CS4720

Sensors

CS4720– MobileApplicationDevelopment

CS4720

SensorCategories• Androidsensorsasseparatedintooneofthreebroadcategories:– Motionsensors– measureforceandrotation– Environmentalsensors– measureparameterssuchasilluminationairtemperatureandpressure

– Positionsensors– measurephysicalpositioningofthedevice

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Hardwarevs.Software• Althoughitmightbenaturaltothinkofallsensorsashardware,thatisn’tthecase

• AsensorinthecaseofAndroidisanycomponentthatprovidesinformationabouttheoutsideworld

• So,some“sensors”areactuallysoftwarecomponentsthattakedatafromhardwaresensorstogeneratedifferentkindsofdata

• Thesearecalled“virtualsensors”

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Sensors?Whatsensors?• Sensorsaren’tguaranteed!• ThereisnoAndroidspecforrequiredsensors!• So,youhavetocheckforthesensorfirst• Androidregisterssensorsintoparticularcategoriesdefinedbyaglobalfinalvariable

• Youcanaskforthedefaultsensorofanycategorytogetthecurrentlyactiveone(yes,youcanhavemorethanone!)

• Also,differentcapabilitiesanddrivers!4

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GettingData• Sensorsworksomewhatsimilarlytoaservice• Inasense,theyarealwaysrunninginthebackground

• Youcanallocateasensoreventlistenertomonitorasensorforchangesto:– Data– Availability– Precision/Resolution– PowerConsumption

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SensorEventListener• Toaccessthedatafromasensor,youneedaSensorEventListener

• YoucanimplementthisclassfromyourActivity• InsideonCreate,youcanaskthesensorservicetoprovidethecurrentdefaultsensorforanygivencategory

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SensorEvent• Atregularintervals,asensorreportsaSensorEvent toallregisteredlisteners

• ASensorEvent hasanarrayassociatedwithitcalledvalues

• Foreachsensor,thedataineachslotinthearrayrepresentsdifferentdata

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SensorEvent - Accelerometer• values[0]– accelerationforceonxaxis• values[1]– accelerationforceonyaxis• values[2]– accelerationforceonzaxis

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DifficultyofUsingAnalogData• Howdoyouread“userintent”?• Didtheymeantodosomething,ordidtheydropthedevice?

• Howcould“shaketoshuffle”messthingsupforrunners?

• Also,it’saLOTofdatacomingreallyfast!• Howdoyounotoverwhelmyourprogram?

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AdvancedSensors• Location• Camera• Microphone/Audio

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LocationServices• Locationservicescomeintwoflavors:

– ThelocationservicethatdirectlyprovidestheGPScoordinateinformation

– GoogleMapsAPI

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LocationServices• Locationservicesisbyfartheeasierofthetwomethodstogetasimplelocation

• Workssimilarlytoothersensors• Seeoldexamplecodeforthis!

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GooglePlayServices• GooglePlayServicesencompassallofthepotentialcloudfeaturesthatGoogleprovidesthroughtheirPlaystore

• Hastobemanuallyaddedintoyourmanifestsoitcanbecompiledintoyourapp

• APIkeysmightberequiredforagivenservicesothatGooglecantrackusage(andchargeasneeded)

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SomeGooglePlayServices• Google+• GoogleAccountLogin• GoogleAnalytics• GoogleMessaging• GoogleDrive• GoogleMaps• GoogleAds• GooglePlayGameservices

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ConnectingtoGooglePlayServices• Toutilizemanyofthese,youinstantiateaninstanceoftheGoogleApiClient classinyourapp

• Wheninstantiated,youconnecttoaparticularservice

• Youthenoverride– onConnected()– onConnectionSuspended()– onConnectionFailed()

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Authorization• Insomecases,yourappneedstobeauthorizedinsomewaybeforeitcanaccesstheservice

• Forinstance,inordertodogoodpublic/privatekeyauthenticationforGoogleSign-In,yourappneedstohaveanAPIkeydigitallysignedbyahashofyoursigningcertificate

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Camera• Twowaystogetanimage

– Sendanintenttothedefaultcameraprogram– Writeyourowncamera

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SendinganIntent(akaEasyWay)// create Intent to take a picture and return control to the

// calling applicationIntent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

// create a file to save the image fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);

// set the image file name intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

// start the image capture IntentstartActivityForResult(intent,CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);

Alsoworksforvideo!

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WritingaCamera(akaHardWay)• VerifythereISacamera• UsetheCameraclass• CreateaCameraPreview classtoshowwhattheCamerasees(theviewfinder)

• Addallbuttonsnecessarytozoom,capture,etc.

• Writecodetograbcurrentpixelsetandwritetofile

• Let’snottalkaboutvideo…19

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Microphone/Audio• Actually,abitdifferent

mRecorder = new MediaRecorder();mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);mRecorder.setOutputFile(mFileName);mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

try {mRecorder.prepare();

} catch (IOException e) {Log.e(LOG_TAG, "prepare() failed");

}

mRecorder.start();

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CoreMotion andCoreLocation• First,let’sdothe“howtodothese”• CoreMotion controlsaccesstotheaccelerometerandgyroscope

• CoreLocation controlsaccesstotheGPS

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CoreLocation

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func createLocationManager(startImmediately startImmediately: Bool){locationManager = CLLocationManager()if let manager = locationManager{

print("Successfully created the location manager")manager.delegate = selfif startImmediately{

manager.startUpdatingLocation()}

}}

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CoreLocation

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func locationManager(manager: CLLocationManager, didUpdateLocationslocations: [CLLocation]) {

if locations.count == 0{//handle error herereturn

}

let newLocation = locations[0]

print("Latitude = \(newLocation.coordinate.latitude)")print("Longitude = \(newLocation.coordinate.longitude)")lat.text = String(newLocation.coordinate.latitude)lon.text = String(newLocation.coordinate.longitude)

}

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CoreLocation

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/* Are location services available on this device? */if CLLocationManager.locationServicesEnabled(){

/* Do we have authorization to access location services? */switch CLLocationManager.authorizationStatus(){case .AuthorizedAlways:

/* Yes, always */createLocationManager(startImmediately: true)

case .AuthorizedWhenInUse:/* Yes, only when our app is in use */createLocationManager(startImmediately: true)

case .Denied:/* No */displayAlertWithTitle("Not Determined",

message: "Location services are not allowed for thisapp")

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CoreMotion - Shake

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// function to allow for detecting a shakeoverride func motionEnded(motion: UIEventSubtype,

withEvent event: UIEvent?) {

if motion == .MotionShake{let controller = UIAlertController(title: "Shake",

message: "The device is shaken",preferredStyle: .Alert)

controller.addAction(UIAlertAction(title: "OK",style: .Default,handler: nil))

presentViewController(controller, animated: true, completion: nil)

}

}

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CoreMotion - Accelerometer

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@IBAction func startAccel(sender: UIButton) {if motionManager.accelerometerAvailable{

let queue = NSOperationQueue()motionManager.startAccelerometerUpdatesToQueue(queue,

withHandler:{data, error in

guard let data = data else{return

}

print("X = \(data.acceleration.x)")print("Y = \(data.acceleration.y)")print("Z = \(data.acceleration.z)")}

)} else {

print("Accelerometer is not available")}

}