Android 百度地图 缩放级别 自适应

很多时候我们需要在百度地图上添加自己的多个Marker，可是如何做到多个Marker能够在同一个手机屏幕视野中显示出来呢？其实也就是控制百度地图的一个自身缩放级别。如下图：

首先，我们得了解百度地图Android SDK v3.5.0从3.5版本开始，它的缩放级别从3-20，总共18个级别，如下：

{"10m", "20m", "50m", "100m", "200m", "500m", "1km", "2km", "5km", "10km", "20km", "25km", "50km", "100km", "200km", "500km", "1000km", "2000km"} 

Level依次为：20、19、18、17、16、15、14、13、12、11、10、9、8、7、6、5、4、3

比如上图中的两个Marker，我们可以先计算出两个点之间的距离，从而判断设置其Level。

mBaiduMap.setMapStatus(MapStatusUpdateFactory.newMapStatus(new MapStatus.Builder().zoom("级别").build()));

最后，如何通过经纬度计算两个Marker之间的距离呢？贴出代码…….

    /**     * 计算两个Marker之间的距离     * @param terminal     * @param latNLng     */    private double calculateDistance() {        double distance = GeoHasher.GetDistance(latitude01, longitude01, latitude02, longitude02);        return distance;    }

再给出一个工具类：

import java.util.HashMap;import java.util.Map;/** * 通过经纬度计算距离的工具类 * @author Botision.Huang */public class GeoHasher {    private static String BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz";    private static double EARTH_RADIUS = 6378.137;    private static double rad(double d) {        return d * Math.PI / 180.0;    }    public static String convertToString(char[] a) {        String s = "";        for (int i = 0; i < a.length; i++) {            s += a[i];        }        return s;    }    public static double GetDistance(double lat1, double lng1, double lat2,            double lng2) {        double radLat1 = rad(lat1);        double radLat2 = rad(lat2);        double a = radLat1 - radLat2;        double b = rad(lng1) - rad(lng2);        double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2)                + Math.cos(radLat1) * Math.cos(radLat2)                * Math.pow(Math.sin(b / 2), 2)));        s = s * EARTH_RADIUS;        return s;    }    public String encode_geohash(double latitude, double longitude,            int precision) {        char[] geohash = new char[precision + 1];        boolean is_even = true;        int i = 0;        double[] lat = new double[2];        double[] lon = new double[2];        double mid;        char bits[] = { 16, 8, 4, 2, 1 };        int bit = 0, ch = 0;        lat[0] = -90.0;        lat[1] = 90.0;        lon[0] = -180.0;        lon[1] = 180.0;        while (i < precision) {            if (is_even) {                mid = (lon[0] + lon[1]) / 2;                if (longitude > mid) {                    ch |= bits[bit];                    lon[0] = mid;                } else                    lon[1] = mid;            } else {                mid = (lat[0] + lat[1]) / 2;                if (latitude > mid) {                    ch |= bits[bit];                    lat[0] = mid;                } else                    lat[1] = mid;            }            is_even = !is_even;            if (bit < 4)                bit++;            else {                geohash[i++] = BASE32.charAt(ch);                bit = 0;                ch = 0;            }        }        geohash[i] = 0;        String s = "";        for (i = 0; i < geohash.length; i++)            s += geohash[i];        return s;    }    public String[] expand(String geoStr) {        String eastNeighbour = getEastNeighbour(geoStr);        String westNeighbour = getWestNeighbour(geoStr);        String northNeighbour = getNorthNeibour(geoStr);        String southNeighbour = getSouthNeibour(geoStr);        String[] expandGeoStr = { geoStr, eastNeighbour, westNeighbour,                northNeighbour, southNeighbour, getNorthNeibour(westNeighbour),                getNorthNeibour(eastNeighbour), getSouthNeibour(westNeighbour),                getSouthNeibour(eastNeighbour) };        return expandGeoStr;    }    public String getEastNeighbour(String geoStr) {        Map<String, Object> map = extractLonLatFromGeoStr(geoStr);        long lon = (Long) map.get("lon") + 1;        return getGeoStrFrom(lon, (String) map.get("latBitStr"), true);    }    public String getWestNeighbour(String geoStr) {        Map<String, Object> map = extractLonLatFromGeoStr(geoStr);        long lon = (Long) map.get("lon") - 1;        return getGeoStrFrom(lon, (String) map.get("latBitStr"), true);    }    public String getNorthNeibour(String geoStr) {        Map<String, Object> map = extractLonLatFromGeoStr(geoStr);        long lat = (Long) map.get("lat") + 1;        return getGeoStrFrom(lat, (String) map.get("lonBitStr"), false);    }    public String getSouthNeibour(String geoStr) {        Map<String, Object> map = extractLonLatFromGeoStr(geoStr);        long lat = (Long) map.get("lat") - 1;        return getGeoStrFrom(lat, (String) map.get("lonBitStr"), false);    }    public Map<String, Object> extractLonLatFromGeoStr(String geoStr) {        boolean is_even = true;        char bits[] = { 16, 8, 4, 2, 1 };        int bit = 0, ch = 0;        int geoIdx;        String lonBitStr = "";        String latBitStr = "";        long lon = 0;        long lat = 0;        for (int i = 0; i < geoStr.length(); i++) {            geoIdx = BASE32.indexOf(geoStr.charAt(i));            for (bit = 0; bit < 5; bit++) {                ch = geoIdx & bits[bit];                if (is_even) {                    if (ch != 0) {                        lonBitStr += "1";                        lon = lon * 2 + 1;                    } else {                        lonBitStr += "0";                        lon = lon * 2;                    }                } else {                    if (ch != 0) {                        latBitStr += "1";                        lat = lat * 2 + 1;                    } else {                        latBitStr += "0";                        lat = lat * 2;                    }                }                is_even = !is_even;            }        }        Map<String, Object> map = new HashMap<String, Object>();        map.put("lonBitStr", lonBitStr);        map.put("latBitStr", latBitStr);        map.put("lat", lat);        map.put("lon", lon);        return map;    }    public String getGeoStrFrom(long lonOrLat, String lonOrLatStr, boolean isLon) {        String lonBitStr = "";        String latBitStr = "";        if (isLon) {            lonBitStr = Long.toBinaryString(lonOrLat);            latBitStr = lonOrLatStr;        } else {            latBitStr = Long.toBinaryString(lonOrLat);            lonBitStr = lonOrLatStr;        }        boolean is_even = true;        String geoStr = "";        int ch, bit;        int geoStrLength = (lonBitStr.length() + latBitStr.length()) / 5;        for (int i = 0; i < lonBitStr.length();) {            ch = 0;            for (bit = 0; bit < 5; bit++) {                if (is_even)                    ch = ch * 2 + lonBitStr.charAt(i) - '0';                else {                    if (i < latBitStr.length())                        ch = ch * 2 + latBitStr.charAt(i) - '0';                    else                        bit--;                    i++;                }                is_even = !is_even;            }            geoStr += BASE32.charAt(ch);            if (geoStr.length() == geoStrLength)                return geoStr;        }        return geoStr;    }}