如何使用Android Studio简单地检索Firebase中的所有项目和值

Question

这是我的代码。我试图在日志中检索它，然后如果它检索到。但我认为这似乎不是正确的方式。希望有人能纠正我，关于如何轻松检索firebase中的所有项目和值。

final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference()
.child("FirstRoot");
databaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
for(DataSnapshot dataSnapshot : snapshot.getChildren()){
//
//                    Map<String,Object> map = (Map<String,Object>) dataSnapshot.getValue();
//                    Object material = map.get("item");
//                    Object value = map.get("value");
//                    int v = Integer.parseInt(String.valueOf(value));
String material  = String.valueOf(dataSnapshot.child("item").getValue());
Log.d("Item:", material);
//                    String item = dataSnapshot.child("item").getValue().toString();;
////                    Float valuee = Float.parseFloat(dataSnapshot.child("valuee").getValue().toString());
//                    entries.add(new PieEntry(13f, item));
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});

Answer 1

尽管从你想把从firebase检索到的数据存储在哪里的问题上还不太清楚。这可能会奏效。。试试

final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference()
.child("FirstRoot");
myRef.addValueEventListener(new ValueEventListener() {

@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue() == null) {
Toast.makeText(getApplicationContext(),"Data Not Available",Toast.LENGTH_LONG).show();
} else {
final String data1 = (Objects.requireNonNull(dataSnapshot.child("data1").getValue())).toString();
final String data2 = (Objects.requireNonNull(dataSnapshot.child("data2").getValue())).toString();
final String data3 = (Objects.requireNonNull(dataSnapshot.child("data3").getValue())).toString();
final String data4 = (Objects.requireNonNull(dataSnapshot.child("data4").getValue())).toString();
model_class model = new model_class(data1,data2,data3,data4);
//do whatever you want with your data
entries.add(new PieEntry(13f, data1));

}

}
@Override
public void onCancelled(@NonNull DatabaseError error) {
throw error.toException(); // never ignore errors
}
}

Answer 2

Kotlin

如果你想从firebase cloud firestore读取数据，你需要简单地编写这段代码。

// Get a Instance from FirebaseFirestore.
val db= FirebaseFirestore.getInstance()
//Get the user current Id.
val uId = auth.currentUser!!.uid
//Instead of XYZ you have to write your collection name and Id in 
//document.
db.collection("XYZ").document(uId)
.get()
.addOnCompleteListener {
if (it.isSuccessful){
//When it is successful you have to do what you want as I have given example that you can understand better through this way you can get userName and you can set into your textView and you can read as many data as you can this is one example.
val documentSnapShot = it.result
val firstName = documentSnapShot.getString("first_name")
tv_Set_ProfileName.text =firstName

}
}