Java – how to automatically fill edit text from the middle?

I'm developing a contact manager project for android.in. I want to automatically fill in the end of the e-mail address in this field when a user registers. For example, when a user enters his or her user name, it should automatically give @ gmail.com or @ outlook.com suggestions, and so on

Well, this is a small part of my code

String[] maindb = {"@gmail.com", "@rediffmail.com", "@hotmail.com", "@outlook.com"};

mail = (AutoCompleteTextView) findViewById(R.id.A1_edt_mail);

ArrayAdapter<String> adpt = new ArrayAdapter<String>(this, R.layout.support_simple_spinner_dropdown_item, maindb);
mail.setAdapter(adpt);

Well, I have this output

But I hope this suggestion should appear when the user enters his / her user name, but it is not

Well, my question is not the repetition of Android how an EditText work as autocomplete. My question is different from this

Thank you in advance

resolvent:

I recommend that you append the text in the email to each string in maindb before setting up the adapter – > use textwatcher to detect changes to the mail view

edit

Maybe that's what you're looking for

final ArrayList<String> maindb = new ArrayList<>();
    maindb.add("@gmail.com");
    maindb.add("@rediffmail.com");
    maindb.add("@hotmail.com");
    maindb.add("@outlook.com");
    final ArrayList<String> compare = new ArrayList<>();
    final ArrayAdapter<String> adpt = new ArrayAdapter<String>(MainActivity.this, R.layout.support_simple_spinner_dropdown_item, compare);
    Word.setAdapter(adpt);
    Word.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
        }

        @Override
        public void afterTextChanged(Editable s) {
            if (s.length() >= 0)
                if (!s.toString().contains("@")) {
                    compare.clear();
                    for (String aMaindb : maindb) {
                        aMaindb = s + aMaindb;
                        compare.add(aMaindb);
                    }
                    adpt.clear();
                    adpt.addAll(compare);
                }
        }
    });

I hope this will help