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.
Some Important Attributes of 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 |
Steps to Implement Spinner
Step 1: Create a new Project
First, we create a new project by following the below steps:
- Click on File, then New => New Project.
- After that include the Kotlin support and click on next.
- Select the minimum SDK as per convenience and click the Next button.
- Then select the Empty activity => Next => Finish.
To create a new Project in Android Studio please refer to How to Create/Start a New Project in Android Studio using Kotlin.
Step 2: Modifying the activity_main.xml
Now open activity_main.xml and insert the below code in it. In this file, we use the TextView and Spinner widgets and also set their attributes.
activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical"
android:background="@color/white"
tools:context=".MainActivity">
<TextView
android:id="@+id/txtView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Select language:"
android:textSize="20sp" />
<Spinner
android:id="@+id/spinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
Layout:
Step 3: 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.
strings.xml:
<resources>
<!-- add the following below to the existing code-->
<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>
Step 4: 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
// rest of the code
}
MainActivity.kt:
package org.geeksforgeeks.demo
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.AdapterView
import android.widget.ArrayAdapter
import android.widget.Spinner
import android.widget.Toast
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
}
}
}
}
}
