Saturday, February 29, 2020

android kotlin - Spinner onItemSelectedListener example

Spinner onItemSelectedListener
The Spinner provides an easy way to select an item from a list. The Spinner always shows its currently selected item only. Other items remain invisible and users can see them when they click on the Spinner itself. On Spinner click, it displays a drop-down menu with all other available items. So, the user can select an item from all of the available items.

The following android application development tutorial will demonstrate to us how we can set an item selected listener for the Spinner widget. The Spinner AdapterView OnItemSelectedListener registers a callback to invoke when an item in this AdapterView has been selected. So developer gets the Spinner selected value immediately when the user selects it or changes their selection.

To populate a Spinner widget with items we have to create an item list. Then we create an instance of ArrayAdapter with this list. After that, we bind the Spinner widget with this ArrayAdapter. So the Spinner widget display items from the list.

Finally, we set the Spinner onItemSelectedListener value to an ArrayAdapter.OnItemSelectedListener. AdapterView OnItemSelectedListener interface onItemSelected() method allows us to get the user-selected item details in real-time and programmatically. So when the user selects an item from the Spinner widget developers can get this selected item’s details and can perform related tasks.

This android kotlin tutorial code is written in an android studio IDE. Copy the code and paste it into your android studio IDE and run it on an emulator to see how we can use Spinner OnItemSelectedListener in an android application.

And how we can get the Spinner selected item details programmatically in real-time when users select an item or change their selection in an application. We displayed screenshots of the emulator screen, which also help you to understand the code without running it on an android device or emulator.
MainActivity.kt

package com.cfsuman.kotlintutorials

import android.os.Bundle
import android.view.View
import android.widget.*
import androidx.appcompat.app.AppCompatActivity


class MainActivity : AppCompatActivity() {
    private lateinit var context:MainActivity

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Get the context
        context = this;

        // Get the widgets reference from XML layout
        val spinner = findViewById<Spinner>(R.id.spinner)
        val textView = findViewById<TextView>(R.id.textView)

        // List of spinner items
        val list = listOf(
            "Ocean Blue",
            "Old lavender",
            "Orchid pink",
            "Rich black",
            "Royal yellow",
            "Rusty red"
        )

        // Initialize an array adapter for spinner
        val adapter = ArrayAdapter(
            context,
            android.R.layout.simple_spinner_dropdown_item,
            list
        )

        // Finally, data bind spinner with adapter
        spinner.adapter = adapter


        // Spinner on item selected listener
        spinner.onItemSelectedListener = object : AdapterView
        .OnItemSelectedListener {
            override fun onItemSelected(
                parent: AdapterView<*>,
                view: View,
                position: Int,
                id: Long
            ) {
                textView.text = "Selected: "
                // Get selected item text
                textView.append(
                    parent.getItemAtPosition(position).toString()
                )
            }

            override fun onNothingSelected(parent: AdapterView<*>?) {
                // Another interface callback
            }
        }
    }
}
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">

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:fontFamily="sans-serif"
        android:textSize="24sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>
More android examples