Android – Proximity Sensor using Kotlin

Proximity Sensor is one of the sensors in mobile devices we use almost daily. This sensor is present in the top section of your phone. The sensor is used to detect the presence of any object in the proximity of the phone. This sensor is used in many calling apps when the user keeps his phone on his ears for listening then the screen automatically turns off so to avoid unnecessary screen touch events while on call. In this article, we will look at How to use Proximity Sensor in android using Kotlin. 

Note: If you are looking to implement the Proximity Sensor in your android application using Java. Check out the following article: How to Use Proximity Sensor in Android using Java

Step by Step Implementation

Step 1: Create a New Project in Android Studio

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Kotlin as the programming language.

Step 2: Add permissions to use the proximity sensor in our Android App

Navigate to app>manifest>AndroidManifest.xml and add the below permission to it in the manifest section. 

XML

<uses-permission android:name="android.hardware.sensor.proximity"/>

Step 3: Working with the activity_main.xml file

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file. Comments are added inside the code to understand the code in more detail.

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <!--on below line we are creating
        a text for heading of our app-->
    <TextView
        android:id="@+id/idTVHeading"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:gravity="center"
        android:padding="4dp"
        android:text="QR Code Generator"
        android:textAlignment="center"
        android:textColor="@color/purple_200"
        android:textSize="18sp"
        android:textStyle="bold" />

    <!--Text view to display sensor status-->
    <TextView
        android:id="@+id/idTVSensorStatus"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:gravity="center"
        android:textAlignment="center"
        android:textColor="@color/black"
        android:textSize="50dp" />

</RelativeLayout>

Step 4: Working with MainActivity.kt file

Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Kotlin

package com.gtappdevelopers.kotlingfgproject
import android.content.Context
import android.hardware.Sensor
import android.hardware.SensorEvent
import android.hardware.SensorEventListener
import android.hardware.SensorManager
import android.os.Bundle
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    // on below line we are creating
    // a variable for our text view.
    lateinit var sensorStatusTV: TextView

    // on below line we are creating
    // a variable for our proximity sensor
    lateinit var proximitySensor: Sensor

    // on below line we are creating
    // a variable for sensor manager
    lateinit var sensorManager: SensorManager

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

        // on below line we are initializing our all variables.
        sensorStatusTV = findViewById(R.id.idTVSensorStatus)

        // on below line we are initializing our sensor manager
        sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager

        // on below line we are initializing our proximity sensor variable
        proximitySensor = sensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY)

        // on below line we are checking if the proximity sensor is null
        if (proximitySensor == null) {
            // on below line we are displaying a toast if no sensor is available
            Toast.makeText(this, "No proximity sensor found in device..", Toast.LENGTH_SHORT).show()
            finish()
        } else {
            // on below line we are registering
            // our sensor with sensor manager
            sensorManager.registerListener(
                proximitySensorEventListener,
                proximitySensor,
                SensorManager.SENSOR_DELAY_NORMAL
            )
        }
    }

    // calling the sensor event class to detect
    // the change in data when sensor starts working.
    var proximitySensorEventListener: SensorEventListener? = object : SensorEventListener {
        override fun onAccuracyChanged(sensor: Sensor, accuracy: Int) {
            // method to check accuracy changed in sensor.
        }

        override fun onSensorChanged(event: SensorEvent) {
            // check if the sensor type is proximity sensor.
            if (event.sensor.type == Sensor.TYPE_PROXIMITY) {
                if (event.values[0] == 0f) {
                    // here we are setting our status to our textview..
                    // if sensor event return 0 then object is closed
                    // to sensor else object is away from sensor.
                    sensorStatusTV.text = "Object is Near to sensor"
                } else {
                    // on below line we are setting text for text view
                    // as object is away from sensor.
                    sensorStatusTV.text = "Object is Away from sensor"
                }
            }
        }
    }
}

Now run your application to see the output of it. 

Output: