Xamarin Custom Keyboard

Question

I am trying to create a custom keyboard for a specific page and I have some problems in handling the listener for all the keys and the documentations for this is very limited.

I am using Xamarin and C# for development:

So here I have an activity (OrderActivity):

mKeyboard = new Keyboard(this,Resource.Layout.Keyboard);
mKeyboardView = this.FindViewById<KeyboardView> (Resource.Id.keyboardview);
mKeyboardView.Keyboard = mKeyboard;

// PROBLEM HERE
mKeyboardView.OnKeyboardActionListener = new KeyboardView.IOnKeyboardActionListener () {};

There is a Keyboard.axml and they display on screen perfectly but I have problems and don't know how to call the listener, anyone here have any tutorials or how to fix this problem? Or is there any alternatives in creating a custom keyboard?

Answer 1

As the name of the listener indicates, it is an Interface you need to implement. C# does currently not allow for anonymous classes just like Java does.

Remember when implementing Java Interfaces you need to inherit from Java.Lang.Object, as it expects a handle.

So your implementation could look something like:

public class KeyboardOnKeyEventArgs : KeyboardKeyCodeEventArgs
{
    public Keycode[] KeyCodes { get; set; }
}

public class KeyboardKeyCodeEventArgs : EventArgs
{
    public Keycode PrimaryCode { get; set; }
}

public class KeyboardOnTextEventArgs : EventArgs
{
    public ICharSequence Text { get; set; }
}

public class MyKeyboardListener : Java.Lang.Object, KeyboardView.IOnKeyboardActionListener
{
    public event EventHandler<KeyboardOnKeyEventArgs> Key;
    public event EventHandler<KeyboardKeyCodeEventArgs> Press;
    public event EventHandler<KeyboardKeyCodeEventArgs> Release;
    public event EventHandler<KeyboardOnTextEventArgs> Text;
    public event EventHandler OnSwipeDown;
    public event EventHandler OnSwipeLeft;
    public event EventHandler OnSwipeRight;
    public event EventHandler OnSwipeUp;

    public void OnKey(Keycode primaryCode, Keycode[] keyCodes)
    {
        if (Key != null)
            Key(this, new KeyboardOnKeyEventArgs {
                KeyCodes = keyCodes,
                PrimaryCode = primaryCode
            });
    }

    public void OnPress(Keycode primaryCode)
    {
        if (Press != null)
            Press(this, new KeyboardKeyCodeEventArgs { PrimaryCode = primaryCode });
    }

    public void OnRelease(Keycode primaryCode)
    {
        if (Release != null)
            Release(this, new KeyboardKeyCodeEventArgs { PrimaryCode = primaryCode });
    }

    public void OnText(ICharSequence text)
    {
        if (Text != null)
            Text(this, new KeyboardOnTextEventArgs {Text = text});

    }

    public void SwipeDown()
    {
        if(OnSwipeDown != null)
            OnSwipeDown(this, EventArgs.Empty);
    }

    public void SwipeLeft()
    {
        if (OnSwipeLeft != null)
            OnSwipeLeft(this, EventArgs.Empty);
    }

    public void SwipeRight()
    {
        if (OnSwipeRight != null)
            OnSwipeRight(this, EventArgs.Empty);
    }

    public void SwipeUp()
    {
        if (OnSwipeUp != null)
            OnSwipeUp(this, EventArgs.Empty);
    }
}

Usage would be:

var keyboardListener = new MyKeyboardListener();
keyboardListener.Press += (s, e) => { /* do something */ };
mKeyboardView.OnKeyboardActionListener = keyboardListener;

EDIT:

Worked a bit more with it, and I cannot reproduce your error.

keyboard.xml

<?xml version="1.0" encoding="utf-8" ?>
<Keyboard xmlns:android="http://schemas.android.com/apk/res/android"
    android:keyWidth="33%p" android:horizontalGap="0px"
    android:verticalGap="0px" android:keyHeight="54dip">

  <Row>
    <Key android:codes="8" android:keyLabel="1" android:keyEdgeFlags="left" />
    <Key android:codes="9" android:keyLabel="2" />
    <Key android:codes="10" android:keyLabel="3" android:keyEdgeFlags="right" />
  </Row>

  <Row>
    <Key android:codes="11" android:keyLabel="4" android:keyEdgeFlags="left" />
    <Key android:codes="12" android:keyLabel="5" />
    <Key android:codes="13" android:keyLabel="6" android:keyEdgeFlags="right" />
  </Row>

  <Row>
    <Key android:codes="14" android:keyLabel="7" android:keyEdgeFlags="left" />
    <Key android:codes="15" android:keyLabel="8" />
    <Key android:codes="16" android:keyLabel="9" android:keyEdgeFlags="right" />
  </Row>
</Keyboard>

Main.axml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <EditText
        android:layout_above="@+id/keyboard_view"
        android:layout_alignParentTop="true"
        android:layout_width="match_parent"
        android:id="@+id/target"
        android:layout_height="wrap_content" />
    <android.inputmethodservice.KeyboardView
        android:id="@+id/keyboard_view"
        android:visibility="gone"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true" />
</RelativeLayout>

slide_up.xml

<?xml version="1.0" encoding="utf-8" ?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
  <translate android:fromYDelta="-50%p" android:toYDelta="0" android:duration="200"/>
  <alpha android:fromAlpha="0.0" android:toAlpha="1.0" android:duration="200" />
</set>

MyKeyboardListener.cs

public class MyKeyboardListener : Java.Lang.Object, KeyboardView.IOnKeyboardActionListener
{
    private readonly Activity _activity;

    public MyKeyboardListener(Activity activity) {
        _activity = activity;
    }

    public void OnKey(Keycode primaryCode, Keycode[] keyCodes)
    {
        var eventTime = DateTime.Now.Ticks;
        var keyEvent = new KeyEvent(eventTime, eventTime, KeyEventActions.Down, primaryCode, 0);
        _activity.DispatchKeyEvent(keyEvent);
    }

    public void OnPress(Keycode primaryCode) { }
    public void OnRelease(Keycode primaryCode) { }
    public void OnText(ICharSequence text) { }
    public void SwipeDown() { }
    public void SwipeLeft() { }
    public void SwipeRight() { }
    public void SwipeUp() { }
}

MainActivity.cs

[Activity(Label = "App14", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
    private Keyboard _keyBoard;
    private EditText _targetView;
    private KeyboardView _keyboardView;

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);

        _keyBoard = new Keyboard(this, Resource.Xml.keyboard);
        _keyboardView = FindViewById<KeyboardView>(Resource.Id.keyboard_view);
        _keyboardView.Keyboard = _keyBoard;
        _keyboardView.OnKeyboardActionListener = new MyKeyboardListener(this);
        _targetView = FindViewById<EditText>(Resource.Id.target);
        _targetView.Touch += (sender, args) => {
            var bottomUp = AnimationUtils.LoadAnimation(this, Resource.Animation.slide_up);
            _keyboardView.StartAnimation(bottomUp);
            _keyboardView.Visibility = ViewStates.Visible;
            args.Handled = true;
        };
    }
}

Keyboard shows and characters are dispatched to the EditText.