QFutureWatcher 类允许监视 QFuture 使用的信号和槽。 更多...
| 头： | #include <QFutureWatcher> |
| qmake: | QT += core |
| Since: | Qt 4.4 |
| 继承： | QObject |
该类在 Qt 4.4 引入。
注意： 此类的所有函数 可重入 .
| QFutureWatcher (QObject * parent = nullptr) | |
| virtual | ~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 () |
| void | cancel () |
| void | pause () |
| void | resume () |
| void | setPaused (bool paused ) |
| void | togglePaused () |
| void | canceled () |
| void | finished () |
| void | paused () |
| void | progressRangeChanged (int minimum , int maximum ) |
| void | progressTextChanged (const QString & progressText ) |
| void | progressValueChanged (int progressValue ) |
| void | resultReadyAt (int index ) |
| void | resultsReadyAt (int beginIndex , int endIndex ) |
| void | resumed () |
| void | started () |
QFutureWatcher 提供信息和通知关于 QFuture 。使用 setFuture () 函数以开始看守特定 QFuture 。 future () 函数返回未来设置采用 setFuture ().
为方便起见，几个 QFuture 函数也可用于 QFutureWatcher： progressValue (), progressMinimum (), progressMaximum (), progressText (), isStarted (), isFinished (), isRunning (), isCanceled (), isPaused (), waitForFinished (), result ()，和 resultAt ()。 cancel (), setPaused (), pause (), resume ()，和 togglePaused () 函数是槽在 QFutureWatcher。
Status changes are reported via the started (), finished (), canceled (), paused (), resumed (), resultReadyAt ()，和 resultsReadyAt () signals. Progress information is provided from the progressRangeChanged (), void progressValueChanged ()，和 progressTextChanged () 信号。
Throttling control is provided by the setPendingResultsLimit () function. When the number of pending resultReadyAt () 或 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.
另请参阅 QFuture and Qt Concurrent .
Constructs a new QFutureWatcher with the given
parent
. Until a future is set with
setFuture
(), the functions
isStarted
(),
isCanceled
()，和
isFinished
() return
true
.
[slot]
void
QFutureWatcher::
cancel
()
Cancels the asynchronous computation represented by the future (). Note that the cancellation is asynchronous. Use waitForFinished () after calling cancel() when you need synchronous cancellation.
Currently available results may still be accessed on a canceled QFuture , but new results will not become available after calling this function. Also, this QFutureWatcher will not deliver progress and result ready signals once canceled. This includes the progressValueChanged (), progressRangeChanged (), progressTextChanged (), resultReadyAt ()，和 resultsReadyAt () 信号。
Be aware that not all running asynchronous computations can be canceled. For example, the QFuture 返回通过 QtConcurrent::run () cannot be canceled; but the QFuture 返回通过 QtConcurrent::mappedReduced () can.
[signal]
void
QFutureWatcher::
canceled
()
This signal is emitted if the watched future is canceled.
[signal]
void
QFutureWatcher::
finished
()
This signal is emitted when the watched future finishes.
[slot]
void
QFutureWatcher::
pause
()
Pauses the asynchronous computation represented by the future (). This is a convenience method that simply calls setPaused (true)。
另请参阅 resume ().
[signal]
void
QFutureWatcher::
paused
()
This signal is emitted when the watched future is paused.
另请参阅 setPaused ().
[signal]
void
QFutureWatcher::
progressRangeChanged
(
int
minimum
,
int
maximum
)
The progress range for the watched future has changed to minimum and maximum
[signal]
void
QFutureWatcher::
progressTextChanged
(const
QString
&
progressText
)
This signal is emitted when the watched future reports textual progress information, progressText .
[signal]
void
QFutureWatcher::
progressValueChanged
(
int
progressValue
)
This signal is emitted when the watched future reports progress, progressValue gives the current progress. In order to avoid overloading the GUI event loop, QFutureWatcher limits the progress signal emission rate. This means that listeners connected to this slot might not get all progress reports the future makes. The last progress update (where progressValue equals the maximum value) will always be delivered.
[signal]
void
QFutureWatcher::
resultReadyAt
(
int
index
)
This signal is emitted when the watched future reports a ready result at index . If the future reports multiple results, the index will indicate which one it is. Results can be reported out-of-order. To get the result, call resultAt (index);
[signal]
void
QFutureWatcher::
resultsReadyAt
(
int
beginIndex
,
int
endIndex
)
This signal is emitted when the watched future reports ready results. The results are indexed from beginIndex to endIndex .
[slot]
void
QFutureWatcher::
resume
()
Resumes the asynchronous computation represented by the future (). This is a convenience method that simply calls setPaused (false).
另请参阅 pause ().
[signal]
void
QFutureWatcher::
resumed
()
This signal is emitted when the watched future is resumed.
[slot]
void
QFutureWatcher::
setPaused
(
bool
paused
)
若 paused is true, this function pauses the asynchronous computation represented by the future (). If the computation is already paused, this function does nothing. This QFutureWatcher will stop delivering progress and result ready signals while the future is paused. Signal delivery will continue once the computation is resumed.
若 paused is false, this function resumes the asynchronous computation. If the computation was not previously paused, this function does nothing.
Be aware that not all computations can be paused. For example, the QFuture 返回通过 QtConcurrent::run () cannot be paused; but the QFuture 返回通过 QtConcurrent::mappedReduced () can.
另请参阅 paused (), pause (), resume ()，和 togglePaused ().
[signal]
void
QFutureWatcher::
started
()
This signal is emitted when this QFutureWatcher starts watching the future set with setFuture ().
[slot]
void
QFutureWatcher::
togglePaused
()
Toggles the paused state of the asynchronous computation. In other words, if the computation is currently paused, calling this function resumes it; if the computation is running, it becomes paused. This is a convenience method for calling setPaused (! isPaused ()).
另请参阅 setPaused (), pause ()，和 resume ().
[虚拟]
QFutureWatcher::
~QFutureWatcher
()
销毁 QFutureWatcher .
Returns the watched future.
另请参阅 setFuture ().
返回
true
if the asynchronous computation has been canceled with the
cancel
() function, or if no future has been set; otherwise returns
false
.
Be aware that the computation may still be running even though this function returns
true
。见
cancel
() 了解更多细节。
返回
true
if the asynchronous computation represented by the
future
() has finished, or if no future has been set; otherwise returns
false
.
返回
true
if the asynchronous computation has been paused with the
pause
() function; otherwise returns
false
.
Be aware that the computation may still be running even though this function returns
true
。见
setPaused
() 了解更多细节。
另请参阅 setPaused () 和 togglePaused ().
返回
true
if the asynchronous computation represented by the
future
() is currently running; otherwise returns
false
.
返回
true
if the asynchronous computation represented by the
future
() has been started, or if no future has been set; otherwise returns
false
.
返回最大 progressValue ().
另请参阅 progressValue () 和 progressMinimum ().
返回最小 progressValue ().
另请参阅 progressValue () 和 progressMaximum ().
Returns the (optional) textual representation of the progress as reported by the asynchronous computation.
Be aware that not all computations provide a textual representation of the progress, and as such, this function may return an empty string.
返回当前进度值，位于 progressMinimum () 和 progressMaximum ().
另请参阅 progressMinimum () 和 progressMaximum ().
Returns the first result in the future (). If the result is not immediately available, this function will block and wait for the result to become available. This is a convenience method for calling resultAt (0).
另请参阅 resultAt ().
Returns the result at index 在 future (). If the result is not immediately available, this function will block and wait for the result to become available.
另请参阅 result ().
开始看守给定 future .
若 future has already started, the watcher will initially emit signals that bring their listeners up to date about the future's state. The following signals will, if applicable, be emitted in the given order: started (), progressRangeChanged (), progressValueChanged (), progressTextChanged (), resultsReadyAt (), resultReadyAt (), paused (), canceled ()，和 finished (). Of these, resultsReadyAt () 和 resultReadyAt () may be emitted several times to cover all available results. progressValueChanged () 和 progressTextChanged () will only be emitted once for the latest available progress value and text.
To avoid a race condition, it is important to call this function after doing the connections.
另请参阅 future ().
The setPendingResultsLimit() provides throttling control. When the number of pending resultReadyAt () 或 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 .
Waits for the asynchronous computation to finish (including cancel ()ed computations).