How to show downloadable message when retrieving data from Firebase database?

Question

I use Firebase to display data in text form. I use asynctask to load data in the background, when I download, I want to show the loaded message before the data is loaded into my text view.

But the popup data loading window is not displayed. (i.e., the doinBackgroundmethod exits immediately), and the user sees an empty text view and only after the Firebase data is loaded once.

How to prevent this and show a process dialog until my text image is loaded with Firebase data?

here is my code
<pre>
<code>
public class LastPage extends AppCompatActivity {
    TextView title, author, article;
    DatabaseReference mDatabase;

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


        title = (TextView) findViewById(R.id.last_page_title);
        author = (TextView) findViewById(R.id.last_page_author);
        article = (TextView) findViewById(R.id.last_page_article);

        mDatabase = FirebaseDatabase.getInstance().getReference();

        new LoadFirebaseData().execute();


    }

    private class LoadFirebaseData extends AsyncTask<Void, Void, Integer>
    {
        private ProgressDialog Dialog = new ProgressDialog(LastPage.this);

        @Override
        protected void onPreExecute()
        {
            try {
                Dialog.setMessage("Doing something...");
                Dialog.show();
            }catch (Exception e)
            {
                e.printStackTrace();
            }

        }

        @Override
        protected void onPostExecute(Integer result)
        {

            if(result==0)
            {
                //do some thing
            }
            // after completed finished the progressbar
            Dialog.dismiss();
        }

        @Override
        protected Integer doInBackground(Void... params) {

            mDatabase.child("version_1_5").child("title").addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    String temp = dataSnapshot.getValue(String.class);
                    title.setText(temp);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

            mDatabase.child("version_1_5").child("author").addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    String temp = dataSnapshot.getValue(String.class);
                    author.setText(temp);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

            mDatabase.child("version_1_5").child("article").addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    String temp = dataSnapshot.getValue(String.class);
                    article.setText(temp);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

            return 0;
        }


    }
}


</code>
</pre>

JSON tree structure:

Root
    Version_1_5
        Title:TitleValue
        Author:AuthorValue
        Article:ArticleValue

Answer 1

addListenerForSingleValueEvent node , node

private ProgressDialog Dialog = new ProgressDialog(LastPage.this);
Dialog.setMessage("Doing something...");
Dialog.show();
mDatabase.child("version_1_5").addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot Snapshot : dataSnapshot.getChildren()) {
            if(Snapshot.getKey().toString().equalsIgnoreCase("Title")){
                String temp = dataSnapshot.getValue(String.class);
                title.setText(temp);
            }
            else if(Snapshot.getKey().toString().equalsIgnoreCase("Author")){
                String temp = dataSnapshot.getValue(String.class);
                author.setText(temp);
            }
            else if(Snapshot.getKey().toString().equalsIgnoreCase("Article")){
                 String temp = dataSnapshot.getValue(String.class);
                article.setText(temp);
            }
        }
        Dialog.hide();
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

Answer 2

, firebase, ,

onPostExecute() , Firebase .

, adapter.notifyDataSetChanged() onPostExecute() doInBackground() , Firebase , , -

@Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressBar.setIndeterminate(true);
        progressBar.setVisibility(View.VISIBLE);
    }

    @Override
    protected String doInBackground(String... params) {
        DataBaseReference = FirebaseDatabase.getInstance().getReference("child").child("something");
            DataBaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot ds : dataSnapshot.getChildren()) {
                        //Code for Fetching data from firebase

                    }
                    categoryDetailsFragmentAdapter.notifyDataSetChanged();
                    progressBar.setVisibility(View.GONE);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
        }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        //progressBar.setVisibility(View.GONE);
        //categoryDetailsFragmentAdapter.notifyDataSetChanged();
    }

, .