问题
I have over 200 polygons to create and I get the location by LocationListenerOnChanged() but I would like to know which polygon I am in based on the current location .
How will I use LatLng to check within within each polygon every 2 miles.And how can I make the entire process faster or will android os has inbuilt function.
I checked a lot of documents related android maps v2 but I did not get any info about it.I appreciate any help w.r.t the topic .Thanks in advance.
回答1:
There is no direct method in android api v2 to know if a latlng lies within a polygon. So you need to do a mathemetical calculation known as point inside polygon check. You can check out the below two methods suggested in earlier posts:
1, Raycasting method
2, Winding number method
If in your case, checking a point against all 200 or more polygons is slowing your app, you can consider reducing the number of polygons to be checked. First of all , for each polygon, other than their vertices, also store an approximate geometric center. Then when you get a new location for checking, find the distance between this location and the geometric center of all the polygons. Now take only few polygons ( say 8) whose centers are closest to the point and then do any of the above point inside polygon check for those chosen polygons.
来源：https://stackoverflow.com/questions/19106556/get-location-address-w-r-t-the-polygon-i-am-in