Xamarin.Forms - Application Preferences Using Xamarin.Essentials

Introduction

Xamarin.Forms code runs on multiple platforms - each of which has its own filesystem. This means that reading and writing the files are 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

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. We are developing Xamarin with Android, iOS and UWP apps, but now Xamarin.Essentials overcomes the problem, so developers can access every native platform API using C#. This plugin provides many APIs so initially, there is no need for more plugins for Xamarin. Xamarin.Essentials plugin impacts your app's minimum size.

Platform Support

Xamarin.Essentials supports the following 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

Application Storage

Xamarin Android - Shared Preferences

Android provides many ways of storing the data of an application. One of the ways is called Shared Preferences. Shared Preferences allows you to save and retrieve the data in the form of a key-value pair.

In order to use shared preferences, you have to call a method, getSharedPreferences() ,that returns a SharedPreference instance pointing to the file that contains the values of preferences.

Xamarin iOS - NSUserDefaults

The NSUserDefaults class provides a way for iOS Apps and Extensions to programmatically interact with the system-wide Default System. By using the Defaults System, the user can configure an app's behavior or styling to meet their preferences (based on the design of the app). For example, to present data in Metric vs Imperial measurements or select a given UI Theme.

UWP - ApplicationDataContainer

Represents a container for app settings. The methods and properties of this class support creating, deleting, enumerating, and traversing the container hierarchy.

Xamarin Forms - Properties Dictionary

The Application subclass has a static Properties dictionary which can be used to store data, in particular for use in the OnStart, OnSleep, and OnResume methods. This can be accessed from anywhere in your Xamarin.Forms code using Application.Current.Properties.

The Properties dictionary uses a string key and stores an object value.

Xamarin.Essentials

Preferences class helps to store application preferences in a key/value store using Xamarin.Essentials

Preferences Supported Data Types

string
int
bool
double
float
long
DateTime

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="Preferences"></Label>
<Entry x:Name="txtValue" Placeholder="Add Value"> </Entry>
<Button x:Name="btnAdd" Text="Add" Clicked="btnAdd_Clicked"/>
<Button x:Name="btnGet" Text="Get" Clicked="btnGet_Clicked" />
<Button x:Name="btnRemove" Text="Remove" Clicked="btnRemove_Clicked" />
<Button x:Name="btnClear" Text="Clear All" Clicked="btnClear_Clicked"/>
</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.

Store Value

The Preferences uses a string key and stores an object value.

MainPage.xaml.cs

void btnAdd_Clicked(object sender, System.EventArgs e)
{
AddValue("mykey", txtValue.Text);
txtValue.Text = string.Empty;
DisplayAlert("Success", "Value Stored", "OK");
}
//Add Value to Preference
public void AddValue(string key, string value)
{
Preferences.Set(key, value);
}

Click the play button to try it out.

Get Value

Preferences stores the objects, so you need to cast its value before using it.

MainPage.xaml.cs

void btnGet_Clicked(object sender, System.EventArgs e)
{
string value = GetValue("mykey");
DisplayAlert("Success", "Your Value is "+value, "OK");
}
//Get Value from Preference
public string GetValue(string key)
{
return Preferences.Get(key,"");
}

Click the play button to try it out

Remove Value

If you want to remove values, you can remove them.

MainPage.xaml.cs

void btnRemove_Clicked(object sender, System.EventArgs e)
{
DeleteValue("mykey");
DisplayAlert("Success", "Removed", "OK");
}
//Remove Preference Value
public void DeleteValue(string key)
{
Preferences.Remove(key);
}

Click the play button to try it out.

Clear Values

If you want clear all Properties, you can use the following code.

MainPage.xaml.cs

void btnClear_Clicked(object sender, System.EventArgs e)
{
Clear();
DisplayAlert("Success", "All Values Cleared", "OK");
}
//Clear all Preference Values
public void Clear()
{
Preferences.Clear();
}

Click the play button to try it out.

I hope you have understood how to use Application preferences Using Xamarin Essentials in Xamarin.Forms.

Thanks for reading. Please share comments and feedback.