, Since the corresponding class has been abolished in Flutter1.20 and above, DatePicker cannot be packaged and compiled with this dependency package. You need to download the source code yourself and package it locally. Change the implementation class DiagnosticableMixin in the theme file inside to Diagnosticable
Some third-party dependent plug-ins have inherited the DiagnosticableMixin class, and the developer has not updated it. Other plug-ins that inherit the DiagnosticableMixin class, such as: flutter_cupertino_date_picker This also needs to be changed to Diagnosticable
