QFutureWatcher Class
The QFutureWatcher class allows monitoring a QFuture using signals and slots. More...
| Header: | #include <QFutureWatcher> |
| qmake: | QT += core |
| Since: | Qt 4.4 |
| Inherits: | QFutureWatcherBase |
Note: All functions in this class are reentrant.
Public Functions
| QFutureWatcher(QObject *_parent = nullptr) | |
| ~QFutureWatcher() | |
| QFuture<T> | future() const |
| bool | isCanceled() const |
| bool | isFinished() const |
| bool | isPaused() const |
| bool | isRunning() const |
| bool | isStarted() const |
| int | progressMaximum() const |
| int | progressMinimum() const |
| QString | progressText() const |
| int | progressValue() const |
| T | result() const |
| T | resultAt(int index) const |
| void | setFuture(const QFuture<T> &future) |
| void | setPendingResultsLimit(int limit) |
| void | waitForFinished() |
- 12 public functions inherited from QFutureWatcherBase
- 29 public functions inherited from QObject
Public Slots
| void | cancel() |
| void | pause() |
| void | resume() |
| void | setPaused(bool paused) |
| void | togglePaused() |
- 5 public slots inherited from QFutureWatcherBase
- 1 public slot inherited from QObject
Signals
| void | canceled() |
| void | finished() |
| void | paused() |
| void | progressRangeChanged(int minimum, int maximum) |
| void | progressTextChanged(const QString &progressText) |
| void | progressValueChanged(int progressValue) |
| void | resultReadyAt(int resultIndex) |
| void | resultsReadyAt(int beginIndex, int endIndex) |
| void | resumed() |
| void | started() |
- 10 signals inherited from QFutureWatcherBase
- 2 signals inherited from QObject
Additional Inherited Members
- 1 property inherited from QObject
- 10 static public members inherited from QObject
- 2 protected functions inherited from QFutureWatcherBase
- 9 protected functions inherited from QObject
Detailed Description
The QFutureWatcher class allows monitoring a QFuture using signals and slots.
QFutureWatcher provides information and notifications about a QFuture. Use the setFuture() function to start watching a particular QFuture. The future() function returns the future set with setFuture().
For convenience, several of QFuture's functions are also available in QFutureWatcher: progressValue(), progressMinimum(), progressMaximum(), progressText(), isStarted(), isFinished(), isRunning(), isCanceled(), isPaused(), waitForFinished(), result(), and resultAt(). The cancel(), setPaused(), pause(), resume(), and togglePaused() functions are slots in QFutureWatcher.
Status changes are reported via the started(), finished(), canceled(), paused(), resumed(), resultReadyAt(), and resultsReadyAt() signals. Progress information is provided from the progressRangeChanged(), void progressValueChanged(), and progressTextChanged() signals.
Throttling control is provided by the setPendingResultsLimit() function. When the number of pending resultReadyAt() or resultsReadyAt() signals exceeds the limit, the computation represented by the future will be throttled automatically. The computation will resume once the number of pending signals drops below the limit.
Example: Starting a computation and getting a slot callback when it's finished:
// Instantiate the objects and connect to the finished signal. MyClass myObject; QFutureWatcher<int> watcher; connect(&watcher, &QFutureWatcher<int>::finished, &myObject, &MyClass::handleFinished); // Start the computation. QFuture<int> future = QtConcurrent::run(...); watcher.setFuture(future);
Be aware that not all running asynchronous computations can be canceled or paused. For example, the future returned by QtConcurrent::run() cannot be canceled; but the future returned by QtConcurrent::mappedReduced() can.
QFutureWatcher<void> is specialized to not contain any of the result fetching functions. Any QFuture<T> can be watched by a QFutureWatcher<void> as well. This is useful if only status or progress information is needed; not the actual result data.
See also QFuture and Qt Concurrent.
Member Function Documentation
QFutureWatcher::QFutureWatcher(QObject *_parent = nullptr)
Default constructs an instance of QFutureWatcher.
QFutureWatcher::~QFutureWatcher()
Destroys the instance of QFutureWatcher.
[slot] void QFutureWatcher::cancel()
[signal] void QFutureWatcher::canceled()
[signal] void QFutureWatcher::finished()
QFuture<T> QFutureWatcher::future() const
See also setFuture().
bool QFutureWatcher::isCanceled() const
bool QFutureWatcher::isFinished() const
bool QFutureWatcher::isPaused() const
bool QFutureWatcher::isRunning() const
bool QFutureWatcher::isStarted() const
[slot] void QFutureWatcher::pause()
[signal] void QFutureWatcher::paused()
See also setPaused().
int QFutureWatcher::progressMaximum() const
int QFutureWatcher::progressMinimum() const
[signal] void QFutureWatcher::progressRangeChanged(int minimum, int maximum)
QString QFutureWatcher::progressText() const
[signal] void QFutureWatcher::progressTextChanged(const QString &progressText)
int QFutureWatcher::progressValue() const
[signal] void QFutureWatcher::progressValueChanged(int progressValue)
T QFutureWatcher::result() const
T QFutureWatcher::resultAt(int index) const
[signal] void QFutureWatcher::resultReadyAt(int resultIndex)
[signal] void QFutureWatcher::resultsReadyAt(int beginIndex, int endIndex)
[slot] void QFutureWatcher::resume()
[signal] void QFutureWatcher::resumed()
void QFutureWatcher::setFuture(const QFuture<T> &future)
See also future().
[slot] void QFutureWatcher::setPaused(bool paused)
See also paused().