Wednesday, August 12, 2015

How to programmatically scroll at the top of a ListView in Android

MainActivity.java

package com.cfsuman.androidtutorials;

import android.os.Bundle;
import android.app.Activity;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Get the widgets reference from XML layout
        Button button = findViewById(R.id.button);
        ListView listView = findViewById(R.id.listView);


        // Initializing a new String Array
        String[] fruits = new String[] {
                "Abiu",
                "Batuan",
                "Black Mulberry",
                "Cape Gooseberry",
                "Desert banana",
                "Eastern May Hawthorn",
                "Fibrous Satinash",
                "Gooseberry",
                "Hairless rambutan",
                "Illawarra Plum",
                "Jelly Palm",
                "Kepel fruit",
                "Little gooseberry tree",
                "Mammee Apple",
                "Nagami Kumquat",
                "Oil Palm",
                "Peanut butter fruit",
                "Queensland Ebony",
                "Red Mulberry",
                "Sageretia",
                "Tahitian apple",
                "Ugni",
                "Vanilla",
                "Watermelon",
                "Yellow Granadilla",
                "Zig Zag Vine"
        };


        // Create a List from String Array elements
        List<String> fruits_list = new ArrayList<String>
                (Arrays.asList(fruits));


        // Create an ArrayAdapter from List
        ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>
                (
                        this,
                        android.R.layout.simple_list_item_1,
                        fruits_list
                );

        // DataBind ListView with items from ArrayAdapter
        listView.setAdapter(arrayAdapter);


        // Scroll to top of the list view
        button.setOnClickListener(v -> {
            // Scroll to position zero, first item of ListView
            listView.smoothScrollToPosition(0);
        });
    }
}
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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_height="match_parent"
    android:background="#DCDCDC"
    android:padding="24dp">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ListView Scroll To Top"
        android:textAllCaps="false"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ListView
        android:id="@+id/listView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginTop="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

</androidx.constraintlayout.widget.ConstraintLayout>