firebase 实时数据库到列表视图？

Question

Is there a way to retrieve all the child nodes to a textView?, i wanted to create a users log where you can tract what kind of transactions users have made, but i can't figure out how to get the nodes, and its list of children.

the code so far:

database = FirebaseDatabase.getInstance();
    String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
    reference = FirebaseDatabase.getInstance().getReference().child("Users").child(uid).child("Logs");
btn1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot datasnapshot) {
                    String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
                    String logs = datasnapshot.child(uid).child("Logs").getValue().toString();

                    tv1.setText(logs);
                }

                @Override
                public void onCancelled(@NonNull DatabaseError error) {

                }
            });

Answer 1

You're attaching a ValueEventListener to path /Users/$uid/Logs in your database, so the datasnapshot in your onDataChange contains the information for that node and any data under it.

When you then try to get the value of datasnapshot.child(uid).child("Logs") from that data snapshot, there is not child $uid/Logs in datasnapshot , so the value is going to be null .

---

To get the value for all the logs, you can

datasnapshot.getValue()

This will return a Map<String, Object> that you can then loop over.

---

Alternatively, you can loop over all the logs by date, and then by time, and print the value of the Date property for each, that'd be something like:

reference.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot datasnapshot) {
        for (DataSnapshot daySnapshot: datasnapshot.getChildren()) {
            Log.d("Firebase", dateSnapshot.getKey());
            for (DataSnapshot timeSnapshot: daySnapshot.getChildren()) {
                Log.d("Firebase", timeSnapshot.getKey());
                Log.d("Firebase", timeSnapshot.child("Date").getValue(String.class));
            }
        }
    }
    ...

To learn how to then show this in a list view or a recycler view, I recommend searching for that: https://www.google.com/search?q=how+to+show+data+from+firebase+in+a+list+view