How to query a specific child value in multiple nodes with firebase android

问题

I want to query a specific child value in multiple nodes, to populate them in a list view by FirebaseListAdapter. I'm passing a firebase reference to FirebaseListAdapter method to listen to, which is in red rectangle in the picture below, And I want to populate in the list view the values of the "category" key only. which are in green rectangle in the picture below.

My code is here:

    catgoryList = (ListView) findViewById(R.id.catList);
    rootRef = FirebaseDatabase.getInstance().getReference();
    restaurantMenuRef = rootRef.child("menu").child(restaurantID);

    FirebaseListAdapter<String> listAdapter = new FirebaseListAdapter<String>
            (this, String.class, R.layout.menu_list_item, restaurantMenuRef ) {
        @Override
        protected void populateView(View v, String s, int position) {
            TextView menuName = (TextView)v.findViewById(R.id.menuName);
            menuName.setText(s);
        }
    };
    catgoryList.setAdapter(listAdapter);

And the layout for the listView containing a TextView to display the category name.

回答1:

You'll need to override FirebaseListAdapter.parseDataSnapshot() to extract the right value from the DataSnapshot:

FirebaseListAdapter<String> listAdapter = new FirebaseListAdapter<String>
        (this, String.class, R.layout.menu_list_item, restaurantMenuRef ) {

    @Override
    protected String parseSnapshot(DataSnapshot snapshot) {
        return snapshot.child("category").getValue(String.class);
    }

    @Override
    protected void populateView(View v, String s, int position) {
        TextView menuName = (TextView)v.findViewById(R.id.menuName);
        menuName.setText(s);
    }
};

来源：https://stackoverflow.com/questions/37558909/how-to-query-a-specific-child-value-in-multiple-nodes-with-firebase-android