我正在尝试获取两个地方之间的距离，我的原点纬度和经度已在程序中进行了硬编码，目标纬度和经度是通过对搜索框中的用户输入进行地理编码来检索的
但是当我单击MapsActivity.java中执行onClick()方法的按钮时，会显示以下错误：
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
at org.json.JSONTokener.nextValue(JSONTokener.java:94)
at org.json.JSONObject.<init>(JSONObject.java:156)
at org.json.JSONObject.<init>(JSONObject.java:173)
at com.example.itachi.com.mmaps.DataParser.parseDirections(DataParser.java:55)
at com.example.itachi.com.mmaps.GetDirectionsData.onPostExecute(GetDirectionsData.java:30)
at com.example.itachi.com.mmaps.GetDirectionsData.onPostExecute(GetDirectionsData.java:9)
at android.os.AsyncTask.finish(AsyncTask.java:651)
at android.os.AsyncTask.-wrap1(AsyncTask.java)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
MapsActivity.java：
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener, LocationListener {
private GoogleMap mMap;
//Google Api
private GoogleApiClient client;
//Location Request Object
private LocationRequest locationRequest;
//Location
private Location lastLocation;
//Marker
private Marker currentLocation;
//Request Location Code
public static final int REQUEST_LOCATION_CODE = 99;
//Origin lat lang
double latitude,longitude;
//destination lat lang
double end_latitude, end_longitude;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
checkLocationPermission();
}
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
switch(requestCode){
case REQUEST_LOCATION_CODE:
if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
//WHEN PERMISSIONS ARE GRANTED
if(ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED){
if(client == null){
buildGoogleApiClient();
}
mMap.setMyLocationEnabled(true);
}
}
else {
Toast.makeText(this, "Permissions Denied", Toast.LENGTH_SHORT).show();
}
return;
}
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
if(ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED){
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
}
protected synchronized void buildGoogleApiClient() {
//Here we build out Google api and then connect
client = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this).addOnConnectionFailedListener(this)
.addApi(LocationServices.API).build();
client.connect();
}
@Override
public void onConnected(@Nullable Bundle bundle) {
//Here we request the location regularly and update the location for a specific interval
locationRequest = new LocationRequest();
locationRequest.setInterval(1000);
locationRequest.setFastestInterval(1000);
locationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
//noinspection deprecation
LocationServices.FusedLocationApi.requestLocationUpdates(client, locationRequest, this);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
@Override
public void onLocationChanged(Location location) {
lastLocation = location;
//Checking if there is any previous location shared
if(currentLocation != null){
//if there is any other location shared remove it
currentLocation.remove();
}
//getting the lat and lang of the location and saving them to LatLang
LatLng latlng = new LatLng(location.getLatitude(), location.getLongitude());
//Setting the marker like its properties , position and etc,.,.
MarkerOptions markerOptions = new MarkerOptions();
markerOptions.position(latlng);
markerOptions.title("Current Location");
markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_BLUE));
//Appending these properties to the marker
currentLocation = mMap.addMarker(markerOptions);
//Move the screen as per the locations saved
mMap.moveCamera(CameraUpdateFactory.newLatLng(latlng));
mMap.animateCamera(CameraUpdateFactory.zoomBy(10));
//After getting the location and updating the marker we have to stop requesting
if(client != null){
//removing the location updating api
//noinspection deprecation
LocationServices.FusedLocationApi.removeLocationUpdates(client, this);
}
}
//Create a method to check the permissions
public boolean checkLocationPermission(){
if(ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED){
if(ActivityCompat.shouldShowRequestPermissionRationale(this,Manifest.permission.ACCESS_FINE_LOCATION)){
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION},REQUEST_LOCATION_CODE);
}
else{
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION},REQUEST_LOCATION_CODE);
}
return false;
}
return true;
}
public void onClick(View view){
if(view.getId() == R.id.B_search){
mMap.clear();
//Collecting the distance using api
Object dataTransfer[] = new Object[2];
String url = getDirectionUrl();
GetDirectionsData getDirectionsData = new GetDirectionsData();
dataTransfer[0] = mMap;
dataTransfer[1] = url;
getDirectionsData.execute(dataTransfer);
// collecting the text entered by the person
EditText tf_location = findViewById(R.id.TF_Location);
String location = tf_location.getText().toString();
List<Address> addressList = null;
MarkerOptions mo = new MarkerOptions();
if(location != ""){
//create an object for geocoding the location
Geocoder geoCoder = new Geocoder(this);
try {
addressList = geoCoder.getFromLocationName(location, 5);
} catch (IOException e) {
e.printStackTrace();
}
for (int i=0; i<addressList.size();i++){
Address myAddress = addressList.get(i);
LatLng latLng = new LatLng(myAddress.getLatitude(),myAddress.getLongitude());
end_latitude = myAddress.getLatitude();
end_longitude = myAddress.getLongitude();
Log.d("lat by pavan gadu",String.valueOf(end_latitude));
Log.d("lon",String.valueOf(end_longitude));
mo.position(latLng);
mo.title("search results");
mMap.addMarker(mo);
mMap.animateCamera(CameraUpdateFactory.newLatLng(latLng));
}
}
}
}
private String getDirectionUrl(){
latitude = 15.5997300;
longitude = 79.6064320;
StringBuilder googleDorectionsUrl = new StringBuilder("https://maps.googleapis.com/maps/api/directions/json?");
//append the origin(tghis is of three ways -1.)send the place name , 2.)send the place lat lang 3.)send the place id
googleDorectionsUrl.append("origin"+latitude+","+longitude);
//append the destination
googleDorectionsUrl.append("&destination"+end_latitude+","+end_longitude);
//append the key
googleDorectionsUrl.append("&key="+"AIzaSyCAcfy-02UHSu2F6WeQ1rhQhkCr51eBL9g");
//return the url
Log.d("Url sending pan gadu:",googleDorectionsUrl.toString());
return googleDorectionsUrl.toString();
}
}
GetDirectionsData.java类：
public class GetDirectionsData extends AsyncTask<Object, String, String> {
String url;
GoogleMap mMap;
String googleDirectionsData;
@Override
protected String doInBackground(Object... objects) {
mMap = (GoogleMap) objects[0];
url = (String)objects[1];
DownloadUrl downloadUrl = new DownloadUrl();
try {
googleDirectionsData = downloadUrl.readUrl(url);
} catch (Exception e) {
e.printStackTrace();
}
return googleDirectionsData;
}
@Override
protected void onPostExecute(String s) {
HashMap<String, String> directionsList = null;
DataParser parser = new DataParser();
directionsList = parser.parseDirections(s);
}
}
DataParser.java类：
public class DataParser {
private HashMap<String, String> getPlace(JSONObject googlePlaceJson){
//Detailos about the place are being stored in the hashmap
HashMap<String, String> googlePlacesMap = new HashMap<>();
//Declaring all the primary data of the place to strings
String placeName = "-NA-";
String vicinity = "-NA-";
String latitude = "";
String longitude = "";
String reference = "";
//fetching dta from the given JSON object and parsing to string
try{
if(!googlePlaceJson.isNull("name")){
placeName = googlePlaceJson.getString("name");
}
if(!googlePlaceJson.isNull("vicinity")){
vicinity = googlePlaceJson.getString("vicinity");
}
latitude = googlePlaceJson.getJSONObject("geometry").getJSONObject("location").getString("lat");
longitude = googlePlaceJson.getJSONObject("geometry").getJSONObject("location").getString("lng");
reference = googlePlaceJson.getString("reference");
googlePlacesMap.put("place_name", placeName);
googlePlacesMap.put("vicinity", vicinity);
googlePlacesMap.put("lat", latitude);
googlePlacesMap.put("lng", longitude);
googlePlacesMap.put("reference", reference);
}
catch (JSONException e) {
e.printStackTrace();
}
//finally return the data
return googlePlacesMap;
}
public HashMap<String, String> parseDirections (String jsonData){
JSONArray jsonArray = null;
JSONObject jsonObject;
try {
jsonObject = new JSONObject(jsonData);
jsonArray = jsonObject.getJSONArray("routs");
} catch (JSONException e) {
e.printStackTrace();
}
return getDuration(jsonArray);
}
private HashMap<String, String> getDuration(JSONArray googleDirectionsJson){
HashMap<String, String> googleDirectionsMap = new HashMap<>();
String duration = "";
String distance = "";
Log.d("Json response",googleDirectionsJson.toString());
return googleDirectionsMap;
}
}
DownloadUrl.java是：
public String readUrl(String myUrl){
String data ="";
InputStream inputStream = null;
HttpURLConnection urlConnection = null;
try {
//getting the url
URL url = new URL(myUrl);
//open connection
urlConnection = (HttpURLConnection) url.openConnection();
//connect the url
urlConnection.connect();
Log.d("message",":in urldownload");
//Read the data
inputStream = urlConnection.getInputStream();
//feed it to BufferReader
BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
//open a string buffer
StringBuffer sb = new StringBuffer();
String line = "";
while((line = br.readLine()) != null){
//append all the data present in the string buffer in line(which is the string object)
sb.append(line);
}
//parse the string buffer to actual string and save in data variabke
data = sb.toString();
//close the buffer
br.close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally {
try {
//close the streem buffer and url connection
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
urlConnection.disconnect();
}
return data;
}
}