Xamarin.Forms - Turn ON/Off Flashlight Using Xamarin Essentials

Introduction

Xamarin.Forms code runs on multiple platforms - each of which has its own filesystem. This means that reading and writing files is most easily done using the native file APIs on each platform. Alternatively, embedded resources are a simpler solution to distribute data files with an app.

Xamarin.Essentials

The Xamarin.Essentials plugin provides 20+ cross-platform APIs for mobile application development. Xamarin.Essentials API works with all Xamarin.Forms, Xamarin.Android, Xamarin.iOS, or UWP applications that can be accessed from shared code. Developers can now access every native platform API using C#. This plugin provides many APIs so initially, there is no need of more plugins for Xamarin. Xamarin.Essentials plugin impacts your app's minimum size.

Platform Support

Xamarin.Essentials supports various platforms and operating systems

Platform	Version
Android	4.4 (API 19) or earlier
iOS	10.0 or higher
UWP	10.0.16299.0 or earlier

Prerequisites

Visual Studio 2017(Windows or Mac)

Setting up a Xamarin.Forms Project

Start by creating a new Xamarin.Forms project. You’ll learn more by going through the steps yourself. Choose the Xamarin.Forms App Project type under Cross-platform/App in the New Project dialog.

Name your app, select “Use Portable Class Library” for shared code, and target both - Android and iOS.

You probably want your project and solution to use the same name as your app. Put it in your preferred folder for projects and click "Create".

You now have a basic Xamarin.Forms app. Click the Play button to try it out.

Setting up the User Interface

Go to MainPage.Xaml and write the following code.

MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:XamarinEssentials"
x:Class="XamarinEssentials.MainPage">
<StackLayout>
<StackLayout HorizontalOptions="Center" VerticalOptions="Start">
<Image Margin="0,50,0,0" x:Name="imgBanner" Source="banner.png" ></Image>
<Image Margin="0,0,0,10" x:Name="imgXamarinEssential" Source="xamarinessential.png" ></Image>
<Label Margin="0,0,0,10" FontAttributes="Bold" FontSize="Large" TextColor="#CA6F1E" HorizontalTextAlignment="Center" Text="Appinfo"></Label>
<Button Text="Flash on" Clicked="Handle_Clicked"></Button>
<Button Text="Flash off" Clicked="Handle_Clicked_1"></Button>
</StackLayout>
</StackLayout>
</ContentPage>

Add Xamarin Essentials

In this step, add Xamarin.Essentials to your project. You can install Xamarin.Essentials via NuGet, or you can browse the source code on GitHub.

Go to Solution Explorer and select your solution. Right-click and select "Manage NuGet Packages for Solution". Search "Xamarin.Essentials" and add Package. Remember to install it for each project (PCL, Android, iO, and UWP).

Xamarin.Essentials requires platform-specific setup - Android

The following steps are necessary for Android.

Xamarin.Essentials supports a minimum Android version of 4.4
Target Android version for compiling must be 8.1, API level 27.

In the Android project's MainActivity that is launched Xamarin.Essentials must be initialized in the OnCreate method.

MainActivity.cs

Xamarin.Essentials.Platform.Init(this, bundle);

Xamarin.Essentials must receive any OnRequestPermissionsResult. write the following code for runtime permission.

MainActivity.cs

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
{
Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}

iOS

No additional setup required.

UWP

No additional setup required.

Permissions

In this step give the following required permissions to your app:

CAMERA
FLASHLIGHT

Limitation

It supports the devices only, not Simulator/Emulator

In this step, write the following code for switching ON the Flashlight.

MainPage.xaml.cs

async void Handle_Clicked(object sender, System.EventArgs e)
{
try
{
// Turn On Flashlight
await Flashlight.TurnOnAsync();
}
catch (FeatureNotSupportedException fnsEx)
{
await ShowAlert(fnsEx.Message);
}
catch (PermissionException pEx)
{
await ShowAlert(pEx.Message);
}
catch (Exception ex)
{
await ShowAlert(ex.Message);
}
}

Now, write the following code for switching Off the Flashlight.

MainPage.xaml.cs

async void Handle_Clicked_1(object sender, System.EventArgs e)
{
try
{
// Turn Off Flashlight
await Flashlight.TurnOffAsync();
}
catch (FeatureNotSupportedException fnsEx)
{
await ShowAlert(fnsEx.Message);
}
catch (PermissionException pEx)
{
await ShowAlert(pEx.Message);
}
catch (Exception ex)
{
await ShowAlert(ex.Message);
}
}

Full code - MainPage.xaml.cs

using Xamarin.Forms;
using Xamarin.Essentials;
namespace XamarinEssentials
{
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
async void Handle_Clicked(object sender, System.EventArgs e)
{
try
{
// Turn On Flashlight
await Flashlight.TurnOnAsync();
}
catch (FeatureNotSupportedException fnsEx)
{
await ShowAlert(fnsEx.Message);
}
catch (PermissionException pEx)
{
await ShowAlert(pEx.Message);
}
catch (Exception ex)
{
await ShowAlert(ex.Message);
}
}
async void Handle_Clicked_1(object sender, System.EventArgs e)
{
try
{
// Turn Off Flashlight
await Flashlight.TurnOffAsync();
}
catch (FeatureNotSupportedException fnsEx)
{
await ShowAlert(fnsEx.Message);
}
catch (PermissionException pEx)
{
await ShowAlert(pEx.Message);
}
catch (Exception ex)
{
await ShowAlert(ex.Message);
}
}
public async Task ShowAlert(string message)
{
await DisplayAlert("Faild", message, "Ok");
}
}
}

Click the Play button to try it out.

Related post

I hope you have understood how to turn the flashlight on or off using Xamarin.Essentials in Xamarin.Forms.

Thanks for reading. Please share comments and feedback.