Place an activity with its layout on the Main Activity on launch

Question

Objective: Modular approach

I am trying to understand an approach where the Main Activity sort of acts like a stage where I stack sub components on top of it having some sort of modular approach.

MainActivity.java (Parent)

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

</android.support.constraint.ConstraintLayout>

---

UserList.java (child)

public class UserList extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_user_list);
    }

    public void initView(ArrayList<UserVO> users) {
        this.users = users;
        userList.setAdapter(new UserListAdapter());
    }

    class UserListAdapter extends BaseAdapter {

        @Override
        public int getCount() {
            return users.size();
        }

        @Override
        public Object getItem(int i) {
            return null;
        }

        @Override
        public long getItemId(int i) {
            return 0;
        }

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            view = layoutInflater.inflate(R.layout.user_list, null);

            TextView givenName = view.findViewById(R.id.givenName);
            givenName.setText(users.get(i).givenName());
            return view;
        }
    }
}

activity_user_list.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".view.components.UserList">

    <ListView
        android:id="@+id/userList"
        android:layout_width="395dp"
        android:layout_height="715dp"
        tools:layout_editor_absoluteX="8dp"
        tools:layout_editor_absoluteY="8dp" />
</android.support.constraint.ConstraintLayout>

I believe ListView requires this somewhere, each cell has a textField

<TextView
    android:id="@+id/givenName"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="8dp"
    android:text="TextView"
    android:textSize="18sp" />

Question

How can I add UserList on app launch to the MainActivity?

Edit

I've followed the same naming convention. Here is an error:

java.lang.IllegalStateException: ArrayAdapter requires the resource ID to be a TextView

Answer 1

Try this using fragments,

Activity Main code,

public class MainActivity extends AppCompatActivity {

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

    loadData();
}

private void loadData() {

    getSupportFragmentManager().beginTransaction()
            .replace(R.id.frame_layout,new ListViewFragment())
            .commit();

}
}

activity_main layout:(need to use frame layout to implement fragments)

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/frame_layout"/>

Here comes the fragment code:

public class ListViewFragment extends Fragment {

private String listItems[] = {"vfvd","vdvvfv","vvddv","vfddvvd"}; //static data
ListView userList;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view =  inflater.inflate(R.layout.fragment_list_view, container, false);



    userList = view.findViewById(R.id.userList);

    ArrayAdapter arrayAdapter = new 
    ArrayAdapter(getActivity(),R.layout.user_list_items,listItems);
    userList.setAdapter(arrayAdapter);

    return view;

}

}

And fragment layout

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ListViewFragment">

<ListView
    android:id="@+id/userList"
    android:layout_width="395dp"
    android:layout_height="715dp"
    tools:layout_editor_absoluteX="8dp"
    tools:layout_editor_absoluteY="8dp" />

code for textview where we need to put the listview data

<?xml version="1.0" encoding="utf-8"?>
<TextView android:id="@+id/givenName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="8dp"
android:text="TextView"
android:textSize="18sp"
xmlns:android="http://schemas.android.com/apk/res/android" />

You have to implement the adapter code in the fragment I just used the static data and I was able to get the feature you wanted. If you need further help I can do it for you comment below. Thank you.