我正在尝试从Firebase获取当前ID位置,并发送到另一个类以从Firebase检索相关ID信息,但是我遇到以下错误,请告诉我该怎么做?
获取纬度和经度的空值?在此处输入图像描述
java.lang.NullPointerException:尝试调用虚拟方法
空对象引用上的'double java.lang.Double.doubleValue()'
在com.example.medicalstore.MapRetrieveActivity $ 1.onDataChange(MapRetrieveActivity.java:62)
public class SupplierNewMedicineList extends AppCompatActivity {
private RecyclerView productsList;
RecyclerView.LayoutManager layoutManager;
private DatabaseReference cartListRef;
private String userID="";
String uID;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_supplier_new_medicine_list);
userID=getIntent().getStringExtra("uid");
productsList=findViewById(R.id.product_list5);
productsList.setHasFixedSize(true);
layoutManager=new LinearLayoutManager(this);
productsList.setLayoutManager(layoutManager);
cartListRef= FirebaseDatabase.getInstance().getReference()
.child("order_list")
.child(userID);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab5);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.supplier_menu, menu);
return true;
}
@Override
protected void onStart() {
super.onStart();
FirebaseRecyclerOptions<Data> options=
new FirebaseRecyclerOptions.Builder<Data>()
.setQuery(cartListRef, Data.class)
.build();
FirebaseRecyclerAdapter<Data, SupplierViewHolder> adapter=new FirebaseRecyclerAdapter<Data, SupplierViewHolder>(options) {
@Override
protected void onBindViewHolder(@NonNull SupplierViewHolder holder, int position, @NonNull Data model) {
uID=getRef(position).getKey();
holder.txtMName.setText(model.getmName());
holder.txtMQuantity.setText(model.getmQuantity());
}
@NonNull
@Override
public SupplierViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.list_layout,parent,false);
SupplierViewHolder holder=new SupplierViewHolder(view);
return holder;
}
};
productsList.setAdapter(adapter);
adapter.startListening();
}
public void onBackPressed() {
super.onBackPressed();
Intent intent = new Intent(SupplierNewMedicineList.this,SupplierNewOrders.class);
startActivity(intent);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
Toast.makeText(this, "Selected Item: " +item.getTitle(), Toast.LENGTH_SHORT).show();
switch (item.getItemId()) {
case R.id.nav_map:
Intent intent = new Intent(SupplierNewMedicineList.this, MapRetrieveActivity.class);
intent.putExtra("uiid",uID);
startActivity(intent);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
另一类是
public class MapRetrieveActivity extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
private String userID="";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map_retrieve);
// 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);
}
/**
* Manipulates the map once available.
* This callback is triggered when the map is ready to be used.
* This is where we can add markers or lines, add listeners or move the camera. In this case,
* we just add a marker near Sydney, Australia.
* If Google Play services is not installed on the device, the user will be prompted to install
* it inside the SupportMapFragment. This method will only be triggered once the user has
* installed Google Play services and returned to the app.
*/
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
userID=getIntent().getStringExtra("uiid");
DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Current Location").child(userID);
ValueEventListener listener = databaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Double latitude = dataSnapshot.child("latitude").getValue(Double.class);
Double longitude = dataSnapshot.child("longitude").getValue(Double.class);
LatLng location = new LatLng(latitude, longitude);
mMap.addMarker(new MarkerOptions().position(location).title("Marker Location"));
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(location, 14F));
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
}
我的Firebase视图是
最佳答案
使用原始数据类型double latitude = ............
要么
Double latitude = new Double(dataSnapshot.child("latitude").getValue(Double.class));