prs/prs.mobile.new/PRS.Mobile/CustomControls/SignatureEditor/SignatureEditor.xaml.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace PRS.Mobile
{

    public class SignatureEditorChangedEventArgs : EventArgs
    {
    }

    public delegate void SignatureEditorChangedEvent(object sender, SignatureEditorChangedEventArgs args);
    
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class SignatureEditor
    {

        public event SignatureEditorChangedEvent Changed;

        public void Load(byte[] data)
        {
            if (data?.Any() == true)
            {
                _frame.Background = new SolidColorBrush(Color.LightGray);
                signaturePad.IsVisible = false;
                _preview.Source = ImageSource.FromStream(() => { return new MemoryStream(data); });
                _preview.IsVisible = true;
                _label.IsVisible = false;
            }
            else
            {
                _frame.Background = new SolidColorBrush(Color.LightYellow);
                _preview.IsVisible = false;
                _preview.Source = null;
                signaturePad.IsVisible = true;
                signaturePad.Clear();
                _label.IsVisible = true;
            }
        }

        public byte[] Save()
        {
            signaturePad.Save();
            if (signaturePad.ImageSource is StreamImageSource source)
            {
                Task<Stream> task = source.Stream(System.Threading.CancellationToken.None);
                Stream stream = task.Result;
                byte[] bytes = new byte[stream.Length];
                stream.Read(bytes, 0, bytes.Length);
                Load(bytes);
                return bytes;
            }
            return new byte[] { };
        }
        
        public SignatureEditor()
        {
            InitializeComponent();
            Load(null);
        }

        private void SignaturePad_OnStrokeCompleted(object sender, EventArgs e)
        {
            Changed?.Invoke(this,new SignatureEditorChangedEventArgs());
        }
        
    }
}