono::milliseconds intervalAsDuration() const

Get the timer trigger interval , The type is std::chrono::milliseconds.

bool isActive() const

The timer returns true when running , Otherwise return false .

bool isSingleShot() const

Whether the timer is a single trigger .

int remainingTime() const

Get the remaining time of the timer .

std::chrono::milliseconds remainingTimeAsDuration() const

Get the remaining time of the timer , The type is std::chrono::milliseconds.

void setInterval(int msec)

Set the interval between timers , The unit is millisecond .

void setInterval(std::chrono::milliseconds value)

Set the interval between timers , The type is std::chrono::milliseconds.

void setSingleShot(bool singleShot)

Set whether the timer is a single trigger .

void setTimerType(Qt::TimerType atype)

Set the accuracy of the timer .

void start(std::chrono::milliseconds msec)

Turn on timer .

int timerId() const

Get the of the timer ID.

Qt::TimerType timerType() const

Get the accuracy of the timer .
nature (Properties)

active:bool

read-only
If the timer runs , This Boolean property returns true , Otherwise return false .

interval:int

This attribute is the trigger interval of the timer , The unit is millisecond .
The default setting here is 0, Once all the events in the window system event queue have been processed , One time interval is 0 Of QTimer It will trigger .

remainingTime:int

read-only
This attribute saves the remaining time , The unit is millisecond .
Return the remaining value of the timer , The unit is millisecond , Until timeout . If the timer is inactive , The returned value will be -1. If the timer expires , The returned value will be 0.

singleShot : bool

This attribute is the single trigger attribute of the timer , If it is a single trigger , It's worth it , Otherwise it is false .

timerType : Qt::TimerType

This attribute is the trigger accuracy of the timer , The default value is Qt::CoarseTimer, See Qt::TimerType.
Public slot (Public Slots)

void start()

Turn on timer .

void start(int msec)

Turn on the timer and set the time interval .

void stop()

off timer
The signal (Signals)

void timeout()

Timer trigger signal .

QTimer *timer = new QTimer(this);
connect(timer, &QTimer::timeout, this, QOverload<>::of(&AnalogClock::update));
timer->start(1000);
//  Here QOverload<>::of Used to distinguish update Overloaded functions for 

Static public functions (Static Public Members)

void singleShot(int msec, const QObject *receiver, const char *member)

Single trigger function .
void singleShot(int msec, Qt::TimerType timerType, const QObject *receiver, const char *member)
void singleShot(int msec, const QObject *receiver, PointerToMemberFunction method)
void singleShot(int msec, Qt::TimerType timerType, const QObject *receiver, PointerToMemberFunction method)
void singleShot(int msec, Functor functor)
void singleShot(int msec, Qt::TimerType timerType, Functor functor)
void singleShot(int msec, const QObject *context, Functor functor)
void singleShot(int msec, Qt::TimerType timerType, const QObject *context, Functor functor)
void singleShot(std::chrono::milliseconds msec, const QObject *receiver, const char *member)
void singleShot(std::chrono::milliseconds msec, Qt::TimerType timerType, const QObject *receiver, const char *member)

Overload protection function (Reimplemented Protected Functions)

virtual void timerEvent(QTimerEvent *e) override

Reload timer events . After using this rewrite ,
enumeration Qt::TimerType

Constant	Value	Description
Qt::PreciseTimer	0	Precision timer
Qt::CoarseTimer	1	Ordinary timer
Qt::VeryCoarseTimer	2	Rough timer

example ：

1. Loop triggers a task ： Display the current time in the app .

QTimer *mpTimer = new QTimer(this);  
mpTimer->callOnTimeout(this,QOverload<>::of(&MainWindow::updateTime));
mpTimer->start(1000);// The interval trigger time is 1 second .

private slots:
void Example::updateTime()
{
    
    qDebug()<<" The current time is "<<QDateTime::currentDateTime();
}

2. Implement a delay function

void delayMs(int ms) // Millisecond delay 
{
    
    QEventLoop loop;// Define a new event loop 
    QTimer::singleShot(Ms, &loop, SLOT(quit()));// Create a single timer , The slot function is the exit function of the event loop 
    loop.exec();// The event loop starts executing , The program will be stuck here , Until the time is up , This cycle is exited 
}