Spinner in Kotlin

Android Spinner is a view similar to a dropdown list which is used to select one option from the list of options. It provides an easy way to select one item from the list of items and it shows a dropdown list of all values when we click on it. The default value of the android spinner will be the currently selected value and by using the Adapter we can easily bind the items to the spinner objects. Generally, we populate our Spinner control with a list of items by using an ArrayAdapter in our Kotlin file. First, we create a new project by following the below steps:

1. Click on File, then New => New Project.
2. After that include the Kotlin support and click on next.
3. Select the minimum SDK as per convenience and click the next button.
4. Then select the Empty activity => next => finish.

Different attributes for Spinner widget

XML attributes	Description
android:id	Used to specify the id of the view.
android:textAlignment	Used to the text alignment in the dropdown list.
android:background	Used to set the background of the view.
android:padding	Used to set the padding of the view.
android:visibility	Used to set the visibility of the view.
android:gravity	Used to specify the gravity of the view like center, top, bottom etc

Modify activity_main.xml file

In this file, we use the TextView and Spinner widgets and also set their attributes. 

XML

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/linear_layout"
    android:gravity = "center">

    <TextView
        android:id="@+id/txtView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Select language:"
        android:textSize = "20dp" />

    <Spinner
        android:id="@+id/spinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@id/txtView"/>

</LinearLayout>

Update strings.xml file

Here, we update the name of the application using the string tag. We also create a list of the items which will be used in the dropdown menu. 

XML

<resources>
    <string name="app_name">SpinnerInKotlin</string>
    <string name="selected_item">Selected item:</string>

    <string-array name="Languages">
        <item>Java</item>
        <item>Kotlin</item>
        <item>Swift</item>
        <item>Python</item>
        <item>Scala</item>
        <item>Perl</item>
    </string-array>
</resources>

Access Spinner in MainActivity.kt file

First, we declare a variable languages to access the strings items from the strings.xml file.

val languages = resources.getStringArray(R.array.Languages)

then, we access the spinner and set ArrayAdaptor to control the list of items.

val spinner = findViewById(R.id.spinner)
        if (spinner != null) {
            val adapter = ArrayAdapter(this,
                android.R.layout.simple_spinner_item, languages)
            spinner.adapter = adapter

Kotlin

package com.geeksforgeeks.myfirstkotlinapp

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

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        // access the items of the list
        val languages = resources.getStringArray(R.array.Languages)

        // access the spinner
        val spinner = findViewById<Spinner>(R.id.spinner)
        if (spinner != null) {
            val adapter = ArrayAdapter(this,
                android.R.layout.simple_spinner_item, languages)
            spinner.adapter = adapter

         spinner.onItemSelectedListener = object :
           AdapterView.OnItemSelectedListener {
             override fun onItemSelected(parent: AdapterView<*>,
                                         view: View, position: Int, id: Long) {
                 Toast.makeText(this@MainActivity,
                    getString(R.string.selected_item) + " " +
                         "" + languages[position], Toast.LENGTH_SHORT).show()
                }

                override fun onNothingSelected(parent: AdapterView<*>) {
                    // write code to perform some action
                }
            }
        }
    }
}

AndroidManifest.xml file

XML

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.geeksforgeeks.myfirstkotlinapp">

<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>

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