Communicating Between A Fragment And An Activity - Best Practices

This question is mostly to solicit opinions on the best way to handle my app. I have three fragments being handled by one activity. Fragment A has one clickable element the photo

Solution 1:

The easiest way to communicate between your activity and fragments is using interfaces. The idea is basically to define an interface inside a given fragment A and let the activity implement that interface.

Once it has implemented that interface, you could do anything you want in the method it overrides.

The other important part of the interface is that you have to call the abstract method from your fragment and remember to cast it to your activity. It should catch a ClassCastException if not done correctly.

There is a good tutorial on Simple Developer Blog on how to do exactly this kind of thing.

I hope this was helpful to you!

Solution 2:

The suggested method for communicating between fragments is to use callbacks\listeners that are managed by your main Activity.

I think the code on this page is pretty clear: http://developer.android.com/training/basics/fragments/communicating.html

You can also reference the IO 2012 Schedule app, which is designed to be a de-facto reference app. It can be found here: http://code.google.com/p/iosched/

Also, here is a SO question with good info: How to pass data between fragments

Solution 3:

It is implemented by a Callback interface:

First of all, we have to make an interface:

publicinterfaceUpdateFrag {
     voidupdatefrag();
}

In the Activity do the following code:

UpdateFrag updatfrag ;

publicvoidupdateApi(UpdateFrag listener) {
        updatfrag = listener;
}

from the event from where the callback has to fire in the Activity:

updatfrag.updatefrag();

In the Fragment implement the interface in CreateView do the following code:

 ((Home)getActivity()).updateApi(new UpdateFrag() {
        @Override
        public void updatefrag() {
              .....your stuff......
        }
 });

Solution 4:

I made a annotation library that can do the cast for you. check this out. https://github.com/zeroarst/callbackfragment/

@CallbackFragmentpublicclassMyFragmentextendsFragment {

    @CallbackinterfaceFragmentCallback {
       voidonClickButton(MyFragment fragment);
    }    
    private FragmentCallback mCallback;

    @OverridepublicvoidonClick(View v) {
        switch (v.getId()) {
            case R.id.bt1
                mCallback.onClickButton(this);
                break;
            case R.id.bt2
                // Because we give mandatory = false so this might be null if not implemented by the host.if (mCallbackNotForce != null)
                mCallbackNotForce.onClickButton(this);
                break;
        }
    }
}

It then generates a subclass of your fragment. And just add it to FragmentManager.

publicclassMainActivityextendsAppCompatActivityimplementsMyFragment.FragmentCallback {

    @OverrideprotectedvoidonCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        getSupportFragmentManager().beginTransaction()
            .add(R.id.lo_fragm_container, MyFragmentCallbackable.create(), "MY_FRAGM")
            .commit();
    }

    Toast mToast;

    @OverridepublicvoidonClickButton(MyFragment fragment) {
        if (mToast != null)
            mToast.cancel();
        mToast = Toast.makeText(this, "Callback from " + fragment.getTag(), Toast.LENGTH_SHORT);
        mToast.show();
    }
}

Solution 5:

There are severals ways to communicate between activities, fragments, services etc. The obvious one is to communicate using interfaces. However, it is not a productive way to communicate. You have to implement the listeners etc.

My suggestion is to use an event bus. Event bus is a publish/subscribe pattern implementation.

You can subscribe to events in your activity and then you can post that events in your fragments etc.

Here on my blog post you can find more detail about this pattern and also an example project to show the usage.