Passing objects in to Fragments

问题:

I've been working with lots of Fragments recently and have been using two distinct methods of passing in objects to the Fragments, but the only difference that I can see is that in the approach taken by FragmentOne below, the object you pass in must implement the Serializable interface (and everything associated with that).

Are there any benefits to using one over the other?

public class FragmentOne extends Fragment {
    public static final String FRAGMENT_BUNDLE_KEY = 
        "com.example.FragmentOne.FRAGMENT_BUNDLE_KEY";

    public static FragmentOne newInstance(SomeObject someObject) {
        FragmentOne f = new FragmentOne();
        Bundle args = new Bundle();
        args.putSerializable(FRAGMENT_BUNDLE_KEY, someObject);
        f.setArguments(args);
        return f;
    }

    public SomeObject getSomeObject() {
        return (SomeObject) getArguments().getSerializable(FRAGMENT_BUNDLE_KEY);
    }
}

and

public class FragmentTwo extends Fragment {
    SomeObject mSomeObject;  

    public static FragmentTwo newInstance(SomeObject someObject) {
        FragmentTwo fragment = new FragmentTwo();
        fragment.setSomeObject(someObject);
        return fragment;
    }

    public void setSomeObject(SomeObject someObject) {
        mSomeObject = someObject;
    }
}

回答1:

There are 3 ways to pass objects to a fragment

They are:

1. Passing the object through a setter is the fastest way, but state will not be restored automatically.
2. setArguments with Serializable objects is the slowest way (but okay for small objects, I think) and you have automatic state restoration.
3. Passing as Parcelable is a fast way (prefer it over 2nd one if you have collection of elements to pass), and you have automatic state restoration.

http://developer.android.com/reference/android/os/Parcelable.html

回答2:

for Collection such as List :

I wanted to share my experience.

you need to implement Parcelable

Just use the putParcelableArrayList method.

ArrayList<LClass> localities = new ArrayList<LClass>;
...
Bundle bundle = new Bundle();
bundle.putParcelableArrayList(KEY_LClass_LIST, localities);
fragmentInstance.setArguments(bundle);

return fragmentInstance;

And retrieve it using...

localities = savedInstanceState.getParcelableArrayList(KEY_LCLass_LIST);

So, unless you need the custom ArrayList for some other reason, you can avoid doing any of that extra work and only implement Parcelable for your Locality class.