如何从Firebase数据库检索单个数据

Question

I need to retrieve single data from Firebase database. Where I have a list view contains id list. Whenever user clicks the listview i need to display the respective value field.

check screen shot of db

here is the code.

 l1.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                        r2= FirebaseDatabase.getInstance().getReference().child("type").child("discord").child("ad");

                        r2.addChildEventListener(new ChildEventListener() {
                        @Override
                        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                            String name1;
                            name1=dataSnapshot.getValue().toString();
                            Toast.makeText(Main2Activity.this, name1, Toast.LENGTH_SHORT).show();
                        }

                        @Override
                        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

                        }

                        @Override
                        public void onChildRemoved(DataSnapshot dataSnapshot) {

                        }

                        @Override
                        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

                        }

                        @Override
                        public void onCancelled(DatabaseError databaseError) {

                        }
                    });





                }
            });

I need to execute the query

select value from table_name where id="01" ;

Answer 1

You need to change this line of code:

name1=dataSnapshot.getValue().toString();

with

name1=dataSnapshot.child("01").getValue(String.class);

Answer 2

Change the addChildEventListener to addValueEventListener .

For example:

r2.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        String name1 = dataSnapshot.child("01").getValue(String.class);
        Toast.makeText(Main2Activity.this, name1, Toast.LENGTH_SHORT).show();
    }
    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.e(TAG, "onCancelled", databaseError.toException());
    }
});

Reference