#Error:

The named parameter ‘backwardsCompatibility‘ isn’t defined.
Try correcting the name to an existing named parameter’s name, or defining a named parameter with the name ‘backwardsCompatibility’.

or backwardsCompatibility is deprecated 

       appBar: AppBar(

              title: Text("Home",
                  style: TextStyle(color: Colors.white, fontSize: 2.5.h)),
              leadingWidth: 10.w,
              titleSpacing: 0,
              backgroundColor: Colors.blue,
              elevation: 0,
              actions: [
                Padding(
                    padding: EdgeInsets.only(right: 20.0),
                    child: GestureDetector(
                      onTap: () {
                        setState(() {
                          showSearchSheet();
                        });
                      },
                      child: Icon(
                        Icons.search,
                        size: 3.h,
                      ),
                    )),

                CommonNotification()
              ],

              backwardsCompatibility: false,

              systemOverlayStyle: SystemUiOverlayStyle(

                  statusBarColor: Colors.blue,

                  statusBarIconBrightness: Brightness.dark),

              toolbarHeight: 55,

            ),

#SystemOverlayStyle:

Creating user interfaces that seamlessly integrate with users’ system preferences is the SystemOverlayStyle feature. It gives programmers the power to change the way system overlays, such as navigation and status bars, look, promoting a unified aesthetic that appeals to users. Your software can now easily change regardless of whether users prefer light or dark themes, increasing user satisfaction.

#Brightness and #systemOverlayStyle’s

Two crucial properties ‘brightness’ and ‘systemOverlayStyle‘ come into play while examining the application of SystemOverlayStyle. These factors together determine how your app’s visuals work with the user’s selected system theme. The system will produce the necessary visual features if the brightness and systemOverlayStyle settings are set up properly.

we must make sure that backwardsCompatibility is set to false in order to use the systemOverlayStyle. This helps the system in selecting the brightness and systemOverlayStyle properties to use.

Change the value of backwardsCompatibility to false so that the system understands we want to employ systemOverlayStyle instead of brightness.

But now , The feature of backwardsCompatibility has been removed after v3.7

#How to resolve :

Code before:

AppBar(
  brightness: Brightness.light,
  textTheme: TextTheme(
    bodyMedium: toolbarTextStyle,
    titleLarge: titleTextStyle,
  )
  backwardsCompatibility: true,
);
AppBarTheme(color: Colors.blue);

Code after:

AppBar(
  systemOverlayStyle: SystemOverlayStyle(statusBarBrightness: Brightness.light),
  toolbarTextStyle: toolbarTextStyle,
  titleTextStyle: titleTextStyle,
);
AppBarTheme(backgroundColor: Colors.blue);

Want to more details …..https://docs.flutter.dev/release/breaking-changes/3-7-deprecations