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Hello Im newebie to android programming。在这里，我不断收到nullreference错误。我正在使用Google Map API并使用azure webservice。我新来stackoverflow这也是为什么我的问题是在一团糟，我的语法也是如此。我收到错误“java.lang.NullPointerException：尝试调用虚拟方法”
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, LocationListener, GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {
private GoogleMap mMap;
private double myLatitude, myLongitude;
private String myUrl;
private static Context context;
private Button set;
private EditText skillCari;
private TextView latlng;
private List<People> finalPeople = new ArrayList<>();
private List<People> myPeople = new ArrayList<>();
private double currentLatitude, currentLongitude;
private GoogleApiClient mGoogleApiClient;
private LocationRequest mLocationRequest;
public Activity currentActivity = this;
private double minLatitude, maxLatitude, minLongitude, maxLongitude;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
// 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);
MapsActivity.context = getApplicationContext();
mGoogleApiClient = new GoogleApiClient.Builder(this).addConnectionCallbacks(this).addOnConnectionFailedListener(this)
.addApi(LocationServices.API).build();
mLocationRequest = LocationRequest.create().setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
.setInterval(10 * 1000).setFastestInterval(1 * 1000);
latlng = (TextView) findViewById(R.id.Latlng);
RecyclerView myRecyle = (RecyclerView) findViewById(R.id.RecycleView);
myRecyle.setHasFixedSize(true);
myRecyle.setLayoutManager(new LinearLayoutManager(this));
final AdapterCard myCard = new AdapterCard();
myRecyle.setAdapter(myCard);
skillCari = (EditText) findViewById(R.id.skill_cari);
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#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 ActivityCompat#requestPermissions for more details.
return;
}
final Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
set = (Button) findViewById(R.id.butSearch);
set.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
myCard.clearData();
BengService service = ServiceFactory.createRetrofitService(BengService.class, BengService.BENG_SERVICE);
service.getSkilledUser(skillCari.getText().toString())
.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Subscriber<List<People>>() {
@Override
public void onCompleted() {
}
@Override
public void onError(Throwable e) {
Log.e("GithubDemo", e.getMessage());
Log.e("GithubDemo", e.toString());
}
@Override
public void onNext(List<People> peoples) {
finalPeople = SaringPeople(peoples, location.getLatitude(), location.getLongitude());
myCard.addData(finalPeople);
TambahMap(mMap, finalPeople);
}
});
}
});
}
public ArrayList<People> SaringPeople(List<People> people, double userLatitude, double userLongitude) {
myLatitude = userLatitude;
myLongitude = userLongitude;
myPeople = people;
ArrayList<People> peopleSample = new ArrayList<>();
double R = 6371;
double radius = 0.300;
double longitudeMin, longitudeMaks, latitudeMin, latitudeMaks;
longitudeMin = (userLongitude - Math.toDegrees(radius/R/Math.cos(Math.toRadians(userLatitude))));
longitudeMaks = (userLongitude + Math.toDegrees(radius/R/Math.cos(Math.toRadians(userLatitude))));
latitudeMaks = (userLatitude + Math.toDegrees(radius/R));
latitudeMin = (userLatitude - Math.toDegrees(radius/R));
for (People myPeople : people) {
if ((myPeople.getLatitude() <= latitudeMaks) && (myPeople.getLatitude() >= latitudeMin) && (myPeople.getLongitude() <= longitudeMaks) && (myPeople.getLongitude() >= longitudeMin)) {
peopleSample.add(myPeople);
}
else{}
}
return peopleSample;
}
public void TambahMap(GoogleMap googleMap, List<People> people) {
Bitmap urlImage;
for (People mypeople : people) {
urlImage = getBitmap(mypeople.getPhotoURL());
LatLng haha = new LatLng(mypeople.getLatitude(), mypeople.getLongitude());
googleMap.addMarker(new MarkerOptions().position(haha).title(mypeople.getFullName()).icon(BitmapDescriptorFactory.fromBitmap(urlImage)));
}
}
public Bitmap getBitmap(String imageUrl) {
try {
URL url = new URL(imageUrl);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream input = connection.getInputStream();
Bitmap bitmap = BitmapFactory.decodeStream(input);
return bitmap;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
@Override
public void onLocationChanged(Location location) {
currentLatitude = location.getLatitude();
currentLongitude = location.getLongitude();
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
@Override
public void onConnected(@Nullable Bundle bundle) {
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#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 ActivityCompat#requestPermissions for more details.
return;
}
Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
if (location == null){
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
} else {
currentLatitude = location.getLatitude();
currentLongitude = location.getLongitude();
}
}
@Override
public void onConnectionSuspended(int i) {
}
我试图运行的方法 “TambahMap” 和 “SaringPeople” 通过点击按钮 “butSearch” 请帮助我..
林正从我的日志
此错误09-26 00:16:04.018 6337-6337/com.example.beng.bengtuak E/GithubDemo: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
09-26 00:16:04.018 6337-6337/com.example.beng.bengtuak E/GithubDemo: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
09-26 00:16:16.386 6337-6337/com.example.beng.bengtuak E/GithubDemo: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
09-26 00:16:16.386 6337-6337/com.example.beng.bengtuak E/GithubDemo: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
对不起，但没有堆栈跟踪，你不会得到任何答复 –
你能解释我怎么可以使用堆栈跟踪？ 谢谢 –
假设你正在使用Android工作室，你应该有一个名为“Android监视器”的东西，将会有一个名为logcat的标签。 –