Flutter/Dart: Generate Random Numbers between Min and Max

A couple of examples of generating a random integer within a given range in Dart (and Flutter as well).

Example 1: Using Random().nextInt() method

The code:

// KindaCode.com
import 'dart:math';
import 'package:flutter/foundation.dart';

// define a reusable function
randomGen(min, max) {
  // the nextInt method generate a non-ngegative random integer from 0 (inclusive) to max (exclusive)
  var x = Random().nextInt(max) + min;

  // If you don't want to return an integer, just remove the floor() method
  return x.floor();
}

void main() {
  int a = randomGen(-99, 99);
  debugPrint(a.toString());
}

Output:

-94

Due to the randomness, it’s very likely that you’ll get a different result each time you execute the code.

Example 2: Using Random.nextDouble() and floor() methods

The code:

// KindaCode.com
import 'dart:math';
import 'package:flutter/foundation.dart';

randomGen(min, max) {
  // the nextDouble() method returns a random number between 0 (inclusive) and 1 (exclusive)
  var x = Random().nextDouble() * (max - min) + min;

  // If you don't want to return an integer, just remove the floor() method
  return x.floor();
}

// Testing
void main() {
  if (kDebugMode) {
    // with posstive min and max
    print(randomGen(10, 100));

    // with negative min
    print(randomGen(-100, 0));
  }
}

Output (the output, of course, is random and will change each time you re-execute your code).

47
-69

The result you get will probably contain min but never contain max.

What’s Next?

Continue learning more about Flutter and Dart by taking a look at the following articles:

• Dart: Convert Map to Query String and vice versa
• Dart: Sorting Entries of a Map by Its Values
• Sorting Lists in Dart and Flutter
• 2 Ways to Create Multi-Line Strings in Dart
• How to remove items from a list in Dart
• Dart regex to validate US/CA phone numbers

You can also check out our Flutter category page or Dart category page for the latest tutorials and examples.