How to detect Scroll Up & Scroll down in Android ListView using Kotlin?

This example demonstrates how to detect Scroll Up & Scroll down in Android ListView using Kotlin.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
   android:gravity="center"
   android:orientation="vertical"
   android:padding="8dp"
   tools:context=".MainActivity">
   <ListView
      android:id="@+id/listView"
      android:layout_width="match_parent"
      android:layout_height="match_parent" />
</LinearLayout>

Step 3 − Add the following code to src/MainActivity.kt

import android.os.Bundle
import android.widget.*
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   private var scrollView: ScrollView? = null
   private lateinit var listView: ListView
   private var numbers = arrayOf(
      "1",
      "2",
      "3",
      "4",
      "5",
      "6",
      "7",
      "8",
      "9",
      "X",
      "11",
      "12",
      "13",
      "14",
      "15",
      "16",
      "17",
      "18",
      "19",
      "20",
      "21",
      "22",
      "23",
      "24",
      "25"
   )
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      scrollView = findViewById(R.id.scrollView)
      val adapter: ArrayAdapter<*> = ArrayAdapter(
         this,
         R.layout.support_simple_spinner_dropdown_item, numbers
      )
      listView = findViewById(R.id.listView)
      listView.adapter = adapter
      listView.setOnScrollListener(object : AbsListView.OnScrollListener {
         private var lastFirstVisibleItem = 0
         override fun onScrollStateChanged(view: AbsListView, scrollState: Int) {}
         override fun onScroll(
            view: AbsListView,
            firstVisibleItem: Int,
            visibleItemCount: Int,
            totalItemCount: Int
         )
         {
            if (lastFirstVisibleItem < firstVisibleItem) {
               Toast.makeText(
                  applicationContext, "Scrolling down the listView",
                  Toast.LENGTH_SHORT
               ).show()
            }
            if (lastFirstVisibleItem > firstVisibleItem) {
               Toast.makeText(
                  applicationContext, "Scrolling up the listView",
                  Toast.LENGTH_SHORT
               ).show()
            }
            lastFirstVisibleItem = firstVisibleItem
         }
      })
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.q11">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen

Azhar

Published on 18-Aug-2020 12:45:43