IndexOutOfBoundsException 索引 0 大小 0 试图编辑填充 arraylist 中的元素

Question

I am trying to edit an element in an already populated arraylist but keep getting that error. The method is called from a fragment but I can't seem to access the arraylist from the fragment or Anything the fragment is associated with. I can change the value I want anywhere else in the same class expect in that method which is called from the fragment. I will really appreciate the help thanks in advance.

Fragment Code

 MainActivity method = new MainActivity();

@Override
public void onDetach() {
    method.updateQuantity(Quantity);
    super.onDetach();
}

MainActivity code

public void updateQuantity(int Quantity){
    items.get(currentitem).setQuantity(Quantity);
}

Answer 1

If items is your ArrayList, then for ArrayList.get , it takes integer(index) as an argument and then returns the element of that index.

So, this items.get(currentitem).setQuantity(Quantity) ) call is very unsafe. Need to check the max index length first then try to access it.

public void updateQuantity(int Quantity){
    if(items != null and currentitem < items.size(){
       items.get(currentitem).setQuantity(Quantity);
    }
}