GridView.builder in Flutter

Introduction

GridView.builder helps you show many items in a neat grid that scrolls smoothly. It builds only what you see on screen to save memory.

Showing a photo gallery with many pictures.

Displaying products in a shopping app in rows and columns.

Making a grid of buttons or icons that users can tap.

Showing a list of cards or tiles that fit nicely in a grid.

Syntax

Flutter

GridView.builder(
  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
    crossAxisCount: 2,
  ),
  itemCount: 10,
  itemBuilder: (context, index) {
    return WidgetHere();
  },
)

gridDelegate controls how many columns or rows the grid has and spacing.

itemBuilder creates each grid item when needed, using the index.

Examples

A grid with 3 columns showing 6 text items labeled by their index.

Flutter

GridView.builder(
  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
    crossAxisCount: 3,
  ),
  itemCount: 6,
  itemBuilder: (context, index) {
    return Text('Item $index');
  },
)

A grid where each item can be up to 150 pixels wide, showing 8 star icons.

Flutter

GridView.builder(
  gridDelegate: SliverGridDelegateWithMaxCrossAxisExtent(
    maxCrossAxisExtent: 150,
  ),
  itemCount: 8,
  itemBuilder: (context, index) {
    return Icon(Icons.star);
  },
)

Sample App

This app shows a grid with 2 columns and 4 colored boxes labeled from Box 0 to Box 3. The boxes have spacing between them and padding around the grid.

Flutter

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: const Text('GridView.builder Example')),
        body: GridView.builder(
          gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
            crossAxisCount: 2,
            mainAxisSpacing: 10,
            crossAxisSpacing: 10,
          ),
          itemCount: 4,
          itemBuilder: (context, index) {
            return Container(
              color: Colors.blue[100 * (index + 1)],
              child: Center(
                child: Text('Box $index', style: const TextStyle(fontSize: 20)),
              ),
            );
          },
          padding: const EdgeInsets.all(10),
        ),
      ),
    );
  }
}

Important Notes

Use itemCount to limit how many items show in the grid.

GridView.builder is efficient for large or infinite lists because it builds items only when needed.

Adjust crossAxisCount or maxCrossAxisExtent in gridDelegate to control grid layout.

Summary

GridView.builder creates scrollable grids efficiently by building items on demand.

Use gridDelegate to set grid columns and spacing.

itemBuilder builds each grid item using its index.

Practice

1. What is the main purpose of GridView.builder in Flutter?

easy

A. To create a grid with static images only

B. To create a fixed grid with all items built at once

C. To create a list view with fixed height items

D. To create a scrollable grid that builds items only when needed

Solution

1. Step 1: Understand GridView.builder behavior

   GridView.builder builds grid items lazily, meaning it creates items only when they scroll into view.

2. Step 2: Compare with other grid types

   Other grid types like GridView.count build all items at once, which is less efficient for large lists.

3. Final Answer:

   To create a scrollable grid that builds items only when needed -> Option D

4. Quick Check:

   GridView.builder = lazy building [OK]

Hint: Remember builder means items build on demand [OK]

Common Mistakes:

• Confusing GridView.builder with GridView.count
• Thinking it builds all items at once
• Assuming it only works with fixed item counts

2. Which of the following is the correct way to specify the number of columns in GridView.builder?

easy

A. gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3)

B. columns: 3

C. crossAxisCount: 3

D. gridColumns: 3

Solution

1. Step 1: Identify gridDelegate usage

   GridView.builder requires a gridDelegate to control layout, such as SliverGridDelegateWithFixedCrossAxisCount.

2. Step 2: Check correct property for columns

   The crossAxisCount property inside SliverGridDelegateWithFixedCrossAxisCount sets the number of columns.

3. Final Answer:

   gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3) -> Option A

4. Quick Check:

   Columns set via gridDelegate.crossAxisCount [OK]

Hint: Use gridDelegate with crossAxisCount for columns [OK]

Common Mistakes:

• Trying to set columns directly on GridView.builder
• Using invalid property names like columns or gridColumns
• Omitting gridDelegate entirely

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

GridView.builder(
  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
  itemCount: 4,
  itemBuilder: (context, index) {
    return Text('Item $index');
  },
)

medium

A. A grid with 2 columns and 4 items labeled Item 0 to Item 3

B. A list with 4 items labeled Item 0 to Item 3

C. A grid with 4 columns and 2 items labeled Item 0 to Item 1

D. An error because itemBuilder returns Text widgets

Solution

1. Step 1: Analyze gridDelegate and itemCount

   The gridDelegate sets 2 columns, and itemCount is 4, so 4 items will be arranged in 2 columns.

2. Step 2: Understand itemBuilder output

   Each itemBuilder call returns a Text widget labeled with the index, from 0 to 3.

3. Final Answer:

   A grid with 2 columns and 4 items labeled Item 0 to Item 3 -> Option A

4. Quick Check:

   2 columns, 4 items, Text widgets labeled [OK]

Hint: Check crossAxisCount and itemCount carefully [OK]

Common Mistakes:

• Confusing columns with itemCount
• Thinking itemBuilder cannot return Text widgets
• Assuming a list instead of a grid

4. Identify the error in this GridView.builder code:

GridView.builder(
  gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3),
  itemBuilder: (context, index) {
    return Container(color: Colors.blue);
  },
)

medium

A. itemBuilder returns Container instead of Text

B. Missing itemCount property causing infinite items

C. gridDelegate is incorrectly defined

D. crossAxisCount cannot be 3

Solution

1. Step 1: Check required properties of GridView.builder

   GridView.builder requires an itemCount to limit the number of items; without it, it builds infinite items.

2. Step 2: Verify other properties

   gridDelegate and itemBuilder are correctly defined; returning Container is valid.

3. Final Answer:

   Missing itemCount property causing infinite items -> Option B

4. Quick Check:

   itemCount missing = infinite build [OK]

Hint: Always include itemCount to avoid infinite items [OK]

Common Mistakes:

• Forgetting itemCount in GridView.builder
• Thinking itemBuilder must return Text only
• Misunderstanding crossAxisCount limits

5. You want to create a grid that shows only even numbers from 0 to 10 using GridView.builder. Which code snippet correctly implements this?

hard

A. GridView.builder(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
itemCount: 5,
itemBuilder: (context, index) {
return Text('Number $index');
},
)

B. GridView.builder(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
itemCount: 11,
itemBuilder: (context, index) {
if (index % 2 == 0) return Text('Number $index');
else return Container();
},
)

C. GridView.builder(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
itemCount: 6,
itemBuilder: (context, index) {
return Text('Number ${index * 2}');
},
)

D. GridView.builder(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
itemCount: 6,
itemBuilder: (context, index) {
return Text('Number $index');
},
)

Solution

1. Step 1: Determine how many even numbers from 0 to 10

   Even numbers are 0, 2, 4, 6, 8, 10 -- total 6 numbers.

2. Step 2: Check itemCount and itemBuilder logic

   GridView.builder( gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2), itemCount: 6, itemBuilder: (context, index) { return Text('Number ${index * 2}'); }, ) uses itemCount 6 and multiplies index by 2 to get even numbers correctly.

3. Step 3: Analyze other options

   GridView.builder( gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2), itemCount: 11, itemBuilder: (context, index) { if (index % 2 == 0) return Text('Number $index'); else return Container(); }, ) creates empty containers for odd indexes, wasting space. The other options do not correctly generate even numbers.

4. Final Answer:

   GridView.builder with itemCount: 6 and Text('Number ${index * 2}') -> Option C

5. Quick Check:

   Use index * 2 with correct itemCount [OK]

Hint: Multiply index by 2 to get even numbers [OK]

Common Mistakes:

• Using itemCount 11 and skipping odd items wastes space
• Not adjusting index to generate even numbers
• Returning empty containers for unwanted items