AsyncTask不适用于实时数据库

Question

有什么方法可以从Firebase实时数据库中获取后台数据吗？ Asynctask不起作用。

我想在从数据库中获取数据时显示进度对话框。

 private class asyncData extends AsyncTask<String,String,String> {
        ProgressDialog Asycdialog = new ProgressDialog(getContext());

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            Asycdialog.setMessage("Loading...");
            Asycdialog.show();
        }

        @Override
        protected String doInBackground(String... strings) {
            Query query = databaseReference.child("").orderByChild("cityWithCountry").equalTo(strings[0]);
            query.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    arrData.clear();
                    if (dataSnapshot.exists()) {
                        // dataSnapshot is the "issue" node with all children with id 0
                        for (DataSnapshot items : dataSnapshot.getChildren()) {
                            // do something with the individual "issues"
                            Log.d("QueryValues",""+items.getValue());
                            DataConstructor ds = items.getValue(DataConstructor.class);
                            arrData.add(ds);
                        }
                    }
                }

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

                }
            });


            return  null;
        }
        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            Asycdialog.dismiss();
        }
    }

这是代码。

Answer 1

尝试一下，让我知道它是否有效。

   Asycdialog.show();
     Query query = databaseReference.child("").orderByChild("cityWithCountry").equalTo(strings[0]);
                query.addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        arrData.clear();
                        if (dataSnapshot.exists()) {
                            // dataSnapshot is the "issue" node with all children with id 0
                            for (DataSnapshot items : dataSnapshot.getChildren()) {
                                // do something with the individual "issues"
                                Log.d("QueryValues",""+items.getValue());
                                DataConstructor ds = items.getValue(DataConstructor.class);
                                arrData.add(ds);
**// check condition and hide your dialog here**
                            }
                        }
                    }

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

                    }
                });