MaterialTextField is not disabled when using tab key navigation

[assemhakmeh]

🐛 Bug Report

After setting a MetialTextField.IsEnabled = false. The control becomes disabled to touch events. However, if the Tab key is used to shift focus between controls, the field can get focused and is writable but with a disabled look.

Expected behavior

The field should be disabled and not allow user input.

Reproduction steps

• Create a simple ContentPage
• Add one of more MaterialTextField controls with IsEnabled = false
• Run the app
• Use the keyboard Tab key to cycle through the controls.

Configuration

Version: 1.5.8

Platform:

• [ ] :iphone: iOS
• [x] :robot: Android
• [ ] :checkered_flag: WPF
• [ ] :earth_americas: UWP
• [ ] :apple: MacOS
• [ ] :tv: tvOS
• [x] :monkey: Xamarin.Forms