How to implement a group view in a ListView in Kotlin Android

How to implement a group view in a ListView in Kotlin Android.

Here is a detailed step-by-step tutorial on how to implement a group view in a ListView in Kotlin Android:

Step 1: Create a new Android project in Android Studio and open the layout file for the activity where you want to implement the group view.

Step 2: Add a ListView widget to your layout file. This will be used to display the groups and their items.

<ListView
    android:id="@+id/listView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

Step 3: Create a new layout file for the group view. This layout will be inflated for each group in the ListView.

<!-- group_item_layout.xml -->
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="8dp"
    android:background="#EEEEEE"
>
    <TextView
        android:id="@+id/groupTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:textColor="#000000"
    />
    <ListView
        android:id="@+id/groupItems"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
    />
</LinearLayout>

Step 4: Create a custom adapter class that extends the BaseAdapter class. This adapter will be responsible for populating the ListView with the groups and their items.

class GroupAdapter(private val context: Context, private val groups: List<Group>) : BaseAdapter() {

    override fun getCount(): Int {
        return groups.size
    }

    override fun getItem(position: Int): Any {
        return groups[position]
    }

    override fun getItemId(position: Int): Long {
        return position.toLong()
    }

    override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View {
        val view: View
        val group = groups[position]

        if (convertView == null) {
            val inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
            view = inflater.inflate(R.layout.group_item_layout, null)
        } else {
            view = convertView
        }

        val groupTitle = view.findViewById<TextView>(R.id.groupTitle)
        groupTitle.text = group.title

        val groupItems = view.findViewById<ListView>(R.id.groupItems)
        val itemsAdapter = ArrayAdapter(context, android.R.layout.simple_list_item_1, group.items)
        groupItems.adapter = itemsAdapter

        return view
    }
}

Step 5: In your activity code, create a list of Group objects and populate it with the groups and their items.

data class Group(val title: String, val items: List<String>)

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val groups = listOf(
            Group("Group 1", listOf("Item 1", "Item 2", "Item 3")),
            Group("Group 2", listOf("Item 4", "Item 5")),
            Group("Group 3", listOf("Item 6", "Item 7", "Item 8", "Item 9"))
        )

        val listView = findViewById<ListView>(R.id.listView)
        val adapter = GroupAdapter(this, groups)
        listView.adapter = adapter
    }
}

Step 6: Run your app and you should see the ListView populated with the groups and their items. Each group will have a title and a sub-list of items.

Congratulations! You have successfully implemented a group view in a ListView in Kotlin Android.