从特定节点firebase数据库中检索数据

2 回答

• 0

  首先创建一个POJO类来获取所需的值，它应该与在Firebase中使用它们的方式相同 .

  public class AppointmentsPojo {
  
      private String appointmentStuts;
  
      public AppointmentsPojo(){
  
      }
  
  
      public String getAppointmentStuts() {
          return appointmentStuts;
      }
  
      public void setAppointmentStuts(String appointmentStuts) {
          this.appointmentStuts = appointmentStuts;
      }
  
  }
  

  然后只需循环 Appointments 以获取每个 appointmentStuts

  mDatabase.child("Appointments").addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
      //Looping inside Appointments to get each appointmentsStuts
      for(DataSnapshot snapshot: dataSnapshot.getChildren()){
      AppointmentsPojo ap = snapshot.getValue(AppointmentsPojo.class);
      //Getting each appointmentStuts
       String appointmentStuts = ap.getAppointmentStuts();
       //To get each father of those appointments 
       String key = snapshot.getKey();
  
        Log.e("Data: " , "" + appointmentStuts );
  
         }
  
    }
  
    @Override
    public void onCancelled(DatabaseError databaseError) {
      System.out.println("The read failed: " + databaseError.getCode());
    }
  });
  

  mDatabase的位置

  DatabaseReference mDatabase;
  
  mDatabase = FirebaseDatabase.getInstance().getReference();
  

  回复于 2024-04-29T19:11:29+08:00
• 1

  要仅从第一个对象获取 appointmentStuts 的值，请使用以下代码：

  DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
  Query query = rootRef.child("Appointments").child(PostKey).limitToFirst(1);
  ValueEventListener valueEventListener = new ValueEventListener() {
      @Override
      public void onDataChange(DataSnapshot dataSnapshot) {
          for(DataSnapshot ds : dataSnapshot.getChildren()) {
              String appointmentStuts = ds.child("appointmentStuts").getValue(String.class);
              Log.d(TAG, appointmentStuts);
          }
      }
  
      @Override
      public void onCancelled(@NonNull DatabaseError databaseError) {
          Log.d(TAG, databaseError.getMessage());
      }
  };
  query.addListenerForSingleValueEvent(valueEventListener);
  

  回复于 2024-04-29T19:11:29+08:00