Develop Reference

Drawing on the MapFragment, while keeping some elements visible

I'm developing an application that has the following goal:
Using the google maps android API 2 I get my current position, and as I start walking the application starts drawing the route I take
The twist is that the map is a "blind" map. Meaning the map is hidden, only the Marker of my current position and a dotted line of my route is shown.
Keep in mind I'm a novice developing to Android, so please be specific. (Thank you)
I managed to create the map, get my current position and zoom in to it (Had no sens to see the whole planet while i want only my current position). And it's pretty accurate so far.
The thing is I don't know what should I do from this point on.
Basicly I need a white View between the Marker and the real map. Also as I advance that View should always be on, over the MapFragment/MapView. Also I wish to keep the zoom and drag functionality's of the MapFragment.
How can I achieve this?
At this point I'm opened to any solutions.
(Been browsing for a few days now the developers site, I have seen that with the ViewOverlay class I can put messages over the map, but I'm not sure what would the correct aproach be in my case...)

To hide the whole map behind the white view I would use Polygon class Polygon Even if you specify Polygon to cover the whole map Markers will be still displayed in front of it and as so user's current position marker will be visible. You also will be able to zoom and drag.
To draw line on map use Polyline class Polyline It will draw users path as a polyline. If you want to stick with dotted line you can use Circle objects to create it. Circle

Android google maps zoom to fit mark and current position

I'm trying to create a custom "my location" button for my app using Google Maps.
What I'm trying to do is to center the map around the location of the user, which is already done and working flawlessly, but also want to zoom in just enough to see a marker of my choice (this is actually the closest of a set of markers I have in memory, but that's not important now).
I haven't been able to find how the zoom variable works here. If I know the marker I want to show is 0.5 GPS units away from me, how can I center the map around me in a way that includes that marker on its boundaries? I'd also use a padding to make sure it perfectly fits in the map.
LatLng my_coordinates = ...;
LatLng closest_mark = ...;
map.animateCamera(CameraUpdateFactory.newLatLng(my_coordinates));
So now I want to modify that code to not only center the position to my_coordinates but also make sure zoom will make closest_mark fit in the viewport
CameraUpdateFactory.newLatLngBounds( ?? , /*padding*/);

I don't think there is a specific zoom variable in the api you can control along with the points in the map. (And LatLngBounds just takes in the upper right and lower left bounds and gets you a view accordingly).
I believe what you could do is with a little geometry. If your marker is very close to your location (you can consider it a rectangle), get the distance between the two and extrapolate that on the opposite direction with the same distance (multiple by a small factor if you want some padding) to get the other coordinates, and then you can get the upper right and lower left coordinates (simple geometry).
If your marker is quite far and the surface of the earth comes into picture, you may have to use the haversine formula (great circle distance).
Hope this helps.

Android: How To: display a map (still image file) with a moving current location pointer

I am trying to create a prototype that could guide a person to his destination place.
place is a wide building with several floors.
i can obtain/retrieve the maps (still images). e.g. current:1F destination:5F; so I can get the still images of 1st,2nd...5th floors (5 image files).
Scenario:
start the application
input the current location (or may automatically set using current location) & destination
click the search route button to search the maps to use (still images) & mark the current location & destination
update the current location upon moving/going to destination
Problem:
I just need to display 1 image file (each floor) at a time then move to other floor by using scroll bar. But.. don't know how to display it.
I can get the current location coordinate via WiFi but don't know how to put it into still image to mark the current location.
For sure there is already look a like sample application available.
Could you share the concepts/ideas or would you include the code snippets. Big Help with my thesis.
Any guidance on the right direction is appreciated.

You have a couple possibilities, create your own MapView like object to provide scrolling ot overlay your map on the Google Api. Example usage of the MapView Api is available through the Location dev guide.
To do this via your own View will be easier if you understand basic graphics programming and transformations for zoom and pan. (If you're good at math it will be no trouble to learn). Use an ImageView with android:scaleType="matrix" override the MotionEvent handler to get the touches then process them into a tranlation and zoom matrix.
To associate the indicator to the image make two pixels into anchor points that coorespond to a real life lat/long. Usually its (0,0) and (width,height) of a rectangular image. Make your life easier and make sure the images are to scale. Then using a second ImageView (for the indicator) draw it on top and move it to the correct place on the screen and make sure the background in this View is transparent as well as the background of your indicator or you'll have a rectangular block "halo".
Be sure to check the accuracies of each location given by the LocationManager.
Additional Content
onCurrentPosition(Location current){
double hypotenuse = upperLeft.distanceTo(current);
double bearing = upperLeft.bearingTo(current);
double currentDistanceX = Math.cos(bearing) * hypotenuse;
// "percentage to mark the position"
double currentPixelX = (currentDistanceX / upperLeft.distanceTo(lowerRight) * Math.cos(upperLeft.bearingTo(lowerRight))) * mapWidth;
moveIndicatorX(currentPixelX);
}

How to detect Google MapView movement in Android?

I'd like to dynamically update the map/ load new map overlays every time my user moves it a certain amount of distance. How do I go about doing this? Is there a listener for every time the user moves the map? Most likely I'd just measure the distance between the center points.
Thanks!

Try this to detect the map movements:
http://pa.rezendi.com/2010/03/responding-to-zooms-and-pans-in.html
On start and after the map has been moved, you should save the current map center. As the article suggests, track ACTION_UP to determine when the user has finished a map movement. Then, compare the new map center with the old map center. To get the map centers use MapView's getMapCenter():
http://code.google.com/android/add-ons/google-apis/reference/com/google/android/maps/MapView.html#getMapCenter()
EDIT: I have done some additional work on this, and have a complete application with code for your enjoyment. This blog post explains a timer solution to this and contains a link to Github source:
http://bricolsoftconsulting.com/extending-mapview-to-add-a-change-event/

The map interface unfortunately does not include any listeners to monitor map actions (zoom/pan). You'll need to set up a timer of some sort that checks the center/zoom levesl to figure out if things have changed and update accordingly.

You could do this by overriding the onTouch(...) method in your Activity (so that every time the user pans the map, you could recalculate the map boundaries). You would need to know the map's zoom level and boundaries, etc, in order to load these overlays based on map distances.

Android custom GPS map application

I want to build an app that uses GPS data and a building map I provide to show the user where in the building on the map they are. This will be done in a specific building that i already know gets GPS and cell service.
At first I thought the easiest way to do this was to see if I could use Google maps to plot the users location and then just "overlay" my custom building map on top of the Google map so that I wouldnt have to deal with any of the gps information or the complexities of the mapping I would just have to scale my "overlay" to fit properly on top of the Google map so that the user was shown in the correct room in a building. I'm wondering if anyone can provide me any information on how to do this or if there is an easier way to accomplish my map. Any information at all is helpful!

You want...
Google Map View
...and more specifically you will probably want to read the subsection appropriately titled: "Part 2: Adding Overlay Items"
EDIT: Whoops! Nevermind! I misread your question... that is only if you want to overlay an item on the map. Sorry...

There is no possibility to use closer zoom level than that you can see on standard GMap i.e. in browser. Other problem is that google uses GeoPoint class based on cardinal microdegrees to draw overlays, and it's accuracy is to low.
You can look on jGarminImg - it's java library - unfortunately written for using with swing, but it should be relatively easy to make it work with android. On the other hand - you have to make your own map.
You can use standard overlays, or you can make your map in kml format and use this example to display it.

You may be able to achieve this with a custom view that displays your building plan and knows the precise co-ordinates of each corner of the building.
When you receive your location updates you can add a marker to your custom view by translating the real world position into a position in the image using something along the lines of:
pseudocode:
markerX = realWorldX - mapStartX;
markerY = realWorldY - mapStartY;
if( isOnMap( markerX, markerY ) )
{
drawMarker( markerX, markerY );
}

Yes you can overlay bitmap images on top of the Google MapView.
All you have to do is subclass the Overlay class, override the draw method, and draw on the canvas. You have to provide a rectangle of GeoPoints (probably the top left and the bottom right corners) to anchor the building bitmap on top of the MapView. You use mapView.getProjection() to translate the latitude and longitude into xy coordinates on the canvas.
I assume drawBitmap(Bitmap bitmap, Rect src, RectF dst, Paint paint) will be useful here. Bear in mind that src and paint can be null. If the GeoPoints you used are accurate, the bitmap will adjust automatically to pans and zooms, although it might get pixelated if the user zooms in too much.
edit: I am not so confident that Google Maps will have your building stays at the exact same GeoPoints in different zoom levels, so you might have to adjust those values for different zoom levels

If you need only the map of the building, it should not be too difficult to plot the location on an image without using Google Maps, provided that you can determine your location as coordinates inside the building.
You need to know two coordinates: north-west and south-east corners of the building map you are using. When you get GPS location updates, the correct location on the map image can be easily calculated based on these corner coordinates.

I would do it like this,
Place a marker on the google map to indicate the position of the building
Drilling down on the building would load your building map as a custom view. Plot the user location on the custom view
I think trying to overlay your building map on a google map while possible will be more complex to code than doing it via a custom view.
Also overlaying the lowest zoom level with your building map is not going to give you enough resolution unless you have a thumping big building. Whole blocks are pretty small
One issue you have probably already considered is the device will revert to cell tower and wifi for it's location when inside the building giving you a less accurate location fix.