Before you can use MobileMapViewer you will need to have a Google Maps account configured so that you can generate an API Key. Instructions for doing this on available from Google: Google Maps Platform, Get Google Maps API Key.

Google Maps is not free to use. Although there is some free usage available for testing your app, your account does get billed based on usage once the small amount of free testing credits are used up.

When you have your API Key, you can add it to your Xojo project using a new App property. Select App in the Navigator and in the Inspector, put the key in the Google Maps API Key field. Note that the key is not saved with text projects and is instead saved as part of the UI state file that is local to the development machine. This prevents the key from being accidently committed to a source code repository.

With the configuration work out of the way, you can now use the control. Drag a MobileMapViewer from the Library onto a screen. When you run the project you’ll see an interactive map that you can swipe, zoom and move around as you like.

This code shows Fenway Park in Boston:

FenwayLocation = New MapLocation("Fenway Park, Boston, MA USA")
FenwayLocation.Title = "Fenway Park"

MapViewer1.ZoomRadius = 5
MapViewer1.GoToLocation(FenwayLocation) // Center map within radius km

MapViewer1.AddLocation(FenwayLocation) // Drop a pin

The MobileMapVIewer API matches what has already been in use for iOS. You can also use the MapLocation class to track specific locations. Although the overall API matches what has been used for iOS, there is one exception: MapLocation.PointsOfInterest() is not yet implemented. Implementing this requires another Google SDK and API Key (the Places API) and is being reviewed for a future release. We may also consider adding alternative mapping engines as well.

Note: You can’t get there from here is an old Maine saying.

Paul learned to program in BASIC at age 13 and has programmed in more languages than he remembers, with Xojo being an obvious favorite. When not working on Xojo, you can find him talking about retrocomputing at Goto 10 and on Mastodon @lefebvre@hachyderm.io.

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Adding New Locations

Previously, the only way to add new locations to a MobileMapViewer on iOS was via code. Starting with Xojo 2023r4, the user can do this with a long press on the Map control itself. This will raise the new Pressed event handler providing the latitude and longitude parameters and allowing you to use these values to add a new MapLocation instance from the values; for example:

Var nl As New MapLocation( latitude, longitude )
MapViewer1.AddLocation nl

In addition, the user can now select any of the Pins previously added to the Map control and drag them to a new destination in the map.

Points of Interest

Another new feature for your Map-based iOS apps is the PointsOfInterest method for the MapLocation class. When this method is called on a MapLocation instance it will return an array of strings with the points of interest that are nearby. For example, relevant landscapes, monuments, museums, etc., just the kind of information the user may be interested in when walking around or when selecting any of the Pins in your app.

This line of code will retrieve points of interest (if any) from a MapLocation instance pointed by the “nl” variable:

Var pois() As String = nl.PointsOfInterest

Track the Distance

Another new method added to the MapLocation class on iOS is DistanceTo. This method is called on a MapLocation instance, expect to receive another MapLocation instance as the parameter. It will return a double value representing the distance, in kilometers, between the locations.

For example, this code added to the Pressed event of the MobileMapViewer will add the distance between a new location where the user long presses on the Map and a previous location saved in a Screen object property:

Var nl As New MapLocation( latitude, longitude )
MapViewer1.AddLocation nl

If PreviousLocation <> Nil Then
  distanceLabel.Text = nl.DistanceTo(PreviousLocation).toString
End If

PreviousLocation = nl

In Summary

With these additions and improvements available in Xojo 2023r4 for MobileMapViewer and MobileLocation on iOS, we expect you will be able to provide even more power and flexibility to your Map-based iOS apps! We can’t wait to see what you do with these!

Javier Menendez is an engineer at Xojo and has been using Xojo since 1998. He lives in Castellón, Spain and hosts regular Xojo hangouts en español. Ask Javier questions on Twitter at @XojoES or on the Xojo Forum.

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