我是编程的初学者。 我写了以下代码（在网上看），但我不明白如何才能使它出现在Toast中。 谁能帮我吗？
我创建了一个接口，在其中放置了代码，以便从url中获取所需的一切，我可以接收JSON格式的答案，但是我不明白如何从响应中接收的JSON中提取距离< / p>
import com.google.android.gms.maps.model.LatLng;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class DataParser {
public List<List<HashMap<String, String>>> parse(JSONObject jObject) {
List<List<HashMap<String, String>>> routes = new ArrayList<>();
JSONArray jRoutes;
JSONArray jLegs;
JSONArray jSteps;
try {
jRoutes = jObject.getJSONArray("routes");
/** Traversing all routes */
for (int i = 0; i < jRoutes.length(); i++) {
jLegs = ((JSONObject) jRoutes.get(i)).getJSONArray("legs");
List path = new ArrayList<>();
/** Traversing all legs */
for (int j = 0; j < jLegs.length(); j++) {
jSteps = ((JSONObject) jLegs.get(j)).getJSONArray("steps");
/** Traversing all steps */
for (int k = 0; k < jSteps.length(); k++) {
String polyline = "";
polyline = (String) ((JSONObject) ((JSONObject) jSteps.get(k)).get("polyline")).get("points");
List<LatLng> list = decodePoly(polyline);
/** Traversing all points */
for (int l = 0; l < list.size(); l++) {
HashMap<String, String> hm = new HashMap<>();
hm.put("lat", Double.toString((list.get(l)).latitude));
hm.put("lng", Double.toString((list.get(l)).longitude));
path.add(hm);
}
}
routes.add(path);
}
}
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
}
return routes;
}
/**
* Method to decode polyline point
*/
private List<LatLng> decodePoly(String encoded) {
List<LatLng> poly = new ArrayList<>();
int index = 0, len = encoded.length();
int lat = 0, lng = 0;
while (index < len) {
int b, shift = 0, result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lng += dlng;
LatLng p = new LatLng((((double) lat / 1E5)),
(((double) lng / 1E5)));
poly.add(p);
}
return poly;
}
}
import android.content.Context;
import android.graphics.Color;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.Toast;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.PolylineOptions;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class PointsParser extends AsyncTask<String, Integer, List<List<HashMap<String, String>>>> {
TaskLoadedCallback taskCallback;
String directionMode = "walking";
MainActivity mainActivity = new MainActivity();
public PointsParser(Context mContext, String directionMode) {
this.taskCallback = (TaskLoadedCallback) mContext;
this.directionMode = directionMode;
}
// 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]);
Log.d("mylog", jsonData[0].toString());
DataParser parser = new DataParser();
Log.d("mylog", parser.toString());
// Starts parsing data
routes = parser.parse(jObject);
// Log.d("routes-->",routes.toString());
Log.d("mylog", "Executing routes");
Log.d("mylog", routes.toString());
} catch (Exception e) {
Log.d("mylog", e.toString());
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;
PolylineOptions lineOptions = null;
String distance = "";
String duration = "";
if(result.size()<1){
//Toast.makeText(getBaseContext(), "No Points", Toast.LENGTH_SHORT).show();
return;
}
// Traversing through all the routes
Log.d("result --> ", result.toString());
for (int i = 0; i < result.size(); i++) {
points = new ArrayList<>();
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(20);
lineOptions.color(Color.BLUE);
Log.d("mylog", "onPostExecute lineoptions decoded");
}
// Drawing polyline in the Google Map for the i-th route
if (lineOptions != null) {
//mMap.addPolyline(lineOptions);
mainActivity.getToast(distance,duration);
taskCallback.onTaskDone(lineOptions);
} else {
Log.d("mylog", "without Polylines drawn");
}
}
}
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class FetchURL extends AsyncTask<String, Void, String> {
Context mContext;
String directionMode = "walking";
public FetchURL(Context mContext) {
this.mContext = mContext;
}
@Override
protected String doInBackground(String... strings) {
// For storing data from web service
String data = "";
directionMode = "walking";
try {
// Fetching the data from web service
data = downloadUrl(strings[0]);
} catch (Exception e) {
Log.d("Background Task", e.toString());
}
return data;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
PointsParser parserTask = new PointsParser(mContext, directionMode);
// Invokes the thread for parsing the JSON data
parserTask.execute(s);
}
private String downloadUrl(String strUrl) throws IOException {
String data = "";
boolean flag = false;
String distance ="";
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);
String[] values = line.split(":");
Log.d("values key--->", values[0]);
Log.d("values value--->", values[1]);
}
data = sb.toString();
Log.d("mylog", "Downloaded URL: " + data.toString());
br.close();
} catch (Exception e) {
Log.d("mylog", "Exception downloading URL: " + e.toString());
} finally {
iStream.close();
urlConnection.disconnect();
}
return data;
}
}
这是主要的：
import android.Manifest;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.Polyline;
import com.google.android.gms.maps.model.PolylineOptions;
public class MainActivity extends AppCompatActivity implements OnMapReadyCallback, TaskLoadedCallback {
private GoogleMap map;
private MarkerOptions start, finish;
private Polyline polyline;
Button position;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 123);
position = findViewById(R.id.position);
MapFragment mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.mapFrag);
mapFragment.getMapAsync(this);
final LatLng init = new LatLng(45.6736241,12.1466323);
final LatLng fin = new LatLng(45.60223647212919,12.241125547197981);
start = new MarkerOptions().position(init).title("Start");
finish = new MarkerOptions().position(fin).title("Finish");
position.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
new FetchURL(MainActivity.this).execute(getUrl(start.getPosition(), finish.getPosition(), "walking"));
}
});
}
@Override
public void onMapReady(GoogleMap googleMap) {
map = googleMap;
map.getUiSettings().setZoomControlsEnabled(true);
map.setMyLocationEnabled(true);
map.addMarker(start);
map.addMarker(finish);
// per settare vista satelitte
// map.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
}
private String getUrl(LatLng origin, LatLng destination, String mode){
String start = "origin=" + origin.latitude + "," + origin.longitude;
String finish = "destination=" + destination.latitude + "," + destination.longitude;
String modeType = "mode=" + mode;
String parameter = start + "&" + finish + "&" + modeType;
String output = "json";
String url = "https://maps.googleapis.com/maps/api/directions/" + output + "?" + parameter +"&key=" + getString(R.string.API_key);
Log.d("url-->", url);
return url;
}
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 + "&key=" + getString(R.string.API_key);;
return url;
}
@Override
public void onTaskDone(Object... values) {
if(polyline != null)
polyline.remove();
//Toast.makeText(getApplicationContext(), "Distance" + values[1], Toast.LENGTH_LONG).show();
polyline = map.addPolyline((PolylineOptions) values[0]);
}
@Override
public void onTaskDone(PolylineOptions polylineOptions, String distance, String duration) {
}
public void getToast(/*PolylineOptions polylineOptions*/ String distance, String duration) {
//if(polylineOptions != null)
// polyline.remove();
Toast.makeText(getApplicationContext(), "Distance" + distance, Toast.LENGTH_LONG).show();
//polyline = map.addPolyline((PolylineOptions) polylineOptions);
}
@Override
public void onPointerCaptureChanged(boolean hasCapture) {
}
}