How to Create a Collapsing ToolBar and FAB on Scroll with RecyclerView in Android? - GeeksforGeeks

18 Jul, 2021
In this article, we are going to create a collapsing Toolbar and Floating action button (FAB) on scroll with RecyclerView. Many popular apps have this effect eg. LinkedIn. Below is the sample video to show what we are going to build. Note that we are going to implement this project using the Kotlin language. 
Step 1: Create a new project
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Kotlin as the programming language.
Step 2: Add view binding dependency
Go to build.gradle(app) and the following dependency inside the android tag and click sync now.
buildFeatures {
     viewBinding true
 }
Step 3: Working with the activity_main.xml file
Go to the activity_main.xml file and refer to the following code. Below is the code for the activity_main.xml file. Comments are added inside the code to understand the code in more detail.
XML
<?xml version="1.0" encoding="utf-8"?><!--first of all you have to change    the layout as CoordinatorLayout.--><androidx.coordinatorlayout.widget.CoordinatorLayout     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">      <!--First child of CoordinatorLayout layout         should be App Bar Layout-->    <com.google.android.material.appbar.AppBarLayout        android:id="@+id/appBarLayout"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">          <!-- Add Material toolbar make the layout_scrollFlags              to scroll|enterAlways (Important)-->        <com.google.android.material.appbar.MaterialToolbar            android:id="@+id/toolbar"            android:layout_width="match_parent"            android:layout_height="?attr/actionBarSize"            app:layout_scrollFlags="scroll|enterAlways"            app:title="@string/app_name" />      </com.google.android.material.appbar.AppBarLayout>      <!--Add a recycler view        inside layout behaviour add "@string/appbar_scrolling_view_behavior" (Important)        by default it comes from the @string-->    <androidx.recyclerview.widget.RecyclerView        android:id="@+id/recyclerView"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:background="#F5F8FD"        android:orientation="vertical"        android:padding="5dp"        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"        app:layout_behavior="@string/appbar_scrolling_view_behavior" />      <!--Add a floating action button        "com.google.android.material.behavior.HideBottomViewOnScrollBehavior" (Important)-->    <com.google.android.material.floatingactionbutton.FloatingActionButton        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="bottom|right"        android:layout_margin="16dp"        android:src="@drawable/ic_baseline_add_24"        app:fabSize="normal"        app:layout_behavior="com.google.android.material.behavior.HideBottomViewOnScrollBehavior"        app:tint="@android:color/white" />  </androidx.coordinatorlayout.widget.CoordinatorLayout>
Step 4: Create a new layout file and name it a single_item.xml file
Go to the single_item.xml file and refer to the following code. Below is the code for the single_item.xml file. It is the single item layout that we will use in RecyclerView.
XML
<?xml version="1.0" encoding="utf-8"?><com.google.android.material.card.MaterialCardView    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    android:layout_width="match_parent"    android:layout_marginBottom="10dp"    android:layout_marginStart="5dp"    android:layout_marginEnd="5dp"    android:layout_height="110dp">      <androidx.constraintlayout.widget.ConstraintLayout        android:layout_width="match_parent"        android:layout_height="match_parent">          <!--Add image view, We will not set any data here.-->        <ImageView            android:id="@+id/iv_language"            android:layout_width="80dp"            android:layout_height="90dp"            android:layout_marginStart="20dp"            android:layout_marginTop="10dp"            android:scaleType="fitCenter"            android:src="@mipmap/ic_launcher"            app:layout_constraintLeft_toLeftOf="parent"            app:layout_constraintTop_toTopOf="parent" />          <!--Text view for showing the language name-->        <TextView            android:id="@+id/tv_lang_name"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_marginStart="30dp"            android:layout_marginTop="30dp"            android:text="Language"            android:textSize="16sp"            android:textStyle="bold"            app:layout_constraintLeft_toRightOf="@id/iv_language"            app:layout_constraintTop_toTopOf="parent" />          <!--Text View for showing the exp-->        <TextView            android:id="@+id/tv_exp"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_marginTop="10dp"            android:text="Exp : 3 years"            app:layout_constraintLeft_toLeftOf="@id/tv_lang_name"            app:layout_constraintTop_toBottomOf="@id/tv_lang_name" />      </androidx.constraintlayout.widget.ConstraintLayout>  </com.google.android.material.card.MaterialCardView>
Step 5: Create a new model class
Create a new class Language.kt we will use data of custom generic “Language” to pass in the list that will be shown in recycler view.
Kotlin
// this is the Language model classclass Language(    val name : String ="",    val exp : String = "")
Step 6: Working with the adapter class
Create a new class RvAdapter.kt this will act as an Adapter class for the recycler view. Comments are added before the code for better understanding.
Kotlin
import android.view.LayoutInflaterimport android.view.ViewGroupimport androidx.recyclerview.widget.RecyclerViewimport com.introidx.collapsingtoolbargfg.databinding.SingleItemBinding  class RvAdapter(    private var languageList: List<Language>) : RecyclerView.Adapter<RvAdapter.ViewHolder>() {      // create an inner class with name ViewHolder    // It takes a view argument, in which pass the     // generated class of single_item.xml    // ie SingleItemBinding and in the     // RecyclerView.ViewHolder(binding.root) pass it like this    inner class ViewHolder(val binding: SingleItemBinding) : RecyclerView.ViewHolder(binding.root)      override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {        val binding = SingleItemBinding.inflate(LayoutInflater.from(parent.context), parent, false)        return ViewHolder(binding)    }      // bind the items with each item of     // the list languageList which than will be    // shown in recycler view    // to keep it simple we are not     // setting any image data to view    override fun onBindViewHolder(holder: ViewHolder, position: Int) {        with(holder) {            with(languageList[position]) {                // set text to language name                binding.tvLangName.text = this.name                // set exp                binding.tvExp.text = this.exp            }        }    }      // return the size of languageList    override fun getItemCount(): Int {        return languageList.size    }}
Step 7: Working with MainActivity.kt
Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.
Kotlin
import androidx.appcompat.app.AppCompatActivityimport android.os.Bundleimport androidx.recyclerview.widget.LinearLayoutManagerimport com.introidx.collapsingtoolbargfg.databinding.ActivityMainBinding  class MainActivity : AppCompatActivity() {      // view binding for the activity    private var _binding: ActivityMainBinding? = null    private val binding get() = _binding!!      // get reference to the adapter class    private var languageList = ArrayList<Language>()    private lateinit var rvAdapter: RvAdapter      override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        _binding = ActivityMainBinding.inflate(layoutInflater)        setContentView(binding.root)          // define layout manager for the Recycler view        binding.recyclerView.layoutManager = LinearLayoutManager(this)                  // attach adapter to the recycler view and also handle item click          // attach adapter to the recycler view        rvAdapter = RvAdapter(languageList)          // add adapter to the recycler view        binding.recyclerView.adapter = rvAdapter          // create objects of Language        // create some row data        val language1 = Language("Java", "3 Year exp")        val language2 = Language("Kotlin", "2 Year exp")        val language3 = Language("Python", "1 Year exp")        val language4 = Language("CPP", "5 Year exp")        val language5 = Language("PHP", "No exp")          // pass raw data t rhe list        languageList.add(language1)        languageList.add(language2)        languageList.add(language3)        languageList.add(language4)        languageList.add(language5)        languageList.add(language3)        languageList.add(language4)        languageList.add(language5)        languageList.add(language3)        languageList.add(language4)        languageList.add(language5)          rvAdapter.notifyDataSetChanged()      }      // on destroy of view make the       // binding reference to null    override fun onDestroy() {        super.onDestroy()        _binding = null    }}
Output:
Android
Kotlin
Android
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