ListView.separated in Flutter - Mini App: Build & Ship

Build: Separated List Screen

This screen shows a scrollable list of items with a separator line between each item.

Target UI

-------------------------
| Item 1               |
-------------------------
| Item 2               |
-------------------------
| Item 3               |
-------------------------
| Item 4               |
-------------------------
| Item 5               |
-------------------------

Use ListView.separated to display a list of 5 items labeled 'Item 1' to 'Item 5'.

Add a thin grey divider line between each item.

Each item should be a ListTile with the item text as the title.

The list should be scrollable if the screen is small.

Starter Code

Flutter

import 'package:flutter/material.dart';

class SeparatedListScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Separated List'),
      ),
      body: // TODO: Add ListView.separated here
    );
  }
}

Task 1

Task 2

Task 3

Task 4

Solution

Flutter

import 'package:flutter/material.dart';

class SeparatedListScreen extends StatelessWidget {
  final List<String> items = ['Item 1', 'Item 2', 'Item 3', 'Item 4', 'Item 5'];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Separated List'),
      ),
      body: ListView.separated(
        itemCount: items.length,
        itemBuilder: (context, index) {
          return ListTile(
            title: Text(items[index]),
          );
        },
        separatorBuilder: (context, index) {
          return Divider(color: Colors.grey, thickness: 1);
        },
      ),
    );
  }
}

We created a list of 5 strings named items. The ListView.separated widget builds each list item using itemBuilder, which returns a ListTile with the item text. The separatorBuilder returns a Divider widget that draws a thin grey line between items. This makes the list easy to read and visually separated. The list scrolls if the screen is small.

Final Result

Completed Screen

-------------------------
| Item 1               |
-------------------------
| Item 2               |
-------------------------
| Item 3               |
-------------------------
| Item 4               |
-------------------------
| Item 5               |
-------------------------

User can scroll up and down to see all items if screen height is small.

Each item is tappable (default ListTile behavior, but no action assigned).

Stretch Goal

Add a tap action that shows a SnackBar with the tapped item's name.

💡 Hint

Wrap ListTile with InkWell or use ListTile's onTap property to show SnackBar using ScaffoldMessenger.

Practice

1. What is the main purpose of using ListView.separated in Flutter?

easy

A. To display a single static widget

B. To create a grid layout with fixed columns

C. To create a scrollable list with separators between items

D. To handle user input forms

Solution

1. Step 1: Understand ListView.separated usage

   ListView.separated is designed to build lists with separators between each item.

2. Step 2: Compare with other options

   Options B, C, and D describe other Flutter widgets or uses unrelated to ListView.separated.

3. Final Answer:

   To create a scrollable list with separators between items -> Option C

4. Quick Check:

   ListView.separated = scrollable list with separators [OK]

Hint: Remember: separated means items with dividers [OK]

Common Mistakes:

• Confusing ListView.separated with GridView
• Thinking it creates static widgets
• Assuming it handles user input

2. Which of the following is the correct syntax to create a ListView.separated with 5 items?

easy

A. ListView.separated(itemCount: 5, itemBuilder: (context, index) => Text('Item $index'), separatorBuilder: (context, index) => Divider())

B. ListView.separated(items: 5, buildItem: (i) => Text('Item $i'), buildSeparator: () => Divider())

C. ListView.separated(count: 5, builder: (context, i) => Text('Item $i'), separator: Divider())

D. ListView.separated(length: 5, item: (context, i) => Text('Item $i'), separatorBuilder: () => Divider())

Solution

1. Step 1: Identify correct parameter names

   The correct parameters are itemCount, itemBuilder, and separatorBuilder.

2. Step 2: Check function signatures

   itemBuilder and separatorBuilder take (context, index) and return widgets.

3. Final Answer:

   ListView.separated(itemCount: 5, itemBuilder: (context, index) => Text('Item $index'), separatorBuilder: (context, index) => Divider()) -> Option A

4. Quick Check:

   Correct parameter names and builder signatures = ListView.separated(itemCount: 5, itemBuilder: (context, index) => Text('Item $index'), separatorBuilder: (context, index) => Divider()) [OK]

Hint: Use itemCount, itemBuilder, separatorBuilder exactly [OK]

Common Mistakes:

• Using wrong parameter names like items or count
• Omitting context or index in builder functions
• Passing widgets directly instead of builder functions

3. What will be the output of this Flutter code snippet?

ListView.separated(
  itemCount: 3,
  itemBuilder: (context, index) => Text('Item $index'),
  separatorBuilder: (context, index) => Divider(color: Colors.red),
)

medium

A. A list with 4 items including dividers as text

B. A scrollable list with 3 items and red dividers between them

C. A scrollable list with 3 items but no dividers

D. Compilation error due to missing separator widget

Solution

1. Step 1: Analyze itemCount and itemBuilder

   There are 3 items labeled 'Item 0', 'Item 1', and 'Item 2'.

2. Step 2: Analyze separatorBuilder

   Between each item, a red colored Divider widget is inserted.

3. Final Answer:

   A scrollable list with 3 items and red dividers between them -> Option B

4. Quick Check:

   itemCount=3 with red Dividers = A scrollable list with 3 items and red dividers between them [OK]

Hint: Separators appear between items, not as extra items [OK]

Common Mistakes:

• Thinking separators add extra list items
• Ignoring the color property of Divider
• Assuming no separators appear without extra code

4. Identify the error in this ListView.separated code:

ListView.separated(
  itemCount: 3,
  itemBuilder: (context) => Text('Item'),
  separatorBuilder: (context, index) => Divider(),
)

medium

A. itemBuilder missing index parameter

B. separatorBuilder missing context parameter

C. itemCount should be inside itemBuilder

D. Divider widget cannot be used as separator

Solution

1. Step 1: Check itemBuilder function signature

   itemBuilder must have two parameters: (context, index). Here it only has (context).

2. Step 2: Verify separatorBuilder signature

   separatorBuilder correctly has (context, index).

3. Final Answer:

   itemBuilder missing index parameter -> Option A

4. Quick Check:

   itemBuilder requires (context, index) parameters [OK]

Hint: itemBuilder always needs context and index [OK]

Common Mistakes:

• Omitting index in itemBuilder
• Confusing separatorBuilder parameters
• Thinking Divider can't be separator

5. You want to create a ListView.separated that shows a list of names but only adds a separator if the next name starts with a different first letter. Which approach is correct?

hard

A. Add all separators unconditionally between items

B. Use a GridView instead of ListView.separated

C. Use itemBuilder to insert Divider widgets manually between items

D. Use separatorBuilder to compare current and next item first letters and return Divider or SizedBox.shrink() accordingly

Solution

1. Step 1: Understand conditional separators

   To add separators only when the next item's first letter differs, separatorBuilder must check adjacent items.

2. Step 2: Implement conditional logic in separatorBuilder

   Return a Divider if letters differ; otherwise, return SizedBox.shrink() to show no separator.

3. Final Answer:

   Use separatorBuilder to compare current and next item first letters and return Divider or SizedBox.shrink() accordingly -> Option D

4. Quick Check:

   Conditional separator logic belongs in separatorBuilder [OK]

Hint: Use separatorBuilder to conditionally show dividers [OK]

Common Mistakes:

• Adding separators unconditionally
• Inserting Dividers inside itemBuilder
• Using GridView which lacks separators