RangeError (index): Invalid value: Not in inclusive range 0..2: 3 i cant fix

Question

i have a problem this my list

             class _FitnessAppState extends State<FitnessApp> {

String img_Header = "https://images.unsplash.com/photo-1517836357463-d25dfeac3438?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=870&q=80"; List trainingImage = [ "https://images.unsplash.com/photo-1534258936925-c58bed479fcb?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1631&q=80", "https://images.unsplash.com/photo-1575052814086-f385e2e2ad1b?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1170&q=80", "https://media.istockphoto.com/photos/picture-of-people-running-on-treadmill-in-gym-picture-id879180126?k=20&m=879180126&s=612x612&w=0&h=WZ1Iqcqv5_rNTNslUscoMg9qAUoNiDG8kWBfVnpPapQ=", ];

Answer 1

your variables are:

String img_Header = "https://images.unsplash.com/photo-1517836357463-d25dfeac3438?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=870&q=80";

List trainingImage = [
"https://images.unsplash.com/photo-1534258936925-c58bed479fcb?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1631&q=80",
"https://images.unsplash.com/photo-1575052814086-f385e2e2ad1b?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1170&q=80",
"https://media.istockphoto.com/photos/picture-of-people-running-on-treadmill-in-gym-picture-id879180126?k=20&m=879180126&s=612x612&w=0&h=WZ1Iqcqv5_rNTNslUscoMg9qAUoNiDG8kWBfVnpPapQ=",
];

the error of RangeError is happened in trainingImage variable as it is a List datatype, that's because you are trying to access an unavailable index inside a List, as example, your list trainingImage has only 3 elements which start by index 0 and ends by index 2:

print(trainingImage[0]);
// output: "https://images.unsplash.com/photo-1534258936925-c58bed479fcb?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1631&q=80"

print(trainingImage[1]);
// output: "https://images.unsplash.com/photo-1575052814086-f385e2e2ad1b?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1170&q=80"

print(trainingImage[2]);
// output: "https://media.istockphoto.com/photos/picture-of-people-running-on-treadmill-in-gym-picture-id879180126?k=20&m=879180126&s=612x612&w=0&h=WZ1Iqcqv5_rNTNslUscoMg9qAUoNiDG8kWBfVnpPapQ="

if you are trying to access the index 3 you will get the error of RangeError:

print(trainingImage[3]);
// output: RangeError (index): Invalid value: Not in inclusive range 0..2: 3

the solution is to always check if an index is available before accessing it:

// as example you want to access the index 3
int index = 3;

// 1st way
if(trainingImage.asMap().containsKey(index))
{
// run this if index 3 is available
}

// 2nd way
if(index < trainingImage.length && index >= 0)
{
// run this if index 3 is available
}

Answer 2

The code snippet that you have provided is fine. Maybe you are accessing wrong index of the list. Can you provide more information please?

However, I'll suggest you to rename the img_Header variable to imgHeader otherwise it will show lowerCamelCase warning.