Hi Brad,
Thanks for your solution. I'm trying to understand how it works.
Is this generic for all zoom levels?
I don't know how to implement the if condition snippet of your code.
Something is missing me or I'm not understanding it right.
Can you explain this value:
latSpan/1E6, is this the simple getLatitudeSpan?
I'm sorry, I'm a little bit overwhelmed with this problem for some
days and I've been really confused.
On Jun 26, 2010, at 3:53 AM, Brad Gies wrote:
Pedro,
I've been working on roughly the same thing today... see the thread
MapView.getLatitudeSpan..
All you're running into is that the map isn't ready when you are
asking for the getLatitudeSpan, so you need to wait until it is
ready...OR...
the formula I've come up with to calculate it is this :
Note that I don't expect this formula is perfect.. and I can
certainly make it more compact and faster by reworking it, but for
working on it I wanted to do it step by step :).
private class LatLonSpans
{
@SuppressWarnings("unused")
public double LatSpan = 0.0;
@SuppressWarnings("unused")
public double LonSpan = 0.0;
}
private LatLonSpans getSpans()
{
LatLonSpans latLonSpans = new LatLonSpans();
Display display = getWindowManager().getDefaultDisplay();
int width = display.getWidth();
int height = display.getHeight();
int zoomLevel = mapView.getZoomLevel();
// zoomToPower times 256 should be equal to the pixels
required to view the entire world
// at the resolution I've set.
double zoomToPower = Math.pow(2, zoomLevel - 1);
// it takes 256 pixels to view the entire world at resolution
1, so this should be the pixels required to view the entire world
// at the resolution I've set.
double entireWorld = zoomToPower * 256;
// Now I need to scale the zoomToPower to my screen size to
figure
// out what I'm really going to see.
//
// this is how many pixels to see 1 degree.
double OneDegree = entireWorld / 360;
// and for height we have x pixels minus 40???? to account
for top bars..... so we will see this much of a degree.
double heightSpan = (height - 40) / OneDegree;
double widthSpan = width / OneDegree;
latLonSpans.LatSpan = heightSpan;
latLonSpans.LonSpan = widthSpan;
return latLonSpans;
}
and I'm using it like this :
if (mapView.getLatitudeSpan() == 0)
{
nvps.add(new BasicNameValuePair("latitudespan",
String.valueOf(latLonSpans.LatSpan)));
}
else
{
nvps.add(new BasicNameValuePair("latitudespan",
String.valueOf(latSpan / 1E6)));
}
Hope it helps... and if anyone can poke holes in my formula ..
PLEASE DO... I'd love to know it doesn't work BEFORE I start relying
on it. :).
On 25/06/2010 5:55 PM, Pedro Teixeira wrote:
New approach that makes more sense:
int latSpan = mapView.getLatitudeSpan();
int longSpan = mapView.getLongitudeSpan();
GeoPoint mapCenter = mapView.getMapCenter();
int topLatitude = mapCenter.getLatitudeE6() + (latSpan/2);
int bottomLatitude = mapCenter.getLatitudeE6() - (latSpan/2);
int leftLongitude = mapCenter.getLongitudeE6() - (latSpan/2);
int rightLongitude = mapCenter.getLongitudeE6() + (latSpan/2);
But this values:
int latSpan = mapView.getLatitudeSpan();
int longSpan = mapView.getLongitudeSpan();
are giving me 36000000 and 0 :/
On Jun 25, 2010, at 9:15 PM, Frank Weiss wrote:
Exactly. You need to pass the neLatitude, neLongitude, swLatitude,
swLongitude as query parameters to your back end web service, which
then returns only POIs whose latitude and longitude fall within
those
bounds, like this Javascript Google Map does:
http://myhome.bankofamerica.com/?findmlo=94114#/findmlo/94105
Notice that it even handles panning and zooming.
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Sincerely,
Brad Gies
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