How do I find the center of multiple points? Android

I have multiple points placed on my MapView and would like to centre the map on these points i.e. not any particular one, just the averaged centre of the lot 开发者_JAVA技巧of them.

I know there's a method for this in the Javascript G. Maps API. I was wondering whether there was a prexisting method to do this in Android?

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What you are trying to calculate is called a Centroid. There are several Java implementations for calculating centroids for a finite set of points (a polygon).

For example: JavaGeom has an implementation for finding the centroid of multiple 2D points.
I'm not sure if there's a standard android implementation for it, but it is fairly simple to implement yourself.

Simple implementation:

public static float[] centroid(float[] points) {
    float[] centroid = { 0, 0 };

    for (int i = 0; i < points.length; i+=2) {
        centroid[0] += points[i];
        centroid[1] += points[i+1];
    }

    int totalPoints = points.length/2;
    centroid[0] = centroid[0] / totalPoints;
    centroid[1] = centroid[1] / totalPoints;

    return centroid;
}

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this question looks suspiciously like one I had some time ago ...

Android MapView -setting zoom automatically until all ItemizedOverlay's are visible

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You could take the average of the points x and y respectively, and then set the span based on these values and introduce a padding like 25% more than the value to insure that there is enough space to focus on it.

for more info check this out: http://code.google.com/android/add-ons/google-apis/reference/index.html

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I would not use the centroid (or barycenter, or centre of mass in case of uniform density), if you need to show a figure (a shapre, an area) in a layout. What I really need to center a figure in a layout, is the maximum and minimum of all the coordinates to show every point.

ArrayList<GeoPoint> track;

public GeoPoint CenterMap() {
    double longitude = 0;
    double latitude = 0;
    double maxlat = 0, minlat = 0, maxlon = 0, minlon = 0;
    int i = 0;
    for (GeoPoint p : track) {
        latitude = p.getLatitude();
        longitude = p.getLongitude();
        if (i == 0) {
            maxlat = latitude;
            minlat = latitude;
            maxlon = longitude;
            minlon = longitude;
        } else {
            if (maxlat < latitude)
                maxlat = latitude;
            if (minlat > latitude)
                minlat = latitude;
            if (maxlon < longitude)
                maxlon = longitude;
            if (minlon > longitude)
                minlon = longitude;
        }
        i++;
    }
    latitude = (maxlat + minlat) / 2;
    longitude = (maxlon + minlon) / 2;
    return new GeoPoint(latitude, longitude);
}

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Don't take the average of points x and y.. Google "centroid psuedocode" and that should be what you want.