notifyDataSetChanged () does not work

0

I'm in a chat application and would like to use notifyDataSetChanged to scroll to the end of the page automatically without the user having to read all the messages. however when I try to use notifyDataSetChanged the Android does not recognize, I'm already in that trouble for at least 3 hours,

public class chatActivity extends AppCompatActivity {

    private Button  add_room;
    private EditText room_name;

    private ListView listView;
    private ArrayAdapter<String> arrayAdapter; //mudei de private pra public
    private ArrayList<String> list_of_rooms = new ArrayList<>();
    private String name;
    private DatabaseReference root = FirebaseDatabase.getInstance().getReference().getRoot();

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



        add_room = (Button) findViewById(R.id.btn_add_room);


        listView = (ListView) findViewById(R.id.listView);

        arrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,list_of_rooms);

        listView.setAdapter(arrayAdapter);

        request_user_name();

        add_room.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                Map<String,Object> map = new HashMap<String, Object>();
                map.put(room_name.getText().toString(),"");
                root.updateChildren(map);

            }
        });

        root.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                Set<String> set = new HashSet<String>();
                Iterator i = dataSnapshot.getChildren().iterator();

                while (i.hasNext()){
                    set.add(((DataSnapshot)i.next()).getKey());
                }

                list_of_rooms.clear();
                list_of_rooms.addAll(set);

                arrayAdapter.notifyDataSetChanged();

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });





        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

                Intent intent = new Intent(getApplicationContext(),Chat_Room.class);
                intent.putExtra("room_name",((TextView)view).getText().toString() );
                intent.putExtra("user_name",name);
                startActivity(intent);
                arrayAdapter.notifyDataSetChanged();

            }
        });

    }

    private void request_user_name() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Enter name:");

        final EditText input_field = new EditText(this);

        builder.setView(input_field);
        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                name = input_field.getText().toString();
            }
        });

        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                dialogInterface.cancel();
                request_user_name();
            }
        });

        builder.show();
    }


}

and

public class Chat_Room  extends AppCompatActivity{




private Button btn_send_msg;
private EditText input_msg;
private TextView chat_conversation;

private String user_name,room_name;
private DatabaseReference root ;
private String temp_key;

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

    btn_send_msg = (Button) findViewById(R.id.btn_send);
    input_msg = (EditText) findViewById(R.id.msg_input);
    chat_conversation = (TextView) findViewById(R.id.textView);

    user_name = getIntent().getExtras().get("user_name").toString();
    room_name = getIntent().getExtras().get("room_name").toString();
    setTitle(" Room - "+room_name);

    root = FirebaseDatabase.getInstance().getReference().child(room_name);

    btn_send_msg.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            Map<String,Object> map = new HashMap<String, Object>();
            temp_key = root.push().getKey();
            root.updateChildren(map);

            DatabaseReference message_root = root.child(temp_key);
            Map<String,Object> map2 = new HashMap<String, Object>();
            map2.put("name",user_name);
            map2.put("msg",input_msg.getText().toString());

            message_root.updateChildren(map2);
            input_msg.setText("");






        }





    });










    root.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {

            append_chat_conversation(dataSnapshot);
        }

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

            append_chat_conversation(dataSnapshot);

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

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

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

}

private String chat_msg,chat_user_name;

private void append_chat_conversation(DataSnapshot dataSnapshot) {

    Iterator i = dataSnapshot.getChildren().iterator();

            while (i.hasNext()) {

                chat_msg = (String) ((DataSnapshot) i.next()).getValue();
                chat_user_name = (String) ((DataSnapshot) i.next()).getValue();

                chat_conversation.append(chat_user_name + " : " + chat_msg + " \n");


            }
}

}
    
asked by anonymous 17.10.2017 / 03:12

1 answer

0

notifyDataSetChanged () only notifies the ListView / RecyclerView that it has new elements, and does not scroll automatically.

After using notify, use the following code to be able to scroll to the last element in the list:

listView.post(new Runnable() {
        @Override
        public void run() {
            listView.setSelection(adapter.getCount() - 1);
        }
    });
    
17.10.2017 / 12:28