Why is onResume method of a Fragment never fired after dismissing a DialogFragment which was launched from the Fragment?

If you just want to call onResume of FragmentA, make a call to startActivityForResult inside your DialogFragment, and start your FragmentActivity. This will call onResume.

public void dismissDialog() {   getActivity().startActivityForResult(getActivity().getIntent(), 10);   dismiss()}

Now Google has released Android Architecture Components library, the best solution is to use a shared ViewModel between both Fragments with your Activity as the one that implements LifecycleRegistryOwner.

Doing this, we will avoid refreshing UI calling onResume and we don't need to code any tricky solution.

A solution could be the following one:

public MyActivity extends AppCompatActivity {    ...}public class FragmentA extends Fragment implements OnClickListener {    ...    private SharedViewModel mSharedViewModel;    @Override    public void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        mSharedViewModel = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);        mSharedViewModel.getData().observe(this, value -> {            updateUIValue(value);        });    }    @Override    public void OnClick(View v) {        if (v == dialogButton) {            showDialog();        }    }    @Override    public void OnClick(View v) {        if (v == dialogButton) {            showDialog();        }    }    public void showDialog() {        String diagName = getResources().getString(R.string.dialog_title);        MyDialog myDialog = MyDialog.newInstance(getFragmentAValue());        myDialog.show(getFragmentManager(), diagName);    }}public class MyDialog extends DialogFragment implements OnClickListener {    ...    private SharedViewModel mSharedViewModel;    @Override    public void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        mSharedViewModel = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);        mSharedViewModel.getData().observe(this, value -> {            updateUIValue(value);        });    }    @Override    public void onClick(View view) {        if (view == acceptButton) {            ...            mSharedViewModel.setValue(newValue);        }        else if (view == cancelButton) {            dismiss();        }    }}public class SharedViewModel extends ViewModel {    final MutableLiveData<Resource<Value>> data = new MutableLiveData<>();    public MutableLiveData<Value> getData() {        return data;    }    public void setValue(Value newValue) {        this.data.setValue(newValue)    }}

Another way is by implementing an interface. Create an interface and let the activity/fragment (which one you need) implements it, then pass itself as an interface object to your DialogFragment.

CustomDialogFragment df = new CustomDialogFragment();Bundle b = new Bundle();b.putSerializable(KEY, this); // current activity/fragment that implements the interfacedf.setArguments(b);df.show(getFragmentManager(), TAG);

Then in your DialogFragment get the listener, and call the listener's method when you need to (in this case after/before you called dismiss()).