Visibility of onSaveInstanceState and onRestoreInstanceState

Question

The methods onSaveInstanceState() and onRestoreInstanceState(Parcelable state) are declared protected in the View class, while in some of its subclasses, like TextView or ListView , they are declared public. To save and restore the state of a ListView after a configuration change, I can directly use those methods, while I can't for other View s like ScrollView . Why those methods are not declared public in the View class? Am I supposed to call those methods directly from my Activity / Fragment or in some other way? To restore the state of a ScrollView I can use a custom subclass that change the visibility of those methods to public: is this the way to go?

import android.content.Context;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.widget.ScrollView;

public class MyScrollView extends ScrollView {

    public MyScrollView(Context context) {
        super(context);
    }

    public MyScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MyScrollView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        super.onRestoreInstanceState(state);
    }

    @Override
    public Parcelable onSaveInstanceState() {
        return super.onSaveInstanceState();
    }

}

Answer 1

- Why those methods are not declared public in the View class?

That is because they are only used to contain View, remember that ScrollView is a subclass of ViewGroup which mainly used for storing other views.

From documentation :

A ViewGroup is a special view that can contain other views (called children.) 
The view group is the base class for layouts and views containers

- To restore the state of a ScrollView I can use a custom subclass that change the visibility of those methods to public

Yes you can but it is just a container there is nothing special to save and also you can post the position that it will just recompute it again

From documentation :

 For example, you will never store your current position on screen because that will be 
 computed again when a new instance of the view is placed in its view hierarchy.

Some examples of things you may store here: the current cursor position in a text view 
(but usually not the text itself since that is stored in a content provider or other 
persistent storage), the currently selected item in a list view.