这可能是一个更通用的解决方案。
#include <QThread>
#include <QTimer>
#include <QObject>
#include <map>
/**
* Singleton to implement simple 'relative' timer.
* Implements busy wait and also timeout-notifications (useful to monitor operations that could hang, etc).
*
* If the whole application is stalled (e.g. when a new device is connected), and we only want to
* wait for a period during which application was 'really' working (not just hanging waiting for OS)
* - then ticks will be missed too. This way - it's should be possible to avoid unnecessary timeouts
* that could happen if global time was measured (especially annoying on WINdows platforms)
*/
class RelativeTimer : public QObject
{
Q_OBJECT
typedef std::multimap <unsigned int, std::pair <QObject*, QString> > Notifications;
public:
/**
* Call to busy-wait for number of ticks.
*/
static void wait_num_of_ticks(unsigned int num_of_ticks_to_wait)
{
if(self.timer_id == 0)
{
qDebug("timer not initialised, call 'RelativeTimer::Init()'");
return;
}
if(num_of_ticks_to_wait > 0)
{
unsigned long until = self.tick_counter + num_of_ticks_to_wait; // it's ok if it wraps around..
while(self.tick_counter != until)
{
QCoreApplication::processEvents(); // let others to their job..
// or comment above out and just busy wait..
}
}
}
/**
* Call to busy-wait until ms_to_wait have elapsed.
* If ms_to_wait is < tick period
* Interval will define 'tick' frequency (and accuracy).
*/
static void wait_ms(unsigned int ms_to_wait)
{
wait_num_of_ticks(num_of_ticks_to_wait(ms_to_wait));
}
/**
* Call to schedule a notification after a given timeout.
* returns notification_id that can be used to cancel this notification.
*/
static unsigned long notify_timeout_ms(unsigned int ms_to_wait,
QObject *receiver,
const char* method_name)
{
unsigned long ticks_to_wait = 0;
if(receiver && method_name)
{
ticks_to_wait = num_of_ticks_to_wait(ms_to_wait);
if(ticks_to_wait > 1)
{
ticks_to_wait += self.tick_counter;
if(ticks_to_wait == 0) // avoid 0 - make it one tick more (to alow to see if successfully added this notif)
{
ticks_to_wait = 1;
}
self.notifications.insert(std::make_pair(ticks_to_wait,
std::make_pair(receiver, method_name)));
qDebug("added delayed call..");
}
else
{
QMetaObject::invokeMethod(receiver, method_name, Qt::QueuedConnection);
ticks_to_wait = 0;
}
}
return ticks_to_wait;
}
/**
* Call to cancel a notification with a given id.
* Specify name if there were more notification with the same id (scheduled for the same tick).
* returns true on successfull cancellation, false otherwise.
*/
static bool cancel_timeout_notification(unsigned long notification_id, QString notification_name="")
{
bool cancelled = false;
if(self.notifications.size())
{
std::pair<Notifications::iterator, Notifications::iterator> to_cancel = self.notifications.equal_range(notification_id);
Notifications::iterator n = to_cancel.first;
for( ;n != to_cancel.second; ++n)
{
if(notification_name.size()== 0 || n->second.second == notification_name)
{
self.notifications.erase(n);
cancelled = true;
break;
}
}
}
return cancelled;
}
static const unsigned int default_tick_period_ms = 100;
/**
* Call this method after event loop is created- to initiate (re-start) timer.
* tick period defines 'tick' frequency (and accuracy of the timer)
* (note on Windows that there's no point to go down below 100ms).
*/
static void Init(unsigned int tick_period_ms = default_tick_period_ms)
{
self.moveToThread(&self.thread);
self.thread.start();
while(!self.thread.isRunning());
self.current_interval = tick_period_ms;
// InitMe() should execute in the thread context..
QMetaObject::invokeMethod(&self, "InitMe", Qt::QueuedConnection);
}
private:
/**
* Internal method to convert ms to number of ticks.
*/
static unsigned int num_of_ticks_to_wait(unsigned int ms_to_wait)
{
if(ms_to_wait > self.current_interval)
{
if(ms_to_wait % self.current_interval)
{
// average it..
ms_to_wait = ms_to_wait + self.current_interval / 2;
}
ms_to_wait /= self.current_interval;
}
else
{
ms_to_wait = 0;
}
return ms_to_wait;
}
/**
* Internal method to handle tick. Increments counter and invokes notifications.
*/
void timerEvent ( QTimerEvent* /*event*/ )
{
tick_counter++;
if(notifications.size())
{
std::pair<Notifications::iterator, Notifications::iterator> to_notify = notifications.equal_range(tick_counter);
Notifications::iterator n = to_notify.first;
for( ;n != to_notify.second; ++n)
{
QMetaObject::invokeMethod(n->second.first,
n->second.second.toStdString().c_str(),
Qt::QueuedConnection);
}
notifications.erase(to_notify.first, to_notify.second);
}
}
private slots:
/**
* Internal slot to initialize the timer. Should be called in this->timer context.
*/
void InitMe()
{
if(timer_id != 0)
{
killTimer(timer_id);
timer_id = 0;
}
tick_counter = 0;
timer_id = self.startTimer(self.current_interval);
}
private:
RelativeTimer()
{
}
~RelativeTimer()
{
thread.quit();
thread.wait();
}
QThread thread;
Notifications notifications;
int timer_id;
unsigned int current_interval;
unsigned long tick_counter;
static RelativeTimer self; // implement it as a signleton.. Define it in your C file, e.g.:
// RelativeTimer RelativeTimer::self;
};
可以像这样使用：
CurrQObjectClass::OnTimeout()
{
// ...
}
CurrQObjectClass::SomeMethod()
{
RelativeTimer::notify_timeout_ms(5000, this, "OnTimeout");
}
但也适用于忙碌的等待：
RelativeTimer::wait_ms(2000);
享受。