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假設我從綠色標記開始我的旅程，並以紅色標記完成我的旅程。我如何計算我完成旅程所花費的距離和時間？ 
我怎樣才能找到我在兩個地點之間旅行所需的距離和時間？
我的代碼是這樣的：
public class MainActivity extends FragmentActivity implements OnMapReadyCallback, LocationListener {
GoogleMap map;
LocationManager locationManager;
ArrayList<LatLng> markerPoints;
TextView tvDistanceDuration;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvDistanceDuration = (TextView) findViewById(R.id.tv_distance_time);
// Initializing
markerPoints = new ArrayList<LatLng>();
// Getting reference to SupportMapFragment of the activity_main
SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
// Getting Map for the SupportMapFragment
fm.getMapAsync(this);
}
private String getDirectionsUrl(LatLng origin, LatLng dest) {
// Origin of route
String str_origin = "origin=" + origin.latitude + "," + origin.longitude;
// Destination of route
String str_dest = "destination=" + dest.latitude + "," + dest.longitude;
// Sensor enabled
String sensor = "sensor=false";
// Building the parameters to the web service
String parameters = str_origin + "&" + str_dest + "&" + sensor;
// Output format
String output = "json";
// Building the url to the web service
String url = "https://maps.googleapis.com/maps/api/directions/" + output + "?" + parameters;
return url;
}
/**
* A method to download json data from url
*/
private String downloadUrl(String strUrl) throws IOException {
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try {
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while ((line = br.readLine()) != null) {
sb.append(line);
}
data = sb.toString();
br.close();
} catch (Exception e) {
Log.d("error downloading url", e.toString());
} finally {
iStream.close();
urlConnection.disconnect();
}
return data;
}
@Override
public void onMapReady(GoogleMap googleMap) {
map = googleMap;
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
if (checkSelfPermission(android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && checkSelfPermission(android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// Activity#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for Activity#requestPermissions for more details.
return;
}
}
map.setMyLocationEnabled(true);
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria();
String bestProvider = locationManager.getBestProvider(criteria, true);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// Activity#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for Activity#requestPermissions for more details.
return;
}
}
Location location = locationManager.getLastKnownLocation(bestProvider);
if (location != null) {
onLocationChanged(location);
}
locationManager.requestLocationUpdates(bestProvider, 20000, 0, this);
// Setting onclick event listener for the map
map.setOnMapClickListener(new OnMapClickListener() {
@Override
public void onMapClick(LatLng point) {
// Already two locations
if (markerPoints.size() > 1) {
markerPoints.clear();
map.clear();
}
// Adding new item to the ArrayList
markerPoints.add(point);
// Creating MarkerOptions
MarkerOptions options = new MarkerOptions();
// Setting the position of the marker
options.position(point);
/**
* For the start location, the color of marker is GREEN and
* for the end location, the color of marker is RED.
*/
if (markerPoints.size() == 1) {
options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
} else if (markerPoints.size() == 2) {
options.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED));
}
// Add new marker to the Google Map Android API V2
map.addMarker(options);
// Checks, whether start and end locations are captured
if (markerPoints.size() >= 2) {
LatLng origin = markerPoints.get(0);
LatLng dest = markerPoints.get(1);
// Getting URL to the Google Directions API
String url = getDirectionsUrl(origin, dest);
DownloadTask downloadTask = new DownloadTask();
// Start downloading json data from Google Directions API
downloadTask.execute(url);
}
}
});
}
@Override
public void onLocationChanged(Location location) {
double latitude = location.getLatitude();
double longitude = location.getLongitude();
LatLng latLng = new LatLng(latitude, longitude);
map.setMapType(GoogleMap.MAP_TYPE_NORMAL);
map.setTrafficEnabled(true);
map.setBuildingsEnabled(true);
map.setIndoorEnabled(true);
map.getUiSettings().isCompassEnabled();
map.getUiSettings().isMyLocationButtonEnabled();
map.moveCamera(CameraUpdateFactory.newLatLng(latLng));
map.animateCamera(CameraUpdateFactory.zoomTo(16));
}
@Override
public void onStatusChanged(String s, int i, Bundle bundle) {
}
@Override
public void onProviderEnabled(String s) {
}
@Override
public void onProviderDisabled(String s) {
}
// Fetches data from url passed
private class DownloadTask extends AsyncTask<String, Void, String> {
// Downloading data in non-ui thread
@Override
protected String doInBackground(String... url) {
// For storing data from web service
String data = "";
try {
// Fetching the data from web service
data = downloadUrl(url[0]);
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}
// Executes in UI thread, after the execution of
// doInBackground()
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
}
/**
* A class to parse the Google Places in JSON format
*/
private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap<String, String>>>> {
// Parsing the data in non-ui thread
@Override
protected List<List<HashMap<String, String>>> doInBackground(String... jsonData) {
JSONObject jObject;
List<List<HashMap<String, String>>> routes = null;
try {
jObject = new JSONObject(jsonData[0]);
DirectionsJSONParser parser = new DirectionsJSONParser();
// Starts parsing data
routes = parser.parse(jObject);
} catch (Exception e) {
e.printStackTrace();
}
return routes;
}
// Executes in UI thread, after the parsing process
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result) {
ArrayList<LatLng> points = null;
PolylineOptions lineOptions = null;
MarkerOptions markerOptions = new MarkerOptions();
String distance = "";
String duration = "";
if (result.size() < 1) {
Toast.makeText(getBaseContext(), "No Points", Toast.LENGTH_SHORT).show();
return;
}
// Traversing through all the routes
for (int i = 0; i < result.size(); i++) {
points = new ArrayList<LatLng>();
lineOptions = new PolylineOptions();
// Fetching i-th route
List<HashMap<String, String>> path = result.get(i);
// Fetching all the points in i-th route
for (int j = 0; j < path.size(); j++) {
HashMap<String, String> point = path.get(j);
if (j == 0) { // Get distance from the list
distance = (String) point.get("distance");
continue;
} else if (j == 1) { // Get duration from the list
duration = (String) point.get("duration");
continue;
}
double lat = Double.parseDouble(point.get("lat"));
double lng = Double.parseDouble(point.get("lng"));
LatLng position = new LatLng(lat, lng);
points.add(position);
}
// Adding all the points in the route to LineOptions
lineOptions.addAll(points);
lineOptions.width(8);
lineOptions.color(Color.RED);
}
tvDistanceDuration.setText("Distance:" + distance + ", Duration:" + duration);
// Drawing polyline in the Google Map for the i-th route
map.addPolyline(lineOptions);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}