It is not a common scenario to grab a hardware key event in your application, because you can simply use controls like Editor or Entry when you need to get input from users. However, if you want to make a more advanced application which handles hardware key inputs more detail or especially when you want to do something with the Smart TV remote control key event, you want to grab hardware key events.
How to get hardware key event
Using EcoreEvent class
There is a class defined in ElmSharp called EcoreEvent. You can use this ElmSharp.EcoreEvent<EcoreEventType> class to create the following ecore event types that are being notified.
- KeyDown
- KeyUp
- MouseButtonDown
- MouseButtonUp
- MouseButtonCancel
- MouseMove
- MouseWheel
- MouseIn
- MouseOut
Implementing in application
Mainpage.xaml
Here is the preparation in the main page of an application to show which key event is occured.
One label named keyDownLabel will show which key down event is occured, the other label named keyDownLabel will show which key up event is occured.
<c:CirclePage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:c="clr-namespace:Tizen.Wearable.CircularUI.Forms;assembly=Tizen.Wearable.CircularUI.Forms"
x:Class="HandleHWKey.MainPage">
<c:CirclePage.Content>
<StackLayout VerticalOptions="CenterAndExpand">
<Label x:Name="keyDownLabel"
Text="Which key is down?"
HorizontalOptions="CenterAndExpand" />
<Label x:Name="keyDownLabel"
Text="Which key is up?"
HorizontalOptions="CenterAndExpand" />
</StackLayout>
</c:CirclePage.Content>
</c:CirclePage>
Mainpage.xaml.cs
Now on the cs file, declare and create EcoreEvent with the proper EcoreKeyEventType like below.
Here I created EcoreEventType.KeyDown and EcoreEventType.KeyUp to grab the hardware key down and up events.
After creations, I added event handlers using On event handler. Both event handler will update the hardware key name and the key code on each labels.
EcoreKeyEventArgs is an EventArgs to record the Ecore event's key name and key code. You can see the defined and supported hardware key name here.
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
using Tizen.Wearable.CircularUI.Forms;
using ElmSharp; // declare using statement
namespace HandleHWKey
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class MainPage : CirclePage
{
EcoreEvent<EcoreKeyEventArgs> _ecoreKeyDown;
EcoreEvent<EcoreKeyEventArgs> _ecoreKeyUp;
public MainPage()
{
InitializeComponent();
_ecoreKeyDown = new EcoreEvent<EcoreKeyEventArgs>(EcoreEventType.KeyDown, EcoreKeyEventArgs.Create);
_ecoreKeyDown.On += _ecoreKeyDown_On;
_ecoreKeyUp = new EcoreEvent<EcoreKeyEventArgs>(EcoreEventType.KeyUp, EcoreKeyEventArgs.Create);
_ecoreKeyUp.On += _ecoreKeyUp_On;
}
private void _ecoreKeyDown_On(object sender, EcoreKeyEventArgs e)
{
keyDownLabel.Text = $"{e.KeyName} ({e.KeyCode})";
}
private void _ecoreKeyUp_On(object sender, EcoreKeyEventArgs e)
{
keyUpLabel.Text = $"{e.KeyName} ({e.KeyCode})";
}
}
}
Running application on emulator
You can see the pressed hardware key name and a key code on the upper label, and the released hardware key name and a key code on the lower label.
For TV developers
If you are developing for Samsung Smart TV and are finding how to simply handle hardware key events, Tizen.TV.UIControls is right there for you. Tizen.TV.UIControls not only provides a variety sets of UI controls for easily creating TV applications, but also have Xamarin.Forms extension features that helps you create TV applications easily.
InputEvents feature in this library is the wrapper for this ElmSharp EcoreEvents so you can easily grab keys, for example remote control keys, in your application. Check out the guides and the API reference for InputEvents.