Android Kotlin: How to change orientation without restarting activity

Introduction

This code demonstrates how to handle screen orientation changes in an Android application written in Kotlin. By default, when a device is rotated, the activity restarts, potentially causing data loss and a disjointed user experience. This example shows how to prevent the activity from restarting and instead update the UI to reflect the new orientation.

Breakdown of the Code

MainActivity.kt:

onCreate: This lifecycle method is called when the activity is first created. Here, the layout (activity_main.xml) is inflated and a random number is generated and displayed on textView.
onConfigurationChanged: This method is called whenever the device configuration changes, including screen orientation.
- It updates textView2 to indicate a configuration change.
- It retrieves the current orientation using newConfig.orientation and displays a corresponding message ("Portrait", "Landscape", etc.) on textView2.

activity_main.xml:

This file defines the layout of the activity. It contains two TextViews:

textView: Displays a randomly generated number.
textView2: Used to display messages about the configuration change and the current orientation.

AndroidManifest.xml (partial):

The relevant part of the manifest file specifies that the activity should handle orientation and screen size changes. This is achieved by adding the line android:configChanges="orientation|screenSize" within the <activity> tag for MainActivity.

Summary

By combining the information from the layout file, activity code, and manifest, this example demonstrates how to gracefully handle screen orientation changes in an Android application. The activity avoids restarting by using the onConfigurationChanged method to update the UI based on the new orientation. This approach helps maintain a smooth and responsive user experience regardless of device rotation.

MainActivity.kt


package com.example.jetpack

import android.content.res.Configuration
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import kotlin.random.Random


class MainActivity : AppCompatActivity() {

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

        val random = Random.nextInt(50)
        textView.text = "\n\nRandom Number : $random"
    }


    override fun onConfigurationChanged(newConfig: Configuration) {
        super.onConfigurationChanged(newConfig)

        textView2.text = "Configuration Changed."

        val orientation = when(newConfig.orientation){
            Configuration.ORIENTATION_PORTRAIT -> "Portrait"
            Configuration.ORIENTATION_LANDSCAPE -> "Landscape"
            Configuration.ORIENTATION_UNDEFINED -> "Undefined"
            else -> "Error"
        }

        textView2.append("\nOrientation : $orientation")
    }
}

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:id="@+id/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:background="#E5E4E2">

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="16dp"
        tools:text="TextView"
        android:gravity="center"
        android:fontFamily="sans-serif-condensed"
        android:textSize="30sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="16dp"
        android:fontFamily="sans-serif-condensed"
        android:gravity="center"
        android:textSize="30sp"
        android:textColor="#1C05B3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView"
        tools:text="TextView" />

</androidx.constraintlayout.widget.ConstraintLayout>

AndroidMenifest.xml [part]


<!--
    android:configChanges="orientation|screenSize"
        this prevent restarting the activity when screen orientation change.
-->
<activity
    android:name=".MainActivity"
    android:configChanges="orientation|screenSize">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>