英文をタップして、単語単位で選択する

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

	SetContentView(Resource.Layout.Main);

	TextView textview = (TextView)FindViewById(Resource.Id.textView1);
	textview.TextFormatted = new Android.Text.SpannableString("Chapter 1\n\nThis is a pen.\nThis is a window.");
	textview.SetTextIsSelectable(true);

	textview.Touch += delegate (object sender, View.TouchEventArgs e)
	{
		var widget = (TextView)sender;
		var buffer = (Android.Text.ISpannable)widget.TextFormatted;

		if (buffer.Length() != 0 && (e.Event.Action == MotionEventActions.Up || e.Event.Action == MotionEventActions.Down || e.Event.Action == MotionEventActions.Move))
		{
			if (e.Event.Action == MotionEventActions.Up)
			{
				var line = widget.Layout.GetLineForVertical((int)e.Event.GetY() + widget.ScrollY - widget.TotalPaddingTop);
				var offset = widget.Layout.GetOffsetForHorizontal(line, (int)e.Event.GetX() + widget.ScrollX - widget.TotalPaddingLeft);

				if (buffer.CharAt(offset) != '\n')
				{
					int start = int.MaxValue;
					for (int i = offset - 1; i >= 0; i--)
					{
						if (Java.Lang.Character.IsLetterOrDigit(buffer.CharAt(i)) != true)
						{
							start = i + 1;
							break;
						}
					}

					int end = int.MinValue;
					for (int i = start + 1; i < buffer.Length(); i++)
					{
						if (Java.Lang.Character.IsLetterOrDigit(buffer.CharAt(i)) != true)
						{
							end = i - 1;
							break;
						}
					}

					if (end >= start)
					{
						Android.Text.Selection.SetSelection(buffer, start, end + 1);
					}
				}
			}
			else if (e.Event.Action == MotionEventActions.Down)
			{
				//
			}
			else if (e.Event.Action == MotionEventActions.Move)
			{
				//
			}
		}
		else
		{
			Android.Text.Selection.RemoveSelection(buffer);
		}
	};			
}

}