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Observer Pattern: The Hidden Magic Behind Flutter State Management

When I first started learning state management in Flutter, it honestly felt like magic. I'd change one variable, call setState , and the screen would just… update. Later I met ValueNotifier and ValueListenableBuilder , and it got even stranger — now only one widget would rebuild while everything around it stayed perfectly still. I hadn't written any code to watch for changes. I hadn't wired anything up. It just worked. And anything that "just works" without me understanding why makes me a little uncomfortable. So I did what any curious developer does: I went down the rabbit hole. I wanted to know how a value "knows" when to tell the UI to rebuild. Who is listening? How does the change travel from my variable to the pixels on screen? That question led me to something much bigger than Flutter — a classic software design pattern called the Observer pattern . Once I understood it, the magic didn't disappear. It just turned into some...
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ListView and ListTile!

Listview and Listtile are basic widgets, which are used to make a scrollable lists of item in a mobile app. They are essential component for building app where we need various type of lists, such as menus, chat message lists and etc.



ListView: Listview is a widget used to create a scrollable list of children. It can hold a list of widgets and automatically handles scrolling when the content exceeds the available space.

ListTile: Listtile widget is designed to represent a single item within a list. It typically contains title, subtitle, leading or trailing icon and can be made tappable.

Key Properties of listTile:

  • Title: The primary content of the list item.
  • Subtitle: Optional secondary content.
  • leading: A widget display before the title.
  • trailing: A widget display after the title.
  • Ontap: A callback function that is triggered when the listtile tapped.

Both Listview and Listtile are highly customizable, and you can style them according to the app design requirements. They are versatile and widely used in Flutter app development for presenting list of data or options to users in an organized and user-friendly manner.

body: Container(
  margin: const EdgeInsets.fromLTRB(0, 10, 8, 0),
  child: ListView(
    itemExtent: 70.0,
    children:  [
      ListTile(
        title: Text(
          "Top Faculties(UITS)",
          style: TextStyle(fontSize: 25, fontWeight: FontWeight.bold, color: Colors.red),
          textAlign: TextAlign.center,
        ),
      ),
      ListTile(
        leading: Container(
           height: double.infinity,
            child: Icon(Icons.computer)
        ),
        title: Text(
          "Computer Science",
          style: TextStyle(fontWeight: FontWeight.bold),
        ),
        subtitle: Text("We are the first it university......"),
        trailing: Text("300000"),
        onTap: () {},
      ),
      ListTile(
        leading: Container(
            height: double.infinity,
            child: Icon(Icons.medical_information)
        ),
        title: Text(
          "Pharmacy",
          style: TextStyle(fontWeight: FontWeight.bold),
        ),
        subtitle: Text("We have best medicine......"),
        trailing: Text("450000"),
        onTap: (){},
      ),
      ListTile(
        leading: Container(
          height: double.infinity,
          child: Icon(Icons.electric_bolt)
        ),
        title: Text(
          "Electrical Engineering",
          style: TextStyle(fontWeight: FontWeight.bold),
        ),
        subtitle: Text("Our students works at best....."),
        trailing: Text("500400"),
        onTap: (){},
      )
    ],
  ),
),

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Observer Pattern: The Hidden Magic Behind Flutter State Management

When I first started learning state management in Flutter, it honestly felt like magic. I'd change one variable, call setState , and the screen would just… update. Later I met ValueNotifier and ValueListenableBuilder , and it got even stranger — now only one widget would rebuild while everything around it stayed perfectly still. I hadn't written any code to watch for changes. I hadn't wired anything up. It just worked. And anything that "just works" without me understanding why makes me a little uncomfortable. So I did what any curious developer does: I went down the rabbit hole. I wanted to know how a value "knows" when to tell the UI to rebuild. Who is listening? How does the change travel from my variable to the pixels on screen? That question led me to something much bigger than Flutter — a classic software design pattern called the Observer pattern . Once I understood it, the magic didn't disappear. It just turned into some...
Post a Comment
Read more