How to Detect Scroll Up and Down Gestures in a ListView in Android?
A ListView in Android is a scrollable list used to display items. Data, which is a list or array of items fetched from a source or hardcoded in the application can be displayed row-wise using a ListView. If the items are less, then the list may not even reach the bottom of the screen. However, if the items are large in number, then they may go beyond the bottom of the screen, where a scroll function takes entry and lets users scroll up and down to discover the covered items.
In this article, we will show you how you could detect scrolls up and down in a ListView. Follow the below steps once the IDE is ready.
Step by Step Implementation
Step 1: Create a New Project in Android Studio
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. We demonstrated the application in Kotlin, so make sure you select Kotlin as the primary language while creating a New Project.
Step 2: Working with the activity_main.xml file
Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file. We implemented a TextView that shall display the scrolling status and a ListView that shall display items.
XML
<?xml version="1.0" encoding="utf-8"?><RelativeLayout android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity"> <TextView android:id="@+id/text_view" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="Scroll Status" android:textSize="20sp" android:gravity="center"/> <ListView android:id="@+id/list_view" android:layout_below="@id/text_view" android:layout_width="match_parent" android:layout_height="match_parent"/> </RelativeLayout> |
Step 3: Working with the MainActivity.kt file
In the main code, we declared an array list of elements (numbers from 1 to 30). Using an adapter this array is displayed into the ListView. A scroll listener is called on the ListView to get information on the first visible item, total visible items, and total item count. A buffer index variable is initially set to 0. Now, according to our algorithm, if the first visible element index is greater than the buffer variable, then we are basically scrolling down. Else we are scrolling up. Now refer to the below code.
Kotlin
import androidx.appcompat.app.AppCompatActivityimport android.os.Bundleimport android.widget.* class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) val mList = arrayOf("1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30",) val mListView = findViewById<ListView>(R.id.list_view) val mTextView = findViewById<TextView>(R.id.text_view) val mAdapter = ArrayAdapter(this, R.layout.support_simple_spinner_dropdown_item, mList) mListView.adapter = mAdapter mListView.setOnScrollListener(object : AbsListView.OnScrollListener{ override fun onScrollStateChanged(view: AbsListView?, scrollState: Int) { // Do nothing } private var lastFirstVisibleItem = 0 override fun onScroll(view: AbsListView?, firstVisibleItem: Int, visibleItemCount: Int, totalItemCount: Int) { if (lastFirstVisibleItem < firstVisibleItem) { // Down mTextView.text = "Scrolling down" } if (lastFirstVisibleItem > firstVisibleItem) { // Up mTextView.text = "Scrolling Up" } lastFirstVisibleItem = firstVisibleItem } }) }} |
Output:
We can see that when we scroll down, the TextView displays “Scrolling Down”. When we scroll up, it displays “Scrolling Up”.
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