NiceAppBar

class CustomAppBarr extends StatelessWidget implements PreferredSizeWidget {
  @override
  Size get preferredSize => Size.fromHeight(160.0);

  @override
  Widget build(BuildContext context) {
    return AppBar(
      flexibleSpace: Container(
        decoration: BoxDecoration(
          gradient: LinearGradient(
            colors: [Color(0xFFEC407A), Color(0xFF8E24AA)],
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
          ),
        ),
      ),
      title: Padding(
        padding: const EdgeInsets.only(top: 18.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              'Events near me',
              style: TextStyle(
                fontSize: 16,
                color: Colors.white70,
              ),
            ),
            Text(
              'California, USA',
              style: TextStyle(
                fontSize: 24,
                fontWeight: FontWeight.bold,
              ),
            ),
          ],
        ),
      ),
      actions: [
        IconButton(
          icon: Icon(Icons.notifications, size: 30),
          onPressed: () {
            // Add notification functionality here
          },
        ),
      ],
      bottom: PreferredSize(
        preferredSize: Size.fromHeight(76.0),  // Adjust this height if needed
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
          child: Column(
            children: [
              TextField(
                decoration: InputDecoration(
                  hintText: 'Search events',
                  prefixIcon: Icon(Icons.search, color: Colors.grey),
                  suffixIcon: Icon(Icons.filter_alt, color: Colors.grey),
                  filled: true,
                  fillColor: Colors.white,
                  border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(30.0),
                    borderSide: BorderSide.none,
                  ),
                ),
              ),
              SizedBox(height: 20,)
            ],
          ),
        ),
      ),
    );
  }
}



Second code:
class CustomAppBar extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      decoration: BoxDecoration(
        color: Colors.blue,
        borderRadius: BorderRadius.only(
          bottomLeft: Radius.circular(35.0),
          bottomRight: Radius.circular(35.0),
        ),
      ),
      padding: EdgeInsets.only(top: MediaQuery.of(context).padding.top),
      child: AppBar(
        backgroundColor: Colors.transparent,
        elevation: 0,
        title: Center(
          child: Text(
            'Custom App Bar',
            style: TextStyle(
              fontSize: 20.0,
              fontWeight: FontWeight.bold,
            ),
          ),
        ),
        automaticallyImplyLeading: false,
      ),
    );
  }
}