When I try to open the Navigation Home the App crashes Navigation Home image I have tried initializing the mMap but the app still crashes. Please help me out
My error > java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.GoogleMap.clear()' on a null object reference at com.example.gpshelper.Activity.home$2.onLocationResult(home.java:138)
Here's my Code
public class home extends AppCompatActivity implements OnMapReadyCallback, NavigationView.OnNavigationItemSelectedListener {
DrawerLayout drawerLayout;
Toolbar toolbar;
NavigationView navigationView;
ActionBarDrawerToggle actionBarDrawerToggle;
GoogleMap mMap;
LocationRequest locationRequest;
FusedLocationProviderClient fusedLocationProviderClient;
LatLng latLng;
FirebaseUser firebaseUser;
FirebaseAuth firebaseAuth;
TextView header_name, header_email;
DatabaseReference databaseReference;
String current_uid;
AlertDialog.Builder builder;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
drawerLayout = findViewById(R.id.drawerlayout);
toolbar = findViewById(R.id.home_toolbar);
setSupportActionBar(toolbar);
navigationView = findViewById(R.id.nev_view);
//navigationView.setNavigationItemSelectedListener(this);
actionBarDrawerToggle = new ActionBarDrawerToggle(this,drawerLayout,toolbar,R.string.app_name,R.string.app_name);
drawerLayout.addDrawerListener(actionBarDrawerToggle);
actionBarDrawerToggle.syncState();
databaseReference = FirebaseDatabase.getInstance().getReference("users");
firebaseAuth = FirebaseAuth.getInstance();
firebaseUser = firebaseAuth.getCurrentUser();
current_uid = firebaseUser.getUid();
callpermissionlistener();
update_location();
dynamicheaderlistener();
}
private void dynamicheaderlistener() {
View header = navigationView.getHeaderView(0);
header_name = header.findViewById(R.id.header_name_text);
header_email = header.findViewById(R.id.header_email_text);
databaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
String current_name = dataSnapshot.child(current_uid).child("firstname").getValue(String.class);
String current_email = dataSnapshot.child(current_uid).child("email").getValue(String.class);
String s1 = "Hi " current_name;
header_name.setText(s1);
header_email.setText(current_email);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
private void update_location() {
if (ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_FINE_LOCATION)== PermissionChecker.PERMISSION_GRANTED &&
ContextCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION)==PermissionChecker.PERMISSION_GRANTED)
{
fusedLocationProviderClient = new FusedLocationProviderClient(this);
locationRequest = new LocationRequest()
.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
.setInterval(3000) //update interval
.setFastestInterval(5000); //fastest interval
fusedLocationProviderClient.requestLocationUpdates(locationRequest, new LocationCallback(){
@Override
public void onLocationResult(LocationResult locationResult) {
if (locationResult != null)
{
mMap.clear();
final double lat = locationResult.getLastLocation().getLatitude();
final double log = locationResult.getLastLocation().getLongitude();
latLng = new LatLng(lat, log);
mMap.addMarker(new MarkerOptions().position(latLng).title("your current location"));
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, 15F));
//update latitude and longitude
Map <String, Object> update = new HashMap<>();
update.put("latitude", lat);
update.put("longitude", log);
databaseReference.child(current_uid).updateChildren(update).addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
//Toast.makeText(home.this, "updated", Toast.LENGTH_SHORT).show();
}
});
}else {
Toast.makeText(home.this,"location not found", Toast.LENGTH_SHORT).show();
}
}
},getMainLooper());
}
else
{
callpermissionlistener();
}
}
private void callpermissionlistener() {
String[] permissions = {Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION};
String rationale = "Please provide location permission so that you can ...";
Permissions.Options options = new Permissions.Options()
.setRationaleDialogTitle("location permission")
.setSettingsDialogTitle("warrning");
Permissions.check(this, permissions, rationale, options, new PermissionHandler() {
@Override
public void onGranted() {
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.fragment_container);
mapFragment.getMapAsync(home.this);
update_location();
}
@Override
public void onDenied(Context context, ArrayList<String> deniedPermissions) {
callpermissionlistener();
}
});
}
@Override
public void onBackPressed() {
if (drawerLayout.isDrawerOpen(GravityCompat.START)){
drawerLayout.closeDrawer(GravityCompat.START);
}
else {
backpressedwarrning();
}
//super.onBackPressed();
}
public void backpressedwarrning(){
builder = new AlertDialog.Builder(home.this);
builder.setMessage(R.string.dialog_message).setTitle(R.string.dialog_title);
builder.setMessage("Do you want to close this application ?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.setTitle("Exit");
alert.show();
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
// LatLng sydney = new LatLng(-34, 151);
//mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
//.moveCamera(CameraUpdateFactory.newLatLng(sydney));
}
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
switch (menuItem.getItemId()){
case R.id.nev_home:
startActivity(new Intent(home.this, home.class));
finish();
break;
case R.id.nev_profile:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new profilefagment()).commit();
/*getSupportActionBar().setTitle("profile");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);*/
break;
case R.id.nev_joiningc:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new joincirclefragment()).commit();
break;
case R.id.nev_invite:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new invitecodefragment()).commit();
break;
case R.id.nev_mycircle:
getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
new mycirclefragment()).commit();
break;
case R.id.nev_logout:
firebaseUser = firebaseAuth.getCurrentUser();
if (firebaseUser != null)
{
firebaseAuth.signOut();
finish();
startActivity(new Intent(home.this, login_screen.class));
}
break;
}
drawerLayout.closeDrawer(GravityCompat.START);
return true;
}
}
CodePudding user response：
It's because somehow before initializing mMap from the onMapReady(), it called mMap.clear();
To prevent the crash, make sure to null-check the mMap first and then access it.
For e.g.
if (mMap != null) {
...
mMap.clear();
mMap.addMarker(...);
mMap. moveCamera(...);
...
}