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In this post we’ll how is possible to invert a boolean value in our XAML page using a ConverterLet’s say that we have a Label that should be visible only if a boolean property is false. In the next example in our XAML we have a Label with the text bound to MyText and this label should be visible only if the boolean property HideMyText is false:

<Label Text="{Binding MyText}" 
       IsVisible="{Binding HideMyText}">
</Label>

How we can do that? An amateur will create a new property ShowMyText whose value will be:ShowMyText = !HideMyTextIf you want to be a mediocre developer you can stop here because it works but if you want to be a great developer, then this solution is not for you and you should continue to read!

IValueConverter

To solve our problem we need to create a converter that will invert our boolean value. This is really easy, we just need to create a new class BooleanConverter (you can user whatever name you prefer):

public class BooleanConverter : IValueConverter, IMarkupExtension
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return !((bool) value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value;
    }

    public object ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }
}

and then use this new converter in our XAML:

<Label Text="{Binding MyText}" 
       IsVisible="{Binding HideMyText, Converter={converters:BooleanConverter}}">
</Label>

So now in our XAML we have a label that is visible when HideMyText is false. YEAH!You need to write this converter only once and then you can use it every time you need it. It’s amazing!

In this tutorial I’ll show you how to create a UrhoSharp project using Xamarin.Forms. This UrhoSharp project will run on Android, iOS and UWP.

A basic game I’ve created using UrhaSharp

Don’t worry if the code seems complicated, it’s not. To help you, I’ll include the source code of this project at the end of the tutorial.

The first step consists in creating a cross-platform project with Xamarin.Forms:

Creating a new cross platform Xamarin project

I suggest you to use a Blank template. Select the platform you need (Android, iOS, UWP to cover everything). Select the .NET Standard code sharing strategy.

Our new Cross Platform Solution

I suggest you to update all the Nuget packages before we start. After that, a nice clean and rebuild should guarantee us a clean start!

INSTALL URHOSHARP

The next step is to add the UrhoSharp.Forms nuget package to our solution. At the time of writing the latest version is 1.9.67. We must install this package in all our projects (.net standard, Android, iOS and UWP).

LET’S START WITH URHOSHARP

As you can imagine, UrhoSharp need a surface where it can draw our world. We can create this surface inside the MainPage.xaml file we have in our project. The MainPage will be similar to this:

As you can imagine, UrhoSharp need a surface where it can draw our world. We can create this surface inside the MainPage.xaml file we have in our project. The MainPage will be similar to this:

<?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:UrhoSharpTutorial"
             xmlns:forms="clr-namespace:Urho.Forms;assembly=UrhoSharp.Forms"
             x:Class="UrhoSharpTutorial.MainPage">

    <StackLayout>
        <!-- Place new controls here -->
        <forms:UrhoSurface x:Name="urhoSurface" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
        </forms:UrhoSurface>
    </StackLayout>

</ContentPage>

Basically we have added an UrhoSurface calling it urhoSurface. This surface will fill our entire screen. Now we need to edit the MainPage.cs to load our UrhoSharp application. The code will be this:

using Xamarin.Forms;

namespace UrhoSharpTutorial
{
    public partial class MainPage : ContentPage
    {
        XamarinExpertApp urhoApp;

        public MainPage()
        {
            InitializeComponent();
        }

        protected override async void OnAppearing()
        {
            StartUrhoApp();
        }

        async void StartUrhoApp()
        {
            urhoApp = await urhoSurface.Show<XamarinExpertApp>(new Urho.ApplicationOptions("Data") { Orientation = Urho.ApplicationOptions.OrientationType.LandscapeAndPortrait });
        }
    }
}

This code will load our XamarinExpert UrhoSharp app inside the urhoSurface when the MainPage appears. Let’s see now how to create the XamarinExpertApp class.

This XamarinExpertApp should inherit from Urho.Application. The code of this class is:

using System.Diagnostics;
using Urho;
using UrhoSharpTutorial.Scenes;

namespace UrhoSharpTutorial
{
    public class XamarinExpertApp : Application
    {
        private BaseScene _mainScene;

        [Preserve]
        public XamarinExpertApp(ApplicationOptions options = null) : base(options)
        {
        }

        static XamarinExpertApp()
        {
            UnhandledException += (s, e) =>
            {
                if (Debugger.IsAttached)
                    Debugger.Break();
                e.Handled = true;
            };
        }

        protected override void Start()
        {
            base.Start();
            Input.Enabled = true;
            Input.SetMouseVisible(true, false);
            Input.TouchEmulation = true;

            StartMainScene();
        }

        private void StartMainScene()
        {
            _mainScene?.Destroy();
            Current.UI.Root.RemoveAllChildren();
            _mainScene = new MainScene(Graphics.Width, Graphics.Height);
        }

        protected override void OnUpdate(float timeStep)
        {
            base.OnUpdate(timeStep);
            _mainScene.OnUpdate(timeStep);
        }
    }
}

This class is our UrhoSharp project. It handles the exceptions and initialises the Input of our project. Inside the Start method, we load our scene. We also override the OnUpdate method so that we can decide what will happen every time that the screen is refreshed.

At this point we should create the mainScene. In this project we have only a scene, but in a more complex project we can have multiple scenes. Maybe one for the menu, another for the game, another for the settings and so on. Because of this, I prefer to create a basic scene calling it BaseScene. The code of this class is this:

using Urho;

namespace UrhoSharpTutorial.Scenes
{
    public class BaseScene
    {
        private int width;
        private int height;
        public Scene Scene;
        public Node CameraNode { get; set; }

        public BaseScene(int width, int height)
        {
            this.width = width;
            this.height = height;
        }

        public void InitScene()
        {
            Scene = new Scene();
            Scene.CreateComponent<Octree>();
        }

        public void CreateCamera(Vector3 vector3)
        {
            CameraNode = Scene.CreateChild("Camera");
            CameraNode.Position = vector3;
            Camera camera = CameraNode.CreateComponent<Camera>();
            camera.Orthographic = true;

            camera.OrthoSize = (float)Application.Current.Graphics.Height * Application.PixelSize;
        }

        public void SetupViewport()
        {
            var renderer = Application.Current.Renderer;
            Viewport vp = new Viewport(Application.Current.Context, Scene, CameraNode.GetComponent<Camera>());
            renderer.SetViewport(0, vp);
            vp.SetClearColor(Color.White);
        }

        public virtual void OnUpdate(float timeStep)
        {
        }

        public virtual void Destroy()
        {
        }
    }
}

In this base class we store the width and the height of our surface (it’s not necessary but it could be handy). Here we have several methods to create our Scene (it’s mandatory to create a Scene, so don’t forget it), to create our Camera (again mandatory, and in this case it’s an orthographic camera) and to setup our viewport (again mandatory). We must do these things every time we need to create a scene and this is why I’ve created this base class.

Now we can finally create our mainScene. I’ll show you a basic code for a mainScene and then a more complex one where I’ll add some methods to handle the inputs and interact with the objects in our scene.

The basic scene is this:

using Urho;

namespace UrhoSharpTutorial.Scenes
{
    public class MainScene : BaseScene
    {
        public MainScene(int width, int height) : base(width, height)
        {
            CreateScene();
        }

        private void CreateScene()
        {
            InitScene();
            CreateCamera(new Vector3(0f, 0f, -15));
         
            SetupViewport();
        }
    }
}

Here we just initialise the scene, create the camera and set the Viewport. Now I can show you a more useful mainScene:

using Urho;

namespace UrhoSharpTutorial.Scenes
{
    public class MainScene : BaseScene
    {
        private MainSceneInput _mainInput;
        public float movementSize = 0.8f;
        public float movementSpeed = 0.25f;

        public MainScene(int width, int height) : base(width, height)
        {
            CreateScene();
        }

        private void CreateScene()
        {
            InitScene();
            CreateCamera(new Vector3(0f, 0f, -15));

            _mainInput = new MainSceneInput(this);
            _mainInput.OnEvaluateNode += MainInput_OnEvaluateNode;

            SetupViewport();
            CreateEvents();
        }

        private void MainInput_OnEvaluateNode(object sender, Node node)
        {
            
        }

        private void CreateEvents()
        {
            Application.Current.Input.TouchBegin += _mainInput.Input_TouchBegin;
            Application.Current.Input.TouchMove += _mainInput.Input_TouchMove;
            Application.Current.Input.TouchEnd += _mainInput.Input_TouchEnd;
            Application.Current.Input.KeyUp += _mainInput.Input_KeyUp;
        }
        
        public override void Destroy()
        {
            base.Destroy();
            Application.Current.Input.TouchBegin -= _mainInput.Input_TouchBegin;
            Application.Current.Input.TouchMove -= _mainInput.Input_TouchMove;
            Application.Current.Input.TouchEnd -= _mainInput.Input_TouchEnd;
            Application.Current.Input.KeyUp -= _mainInput.Input_KeyUp;
        }
    }
}

What I’ve added here is some logic to interact with our world. Precisely I’ve created several methods to handle the touches on the screen. I’ve implemented all the methods inside another class called MainSceneInput. The code of this class is:

using System;
using Urho;
using Urho.Actions;

namespace UrhoSharpTutorial.Scenes
{
    internal class MainSceneInput
    {
        private readonly MainScene _scene;

        public event EventHandler<Node> OnEvaluateNode;

        public MainSceneInput(MainScene scene)
        {
            _scene = scene;
        }

        private Node GetSelectedNode(float objX, float objY)
        {
            Ray cameraRay = _scene.CameraNode.GetComponent<Camera>().GetScreenRay(objX / Application.Current.Graphics.Width, objY / Application.Current.Graphics.Height);
            var result = _scene.Scene.GetComponent<Octree>().RaycastSingle(cameraRay, RayQueryLevel.Triangle, 100);
            return result?.Node;
        }

        public void Input_TouchBegin(TouchBeginEventArgs obj)
        {
            Node selectedNode = GetSelectedNode((float)obj.X, (float)obj.Y);
            OnEvaluateNode?.Invoke(this, selectedNode);
        }

        public void Input_TouchMove(TouchMoveEventArgs obj)
        {
            Node selectedNode = GetSelectedNode((float)obj.X, (float)obj.Y);
            OnEvaluateNode?.Invoke(this, selectedNode);
        }

        public async void Input_TouchEnd(TouchEndEventArgs obj)
        {

        }

        internal void Input_KeyUp(KeyUpEventArgs obj)
        {
            if (obj.Key == Key.I)
            {
                var camera = _scene.CameraNode.GetComponent<Camera>();
                camera.Zoom += 0.05f;
            }
            else if (obj.Key == Key.O)
            {
                var camera = _scene.CameraNode.GetComponent<Camera>();
                camera.Zoom -= 0.05f;
            }
            else if (obj.Key == Key.W)
            {
                _scene.CameraNode.RunActions(new MoveTo(_scene.movementSpeed, new Vector3(_scene.CameraNode.Position2D.X, _scene.CameraNode.Position2D.Y + _scene.movementSize, -1.0f)));
            }
            else if (obj.Key == Key.S)
            {
                _scene.CameraNode.RunActions(new MoveTo(_scene.movementSpeed, new Vector3(_scene.CameraNode.Position2D.X, _scene.CameraNode.Position2D.Y - _scene.movementSize, -1.0f)));
            }
            else if (obj.Key == Key.A)
            {
                _scene.CameraNode.RunActions(new MoveTo(_scene.movementSpeed, new Vector3(_scene.CameraNode.Position2D.X - _scene.movementSize, _scene.CameraNode.Position2D.Y, -1.0f)));
            }
            else if (obj.Key == Key.D)
            {
                _scene.CameraNode.RunActions(new MoveTo(_scene.movementSpeed, new Vector3(_scene.CameraNode.Position2D.X + _scene.movementSize, _scene.CameraNode.Position2D.Y, -1.0f)));
            }
        }
    }
}

In this class I have a method to evaluate which object the user has touched (in that case the OnEvaluateNode method will be called with the selected node). And another method to move the camera using the keyboard (of course you can change this as you want, this is just an example on how to intercept these events).

Conclusion

All the code added until now is a basic empty template for every UrhoSharp project you want to create. You can use this template as a starting point for your UrhoSharp projects.

I’ve added on bitbucket this source code with just a simple code to add a sprite to our scene, so from there it can be easier for you to add all the sprites you need. The link is: https://bitbucket.org/marcojak81/urhosharpbasictemplate/src/master/

I’ll create later other more advanced tutorial on UrhoSharp.

As usual, if you have questions, please ask me and I’ll try to help you.

How to add a Checkbox in Xamarin.Forms

May 14, 2019 | Tutorial | No Comments

We are going to show step by step how to create a Checkbox for Xamarin.Forms with a very simple code without the use of Custom Renderers.This checkbox will work on every platform: Android, iOS, UWP… and the final result will be something like:

Checkbox disabled
Checkbox disabled
Checkbox enabled
Checkbox enabled

There are just two steps you need to do:

  • Add your images
  • Create the Checkbox class

After the two steps, I’m going to show you a small example on how to use this checkbox.

Add the Checkbox images

The first thing to do is to choose two images for the checkbox, one enabled and the other disabled (similat to the ones you can see in the previous images).

Add the images as embedded resources
Add the images as embedded resources

Create an Images folder inside your PCL/.NetStandard project and add the two images in it. Be sure to set the two images as Embedded Resources (as in the previous image).

Add the Checkbox class

Now it’s time to create our checkbox class. Inside your PCL/.NetStandard project create the file Checkbox:

using System;
using System.Windows.Input;
using Xamarin.Forms;

namespace Tutorial02
{
    public class Checkbox : StackLayout
    {
        public event EventHandler CheckedChanged;
        private readonly Image _image;

        private readonly Label _label;
        //CHANGE THESE 2 STRINGS ACCORDING TO YOUR NAMESPACE AND IMAGE

        static string imgUnchecked = "Tutorial02.Images.unchecked.png";
        static string imgChecked = "Tutorial02.Images.checked.png";
        public static readonly BindableProperty CommandProperty = BindableProperty.Create("Command", typeof(ICommand), typeof(Checkbox));

        public static readonly BindableProperty CheckedProperty = BindableProperty.Create("Checked", typeof(Boolean?), typeof(Checkbox), null,
            BindingMode.TwoWay, propertyChanged: CheckedValueChanged);

        public static readonly BindableProperty TextProperty =
            BindableProperty.Create("Text", typeof(String), typeof(Checkbox), null, BindingMode.TwoWay, propertyChanged: TextValueChanged);

        public ICommand Command
        {
            get => (ICommand) GetValue(CommandProperty);
            set => SetValue(CommandProperty, value);
        }

        public Boolean? Checked
        {
            get => (bool?) GetValue(CheckedProperty);
            set => SetValue(CheckedProperty, value);
        }

        public String Text
        {
            get => (string) GetValue(TextProperty);
            set => SetValue(TextProperty, value);
        }

        public Checkbox()
        {
            Orientation = StackOrientation.Horizontal;
            BackgroundColor = Color.Transparent;
            _image = new Image()
                {Source = ImageSource.FromResource(imgUnchecked), HeightRequest = 35, WidthRequest = 35, VerticalOptions = LayoutOptions.Center};
            var tg = new TapGestureRecognizer();
            tg.Tapped += Tg_Tapped;
            _image.GestureRecognizers.Add(tg);
            Children.Add(_image);
            _label = new Label() {VerticalOptions = LayoutOptions.Center};
            _label.GestureRecognizers.Add(tg);
            Children.Add(_label);
        }

        private void Tg_Tapped(object sender, EventArgs e)
        {
            Checked = !Checked;
        }

        private static void CheckedValueChanged(BindableObject bindable, object oldValue, object newValue)
        {
            if (newValue != null && (Boolean) newValue) ((Checkbox) bindable)._image.Source = ImageSource.FromResource(imgChecked);
            else ((Checkbox) bindable)._image.Source = ImageSource.FromResource(imgUnchecked);
            ((Checkbox) bindable).CheckedChanged?.Invoke(bindable, EventArgs.Empty);
            ((Checkbox) bindable).Command?.Execute(null);
        }

        private static void TextValueChanged(BindableObject bindable, object oldValue, object newValue)
        {
            if (newValue != null) ((Checkbox) bindable)._label.Text = newValue.ToString();
        }
    }
}

Your are now ready to use the checkbox in your apps and it will work for every platform supported by Xamarin. GREAT!Now I’ll show you a small example on how to use this checkbox inside your App:

Add the Checkbox to your ContentPage

Inside the our ContentPage we have set the ViewModel and then added the checkbox:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"             
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"             
             xmlns:local="clr-namespace:Tutorial02"
             xmlns:viewModel="clr-namespace:SafePhoto2.ViewModel;assembly=SafePhoto2"
             x:Class="Tutorial02.MainPage">
    <ContentPage.BindingContext>
        <viewModel:MainViewModel />
    </ContentPage.BindingContext>
    <local:Checkbox VerticalOptions="CenterAndExpand"                     
                    HorizontalOptions="CenterAndExpand"                     
                    Checked="{Binding IsChecked}"                     
                    Text="{Binding TextCheckBox}"                     
                    Command="{Binding OnCheckedChanged}">

    </local:Checkbox>
</ContentPage>

The checkbox has two important properties: Checked and Text.

  • Checked is bound to the IsChecked property of the ViewModel and indicates if the checkbox is checked or not
  • Text is bound to the TextCheckBox property of the ViewModel and is the text that appears next to the CheckBox image

In case you want to execute an action after the status of the checkbox is changed, you can use Command  (bound to the OnCheckedChanged inside the ViewModel) otherwise you can remove it from your XAML.

Create the ViewModel

The ViewModel used in our example is very easy and you can change it as you prefer. For this simple example we have just created a basic ViewModel:

using System.ComponentModel;
using System.Runtime.CompilerServices;
using Xamarin.Forms;

namespace Tutorial02
{
    public class MainViewModel : INotifyPropertyChanged
    {
        private bool _isChecked;
        private string _textCheckBox;
        public event PropertyChangedEventHandler PropertyChanged;

        public bool IsChecked
        {
            get => _isChecked;
            set
            {
                _isChecked = value;
                TextCheckBox = _isChecked ? "Is Enabled" : "Is Disabled";
                OnPropertyChanged();
            }
        }

        public string TextCheckBox
        {
            get => _textCheckBox;
            set
            {
                _textCheckBox = value;
                OnPropertyChanged();
            }
        }

        public Command OnCheckedChanged { get; set; }

        public MainViewModel()
        {
            OnCheckedChanged = new Command(OnCheckBoxChanged);
        }

        private void OnCheckBoxChanged()
        {
        }

        protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

As usual the ViewModel inherits from INotifyPropertyChanged.We have added two properties IsChecked and TextCheckBox and the Command OnCheckedChanged required only if we want to execute an action after the status of the checkbox is changed.When the IsChecked value changes, we set the Checkbox text to Is Enabled or Is Disabled according to its value.

Conclusion

In this tutorial we have seen how to create a Checkbox in Xamarin.Forms.The code is incredibly easy and ready to be used (you can copy and paste the code and it will work).If you have questions or doubts leave here a comment.If you need more info about the MVVM pattern in Xamarin you can check the Microsoft documentation here: https://docs.microsoft.com/en-us/xamarin/xamarin-forms/xaml/xaml-basics/data-bindings-to-mvvm

If you create a button on Android and write its text in lowercase (“my text”), when you launch the app, you can see that the text is all uppercase (“MY TEXT”).This is not a bug but the standard style for Android.Sometimes we prefer to have our text in lowercase so here I’ll show you different methods to do it.First of all, consider a very easy Page:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"             
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"             
             xmlns:local="clr-namespace:Tutorial02"             
             x:Class="Tutorial02.MainPage">
    <Button Text="My Text!"            
            VerticalOptions="Center"            
            HorizontalOptions="Center" />
</ContentPage>

If we run the app on Android, we see that the button text will be : “MY TEXT!” all uppercase. Now let’s see how we can make it lowercase:

CUSTOM RENDERERS

First of all, create an empty class MyButton in you PCL/.NetStandard project:

public class MyButton : Button
{        
}

Now we have to replace the Button with MyButton:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"             
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"             
             xmlns:local="clr-namespace:Tutorial02"             
             x:Class="Tutorial02.MainPage">
    <local:MyButton Text="My Text!"    <- CHANGE HERE          
                    VerticalOptions="Center"            
                    HorizontalOptions="Center" />
</ContentPage>

The next step is to create the custom render, so inside the Android project, create the class MyButtonRenderer:

[assembly: ExportRenderer(typeof(MyButton), typeof(MyButtonRenderer))]
namespace YOURNAMESPACEHERE
{
    public class MyButtonRenderer : ButtonRenderer
    {
        public MyButtonRenderer(Context context) : base(context)
        {
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
        {
            base.OnElementChanged(e);
            var button = this.Control;
            button.SetAllCaps(false);
        }
    }
}

It’s very important to add the first line[assembly: ExportRenderer(typeof(MyButton), typeof(MyButtonRenderer))]otherwise the Custom Renderer will not work.If we run the code, we see that now the button text is: “My Text!”.

EDIT THE STYLES.XML FILE

In your Android project open the styles.xml file inside the folder “Resources/values”, it will be something similar to:

<style name="MainTheme" parent="MainTheme.Base">  </style>
  <!-- Base theme applied no matter what API -->
  <style name="MainTheme.Base" parent="Theme.AppCompat.Light.DarkActionBar">
    <!--If you are using revision 22.1 please use just windowNoTitle. Without android:-->
    <item name="windowNoTitle">true</item>
    <!--We will be using the toolbar so no need to show ActionBar-->
    <item name="windowActionBar">false</item>
    <!-- Set theme colors from http://www.google.com/design/spec/style/color.html#color-color-palette -->
    <!-- colorPrimary is used for the default action bar background -->
    <item name="colorPrimary">#2196F3</item>
    <!-- colorPrimaryDark is used for the status bar -->
    <item name="colorPrimaryDark">#1976D2</item>
    <!-- colorAccent is used as the default value for colorControlActivated         which is used to tint widgets -->
    <item name="colorAccent">#FF4081</item>
    <!-- You can also set colorControlNormal, colorControlActivated         colorControlHighlight and colorSwitchThumbNormal. -->
    <item name="windowActionModeOverlay">true</item>
    <item name="android:datePickerDialogTheme">@style/AppCompatDialogStyle</item>
  </style>
  <style name="AppCompatDialogStyle" parent="Theme.AppCompat.Light.Dialog">
    <item name="colorAccent">#FF4081</item>
  </style>

To this file add these lines:

<style name="myTheme" parent="Theme.AppCompat.NoActionBar">
    <item name="android:textAppearanceButton">@style/mybutton.text</item>
  </style>
  <style name="mybutton.text" parent="Base.TextAppearance.AppCompat.Button">
    <item name="textAllCaps">false</item>
    <item name="android:textAllCaps">false</item>
  </style>

so that your styles.xml will be: 

<resources>
  <style name="MainTheme" parent="MainTheme.Base">  </style>
  <!-- Base theme applied no matter what API -->
  <style name="MainTheme.Base" parent="Theme.AppCompat.Light.DarkActionBar">
    <!--If you are using revision 22.1 please use just windowNoTitle. Without android:-->
    <item name="windowNoTitle">true</item>
    <!--We will be using the toolbar so no need to show ActionBar-->
    <item name="windowActionBar">false</item>
    <!-- Set theme colors from http://www.google.com/design/spec/style/color.html#color-color-palette -->
    <!-- colorPrimary is used for the default action bar background -->
    <item name="colorPrimary">#2196F3</item>
    <!-- colorPrimaryDark is used for the status bar -->
    <item name="colorPrimaryDark">#1976D2</item>
    <!-- colorAccent is used as the default value for colorControlActivated         which is used to tint widgets -->
    <item name="colorAccent">#FF4081</item>
    <!-- You can also set colorControlNormal, colorControlActivated         colorControlHighlight and colorSwitchThumbNormal. -->
    <item name="windowActionModeOverlay">true</item>
    <item name="android:datePickerDialogTheme">@style/AppCompatDialogStyle</item>
    <item name="android:textAppearanceButton">@style/mybutton.text</item>
  </style>
  <style name="AppCompatDialogStyle" parent="Theme.AppCompat.Light.Dialog">
    <item name="colorAccent">#FF4081</item>
  </style>
  <style name="myTheme" parent="Theme.AppCompat.NoActionBar">
    <item name="android:textAppearanceButton">@style/mybutton.text</item>
  </style>
  <style name="mybutton.text" parent="Base.TextAppearance.AppCompat.Button">
    <item name="textAllCaps">false</item>
    <item name="android:textAllCaps">false</item>
  </style>
</resources>

USE AN EFFECT

In your Android project create the class ButtonEffect:

[assembly: ResolutionGroupName("MyCompany")]
[assembly: ExportEffect(typeof(Tutorial02.Droid.ButtonEffect), "ButtonEffect")]

namespace Tutorial02.Droid
{
    public class ButtonEffect : PlatformEffect
    {
        protected override void OnAttached()
        {
            try
            {
                var control = Control as Android.Widget.Button;
                control.SetAllCaps(false);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Cannot set property on attached control. Error: ", ex.Message);
            }
        }

        protected override void OnDetached()
        {
        }

        protected override void OnElementPropertyChanged(System.ComponentModel.PropertyChangedEventArgs args)
        {
            base.OnElementPropertyChanged(args);
        }
    }
}

In your PCL/.NetStandard project create the class ButtonEffect:

public class ButtonEffect : RoutingEffect
{
    public ButtonEffect() : base("MyCompany.ButtonEffect")
    {
    }
}

Now you need to change your ContentPage to attach the Effect to your button:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"             
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"             
             xmlns:local="clr-namespace:Tutorial02"             
             x:Class="Tutorial02.MainPage">
    <Button Text="My Text!"            
            VerticalOptions="Center"           
            HorizontalOptions="Center">
        <Button.Effects>
            <local:ButtonEffect />
        </Button.Effects>
    </Button>
</ContentPage>

Conclusion

We have seen three methods to remove the Uppercase from your Android button:

  • Custom Renderers
  • Styles
  • Effects

All the methods do the same thing so it’s up to you to decide which method to use. Remember that Custom Renderers and Effects are very important in Xamarin so it’s important to understand them very well.

Xamarin.Forms is fantastic, you write your code once inside your PCL/.NetStandard project and it will run on many different platforms.However sometimes we need to access directly the native platform. To do so, we can use something called DependencyService.DependencyService allows us to use platform-specific functionality from shared code.To use the DependencyService we need:

  • An interface inside our shared code
  • An implementation for each platform
  • A registration

After the DependencyService is ready, then we can call it from our shared code.If we want to add a Sqlite database to our Xamarin.Forms project, because we cannot create it directly in our shared code, we need to use a DependencyService so in this tutorial we are going to see how to use the DependencyService to create and use a Sqlite database in our multi platform app.

TUTORIAL

First of all, let’s create an empty Xamarin.Forms project using a .NetStandard project. For a tutorial on how to create a Xamarin.Forms project, you can read this guide: http://www.xamarinexpert.it/2018/03/03/xamarin-forms-a-guide-for-beginners/

Empty Xamarin Project
Fig.1 Structure of an empty Xamarin.Forms Project

In the first image you can see the structure of a Xamarin.Forms project.As we said, the creation of a DependencyService consists of 3 steps.

First Step – The interface

Now the first step to do, is to create the Interface for our DependencyService.Let’s create and add an interface called ISql to our .NetStandard project:

public interface ISql
{
    SQLiteConnection GetConnection(string dbname = "database.db3");
    SQLiteAsyncConnection GetConnectionAsync(string dbname = "database.db3");
}

This interface exposes two methods:GetConnection: Get a connection for the Sqlite database.GetConnectionAsync: Get an async connection for the Sqlite database.Really easy. Don’t you think?

Second Step – The implementation

Inside this second step, we need to implement the interface in each platform. Let’s start with Android

Android

We need to create in Android a class the implements the ISql interface, let’s call this class SqlImplementation:

public class SqlImplementation : ISql
{
    public SQLiteConnection GetConnection(string dbname = "database.db3")
    {
        var sqliteFilename = dbname;
        string documentsPath = System.Environment.GetFolderPath(Environment.SpecialFolder.Personal);
        // Documents folder
        var path = Path.Combine(documentsPath, sqliteFilename);
        var conn = new SQLiteConnection(path, SQLiteOpenFlags.ReadWrite | SQLiteOpenFlags.Create | SQLiteOpenFlags.FullMutex);
        return conn;
    }

    public SQLiteAsyncConnection GetConnectionAsync(string dbname = "database.db3")
    {
        var sqliteFilename = dbname;
        string documentsPath = System.Environment.GetFolderPath(Environment.SpecialFolder.Personal); // Documents folder
        var path = Path.Combine(documentsPath, sqliteFilename);
        return new SQLiteAsyncConnection(path);
    }
}

We have basically implemented the two methods of our ISql interface. These two methods return the native connection to an Android Sqlite database.

iOS

Now we need to create the same class inside the native  iOS project:

public class SqlImplementation : ISql
{
    public SQLiteConnection GetConnection(string dbname = "database.db3")
    {
        var sqliteFilename = dbname;
        string documentsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal); // Documents folder

        var path = Path.Combine(documentsPath, sqliteFilename);
        var conn = new SQLiteConnection(path, SQLiteOpenFlags.ReadWrite | SQLiteOpenFlags.Create | SQLiteOpenFlags.FullMutex);
        return conn;
    }

    public SQLiteAsyncConnection GetConnectionAsync(string dbname = "database.db3")
    {
        var sqliteFilename = dbname;
        string documentsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal); // Documents folder
        var path = Path.Combine(documentsPath, sqliteFilename);
        return new SQLiteAsyncConnection(path);
    }
}

As you can see the code is basically the same but it’s IMPORTANT to add the implementation to each platform you need to use, otherwise you’ll get an error.

UWP

Now it’s time to implement the interface for UWP:

public class SqlImplementation : ISql
{
    public SQLiteConnection GetConnection(string dbname = "database.db3")
    {
        var sqliteFilename = dbname;
        var path = Path.Combine(ApplicationData.Current.LocalFolder.Path, sqliteFilename);
        var conn = new SQLiteConnection(path, SQLiteOpenFlags.ReadWrite | SQLiteOpenFlags.Create | SQLiteOpenFlags.FullMutex);
        return conn;
    }

    public SQLiteAsyncConnection GetConnectionAsync(string dbname = "database.db3")
    {
        var sqliteFilename = dbname;
        var path = Path.Combine(ApplicationData.Current.LocalFolder.Path, sqliteFilename);
        return new SQLiteAsyncConnection(path);
    }
}

and this concludes the second step.

Third Step – The registration

it’s extremely important to register the DependencyService otherwise it will not work.Don’t worry, this step is incredibly easy, the only thing you need to do is to add this line of code in each SqlImplementation class just before the namespace:

[assembly: Dependency(typeof(SqlImplementation))]

so for example the final code of your Android implementation will be:

[assembly: Dependency(typeof(SqlImplementation))]

namespace YOURNAMESPACE
{
    public class SqlImplementation : ISql
    {
        public SQLiteConnection GetConnection(string dbname = "database.db3")
        {
            var sqliteFilename = dbname;
            string documentsPath = System.Environment.GetFolderPath(Environment.SpecialFolder.Personal); // Documents folder
            var path = Path.Combine(documentsPath, sqliteFilename);
            var conn = new SQLiteConnection(path, SQLiteOpenFlags.ReadWrite | SQLiteOpenFlags.Create | SQLiteOpenFlags.FullMutex);
            return conn;
        }

        public SQLiteAsyncConnection GetConnectionAsync(string dbname = "database.db3")
        {
            var sqliteFilename = dbname;
            string documentsPath = System.Environment.GetFolderPath(Environment.SpecialFolder.Personal); // Documents folder
            var path = Path.Combine(documentsPath, sqliteFilename);
            return new SQLiteAsyncConnection(path);
        }
    }
}

REMEMBER to add the assembly line to EACH of your SqlImplementation classes.

HOW TO USE IT

Now the DependencyService is ready, we just need to call use it. If we want to get the SqLite connection we just need to use a single line of code inside our share code:

SQLiteConnection database = DependencyService.Get<ISQLite>().GetConnection();

Now you have your sql connection in you shared code so you can start to use your SqLite database.

Sqlite Plugin

It’s extremely easy to use the DependencyService to add a Sqlite database to your Xamarin.Forms app, but if you want an already made solution, you can use my Sqlite plugin so after you install it, you can directly use your database with a single line of code:

SQLiteConnection conn = MTSql.Current.GetConnection("yourdatabasename.db3");

It cannot be easier than that.You can find a tutorial on how to use the plugin here: http://www.xamarinexpert.it/2018/03/01/sqlite-made-easy/The official page is here: http://www.xamarinexpert.it/plugins/mt-sqlite/You can find the nuget package here: https://www.nuget.org/packages/MarcTron.Sqlite

More

You have doubts about the DependencyService or Sql? You want to know more? Ask me adding a comment below this article.

Admob for Xamarin made easy

May 6, 2019 | Guide, Plugin, Tutorial | 86 Comments

In this tutorial I’ll show you how to monetize your Xamarin apps with AdMob using my MTAdmob plugin.

Important: If you receive errors compiling the code for iOS, install the package Xamarin.Google.iOS.MobileAds in your iOS project.

UPDATE 16/10/2019: MTAdmob is now Open Source on Github: https://github.com/marcojak/MTAdmobUPDATE 11/10/2019: VERY IMPORTANT!!! The new version 1.4.4 is out. There is an issue in the latest Xamarin.Google.iOS.MobileAds 7.47. Because of this, in your iOS project you have to install the plugin Xamarin.Google.iOS.SignIn 4.4.0 too. This will let you compile and use MobileAds.

UPDATE 1/May/2019: I’ve released the new version 1.3 thas sovles some issues with iOS and improves performances.

UPDATE: From version 1.2, MTAdmob supports also Google ads rewarded videos for Android and iOS

UPDATE: I’ve added on github the source code of a project to test this Admob plugin. You can find it here: https://github.com/marcojak/TestMTAdmob

To help you to speed up your Xamarin development, I’ve created a set of plugins, one of them is MTAdmob. Thanks to this plugin you can add Admob banners and Insterstitials in just few lines of code. It couldn’t be easier than that and I’ll show you.

Install the plugin

First of all, right click on your Xamarin solution and select “Manage Nuget packages for Solution”

manage nuget

Visual Studio will open a new screen where you can search and install one or more nuget packages. In this case we can search for the MTAdmob plugin. Searching for MarcTron will show you all my packages (I’m sure you can find other useful plugins that I’ve written), and we can select the MTAdmob plugin as showed in the next image.

It’s very important that you install the plugin in your PCL/.Net standard project and in your platform projects (Android, iOS, UWP).

After the Admob plugin is installed we can add banners and insterstitials to our projects.

Add Ads to our project

With version 1.0 the MTAdmob plugin supports banner and interstitials for Android and iOS. If you would like to see the plugin supporting also the UWP platform, let me now and I’ll add the support in a new version.

As I’ve said we can add Banners and Interstitials Admob ads to our project. Let’s start with the Banners

How to add an Admob Banner

An Admob banner is just a view inside our page. It means that we can add it using XAML or C#. First of all let’s see how to add an Admob banner using XAML.

Add an Admob Banner with XAML

In MTAdmob to use an Admob banner I’ve created a custom control called AdView, so to use it we can use this code:

<?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:controls="clr-namespace:MarcTron.Plugin.Controls;assembly=Plugin.MtAdmob"
             x:Class="Test.MTAdmob.MainPage">

<StackLayout>
    <Label Text="Let's test an Admob Banner!" 
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />
    <!-- Place the Admob controls here -->
    <controls:MTAdView/>
</StackLayout>

In this example we have created a StackLayout with 2 controls: a label and an AdView (our Admob banner). Easy! Isn’t it???

The AdView control is basically a View so you can use all the properties you can think of like: HorizontalOptions, VerticalOptions, IsVisible…

In addition to these properties, I’ve added in AdView two other properties: AdsId and PersonalizedAds.

AdsId: Allows you to add the Banner Id (you can find it in your Admob account)

PersonalizedAds: This allow you to use non personalized ads. For example in case of GPDR. Of course it’s better to use personalized Ads.

To use these properties you can update the previous code to:

<controls:AdView PersonalizedAds="true" AdsId="xxxxxxxxxxxxxxxxxx"/>

Add an Admob Banner with C#

In case you don’t write your pages with XAML or you write your UI in C# or you want to add your view only in some cases, you can add your Admob Banner using this code:

using MarcTron.Plugin;
...
MTAdView ads = new MTAdView();

Of course you need to attach this View to your layout, but you know how to do it (If not, feel free to ask).

To use the custom properties you can change the previous code to:

...
MTAdView ads = new MTAdView();
ads.AdsId = "xxx";
ads.PersonalizedAds = true;

Also in this case, to add an Admob banner is INCREDIBILY EASY!!!

Global Custom Properties

As you have seen, the properties AdsId and PersonalizedAds belong to a single AdView. It means that you have to set them for every Admob Banner.

To make things even easier I’ve added the option to set these properties only once. To do so, you can use this C# code:

CrossMTAdmob.Current.UserPersonalizedAds = true;
CrossMTAdmob.Current.AdsId = "xxxxxxxxxxxxxxxx";

In this case all your Admob banner will show personalized ads and will have the same Id.

If you set local and global properties, the local ones will have higher priority.

Use of Banner Events

I’ve added 4 events to the Admob banner that you could find nice to have. These events are:

  • AdsClicked When a user clicks on the ads
  • AdsClosed When the user closes the ads
  • AdsImpression Called when an impression is recorded for an ad.
  • AdsOpened When the ads is opened

To use these events you can write this code:

AdView myAds = new AdView();
myAds.AdsClicked += MyAdsAdsClicked;
myAds.AdsClosed += MyAds_AdVClosed;
myAds.AdsImpression += MyAds_AdVImpression;
myAds.AdsOpened += MyAds_AdVOpened;

Of course you can use these events also if you have declared your AdView in your XAML code.

Admob Interstitials

Now that we know how to add Admob banners using my plugin MTAdmob, let’s see how we can add Admob Interstitials. If possible, to add an Admob interstitial is even easier. You just need a single line of code. Don’t you believe me? Look here how to show an Admob interstitial:

CrossMTAdmob.Current.ShowInterstitial("ca-app-pub-xxxxxxxxxxxxxxxx/xxxxxxxxxx");

I told you!!! That’s it!!! With that line of code you have just showed an Interstitial in you app. Of course you need to replace that string with the Insterstitial ID you can find in your Admob account.

Events for Interstitials

There 3 events that you can use with Interstitials:

OnInterstitialLoaded        When it's loaded
OnInterstitialOpened        When it's opened      
OnInterstitialClosed        When it's closed

Rewarded Video

From version 1.1 the plugin supports the amazing Rewarded Video too.

To show a rewarded video you just need a single line of code:

CrossMTAdmob.Current.ShowRewardedVideo("xx-xxx-xxx-xxxxxxxxxxxxxxxxx/xxxxxxxxxx");

Events for Rewarded videos

There are 7 events that you can use with the Rewarded video Ads:

OnRewarded                          When the user gets a reward
OnRewardedVideoAdClosed             When the ads is closed
OnRewardedVideoAdFailedToLoad       When the ads fails to load
OnRewardedVideoAdLeftApplication    When the users leaves the application
OnRewardedVideoAdLoaded             When the ads is loaded
OnRewardedVideoAdOpened             When the ads is opened
OnRewardedVideoStarted              When the ads starts

Initialization

Before you can use the Admob banners and Interstitials, you need to initialize it. You need to do it only once so it makes sense to initialize it onside the OnCreate method in Android and FinishedLaunching in iOS.

In your Android project add this line in your OnCreate method:

MobileAds.Initialize(ApplicationContext, "ca-app-pub-xxxxxxxxxxxxxxxx~xxxxxxxxxx");

In your iOS project add this line in your FinishedLaunching method:

MobileAds.SharedInstance.Start(CompletionHandler);

private void CompletionHandler(InitializationStatus status){}

In iOS you should install the package Xamarin.Google.iOS.MobileAds and Xamarin.Google.iOS.SignIn!

You need to add to your Info.plist file this:

	<key>GADApplicationIdentifier</key>
	<string>YOUR APP ID</string>
	<key>GADIsAdManagerApp</key>
	<true/>

Android Project (Important)

In your AndroidManifest you should add these lines:

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

<application android:label="Test.MTAdmob.Android">
    <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version"/>
    <meta-data android:name="com.google.android.gms.ads.APPLICATION_ID" android:value="ca-app-pub-xxxxxxxxxxxxxxxx~yyyyyyyyyy"/>
    <activity android:name="com.google.android.gms.ads.AdActivity" android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" android:theme="@android:style/Theme.Translucent" />
</application>

iOS Project (Important)

From version 1.4.4 you need to manually install the packages: Xamarin.Google.iOS.MobileAds and Xamarin.Google.iOS.SignIn! If you don’t install them, your app will not compile.

Some useful links

Conclusion

This Admob MTAdmob plugin is incredibly easy to use but in case you need help, or you want to suggest a new feature or for any other reason, write me.

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