Why does the custom ArrayAdapter constructor in this example not match the superclass constructor exactly?

Question

I was following a tutorial on creating a custom ArrayAdapter for a ListView in Android. Here is the custom adapter class from the tutorial:

public class NumbersViewAdapter extends ArrayAdapter<NumbersView> { 
  
    // invoke the suitable constructor of the ArrayAdapter class 
    public NumbersViewAdapter(@NonNull Context context, ArrayList<NumbersView> arrayList) { 
        
          // pass the context and arrayList for the super  
          // constructor of the ArrayAdapter class 
        super(context, 0, arrayList); 
    } 

How does the argument pass in doesn't have to match the constructor in the super class? To be more clear, I thought the argument pass in: NumbersViewAdapter(@NonNull Context context, ArrayList<NumbersView> arrayList) has to match with: super(context, 0, arrayList)

second of all, I saw no constructor has the argument pass in as such (@NonNull Context context, ArrayList<NumbersView> arrayList). The only thing I think is close with it is

public ContactListAdapter(@NonNull Context context, int resource, @NonNull ContactInfo[] objects) {
        super(context, resource, objects);
    }

I haven't try out anything yet

Answer 1

Basically, this is a constructor overloading. This concept is used to provide various version of your class initialised with different parameters. By doing so, you can accept optional parameter or sometimes not to pass at all with minimum invocations.

Check this reference to understand it in details.

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Back to your question:

The constructor that you have

NumbersViewAdapter(@NonNull Context context, ArrayList<NumbersView> arrayList)

does not exists on the ArrayAdapter.

Check the public constructors available on ArrayAdapter here:

Since, the closest contractors to your implementation is following:

public ArrayAdapter (Context context, int resource, List<T> objects)

You have to pass one more parameter for resource in the super call in the middle.

Hence, you have to call super(context, 0, arrayList); with resource as 0.

Although you can actuality provide any resource as layout file as well which can be used for this adapter item view later on.