[forms-devel] Fwd: Fixing SetNativeControl logic when replacing native controls

[Toni Petrina]

Hi everyone,

 

In the middle of writing the proposal and testing out the code that will fix the issue below I stumbled upon the following code in Xamarin.Forms.Platform.Android.AppCompat namespace:

 

    public abstract class ViewRenderer<TView, TControl> : Android.ViewRenderer<TView, TControl> where TView : View where TControl : global::Android.Views.View
    {
        protected abstract TControl CreateNativeControl();
    }  

 

This is exactly what I am proposing, but pulled up to the Android.ViewRenderer class.

Should I continue writing my proposal and can I send pull request into the evolution repository or do we have to discuss it here first?

 

Cheers

Toni Petrina



Begin forwarded message:

 

From: Toni Petrina <tonipetrina at hotmail.com>

Subject: [forms-devel] Fixing SetNativeControl logic when replacing native controls

Date: 2 July 2016 at 18:22:42 GMT+2

To: <forms-devel at lists.xamarin.com>

 

Hi,

 

It is hard to replace a native control inside a renderer with your own. You cannot even replace ListView in Android because there are nasty NullRefs happening if you do so! Consider the following code:

 

var ctx = Context;
nativeListView = new AListView(ctx);
_refresh = new SwipeRefreshLayout(ctx);
_refresh.SetOnRefreshListener(this);
_refresh.AddView(nativeListView, LayoutParams.MatchParent);
SetNativeControl(nativeListView, _refresh);

 

 

If I want to use my subclass instead of Android.Widget.ListView, I have to reimplement entire ListViewRenderer which is impossible due to all internal classes. It would be much better if there is a method called GetNativeControll so that the above code looks more like:

 

protected override AListView GetNativeControl() => new AListView(Context);

 ())

var ctx = Context;
nativeListView = GetNativeControl();


This way I can override the default control to be used with my own subclass.

 

Cheers

Toni Petrina

 

P.S. Not having markdown in email is frustrating!

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