我正在使用android中的地图静态api开发一个应用程序
这是业务逻辑，用这个位置从google静态api获取用户位置请求并围绕这个位置画一个圆圈
这是我正在使用的代码
https://maps.googleapis.com/maps/api/staticmap?center=29.31166,47.481766&zoom=7&size=600x300&maptype=roadmap&key=My Key
现在的问题是如何在它周围画一个圆圈，我搜索了它，发现它是使用路径完成的，但不明白如何获得该路径
【问题讨论】：
标签： android google-maps android-maps-v2 google-static-maps
你只需要像Developers Guide一样绘制路径：
http://maps.googleapis.com/maps/api/staticmap?center=29.31166,47.48177&zoom=7&size=600x300&path=color:0x0000FFFF|weight:3|fillcolor:0x0000FF77|<FIRST_POINT_LAT>,<FIRST_POINT_LNG>|<SECOND_POINT_LAT>,<SECOND_POINT_LNG>|...|<LAST_POINT_LAT>,<LAST_POINT_LNG>&key=<YOUR_API_KEY>
<FIRST_POINT_LAT>,<FIRST_POINT_LNG>|<SECOND_POINT_LAT>,<SECOND_POINT_LNG>|...|<LAST_POINT_LAT>,<LAST_POINT_LNG> 是你的圆路径的坐标。对于它的计算，你可以使用这样的方法：
private List<LatLng> getCirclePoints(LatLng center, double radius) {
List<LatLng> circlePoints = new ArrayList<>();
// convert center coordinates to radians
double lat_rad = Math.toRadians(center.latitude);
double lon_rad = Math.toRadians(center.longitude);
double dist = radius / 6378137;
// calculate circle path point for each 5 degrees
for (int deg = 0; deg < 360; deg += 5) {
double rad = Math.toRadians(deg);
// calculate coordinates of next circle path point
double new_lat = Math.asin(Math.sin(lat_rad) * Math.cos(dist) + Math.cos(lat_rad) * Math.sin(dist) * Math.cos(rad));
double new_lon = lon_rad + Math.atan2(Math.sin(rad) * Math.sin(dist) * Math.cos(lat_rad), Math.cos(dist)
- Math.sin(lat_rad) * Math.sin(new_lat));
// convert new lat and lon to degrees
double new_lat_deg = Math.toDegrees(new_lat);
double new_lon_deg = Math.toDegrees(new_lon);
circlePoints.add(new LatLng(new_lat_deg, new_lon_deg));
}
return circlePoints;
}
您可以用这种方式格式化静态地图 API URL：
private String buildStaticApiUrlWithCircle(LatLng mapCenter, int zoom, int width, int height,
LatLng circleCenter, double circleRadius, int pathWeight, String pathColor, String fillColor) {
List<LatLng> circlePoints =getCirclePoints(circleCenter, circleRadius);
StringBuilder url = new StringBuilder();
url.append("http://maps.googleapis.com/maps/api/staticmap?");
url.append(String.format("center=%8.5f,%8.5f", mapCenter.latitude, mapCenter.longitude));
url.append(String.format("&zoom=%d", zoom));
url.append(String.format("&size=%dx%d", width, height));
// set circle path properties
url.append(String.format("&path="));
url.append(String.format("color:%s", pathColor));
url.append(String.format("|weight:%d", pathWeight));
url.append(String.format("|fillcolor:%s", fillColor));
// add circle path points
for (LatLng point : circlePoints) {
url.append(String.format("|%8.5f,%8.5f", point.latitude, point.longitude));
}
// add API key to URL
url.append(String.format("&key=%s", <YOUR_API_KEY>)));
return url.toString();
}
圆形路径和填充颜色应设置为String"0xRRGGBBAA"格式，其中RR - 红色通道的值，GG - 绿色通道的值，BB - 蓝色通道的值和@ 987654334@ - alpha 通道的值（例如"0x0000FFFF" - 纯蓝色不透明，"0xFF000077" - 纯红色 50% 透明等等）。
当你这样使用buildStaticApiUrlWithCircle()时：
...
int mapZoom = 7;
int mapWidth = 600;
int mapHeight = 300;
LatLng mapCenter = new LatLng(29.31166, 47.481766);
LatLng circleCenter = new LatLng(29.376297, 47.976379);
double circleRadiusMerers = 35000;
String circlePathColor = "0x0000FFFF";
String circleFillColor = "0x0000FF99";
String mapUrl = buildStaticApiUrlWithCircle(mapCenter, mapZoom, mapWidth, mapHeight,
circleCenter, circleRadiusMerers, 3, circlePathColor, circleFillColor);
try {
Bitmap mapBitmap = new GetStaticMapAsyncTask().execute(mapUrl).get();
mMapImageView.setImageBitmap(mapBitmap);
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
...
GetStaticMapAsyncTask 在哪里：
private class GetStaticMapAsyncTask extends AsyncTask<String, Void, Bitmap> {
protected void onPreExecute() {
super.onPreExecute();
}
protected Bitmap doInBackground(String... params) {
Bitmap bitmap = null;
HttpURLConnection connection = null;
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.connect();
int responseCode = connection.getResponseCode();
InputStream stream = connection.getInputStream();
bitmap = BitmapFactory.decodeStream(stream);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
}
return bitmap;
}
@Override
protected void onPostExecute(Bitmap result) {
super.onPostExecute(result);
}
}
你会得到类似的东西：
另外，您可以使用Google Maps Lite Mode 代替静态地图 API（Lite 模式支持绘制圆圈）。甚至，如果您需要在地图的中心精确绘制圆圈 - 直接在位图画布上绘制。例如，您可以这样修改GetStaticMapAsyncTask 的doInBackground()：
protected Bitmap doInBackground(String... params) {
Bitmap bitmap = null;
HttpURLConnection connection = null;
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.connect();
int responseCode = connection.getResponseCode();
InputStream stream = connection.getInputStream();
Bitmap mapBitmap = BitmapFactory.decodeStream(stream);
Paint locaionMarkerPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
locaionMarkerPaint.setColor(Color.BLUE);
bitmap = Bitmap.createBitmap(mapBitmap.getWidth(), mapBitmap.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
canvas.drawBitmap(mapBitmap,0,0, null);
canvas.drawCircle(mapBitmap.getWidth()/ 2, mapBitmap.getHeight() / 2, 20, locaionMarkerPaint);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
}
return bitmap;
}
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