Question

我需要从我的数据库中接收这两个值我需要将这些值放在标记中而且我不知道如何将收到的数据库的纬度和经度放到标记

这是我使用的方法：

          public static DatabaseReference getPostRef() {
    return FirebaseDatabase.getInstance()
            .getReference(Constantes.POSTS_KEY);
}
public static Query getPostQuery() {
    return getPostRef().orderByChild(Constantes.TIME_CREATED_KEY);
}
public static DatabaseReference getMyPostRef() {
    return FirebaseDatabase.getInstance().getReference(Constantes.MY_POSTS)
            .child(getCurrentUser().getEmail().replace(".", ","));
}

// USER ID
public static String getUid() {
    String path = FirebaseDatabase.getInstance().getReference().push().toString();
    return path.substring(path.lastIndexOf("/") + 1);
}

我使用它来发送数据

 FirebaseUtils.getPostRef().child(postUid).setValue(mPost);

这是我的模特课：

 public class Post implements Serializable {

private String photoPortadaUrl;

private String organizadoPor;

private String mes;
private String dia;

private String hora;
private String minutos;

private String titulo;
private String descripicion;
private String costo;

private double latitud;
private double longitud;

public Post(){

}

public Post(String photoPortadaUrl, String organizadoPor, String mes, String dia, String hora, String minutos, String titulo, String descripicion, String costo, double latitud, double longitud) {
    this.photoPortadaUrl = photoPortadaUrl;
    this.organizadoPor = organizadoPor;
    this.mes = mes;
    this.dia = dia;
    this.hora = hora;
    this.minutos = minutos;
    this.titulo = titulo;
    this.descripicion = descripicion;
    this.costo = costo;
    this.latitud = latitud;
    this.longitud = longitud;
}


public String getPhotoPortadaUrl() {
    return photoPortadaUrl;
}

public void setPhotoPortadaUrl(String photoPortadaUrl) {
    this.photoPortadaUrl = photoPortadaUrl;
}

public String getTitulo() {
    return titulo;
}

public void setTitulo(String titulo) {
    this.titulo = titulo;
}

public String getOrganizadoPor() {
    return organizadoPor;
}

public void setOrganizadoPor(String organizadoPor) {
    this.organizadoPor = organizadoPor;
}

public String getMes() {
    return mes;
}

public void setMes(String mes) {
    this.mes = mes;
}

public String getDia() {
    return dia;
}

public void setDia(String dia) {
    this.dia = dia;
}

public String getHora() {
    return hora;
}

public void setHora(String hora) {
    this.hora = hora;
}

public String getMinutos() {
    return minutos;
}

public void setMinutos(String minutos) {
    this.minutos = minutos;
}

public String getDescripicion() {
    return descripicion;
}

public void setDescripicion(String descripicion) {
    this.descripicion = descripicion;
}

public String getCosto() {
    return costo;
}

public void setCosto(String costo) {
    this.costo = costo;
}

public double getLatitud() {
    return latitud;
}

public void setLatitud(double latitud) {
    this.latitud = latitud;
}

public double getLongitud() {
    return longitud;
}

public void setLongitud(double longitud) {
    this.longitud = longitud;
}

}

但是为了接收数据或阅读它们，我这样做：我把相关的代码：

            public class NavActivity extends AppCompatActivity {

private Post mPost;

  protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_nav);
  mPost = new Post();
 }


 public void onMapReady(GoogleMap googleMap) {
   FirebaseUtils.getPostRef().child(postuid).addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        mPost = dataSnapshot.getValue(Post.class);

        // HERE IS THE ERROR
        //When I try to read the data it gives me an exception which I will put down


        /* 
         I try with this 
          but i get the same exception

           Post LPOst = dataSnapshot.getValue(Post.class);

           Log.d("Dep", LPOst.getTitulo());
         */

        Log.d("Dep", mPost.getTitulo());
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});



 }

}

我得到了这个例外：

      java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.octacorp.octa.strank.models.Post.getTitulo()' on a null object reference
                                                                      at com.octacorp.octa.strank.Activities.NavActivity$5.onDataChange(NavActivity.java:333)

我该怎么办？

Answer 1

您需要一个值事件侦听器。如果您不希望每次更改时都提取数据，则可以使用单个事件监听器。

如何在Firebase数据库中接收特定值（读取或接收数据时出现问题）

1 个答案: