贵有恒，何必三更起、五更眠、最无益，只怕一日曝、十日寒。这篇文章主要讲述尝试在空对象引用上调用虚方法'
double android.location.Location.getLatitude（）'
[duplicate]相关的知识，希望能为你提供帮助。
这个问题在这里已有答案：
- What is a NullPointerException, and how do I fix it? 12个答案
我在尝试在null对象上调用虚方法double android.location.Location.getLatitude（）时遇到NullPointerException。
package com.kelompok8.kontakservicekonser;
<
LIST IMPORT>
public class Welcome extends FragmentActivity implements OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener
{private GoogleMap mMap;
//Play Servisprivate static final int MY_PERMISSION_REQUEST_CODE = 7000;
private static final int PLAY_SERVICE_RES_REQUEST = 7001;
private LocationRequest mLocationRequest;
private GoogleApiClient mGoogleApiClient;
private Location mLastLocation;
private static int UPDATE_INTERVAL = 5000;
private static int FATEST_INTERVAL = 3000;
private static int DISPLACEMENT = 10;
DatabaseReference drivers;
GeoFire geoFire;
Marker mCurrent;
MaterialAnimatedSwitch location_switch;
SupportMapFragment mapFragment;
//Animasi
private List<
LatLng>
polyLineList;
private Marker teknisiMarker;
private float v;
private double lat, lng;
private Handler handler;
private LatLng startPosition, endPosition, currentPosition;
private int index, next;
private Button btnGo;
private EditText edtPlace;
private String destination;
private PolylineOptions polylineOptions,blackPolylineOptions;
private Polyline blackPolyLine, greyPolyline;
private IGoogleAPI mService;
Runnable drawPathRunnable=new Runnable() {
@Override
public void run() {
if (index<
polyLineList.size()-1)
{
index++;
next = index;
}
if (index <
polyLineList.size()-1)
{
startPosition = polyLineList.get(index);
endPosition = polyLineList.get(next);
}ValueAnimator valueAnimator = ValueAnimator.ofFloat(0,1);
valueAnimator.setDuration(3000);
valueAnimator.setInterpolator(new LinearInterpolator());
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator valueAnimator) {
v = valueAnimator.getAnimatedFraction();
lng = v*endPosition.longitude+(1-v)*startPosition.longitude;
lat = v*endPosition.latitude+(1-v)*startPosition.latitude;
LatLng newPos = new LatLng(lat,lng);
teknisiMarker.setPosition(newPos);
teknisiMarker.setAnchor(0.5f,0.5f);
teknisiMarker.setRotation(getBearing(startPosition,newPos));
mMap.moveCamera(CameraUpdateFactory.newCameraPosition(
new CameraPosition.Builder()
.target(newPos)
.zoom(15.5f)
.build()));
}
});
valueAnimator.start();
handler.postDelayed(this,3000);
}
};
private float getBearing(LatLng startPosition, LatLng endPosition) {
double lat = Math.abs(startPosition.latitude - endPosition.latitude);
double lng = Math.abs(startPosition.longitude - endPosition.longitude);
if (startPosition.latitude <
endPosition.latitude &
&
startPosition.longitude <
endPosition.longitude)
return (float)(Math.toDegrees(Math.atan(lng/lat)));
else if (startPosition.latitude >
= endPosition.latitude &
&
startPosition.longitude <
endPosition.longitude)
return (float)((90-Math.toDegrees(Math.atan(lng/lat)))+90);
else if (startPosition.latitude >
= endPosition.latitude &
&
startPosition.longitude >
= endPosition.longitude)
return (float)(Math.toDegrees(Math.atan(lng/lat))+180);
else if (startPosition.latitude <
endPosition.latitude &
&
startPosition.longitude >
= endPosition.longitude)
return (float)((90-Math.toDegrees(Math.atan(lng/lat)))+270);
return -1;
}@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_welcome);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
//Init Viewlocation_switch = (MaterialAnimatedSwitch) findViewById(R.id.location_switch);
location_switch.setOnCheckedChangeListener(new MaterialAnimatedSwitch.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(boolean isOnline) {
if(isOnline)
{
startLocationUpdates();
displayLocation();
Snackbar.make(mapFragment.getView(),"You Are Online",Snackbar.LENGTH_SHORT)
.show();
}
else
{
stopLocationUpdates();
mCurrent.remove();
mMap.clear();
handler.removeCallbacks(drawPathRunnable);
Snackbar.make(mapFragment.getView(),"You Are Offline",Snackbar.LENGTH_SHORT)
.show();
}}
});
polyLineList = new ArrayList<
>
();
btnGo = (Button) findViewById(R.id.btnGo);
edtPlace = (EditText) findViewById(R.id.edtPlace);
btnGo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
destination = edtPlace.getText().toString();
destination = destination.replace(" ","+");
//Replace spasi dengan + untuk Fecth data
Log.d("KELOMPOK8", destination);
getDirection();
}
});
//Geo Firedrivers = FirebaseDatabase.getInstance().getReference("Drivers");
geoFire = new GeoFire(drivers);
setUpLocation();
mService = Common.getGoogleAPI();
}private void getDirection() {
currentPosition = new LatLng (mLastLocation.getLatitude(), mLastLocation.getLongitude());
String requestApi = null;
try{
requestApi = "https://maps.googleapis.com/maps/api/directions/json?"+
"mode=driving&
"+
"transit_routing_preference=less_driving"+
"origin="+currentPosition.latitude+","+currentPosition.longitude+"&
"+
"destination="+destination+"&
"+
"key="+getResources().getString(R.string.google_direction_api);
Log.d("KELOMPOK8",requestApi);
//Print URL
mService.getPath(requestApi)
.enqueue(new Callback<
String>
() {
@Override
public void onResponse(Call<
String>
call, Response<
String>
response) {
try {
JSONObject jsonObject = new JSONObject(response.body().toString());
JSONArray jsonArray = jsonObject.getJSONArray("routes");
for (int i=0;
i<
jsonArray.length();
i++)
{
JSONObject route = jsonArray.getJSONObject(i);
JSONObject poly = route.getJSONObject("overview_polyline");
String polyline = poly.getString("points");
polyLineList = decodePoly(polyline);
}//Ajusting BoundsLatLngBounds.Builder builder = new LatLngBounds.Builder();
for (LatLng latLng:polyLineList)
builder.include(latLng);
LatLngBounds bounds = builder.build();
CameraUpdate mCameraUpdate = CameraUpdateFactory.newLatLngBounds(bounds,2);
mMap.animateCamera(mCameraUpdate);
polylineOptions = new PolylineOptions();
polylineOptions.color(Color.GRAY);
polylineOptions.width(5);
polylineOptions.startCap(new SquareCap());
polylineOptions.endCap(new SquareCap());
polylineOptions.jointType(JointType.ROUND);
polylineOptions.addAll(polyLineList);
greyPolyline = mMap.addPolyline(polylineOptions);
blackPolylineOptions = new PolylineOptions();
blackPolylineOptions.color(Color.BLACK);
blackPolylineOptions.width(5);
blackPolylineOptions.startCap(new SquareCap());
blackPolylineOptions.endCap(new SquareCap());
blackPolylineOptions.jointType(JointType.ROUND);
blackPolyLine = mMap.addPolyline(blackPolylineOptions);
mMap.addMarker(new MarkerOptions()
.position(polyLineList.get(polyLineList.size()-1))
.title("Pick Up Location"));
//AnimationValueAnimator polyLineAnimator = ValueAnimator.ofInt(0,100);
polyLineAnimator.setDuration(2000);
polyLineAnimator.setInterpolator(new LinearInterpolator());
polyLineAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator valueAnimator) {
List<
LatLng>
points = greyPolyline.getPoints();
int percentValue = https://www.songbingjia.com/android/(int)valueAnimator.getAnimatedValue();
int size = points.size();
int newPoints = (int)(size *(percentValue/100.0f));
List<
LatLng>
p = points.subList(0,newPoints);
blackPolyLine.setPoints(p);
}
});
polyLineAnimator.start();
teknisiMarker = mMap.addMarker(new MarkerOptions().position(currentPosition)
.flat(true)
.icon(BitmapDescriptorFactory.fromResource(R.drawable.car)));
handler = new Handler();
index=-1;
next=1;
handler.postDelayed(drawPathRunnable,3000);
} catch (JSONException e) {
e.printStackTrace();
}}@Override
public void onFailure(Call<
String>
call, Throwable t) {
Toast.makeText(Welcome.this,""+t.getMessage(),Toast.LENGTH_SHORT).show();
}
});
}catch (Exception e)
{
e.printStackTrace();
}}private List decodePoly(String encoded) {List 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;
}@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
switch (requestCode)
{
case MY_PERMISSION_REQUEST_CODE:
if(grantResults.length >
0 &
&
grantResults[0] == PackageManager.PERMISSION_GRANTED)
{
if (checkPlayServices()) ;
{
buildGoogleApiClient();
createLocationRequest();
if (location_switch.isChecked())
displayLocation();
}}
}
}private void setUpLocation() {
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED &
&
ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED){
//request runtime permission
ActivityCompat.requestPermissions(this, new String[]{
Manifest.permission.ACCESS_COARSE_LOCATION,
Manifest.permission.ACCESS_FINE_LOCATION
}, MY_PERMISSION_REQUEST_CODE);
} else {
if (checkPlayServices()) ;
{
buildGoogleApiClient();
createLocationRequest();
if (location_switch.isChecked())
displayLocation();
}
}
}private void createLocationRequest() {
mLocationRequest= new LocationRequest();
mLocationRequest.setInterval(UPDATE_INTERVAL);
mLocationRequest.setFastestInterval(FATEST_INTERVAL);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
mLocationRequest.setSmallestDisplacement(DISPLACEMENT);
}private void buildGoogleApiClient() {mGoogleApiClient= new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
mGoogleApiClient.connect();
}private boolean checkPlayServices() {
int resultCode = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
if (resultCode != ConnectionResult.SUCCESS) {
if (GooglePlayServicesUtil.isUserRecoverableError(resultCode))
GooglePlayServicesUtil.getErrorDialog(resultCode, this, PLAY_SERVICE_RES_REQUEST).show();
else {
Toast.makeText(this, "Device ini tidak Cocok", Toast.LENGTH_SHORT).show();
finish();
}
return false;
}
return true;
}private void stopLocationUpdates() {
if(ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED &
&
ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED){
return;
}LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient,this);
}private void displayLocation() {
if(ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED &
&
ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED){
return;
}mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
if (mLastLocation!=null)
{
{
if(location_switch.isChecked())
{
final double latitude = mLastLocation.getLatitude();
final double longitude = mLastLocation.getLongitude();
geoFire.setLocation(FirebaseAuth.getInstance().getCurrentUser().getUid(), new GeoLocation(latitude, longitude), new GeoFire.CompletionListener() {
@Override
public void onComplete(String key, DatabaseError error) {
if ((mCurrent) !=null)
mCurrent.remove();
mCurrent = mMap.addMarker(new MarkerOptions()
.position(new LatLng(latitude, longitude))
.title("Your Location"));
//Memindah Kamera ke Posisi kitamMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(latitude, longitude),15.0f));
//Animasi
rotateMarker (mCurrent,-360,mMap);
}});
}
}
}
else
{
Log.d("ERROR","Tidak bisa mengambil Lokasi");
}}private void rotateMarker(final Marker mCurrent, final floati, GoogleMap mMap) {
final Handler handler = new Handler();
final long start = SystemClock.uptimeMillis();
final float startRotation = mCurrent.getRotation();
final long duration = 1500;
final Interpolator interpolator = new LinearInterpolator();
handler.post(new Runnable() {
@Override
public void run() {
long elepsed = SystemClock.uptimeMillis() - start;
float t = interpolator.getInterpolation((float)elepsed/duration);
float rot = t*i+(1-t)*startRotation;
mCurrent.setRotation(-rot >
180?rot/2:rot);
if (t<
1.0)
{
handler.postDelayed(this,16);
}
}
});
}private void startLocationUpdates() {
if(ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED &
&
ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED){
return;
}LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest,this);
}@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
mMap.setTrafficEnabled(false);
mMap.setIndoorEnabled(false);
mMap.setBuildingsEnabled(false);
mMap.getUiSettings().setZoomControlsEnabled(true);
}@Override
public void onConnected(@Nullable Bundle bundle) {
displayLocation();
startLocationUpdates();
}@Override
public void onConnectionSuspended(int i) {
mGoogleApiClient.connect();
}@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {}@Override
public void onLocationChanged(Location location) {
mLastLocation = location;
displayLocation();
}
}
除外的原因
private void getDirection() {
currentPosition = new LatLng (mLastLocation.getLatitude(), mLastLocation.getLongitude());
String requestApi = null;
try{
requestApi = "https://maps.googleapis.com/maps/api/directions/json?"+
"mode=driving&
"+
"transit_routing_preference=less_driving"+
"origin="+currentPosition.latitude+","+currentPosition.longitude+"&
"+
"destination="+destination+"&
"+
"key="+getResources().getString(R.string.google_direction_api);
Log.d("KELOMPOK8",requestApi);
//Print URL
mService.getPath(requestApi)
.enqueue(new Callback<
String>
() {
@Override
public void onResponse(Call<
String>
call, Response<
String>
response) {
try {
JSONObject jsonObject = new JSONObject(response.body().toString());
JSONArray jsonArray = jsonObject.getJSONArray("routes");
for (int i=0;
i<
jsonArray.length();
i++)
{
JSONObject route = jsonArray.getJSONObject(i);
JSONObject poly = route.getJSONObject("overview_polyline");
String polyline = poly.getString("points");
polyLineList = decodePoly(polyline);
【尝试在空对象引用上调用虚方法' double android.location.Location.getLatitude（）' [duplicate]】列表导入
答案你忘了初始化Location，只需添加：
LocationManager locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
Criteria criteria = new Criteria();
String provider = locationManager.getBestProvider(criteria, true);
Location location = locationManager.getLastKnownLocation(provider);
关于
onCreate()方法：之后从位置获取lat＆lng：
double lat = location.getLatitude();
double lng = location.getLongitude();
LatLng latLng = new LatLng(lat, lng);
快乐的编码!!
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