CODEWITHSUNDEEP
javaandroidandroid-fragments
Piotr Aleksander Chmielowski
Piotr Aleksander Chmielowski

Reputation: 6451

Can I prevent calling Fragment's constructor from the code?

In my Fragment I have a static newInstance method which takes some arguments, puts them in the Bundle, creates new Fragment with this Bundle:

public static Fragment newInstance(final CommandWithNumber command) {
    final CallsFragment fragment = new CallsFragment();
    final Bundle args = new Bundle();
    args.putSerializable(SHOW_DETAILS_COMMAND, command);
    fragment.setArguments(args);
    return fragment;
}

Is there a way to prevent calling new CallsFragment() in other places in the code and force developers to use newInstance method?

Of course, I can't make CallsFragment private because OS needs public one. Maybe there is a way to show warning or so, if someone tries to create an instance with the constructor?

Upvotes: 2

Views: 185

Answers (1)

thepoosh
thepoosh

Reputation: 12587

you should NOT be using a Fragment's constructor for anything, the system uses it for restoring configuration changes. there must be a public constructor that takes no arguments in a Fragment class

All subclasses of Fragment must include a public no-argument constructor. The framework will often re-instantiate a fragment class when needed, in particular during state restore, and needs to be able to find this constructor to instantiate it. If the no-argument constructor is not available, a runtime exception will occur in some cases during state restore.

from the Documentation

EDIT: after discussing this further in the comment section and understanding what you want to do, you should add a @Deprecated annotation with javadocs saying why you shouldn't use this constructor internally, something like this:

/**
* this should <b>NEVER</b> be used, always use the newInstance method instead
**/
@Deprecated
public CallsFragment() {
  // EMPTY METHOD
}

Upvotes: 5

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