thumbColor property Null safety

MaterialStateProperty<Color?>? thumbColor
final

The color of this Switch's thumb.

Resolved in the following states:

link
This example resolves the thumbColor based on the current MaterialState of the Switch, providing a different Color when it is MaterialState.disabled. 
Switch(
  value: true,
  onChanged: (_) => true,
  thumbColor: MaterialStateProperty.resolveWith<Color>((Set<MaterialState> states) {
    if (states.contains(MaterialState.disabled)) {
      return Colors.orange.withOpacity(.48);
    }
    return Colors.orange;
  }),
)

If null, then the value of activeColor is used in the selected state and inactiveThumbColor in the default state. If that is also null, then the value of SwitchThemeData.thumbColor is used. If that is also null, then the following colors are used:

StateLight themeDark theme
DefaultColors.grey.shade50Colors.grey.shade400
SelectedThemeData.toggleableActiveColorThemeData.toggleableActiveColor
DisabledColors.grey.shade400Colors.grey.shade800

Implementation

final MaterialStateProperty<Color?>? thumbColor;