从Google Firebase检索数据并在android studio应用程序的列表视图中显示

Question

My team and I are working on an android studio project. We can add data to the firebase. We are trying to retrieve data from the database but we think that we cannot reference the correct ID to retrieve data in a list view. We are trying to retrieve the amount, type and start under the Feedings Class. This is how our firebase database is set up.

Here is my code:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_feeding_list);

    mListView = (ListView) findViewById(R.id.listView);

    mAuth = FirebaseAuth.getInstance();
    database = FirebaseDatabase.getInstance();
    //myRef = database.getReference();
    FirebaseUser user = mAuth.getCurrentUser();
    userID = user.getUid();
    myRef = database.getReference("/Users/" + userID + "/Feedings");

    mAuthListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            FirebaseUser user = firebaseAuth.getCurrentUser();
            if(user != null){
                Log.d(TAG, "Signed in" + user.getUid());
                toastMessage("Successfully signed in: ");
            }else{
                Log.d(TAG, "Currently signed out");
            }

        }
    };

    myRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            showData(dataSnapshot);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

}

private void showData(DataSnapshot dataSnapshot) {
    for(DataSnapshot ds: dataSnapshot.getChildren()){
        Feeding feeding = new Feeding();
        feeding.setAmount(ds.child(userID).getValue(Feeding.class).getAmount());

        Log.d(TAG, "showData: name: " + feeding.getAmount());

        ArrayList<String> arrayList = new ArrayList<>();
        arrayList.add(feeding.getAmount());
        ArrayAdapter adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1, arrayList);
        mListView.setAdapter(adapter);
    }
}

@Override
public void onStart(){
    super.onStart();
    mAuth.addAuthStateListener(mAuthListener);
}

@Override
public void onStop(){
    super.onStop();
    if(mAuthListener != null){
        mAuth.removeAuthStateListener(mAuthListener);
    }
}


private void toastMessage(String message){
    Toast.makeText(this, message, Toast.LENGTH_LONG).show();
}

}

Answer 1

try to use the reference like this, it's provided in the official docs. and be aware of your ShowData method it's not correct.

myRef = database.getReference();  

  myRef.child("Users").child(userID).child("Feedings")
   .getReference().addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            showData(dataSnapshot);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });




private void showData(DataSnapshot dataSnapshot) {
    ArrayList<String> arrayList = new ArrayList<>();

    for(DataSnapshot ds: dataSnapshot.getChildren()){
        Feeding feeding = ds.getValue(Feeding.class);
        Log.d(TAG, "showData: name: " + feeding.getAmount());
        arrayList.add(feeding.getAmount());

    }


        ArrayAdapter adapter = new 
        ArrayAdapter(this,android.R.layout.simple_list_item_1, arrayList);
        mListView.setAdapter(adapter);
}