調(diào)用 (user.getlat) 和 (user.getlng) 時出現(xiàn)問題。我已經(jīng)全局聲明了用戶對象，并在 getUserData() 方法中對其進行了初始化。但是當我運行應用程序時，應用程序崩潰并且在 logcat 中說：java.lang.NullPointerException：嘗試在空對象引用上調(diào)用虛擬方法“double com.example.profile.User.getLat()”public class Profile extends FragmentActivity implements OnMapReadyCallback {private GoogleMap mMap;private LocationManager locationManager;private LocationListener locationListener;private FirebaseAuth mAuth;DatabaseReference database = FirebaseDatabase.getInstance().getReference();DatabaseReference myRef = database.child("users");User user;@Overrideprotected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_profile); SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager() .findFragmentById(R.id.mapFragment); mapFragment.getMapAsync(this); mAuth = FirebaseAuth.getInstance();}public void getUserData(){ String uID = mAuth.getCurrentUser().getUid(); myRef.child(uID).addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { dataSnapshot.getChildren(); user = dataSnapshot.getValue(User.class); Toast.makeText(Profile.this, "" + user.lng, Toast.LENGTH_LONG).show(); // Prints the value normally! } @Override public void onCancelled(DatabaseError databaseError) { Toast.makeText(Profile.this, "Failed to read from database!", Toast.LENGTH_LONG).show(); } });}@Overridepublic void onMapReady(GoogleMap googleMap) { mMap = googleMap; LatLng userL = new LatLng(user.getLat(),user.getLng()); // The problem occurs here! mMap.clear(); mMap.addMarker(new MarkerOptions().position(userL).title("Your Location")); mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(userL,17));}}
1 回答
神不在的星期二
TA貢獻1963條經(jīng)驗 獲得超6個贊
首先，您沒有getUserData()在任何地方調(diào)用方法。我讀到您也嘗試添加該邏輯onCreate()，但是沒有用。
添加偵聽器并不意味著您會立即獲得預期的結果。
僅使用該onMapReady()方法設置地圖，設置不依賴于User. 僅在檢測到User數(shù)據(jù)更改時添加/修改地圖標記。查看更改：
public void getUserData(){
String uID = mAuth.getCurrentUser().getUid();
myRef.child(uID).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
dataSnapshot.getChildren();
user = dataSnapshot.getValue(User.class);
LatLng userL = new LatLng(user.getLat(),user.getLng());
if(mMap!=null){
mMap.clear();
mMap.addMarker(new MarkerOptions().position(userL).title("Your
Location"));
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(userL,17));
}
Toast.makeText(Profile.this, "" + user.lng, Toast.LENGTH_LONG).show(); // Prints the value normally!
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(Profile.this, "Failed to read from database!", Toast.LENGTH_LONG).show();
}
});
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
}
請調(diào)用該方法getUserData()或?qū)⑵浯a移入onCreate().
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