Text color in fullscreen mode and input decoration filled color

When using a light theme and using mode fullscreen the textfield is placed in the appbar.
The appbar can be dark event though the brightness is light. This results with the unreadable text.
In your code if the brightness is light you set the text and hint color to black87.
In addition sometimes we use a default color fill for the text fields in our app which is not applicable to when a text field is placed in the appbar.
Please add 'filled: false' or at least let us control these two options.
Text field filled
Text color
Hint color

Thanks