Develop Reference

Check if latitude and longitude lies in geofenceing radius

I'm working on an application. I need geo-fencing to check whether a particular
latitude and longitude lies within a specific radius. I'm following a tutorial on geo-fencing but my problem is that I dont know where to pass the latitude and longitude that I want to check
Tutorial Link:
https://code.tutsplus.com/tutorials/how-to-work-with-geofences-on-android--cms-26639

Here
.setCircularRegion( LATITUDE, LONGITUDE, RADIUS)
When the IntentService detect the transition (enter, exit or dwell) on region specified the onHandleIntent() will be called and you can do your action (alert or anything)

#tkrz 's formula is correct.
(lat-center_lat)^2 + (lon - center_lon)^2 < radius^2
The left side is square of distance between my location to the geofence center point. The right part is square of radius of the geofence circle.
Lets say, if the distance is smaller than the radius of the circle, it means I am standing inside the geofence area, and vice versa.

If you only want to check this (not using mechanism for notifications) you will need some math:
(lat-center_lat)^2 + (lon - center_lon)^2 < radius^2

Move markers by a specific distance in meters from where they are

I have a collection of items and some of them may have the same coordinates.
As a result they are displayed as 1 marker in Google Maps since the markers are painted one on top of each other.
To address this I tried to "move" those markers by a few meters so that the markers do not collide.
I would like to move them to a 5 meters from where their location is.
I did the following following another SO answer:
double newLat = item.getLatitude() + (Math.random() - .005) / 15000;
double newLon = item.getLongitude() + (Math.random() - .005) / 15000;
The problem is that this moves the items a bit but it seems that some are moved by 4m others by 3m and I would like if possible to ensure that I will be between 4-6 meters (min/max)
How can I change my formula to do this?

I think that the best option could be using the SphericalUtil. computeOffset method from the Google Maps Android API Utility Library:
computeOffset
public static LatLng computeOffset(LatLng from,
double distance,
double heading)
Returns the LatLng resulting from moving a distance from an origin in the specified heading (expressed in degrees clockwise from north).
Parameters:
from - The LatLng from which to start.
distance - The distance to travel.
heading - The heading in degrees clockwise from north.
In your case you can set the distance to be 5 meters and randomise the heading parameter to be something between 0 and 360 degrees:
Random r = new Random();
int randomHeading = r.nextInt(360);
LatLng newLatLng = SphericalUtil.computeOffset(oldLatLng, 5, randomHeading);

How can I trigger the Several Functionality of Google Maps in my App

I am trying to create a maps app for a certain city that have some stored latitude and longitude for certain landmarks in the city. In the map,
you can only zoom in and zoom out within the boundaries of the city
While the app is open, when you reach a certain range of lat and long coordinates within a certain radius around the landmark, it will trigger and activity that will display details about the landmark and also a voice recording about the landmark
also, the map must also have the "directions" functionality in it, where it can show several possible ways for you to get to a certain location (like landmark) from your present location and also display the distance between two points
I've already tried a GPS program from androidhive that detects your lat and long coordinates. I'm also trying to understand how to acquire and use the google maps api. I would like to know the possible approaches in doing it since I'm still new to android.
Thanks in Advance!

you can zoom with specific mile or kmeter by this code:this is for two mile:
Display display = getWindowManager().getDefaultDisplay();
// double equatorLength = 3218; // in meters
double equatorLength = 40075004; // in meters
double widthInPixels = display.getWidth();
double metersPerPixel = equatorLength / 256;
int zoomLevel = 1;
// 2 mile=3218 mtr
while ((metersPerPixel * widthInPixels) > 3218) {
metersPerPixel /= 2;
++zoomLevel;
}
return zoomLevel;
hope this is helpfull for "you can only zoom in and zoom out within the boundaries of the city"

Get pixel distance in meters for mapView

I want to know how much meters is a certain pixel distance, at a given zoom level.
Reason: I want to know the radius, in meters, of a circle in the mapView, which fits perfectly in the mapView -> radiusPixels = mapView.getWidth()/2;
I found the method mapView.getProjection().metersToEquatorPixels(radiusMeters), which does the opposite of that what I need. But there's no inverse for this method or anything else useful.
My (probably naive) approach to solve it is as follows:
private double getFittingRadiusInMeters() {
return getMeters(mapView.getWidth() / 2);
}
private double getMeters(int pixels) {
Projection proj = mapView.getProjection();
Point mapCenterPixels = new Point(mapView.getWidth() / 2, mapView.getHeight() / 2);
//create 2 geopoints which are at pixels distance
GeoPoint centerGeoPoint = proj.fromPixels(mapCenterPixels.x, mapCenterPixels.y);
GeoPoint otherGeoPoint = proj.fromPixels(mapCenterPixels.x + pixels, mapCenterPixels.y);
Location loc = new Location("");
loc.setLatitude(centerGeoPoint.getLatitudeE6() / 1E6);
loc.setLongitude(centerGeoPoint.getLongitudeE6() / 1E6);
Location loc2 = new Location("");
loc2.setLatitude(otherGeoPoint.getLatitudeE6() / 1E6);
loc2.setLongitude(otherGeoPoint.getLongitudeE6() / 1E6);
return loc.distanceTo(loc2);
}
But it doesn't work well. I always get circles which are far smaller than the mapView - the radius is too small.
I know the distanceTo method says "approximate" but the radius differ significantly from the expected size. Should not be an effect of the approximation.
Thanks.

There is a small mistake in your approach.
You are calculating the value for screen half with at screen center level. The distance found is only valid to draw a circle at the same Latitude value (the Longitude may change without problem).
Because earth is shperic, the distance for the same number of pixels calculated at different Latitude levels, produces different results. Moving from Equador level to position closer to Pole level, same number of pixels result a in smaller distance in meters.
However, this will only be noticable if you call getFittingRadiusInMeters() with map positioned in a very distant Latitude from where you draw the circle.
Otherwise, it should work fine.
Solution
The method getMeters() should receive as parameter a GeoPoint (or at least the Latitude) that should be used to calculate the distance.
Regards.

Android: MapView.GetLatitudeSpan(), GetLongitudeSpan() Anomaly?

I'm working on a mapping app that plots pins on a MapView based on a user's query. I'm trying to scale the map to fit all the results pins, but I've run into a seemingly strange situation.
I have two variables set up:
latSpan is the difference between the maximum latitude and minimum latitude of any of the results points
lonSpan is the difference between the maximum longitude and minimum longitude of any of the results points
This method
while ((mapView.getLatitudeSpan()) < latSpan) || (mapView.getLongitudeSpan() < lonSpan)){
mapController.zoomOut();
}//end of while loop
is supposed to zoom out to make sure all the pins fit on the viewable map screen.
But I'm experiencing something rather strange. The results of mapView.getLatitudeSpan() and mapView.getLongitudeSpan() are routinely greater than my latSpan and lonSpan values, so the MapController doesn't zoom out enough.
My map is zoomed in pretty far--level 15 or higher.
As an example, one set of search results gave the following values:
latSpan = 17928
lonSpan = 11636
mapView.getLatitudeSpan() = 21933
mapView.getLongitudeSpan() = 20598
Based on these numbers, you wouldn't think that the MapController would need to zoom out. Yet there are pins plotted both above the top and below the bottom of the screen. I changed my WHILE loop to read
while ((mapView.getLatitudeSpan() - 6000) < latSpan...
and that helps, but the right query will still cause issues.
But the real question is, why is this happening?

I'm not sure why you're code isn't working from the snippet provided. Its possible that you are not converting your latSpan and lonSpan to microDegrees (as shown below) and this would cause some issues.
Also if you're trying to make sure your mapView is showing all of the results, there's not much point trying to determine if it needs to zoom before zooming, just zoom it every time. If it turns out that it doesn't need to zoom then nothing will appear to happen and if it does then it does.
You can set a map up to encompass all of your points and move to the centroid of the points as follows:
GeoPoint max = new GeoPoint(maxLatitude, maxLongitude);
GeoPoint min = new GeoPoint(minLatitude, minLongitude);
int maxLatMicro = max.getLatitudeE6();
int maxLonMicro = max.getLongitudeE6();
int minLatMicro = min.getLatitudeE6();
int minLonMicro = min.getLongitudeE6();
GeoPoint center = new GeoPoint((maxLatMicro+minLatMicro)/2,(maxLonMicro + minLonMicro)/2);
controller.zoomToSpan(maxLatMicro - minLatMicro, maxLonMicro - minLonMicro);
controller.animateTo(center);