RecyclerView LinearLayoutmanager Kotlin

RecyclerView is a flexible and efficient version of ListView and GridView. It is used to display large sets of data in a list or grid.

LinearLayoutManager is a default layout manager used in RecyclerView. It arranges items in a vertical or horizontal linear layout. It is defined in the android.support.v7.widget.LinearLayoutManager package.

Kotlin is a modern, statically typed, cross-platform programming language. It is designed to be concise, safe, and interoperable with Java.

Prerequisites

• Android Studio 3.0 or higher
• Kotlin plugin for Android Studio

Implementation

1. Add RecyclerView to layout

Add RecyclerView to your layout file. In this example, we will use a vertical LinearLayout.

<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/myRecyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

2. Create RecyclerView Adapter

Create an adapter that extends RecyclerView.Adapter. The adapter is responsible for creating and binding views for each item in the data set.

class MyAdapter(private val myData: List<String>): RecyclerView.Adapter<MyAdapter.MyViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.my_item_layout, parent, false)
        return MyViewHolder(view)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.bind(myData[position])
    }

    override fun getItemCount() = myData.size

    class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        fun bind(item: String) {
            itemView.findViewById<TextView>(R.id.textView).text = item
        }
    }
}

3. Create RecyclerView LayoutManager

Create a LayoutManager that extends LinearLayoutManager. The LayoutManager is responsible for measuring and laying out views.

class MyLayoutManager(context: Context) : LinearLayoutManager(context) {

    override fun canScrollVertically() = true

    override fun canScrollHorizontally() = true
}

4. Set LayoutManager and Adapter to RecyclerView

Set the LayoutManager to RecyclerView and create an instance of the adapter. Then, set the adapter to RecyclerView.

val myRecyclerView = findViewById<RecyclerView>(R.id.myRecyclerView)
myRecyclerView.layoutManager = MyLayoutManager(this)
val myData = listOf("Item 1", "Item 2", "Item 3")
myRecyclerView.adapter = MyAdapter(myData)

Conclusion

In this tutorial, we have shown how to use RecyclerView with LinearLayoutManager and Kotlin. RecyclerView can be used to display large sets of data in a list or grid, and LinearLayoutManager arranges items in a linear layout. Kotlin is a modern, concise, and safe programming language that can be used to develop Android applications.