Android – displays the progress dialog box when retrieving data from the firebase database

I hope the activity must display the progress dialog box when getting data from the firebase database. It doesn't display anything and crashes. This is my code as follows

Public class profilemain extends appcompatactivity{

private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;

 private ProgressDialog progressDialog;

DatabaseReference mref = 
FirebaseDatabase.getInstance().getReference("users");
ListView mlistview;
ArrayList<String> arrayList=new ArrayList<>();
ArrayAdapter<String> arrayAdapter;

private BottomNavigationView.OnNavigationItemSelectedListener 
 mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_home:
progressDialog.show();
                startActivity(new 
Intent(profilemain.this,profilemain.class));
                return true;
            case R.id.navigation_dashboard:
                Toast.makeText(profilemain.this,"hi 
hello",Toast.LENGTH_SHORT).show();
                return true;
            case R.id.navigation_notifications:
                Toast.makeText(profilemain.this,"hi 
hello",Toast.LENGTH_SHORT).show();
                return true;
            case R.id.navigation_signout:

                Toast.makeText(profilemain.this,"You have successfully 
Signed out",Toast.LENGTH_SHORT).show();
                mAuth.signOut();
                return true;
        }
        return false;
    }

};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_profilemain);
   progressDialog.setMessage("loading");
    progressDialog.setTitle("database is");

    mlistview=(ListView) findViewById(R.id.listview);

    Firebase.setAndroidContext(this);

    DatabaseReference ref = FirebaseDatabase.getInstance()
            .getReference("users");
    //mref=new Firebase("https://stark-1dffd.firebaseio.com/users");
    arrayAdapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,arrayList);
    mlistview.setAdapter(arrayAdapter);


    mref.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            String value= dataSnapshot.getValue(String.class);

            arrayList.add(value);
            arrayAdapter.notifyDataSetChanged();
            //

            //

        }

        @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) {

        }
    });


    BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
    mAuth = FirebaseAuth.getInstance();


    mAuthListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            if (firebaseAuth.getCurrentUser()==null){
                startActivity(new
                        Intent(profilemain.this,MainActivity.class));

            }
        }
    };



}

@Override
protected void onStart() {
    super.onStart();

    mAuth.addAuthStateListener(mAuthListener);
}

      Process: com.food.sheenishere.stark, PID: 16408

com.google.firebase.database.DatabaseException: Failed to convert value of type 
java.util.HashMap to String

at com.google.android.gms.internal.zg.zzb(UnkNown Source)

at com.google.android.gms.internal.zg.zza(UnkNown Source)

at com.google.firebase.database.DataSnapshot.getValue(UnkNown Source)

at com.food.sheenishere.stark.home$1.onChildAdded(home.java:49)

at com.google.android.gms.internal.px.zza(UnkNown Source)

at com.google.android.gms.internal.vj.zzHX(UnkNown Source)

   at com.google.android.gms.internal.vp.run(UnkNown Source)

at android.os.Handler.handleCallback(Handler.java:751)

at android.os.Handler.dispatchMessage(Handler.java:95)

at android.os.Looper.loop(Looper.java:154)

at android.app.ActivityThread.main(ActivityThread.java:6119)

at java.lang.reflect.Method.invoke(Native Method)

   at 

com.android.internal.os.ZygoteInit $MethodAndArgsCaller.run(ZygoteInit.java:886)

    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
07-15 20:49:51.645 16408-16435/com.food.sheenishere.stark W/DynamiteModule: 
Local module descriptor class for com.google.firebase.auth not found.

resolvent:

The problem in your code is that you are trying to use the show(), setMessage ("loading") and settitle ("database is") methods on an uninitialized ProgressDialog object

To solve your problem, you need to use the following code:

ProgressDialog progressDialog = new ProgressDialog(this);

It will certainly solve your problem