User1544 postedOK, after playing around with Xamarin.Forms.Labs and the official examples for Xamarin.Forms I was able to extend ImageCell and add a BackgroundImageProperty (only for Android right now). I'm not sure about the quality of this code. Did I go the correct way to extend Xamarin.Forms?
ExtendedImageCell:
`
using System;
using System.Linq.Expressions;
using Xamarin.Forms;
namespace WosiDev.Core.Components
{
public class ExtendedImageCell : ImageCell
{
public static readonly BindableProperty BackgroundImageSourceProperty
= BindableProperty.Create
((Expression>)(w => w.BackgroundImageSource)
, (ImageSource)null, BindingMode.OneWay, (BindableProperty.ValidateValueDelegate)null,
(BindableProperty.BindingPropertyChangedDelegate)((bindable, oldvalue, newvalue)
=> ((Element)bindable).ToString())
, (BindableProperty.BindingPropertyChangingDelegate)null,
(BindableProperty.CoerceValueDelegate)null);
[TypeConverter(typeof(ImageSourceConverter))]
public ImageSource BackgroundImageSource
{
get { return (ImageSource)GetValue(BackgroundImageSourceProperty); }
set { SetValue(BackgroundImageSourceProperty, value); }
}
}
}
`
ExtendedImageCellRenderer:
`using Xamarin.Forms.Platform.Android;
using Xamarin.Forms;
WosiDev.Droid.Renderers
using Android.Widget;
using Android.Graphics.Drawables;
using Android.Graphics;
using View = global::Android.Views.View;
using ViewGroup = global::Android.Views.ViewGroup;
using Context = global::Android.Content.Context;
using WosiDev.Core.Components;
using System.Threading.Tasks;
[assembly: ExportCell(typeof(ExtendedImageCell), typeof(ExtendedImageCellRenderer))]
namespace WosiDev.Droid.Renderers
{
public class ExtendedImageCellRenderer : ImageCellRenderer
{
protected override View GetCellCore (Cell item, View convertView, ViewGroup parent, Context context)
{
var cell = (LinearLayout)base.GetCellCore (item, convertView, parent, context);
SetBackgroundImageSourceAsync(cell, (ExtendedImageCell)item, context);
return cell;
}
private async Task SetBackgroundImageSourceAsync(Android.Widget.LinearLayout targetLayout, ExtendedImageCell model, Context context)
{
var source = model.BackgroundImageSource;
using (var bitmap = await GetBitmapAsync(source, context))
{
if (bitmap != null)
{
Drawable drawable = new BitmapDrawable(bitmap);
var scaledDrawable = drawable;
targetLayout.SetBackgroundDrawable(scaledDrawable);
}
}
}
private async Task<Bitmap> GetBitmapAsync(ImageSource source, Context context)
{
var handler = GetHandler(source);
var returnValue = (Bitmap)null;
returnValue = await handler.LoadImageAsync(source, context);
return returnValue;
}
private static IImageSourceHandler GetHandler(ImageSource source)
{
IImageSourceHandler returnValue = null;
if (source is UriImageSource)
{
returnValue = new ImageLoaderSourceHandler();
}
else if (source is FileImageSource)
{
returnValue = new FileImageSourceHandler();
}
else if (source is StreamImageSource)
{
returnValue = new StreamImagesourceHandler();
}
return returnValue;
}
}
}`
[You may need this file from Xamarin.Forms.Labs to compile this code: https://raw.githubusercontent.com/XForms/Xamarin-Forms-Labs/d679815e4340fce3f5675e4a1e27b8683f024699/src/Xamarin.Forms.Labs/Xamarin.Forms.Labs/Controls/ImageButtonSourceConverter.cs]
Feel free to use and extend these snippets. If anybody from Xamarin.Forms.Labs reads this: Yes, you can use it.
