Android LBS

7/28/2019 Android LBS

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Development


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Android

Loca+onBasedServices


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GPS Itisaradio-naviga+onsystemconsis+ngof24

satellitesorbi+ngtheearth,andtheirrespec+vegroundsta+ons.Tocalculateaposi+on,thesesatellitesserveasreferencepointswhencalcula+ngposi+onsrela+vetoamaEerofmeters.

Inotherwords,GPStriangulatestheposi+onofasatellite,itsgroundsta+onandtheareayouwanttolocate.However,thisisdoneinamorescien+ficandfinitemeasurementoftravel+me,distance,signalexperiences,andatmosphericdelays.

TomeasureGPSpoints,youmustuseaGPSreceiverthatcalculatesitsposi+onbythesignalstransmiEedtothesatellites.Thesesatellitessendmessagescontaininginforma+onsuchasthe+methemessagewassentandthesatellitesorbitalinforma+on.Onceitreceivesthisinforma+on,theGPSreceiverwillthenmeasurethetransit+meofthesentmessageandcalculatethedistanceoftheGPSreceivertotheeachofthesatellites.

Theloca+onisthendisplayedthroughGPSmaps


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Celltower

Analterna+vemethodtodeterminetheloca+onofacellphoneistoes+mateitsdistancetothreenearbycelltowers.

Distanceofthephonetoeachantennacouldbees2mated

baseduponthelag2mebetweenthemomentthetowersendsapingtothephoneandreceivestheansweringpingback.


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Long&Lat

La+tude&LongitudeLa+tudeinGPS-Decimalnota+on:90.00000(North)to-90.000000

(South)

LongitudeGPS-Decimalnota+on:180.000000(ast)to-180.000000(West)


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Loca+onbasedservices(LBS)

Differenttechnologyusedtofindthedevicescurrentloca+on Twomainelements

Loca+onManager Providehookstotheloca+on-basedservices

Loca+onProvider achofwhichrepresentsadifferentloca+on-findingtechnologyusedto

determinethedevicescurrentloca+on

UsingtheLoca+onManager,youcan: Obtainyourcurrentloca+on TrackMovement Setproximityalertsfordetec+ngmovementintoandoutofaspecified

area


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Loca+onProvider

Dependingonthedevice,theremaybeseveraltechnologiesthatAndroidcanusetodeterminethecurrentloca+on

achtechnology,orLoca+onProvider,willofferdifferentcapabili+esincludingpowerconsump+on,monetarycost,accuracy,andtheabilitytodetermineal+tude,speed,orheadinginforma+on


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Loca+onProvider

Loca+onManagerclassincludessta+cstringconstantsthatreturntheprovidernameforthetwomostcommonLoca+onProviders Loca+onManager.GPS_PROVIDR Loca+onManager.NTWORK_PROVIDR

TogetalistofnamesforalltheprovidersBooleanenabledOnly=true;

Listproviders

=loca+onManager.getProviders(enabledOnly);


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Loca+onProvider

Mostscenarios,toexplicitlychoosetheloca+onprovidertouse

SpecifytherequirementsthataprovidermustmeetandletAndroiddeterminethebesttechnologytouse

UseCriteriaclasstodictatetherequirementsofaproviderintermsof Accuracy Power Cost Abilitytoreturnvaluesofal+tude,speed,andbearing


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Criteriaxample

.g.Criteriacriteria=newCriteria();

criteria.setAccuracy(Criteria.ACCURACY_COARS);

criteria.setPowerRequirement(Criteria.POWR_LOW);

criteria.setAl+tudeRequired(false);

criteria.setBearingRequired(false);criteria.setSpeedRequired(false);

criteria.setCostAllowed(true);

StringbestProvider=loca+onManager.getBestProvider(criteria,true);


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Criteria

IfmorethanoneLoca+onProvidermatches,theonewiththegreatestaccuracyisreturned.

IfnoLoca+onProvidermeetrequirements,thecriteriaisloosened,inthefollowingorder:PowerusedAccuracyAbilitytoreturnbearing,speedandal+tude


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Loca+onManager

ThepurposeofLBSistofindthephysicalloca+onofthedevice AccesstoLBSsishandledusingtheLoca+onManagersystem

Service.

ToaccesstheLoca+onManager,requestaninstanceoftheLOCATION_SRVICusingthegetSystemServicemethod .g.

StringserviceString=Context.LOCATION_SRVIC

Loca+onManagerloca+onManager;

loca+onManager=

(Loca+onManager)getSystemService(serviceString);


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Loca+onManager

BeforeusageofLoca+onManager Adduses-permissiontagstoyourmanifesttosupportaccesstotheLBShardware Defaultproviders

GPS Network

GPSproviderrequiresFinepermission NetworkproviderrequiresCoarsepermission

.g.


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RetrievingLoca+on

UsegetLastKnownLoca+onmethod .g.

Stringprovider=Loca+onManager.GPS_PROVIDR

Loca+onloca+on=loca+onManager.getLastKnowLoca+on(provider);

DoesnotasktheLoca+onProvidertoupdatethecurrentPosi+on.

Loca+onobjectreturns La+tude&Longitude Bearing Speed Timetheloca+onfixwastaken


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Geocoding

Translatebetweenstreetaddressesandlongitude/la+tudemapcoordinates.

Geocodingclassprovidestwogeocodingfunc+ons:

ForwardGeocoding Findthela+tudeandlongitudeofanaddress

ReverseGeocoding Findthestreetaddressforagivenla+tudeandlongitude


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Geocoding

Resultsarecontextualizedusingalocale Localeisusedtodefineyourusualloca+onandlanguage .g.

Geocodergeocoder=newGeocoder

(getApplica+onContext(),Locale.getDefault()); Geocodingfunc+onsreturnalistofAddressobjects Listcancontainseveralpossibleresults,uptoalimit

specifiedwhenmakingthecall


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Geocoding:warning

Geocodinglookupsareperformedsynchronously,sotheywillblockthecalling

thread.

Slowdataconnec+onscanleadtoanApplica+onUnresponsivedialog

BesttomovelookupsintoaServiceorbackgroundthread


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ReverseGeocoding

Returnsstreetaddresssforphysicalloca+ons,specifiedbylatutude/longitudepairs.

Passthetargetla+tudeandlongitudetoGeocodersgetFromLoca+onmethod

Returnalistofpossibleaddresses Returnnullifcouldnotresolveanyaddresses


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ReverseGeocoding:xample

Loca+on=loca+onManager.getLastKnownLoca+on(Loca+onManager.GPS_PROVIDR);

Doublela+tude=loca+on.getLa+tude();

Doublelongitude=loca+on.getLongitude();

Geocodergc=newGeocoder(this,Locale.getDefault());

Listaddresses=null;

Try{

addresses

=gc.getFromLoca+on(la+tude,longitude,10);

}catch(IOxcep+one){}


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ForwardGeocoding

Determinesmapcoordinatesforagivenloca+on CallgetFromLoca+onNameonaGeocoderinstance Passintheloca+onandthemaximumnumberofresultstoreturn

.g.Listresult=geocoder.getFromLoca+onName(aStreetAddress,

maxResults);

Returnedlistofaddresscanincludemul+plepossiblematchesforthenamedloca+on

achresultwillincludela+tudeandlongitudeandanyaddi+onaladdressinforma+onavaliableforthosecoordinates


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Forwardgeocoding

Ifnomatchesarefound,nullwillbereturned Availability,accuracy,andgranularityofgeocodingresults

willdependen+relyonthedatabaseavailableforthearea

Localespecifiedwhencrea+ngthegeocoderobjectispar+cularlyimportant

Thelocaleprovidesthegeographicalcontextforinterpre+ngsearchrequests,asthesameloca+onnamescanexistinmul+pleareas.

Considerselec+ngaregionalLocaletohelpavoidplacenameambiguity


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ForwardGeocoding:xample

GeocoderfwdGeocoder=Geocoder(this,Locale.US);

StringstreetAddress=180AngMoKioAvenue8Singapore

Listloca+ons=null;

Try{

loca+ons=fwdGeocoder.getFromLoca+onName(streetAddress,10);

}


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Map-BasedAc+vi+es

UsageofMapView Featureaninterac+vemap SupportsbothOverlaysandbypinningViewstogeographical

loca+ons

Offercontrolofthemapdisplay,lengyoucontrolthe

zoom loca+on displaymodes

Satellite Street Traffic


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Suppor+ngclasses

MapView ActualMapView

MapAc+vity BaseclassextendedtocreateanewAc+vitythatcanincludeaMapView.TheMapAc+vity

classhandlestheapplica+onlifecycleandbackgroundservicemanagementrequiredfordisplayingmaps.Asaresult,canonlyuseaMapViewwithinMapAc+vity-derivedAc+vi+es

Overlay

Classusedtoannotatemaps.nablestheusageofacanvastodrawanynumberoflayersthataredisplayedontopofaMapView

MapController Usedtocontrolthemap,allowingdeveloperstosetthecenterloca+onandzoomlevels

MyLoca+onOverlay Aspecialoverlaythatcanbeusedtodisplaythecurrentposi+onandorienta+onofthedevice

ItemizedOverlaysandOverlayItems Usedtogethertocreatealayrofmapmarkers,displayedusingdrawablewithassociatedtext.


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Crea+ngamap-basedac+vity

CreateanewAc+vitythatextendsMapAc+vity AddaMapViewtothelayouttodisplayaGoogleMapsinterfaceelement Maplibraryisnotastandardpackage,itmustbeexplicitlyincludedinthe

applica+onmanifest

Addusingauses-librarytagwithintheapplica+onnode .g.

Googlemapdownloadsthemap+lesondemand Requirespermissiontousetheinternet

.g.


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xample:Java

publicclassmyMapextendsMapAc+vity{

privateMapViewmapView;

/**Calledwhentheac+vityisfirstcreated.*/

@OverridepublicvoidonCreate(BundlesavedInstanceState){

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

mapView=(MapView)findViewById(R.id.map_view);

}

}


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xample:Xml


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xample:Manifest


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Moreexamples..

@Prac+cal

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