flicker black background MaterialTextField xamarin forms Android

## 🐛 Bug Report

In Android when the page is loading there is a small flicker in the black color entry, the CardBackgroundColor="Transparent" property works fine but that flicker generates a bad experience on different android devices, also if I add this in CollectionView header, this flicker it's constant

### Expected behavior

No black Flicker

### Reproduction steps

When page is load

- Put a materialtextfield on a page, navigate to this page

When CollectionVIew has header and the header view contains MaterialTextField

- Put a materialtextfield on a header view on a CollectionView, typing in MaterialTextField

### Configuration

**Version:** 1.8
Xamarin Forms 5.0.0.2337

**Platform:**
- [ ] :iphone: iOS
- [ X] :robot: Android
- [ ] :checkered_flag: WPF
- [ ] :earth_americas: UWP
- [ ] :apple: MacOS
- [ ] :tv: tvOS
- [ ] :monkey: Xamarin.Forms