我必须制作一个项目,需要计算从我的位置到目标位置的距离,并在文本视图中显示。请注意,当我的位置发生变化时,该距离会更新。是否可以制作这样类型的项目?
[备注:不使用Google地图进行实现。目标经度,纬度已知。只需找到我的位置并进行计算]
查看Google Android开发页面上的文档,以了解如何监听位置更改。 http://developer.android.com/guide/topics/location/obtaining-user-location.html
您可以使用此函数确定当前(起始)点与目标点之间的距离。
/**
* using WSG84
* using the Metric system
*/
public static float getDistance(double startLati, double startLongi, double goalLati, double goalLongi){
float[] resultArray = new float[99];
Location.distanceBetween(startLati, startLongi, goalLati, goalLongi, resultArray);
return resultArray[0];
}
Location.distanceBetween
会给出两点之间的直线距离。如果你想要两个地理点之间路径的距离,那么可以使用这个类来实现:
public class GetDistance {
public String GetRoutDistane(double startLat, double startLong, double endLat, double endLong)
{
String Distance = "error";
String Status = "error";
try {
Log.e("Distance Link : ", "http://maps.googleapis.com/maps/api/directions/json?origin="+ startLat +","+ startLong +"&destination="+ endLat +","+ endLong +"&sensor=false");
JSONObject jsonObj = parser_Json.getJSONfromURL("http://maps.googleapis.com/maps/api/directions/json?origin="+ startLat +","+ startLong +"&destination="+ endLat +","+ endLong +"&sensor=false");
Status = jsonObj.getString("status");
if(Status.equalsIgnoreCase("OK"))
{
JSONArray routes = jsonObj.getJSONArray("routes");
JSONObject zero = routes.getJSONObject(0);
JSONArray legs = zero.getJSONArray("legs");
JSONObject zero2 = legs.getJSONObject(0);
JSONObject dist = zero2.getJSONObject("distance");
Distance = dist.getString("text");
}
else
{
Distance = "Too Far";
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return Distance;
}
这将为您提供两个点之间的距离或道路长度。
这里是解析JSON api的parser_Json类
public class parser_Json {
public static JSONObject getJSONfromURL(String url){
//initialize
InputStream is = null;
String result = "";
JSONObject jArray = null;
//http post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
//convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result=sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
//try parse the string to a JSON object
try{
jArray = new JSONObject(result);
}catch(JSONException e){
Log.e("log_tag", "Error parsing data "+e.toString());
}
return jArray;
}
public static InputStream retrieveStream(String url) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet getRequest = new HttpGet(url);
try {
HttpResponse getResponse = client.execute(getRequest);
final int statusCode = getResponse.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
return null;
}
HttpEntity getResponseEntity = getResponse.getEntity();
return getResponseEntity.getContent();
}
catch (IOException e) {
getRequest.abort();
}
return null;
}
}
:闭合一个 HTML 段落标签。使用 LocationServices
可以很容易地确定您的位置,并在每次接收到更新时更新您的 TextView
显示新的距离。