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This article introduces the relevant knowledge of "how to use Flutter location package to obtain geographical location". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Get the geographic location in Flutter

Today, discovering user locations is a very common and powerful use case for mobile applications. If you've ever tried to implement location in Android, you know how complex and confusing the sample code can become.

But this is different from Flutter-it has a lot of amazing packages that abstract boilerplate code for you and make geolocation a dream. Another good thing is that you can get these features on Android and iOS.

Let's take a quick look at what we are building today to collect location data:

This article will take you through two of the most popular and easy-to-use Flutter geolocation packages.

Let's start with location, which is Flutter's favorite package. There's nothing to it. With three simple steps, you can get the current user location and process location permissions.

precondition

Before we move on, let's take a quick look at what we need:

The FlutterSDK

Editor: you can use Visual Code or Android Studio

At least a rudimentary understanding of Flutter

That's pretty much it!

Use Flutter location package Settings

Add dependencies to your file: pubspec.yaml

Location: ^ 4.3.0

Because Android and iOS handle permissions differently, we have to add them separately on each platform.

Android version

Add the following location permissions to: AndroidManifest.xml

If you also want to access the user's location in the background, use the API before accessing the background location and add background permissions in the manifest file: enableBackgroundMode ({bool enable})

For iOS

Add the following location permissions to: Info.plist

NSLocationWhenInUseUsageDescription this application requires access to your location

NSLocationWhenInUseUsageDescription is the only license you need. This also allows you to access the background location, and the only thing to note is that when the application accesses the location in the background, a blue badge appears in the status bar. Unlike Android, we added separate permissions to access the user's location in the background.

Location permission

We need to check the location service status and permission status before requesting the user location, which can be easily done with the following lines of code:

Location location = new Location (); bool _ serviceEnabled;PermissionStatus _ permissionGranted;_serviceEnabled = await location.serviceEnabled (); if (! _ serviceEnabled) {_ serviceEnabled = await location.requestService (); if (! _ serviceEnabled) {return null;}} _ permissionGranted = await location.hasPermission (); if (_ permissionGranted = = PermissionStatus.denied) {_ permissionGranted = await location.requestPermission (); if (_ permissionGranted! = PermissionStatus.granted) {return null;}}

First, we create an object provided by the Location () package, and location in turn provides us with two useful methods. Check if the device location is enabled or if the user has manually disabled it. ``serviceEnabled ()

For the latter, we display a native prompt that allows the user to quickly enable the location by calling, and then we check again if they enable it from the prompt. RequestService ()

Once we have determined that location service is enabled, the next step is to check whether our application has the necessary permissions to use it by calling it, which will return .hasPermission () ``PermissionStatus

PermissionStatus is an enumeration that can have one of the following three values:

PermissionStatus.granted: location service permission has been granted

PermissionStatus.denied: location service permission denied

PermissionStatus.deniedForever: the location service permission is permanently denied by the user. This applies only to iOS. The dialog box requestPermission () is not displayed in this case.

If the status is, we can call the system prompt that displays the requested location permission. For status, we can access location immediately, so we return a .null, ``requestPermission () ``granted``null

If you also want to access the user location in the background, use. Location.enableBackgroundMode (enable: * * true**)

Get the current location

If location services are available and the user has been granted location permissions, then we only need two lines of code to get the user's location-no, I'm not kidding:

LocationData _ locationData;_locationData = await location.getLocation ()

The LocationData class provides the following location information:

Class LocationData {final double latitude; / / Latitude, in degrees final double longitude; / / Longitude, in degrees final double accuracy; / / Estimated horizontal accuracy of this location, radial, in meters final double altitude; / / In meters above the WGS 84 reference ellipsoid final double speed; / / In meters/second final double speedAccuracy; / / In meters/second, always 0 on iOS final double heading; / / Heading is the horizontal direction of travel of this device, in degrees final double time; / / timestamp of the LocationData final bool isMock; / / Is the location currently mocked}

You can also get continuous callbacks by adding onLocationChanged listeners to listen for location updates when the user's location changes, which is a good use case for taxi applications, driver / rider applications, and so on:

Location.onLocationChanged.listen ((LocationData currentLocation) {/ / current user location})

Note that once you want to stop listening to updates, don't forget to unsubscribe to the stream.

Look at that! Now we have the current latitude and longitude of the user's location.

Let's use these latitude and longitude values to get the user's full address or reverse geocoding.

To do this, we will use another amazing Flutter package: geocode.

Use Flutter geocoding package settings

Add dependencies to your file: pubspec.yaml

Dependencies: geocode: 1.0.1 get the address

It's easy to get an address. Just call. okay! The complete function with null check is as follows: reverseGeocoding (latitude: lat, longitude: lang)

Future _ getAddress (double? Lat, double? Lang) async {if (lat = = null | | lang = = null) return ""; GeoCode geoCode = GeoCode (); Address address = await geoCode.reverseGeocoding (latitude: lat, longitude: lang); return "${address.streetAddress}, ${address.city}, ${address.countryName}, ${address.postal}";}

It's not that simple!

The complete code is as follows:

Class GetUserLocation extends StatefulWidget {GetUserLocation ({Key? Key, required this.title}): super (key: key); final String title; @ override _ GetUserLocationState createState () = > _ GetUserLocationState ();} class _ GetUserLocationState extends State {LocationData? CurrentLocation; String address = "" @ override Widget build (BuildContext context) {return Scaffold (appBar: AppBar (), body: Center (child: Padding (padding: EdgeInsets.all), child: Column (mainAxisAlignment: MainAxisAlignment.center, children: [if (currentLocation! = null) Text ("Location: ${currentLocation?.latitude}, ${currentLocation?.longitude}") If (currentLocation! = null) Text ("Address: $address"), MaterialButton (onPressed: () {_ getLocation (). Then ((value) {LocationData? Location = value; _ getAddress (location?.latitude, location?.longitude) .then (value) {setState (() {currentLocation = location; address = value;}) }, color: Colors.purple, child: Text ("Get Location", style: TextStyle (color: Colors.white),],)) } Future _ getLocation () async {Location location = new Location (); LocationData _ locationData; bool _ serviceEnabled; PermissionStatus _ permissionGranted; _ serviceEnabled = await location.serviceEnabled (); if (! _ serviceEnabled) {_ serviceEnabled = await location.requestService (); if (! _ serviceEnabled) {return null;}} _ permissionGranted = await location.hasPermission (); if (_ permissionGranted = = PermissionStatus.denied) {_ permissionGranted = await location.requestPermission () If (_ permissionGranted! = PermissionStatus.granted) {return null;}} _ locationData = await location.getLocation (); return _ locationData;} Future _ getAddress (double? Lat, double? Lang) async {if (lat = = null | | lang = = null) return ""; GeoCode geoCode = GeoCode (); Address address = await geoCode.reverseGeocoding (latitude: lat, longitude: lang); return "${address.streetAddress}, ${address.city}, ${address.countryName}, ${address.postal}";} common traps

Although these packages make our lives easier, and we don't have to deal with the complex process of accessing locations locally in Android and iOS, you may face a lot of problems. Let's take a look at them and the steps that can help you fix these problems:

Application memory leak: if you have been listening to location updates, be sure to unsubscribe from streaming once you want to stop listening to updates

The user must accept location permissions to always allow the use of background locations. The always allowed Android 11 option is not displayed in the location permissions dialog box prompt. The user must enable it manually from the application settings

Users may permanently refuse to locate on the iOS, so native prompts for location permissions are not displayed. Be sure to handle this edge case requestPermisssions ()

Users may revoke location permissions from application settings at any time, so before accessing location data, be sure to check them when the application resumes

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