Select unique random indexes from a list in Dart

The goal here is to select 4 unique index id's from a given list in Dart. 

Hardcoded: source list, how many numbers to pick, zero excluded, printing the selected items list as having 4 elements.

import 'dart:math';
void main() {
    List<int> numbers = [1, 2, 3, 4, 5,6,7,8,9];
  
 
  List<int> pickedList =[];
  
  /// pick 4 random numbers
  
  for(var i=0; pickedList.length <4 ;i++) {
        var picked = new Random().nextInt(numbers.length);
        // skip the generated 0
        if(picked >0 && !pickedList.asMap().containsValue(picked)) 
        {
            pickedList.add(picked);
        } //for i to 4
   } ///picked > 0 && not yet picked
  print('Here are you selected numbers. No repeats');
  
  print('=======');
  for (var i =0; i<4; i++) {
    print(pickedList[i]);
  }
//   print(pickedList.asMap());
} /// /main