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296 |
296 |
297 /*! |
297 /*! |
298 Start retrieving values from the sensor. |
298 Start retrieving values from the sensor. |
299 Returns true if the sensor was started, false otherwise. |
299 Returns true if the sensor was started, false otherwise. |
300 |
300 |
301 Note that the sensor may fail to start for several reasons. |
301 The sensor may fail to start for several reasons. |
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302 |
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303 Once an application has started a sensor it must wait until the sensor receives a |
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304 new value before it can query the sensor's values. This is due to how the sensor |
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305 receives values from the system. Sensors do not (in general) poll for new values, |
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306 rather new values are pushed to the sensors as they happen. |
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307 |
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308 For example, this code will not work as intended. |
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309 |
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310 \badcode |
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311 sensor->start(); |
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312 sensor->reading()->x(); // no data available |
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313 \endcode |
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314 |
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315 To work correctly, the code that accesses the reading should ensure the |
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316 readingChanged() signal has been emitted. |
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317 |
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318 \code |
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319 connect(sensor, SIGNAL(readingChanged()), this, SLOT(checkReading())); |
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320 sensor->start(); |
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321 } |
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322 void MyClass::checkReading() { |
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323 sensor->reading()->x(); |
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324 \endcode |
302 |
325 |
303 \sa QSensor::busy |
326 \sa QSensor::busy |
304 */ |
327 */ |
305 bool QSensor::start() |
328 bool QSensor::start() |
306 { |
329 { |
337 |
360 |
338 The reading class provides access to sensor readings. |
361 The reading class provides access to sensor readings. |
339 |
362 |
340 Note that this will return 0 until a sensor backend is connected to a backend. |
363 Note that this will return 0 until a sensor backend is connected to a backend. |
341 |
364 |
342 \sa isConnectedToBackend() |
365 Also note that readings are not immediately available after start() is called. |
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366 Applications must wait for the readingChanged() signal to be emitted. |
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367 |
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368 \sa isConnectedToBackend(), start() |
343 */ |
369 */ |
344 |
370 |
345 QSensorReading *QSensor::reading() const |
371 QSensorReading *QSensor::reading() const |
346 { |
372 { |
347 return d->cache_reading; |
373 return d->cache_reading; |
386 |
412 |
387 /*! |
413 /*! |
388 \fn QSensor::readingChanged() |
414 \fn QSensor::readingChanged() |
389 |
415 |
390 This signal is emitted when the reading has changed. |
416 This signal is emitted when the reading has changed. |
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417 |
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418 Before this signal has been emitted for the first time, the sensor reading will |
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419 have uninitialized data. |
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420 |
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421 \sa start() |
391 */ |
422 */ |
392 |
423 |
393 /*! |
424 /*! |
394 \property QSensor::outputRanges |
425 \property QSensor::outputRanges |
395 \brief a list of output ranges the sensor supports. |
426 \brief a list of output ranges the sensor supports. |