Thursday, August 13, 2015

How to set selected item of Spinner programmatically in Android

Select An Item From Spinner Programmatically
Spinner is a popular widget in Android SDK. Spinner allows selecting one value at a time. The Spinner shows a selected value on the visible area. Others values stay hidden but can explore on a drop-down menu. Android developers can add a Spinner widget in their XML layout file by using the Spinner tag and available attributes.

Spinner items are populated inside the java or kotlin file. Android developers can easily add items to a Spinner widget by using an array adapter. And they can generate an array adapter from an array and array list. The Spinner setAdapter method binds the array adapter with the Spinner widget and shows available items in the widget. By default Spinner's first item is it selected item.

Android app developers can select an item from Spinner available items programmatically in their scripting java or kotlin file. This android development tutorial will demonstrate to you how can we select an item from the Spinner widget programmatically on the Button click event.

To do that, at first we put a Spinner widget to our XML layout file. Next step, we populate a String array with values and convert it to an array list then we build an array adapter with this array list. After creating the array adapter we data-bind Spinner with the array adapter by using the Spinner setAdapter method inside the java or kotlin file. In that way, we populate the Spinner with items. By default, the Spinner first item is now selected initially.

We also add a Button element to our XML layout file. On the Button click event, we will select another item from the Spinner widget. The Spinner setSelection() method allows us to select an item from Spinner programmatically. Spinner setSelection() method takes an argument named ‘position’ and its data type is int. The position is the index of Spinner items and the index is zero-based. In this example, we passed 2 to our setSelection() method and that’s why the Spinner thirds item is dynamically selected now.
MainActivity.java

package com.cfsuman.androidtutorials;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
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);
                Spinner spinner = findViewById(R.id.spinner);


                // Initializing a String Array
                String[] plants = new String[]{
                        "Laceflower",
                        "California sycamore",
                        "Mountain mahogany",
                        "Butterfly weed",
                        "Carrot weed"
                };


                // Convert array to a list
                List<String> plantsList = new ArrayList<>
                        (Arrays.asList(plants));


                // Initializing an ArrayAdapter
                ArrayAdapter<String> spinnerArrayAdapter
                        = new ArrayAdapter<String>(
                        this,
                        android.R.layout.simple_dropdown_item_1line,
                        plantsList
                );


                // Set the drop down view resource
                spinnerArrayAdapter.setDropDownViewResource(
                        android.R.layout.simple_dropdown_item_1line
                );


                // Set a button click listener
                button.setOnClickListener(v -> {
                        // Select the Spinner element at index position 2
                        // It will select third element/item from Spinner
                        spinner.setSelection(2);
                });


                // Finally, data bind the spinner object with adapter
                spinner.setAdapter(spinnerArrayAdapter);
        }
}
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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#DCDCDC"
    android:padding="32dp">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Select Third Item From Spinner"
        android:textAllCaps="false"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

</androidx.constraintlayout.widget.ConstraintLayout>