Why is the received data not displayed?

Question

Java

I want to receive data from the second activity and display it in the listView in the first one, but for some reason nothing appears on the screen.
The code itself:
The first activity, in it I create a second activity and display a listView on the screen

public class MainActivity extends AppCompatActivity {

    public List<String> list;

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

        list = new ArrayList<>();

        ArrayAdapter<String> adapter = new ArrayAdapter<>(this, R.layout.array_adapter, list);

        ListView lv = (ListView)findViewById(R.id.listView);
        lv.setAdapter(adapter);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        Intent intent = getIntent();
        String item = intent.getStringExtra("main");
        list.add(item);
    }

    public void floatinButton1OnClick(View view) {
        Intent intent = new Intent(this, AddElement.class);
        startActivityForResult(intent, 1);
    }
}

The second activity, in it I read the data from the editText and pass it to the first activity

public class AddElement extends AppCompatActivity {

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

    public void floatingButton1OnClick_AddElement(View view) {

        TextView textView = (TextView)findViewById(R.id.editText1_add_element);
        String main_item = textView.getText().toString();

        Intent intent = new Intent(this, MainActivity.class);
        intent.putExtra("main", main_item);

        setResult(RESULT_OK, intent);
        finish();
    }

Answer 1

So you just add an element to the list, and the adapter itself does not inform about it, therefore it is not displayed