This is my first time using MVVM architecture.I am also using LiveData. I simply retrieve data from server using Retrofit.So upon clicking a button in the View(MainActivity.class) I invoke the ViewModel class's method(handleRetrofitcall()) to take up the duty of Api calling from the Model class(Retrofit Handler.class).The Model class upon retrieving the data informs the ViewModel of the data(which is actually the size of items).I set the size to LiveData and try to listen for it.Unfortunately I couldn't.For detailed analysis please go through the code.
Model...
RetrofitHandler.class:
public class RetrofitHandler {
private ApiInterface apiInterface;
private SimpleViewModel viewModel;
public void getData(){
apiInterface= ApiClient.getClient().create(ApiInterface.class);
Call<Unknownapi> call=apiInterface.doGetListResources();
call.enqueue(new Callback<Unknownapi>() {
#Override
public void onResponse(Call<Unknownapi> call, Response<Unknownapi> response) {
List<Unknownapi.Data> list;
Unknownapi unknownapi=response.body();
list=unknownapi.getData();
viewModel=new SimpleViewModel();
viewModel.postValue(list.size());
Log.e("Size",Integer.toString(list.size()));
}
#Override
public void onFailure(Call<Unknownapi> call, Throwable t) {
}
});
}
}
ViewModel....
SimpleViewModel.class:
public class SimpleViewModel extends ViewModel {
private RetrofitHandler retrofitHandler;
private int size;
private MutableLiveData<Integer> mutablesize=new MutableLiveData<>();
public SimpleViewModel() {
super();
}
#Override
protected void onCleared() {
super.onCleared();
}
public void handleRetrofitcall(){
retrofitHandler=new RetrofitHandler();
retrofitHandler.getData();
}
public void postValue(int size){
this.size=size;
mutablesize.postValue(this.size);
Log.e("lk","f");
}
public MutableLiveData<Integer> getObject() {
return mutablesize;
}
}
View.....
MainActivity.class:
public class MainActivity extends AppCompatActivity {
private TextView status;
private SimpleViewModel viewModel;
private Observer<Integer> observer;
private MutableLiveData<Integer> mutableLiveData;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
status=findViewById(R.id.status);
viewModel=ViewModelProviders.of(MainActivity.this).get(SimpleViewModel.class);
observer=new Observer<Integer>() {
#Override
public void onChanged(#Nullable Integer integer) {
Log.e("lk","f");
status.setText(Integer.toString(integer));
}
};
viewModel.getObject().observe(MainActivity.this,observer);
findViewById(R.id.retrofit).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
viewModel.handleRetrofitcall();
}
});
}
#Override
protected void onDestroy() {
if (observer!=null){
viewModel.getObject().removeObserver(observer);
}
super.onDestroy();
}
}
You're creating a new ViewModel in the RetrofitHandler, so nothing is observing that viewmodel. Instead of having the RetrofitHandler rely on a ViewModel internally, it's probably safer to handle the Retrofit callback inself, and post data there.
public void handleRetrofitcall(){
retrofitHandler=new RetrofitHandler();
retrofitHandler.getData(new Callback<List<Unknownapi.Data>> {
// add actual callback implementation here
); // add a callback here, so that the data is available in the view model. Then post the results from here.
}
Edit: More clarification.
In the Activity, you're correctly creating a ViewModel and observing it (we'll call that ViewModel A). ViewModel A is then creating a RetrofitHandler and calling getData on that Retrofithandler. The issue is that RetrofitHandler is creating a new ViewModel in getData (which I'm going to call ViewModel B).
The issue is that the results are being posted to ViewModel B, which nothing is observing, so it seems like nothing is working.
Easy way to avoid this issue is to make sure that only an Activity/Fragment is relying on (and creating) ViewModels. Nothing else should know about the ViewModel.
Edit 2: Here's a simple implementation. I haven't tested it, but it should be more or less correct.
// shouldn't know anything about the view model or the view
public class RetrofitHandler {
private ApiInterface apiInterface;
// this should probably pass in a different type of callback that doesn't require retrofit
public void getData(Callback<Unknownapi> callback) {
// only create the apiInterface once
if (apiInterface == null) {
apiInterface = ApiClient.getClient().create(ApiInterface.class);
}
// allow the calling function to handle the result
apiInterface.doGetListResources().enqueue(callback);
}
}
// shouldn't know how retrofit handler parses the data
public class SimpleViewModel extends ViewModel {
private RetrofitHandler retrofitHandler = new RetrofitHandler();
// store data in mutableSize, not with a backing field.
private MutableLiveData<Integer> mutableSize = new MutableLiveData<>();
public void handleRetrofitCall() {
// handle the data parsing here
retrofitHandler.getData(new Callback<Unknownapi>() {
#Override
public void onResponse(Call<Unknownapi> call, Response<Unknownapi> response) {
Unknownapi unknownapi = response.body();
int listSize = unknownapi.getData().size;
// set the value of the LiveData. Observers will be notified
mutableSize.setValue(listSize); // Note that we're using setValue because retrofit callbacks come back on the main thread.
Log.e("Size", Integer.toString(listSize));
}
#Override
public void onFailure(Call<Unknownapi> call, Throwable t) {
// error handling should be added here
}
});
}
// this should probably return an immutable copy of the object
public MutableLiveData<Integer> getObject() {
return mutableSize;
}
}
public class MainActivity extends AppCompatActivity {
private TextView status;
// initialize the view model only once
private SimpleViewModel viewModel = ViewModelProviders.of(MainActivity.this).get(SimpleViewModel.class);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
status = findViewById(R.id.status);
// observe the view model's changes
viewModel.getObject().observe(this, new Observer<Integer>() {
#Override
public void onChanged(#Nullable Integer integer) {
// you should handle possibility of interger being null
Log.e("lk","f");
status.setText(Integer.toString(integer));
}
});
findViewById(R.id.retrofit).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// call the view model's function
viewModel.handleRetrofitCall();
}
});
}
}
I'm trying to build a dialog that shows a list of items fetched from the network. Because I know that this isn't the only time that I will need this type of dialog I would like to build a base dialog (NetworkDialog) that handles the different errors that can happen when trying to fetch data from the network (ie. noServerResponse, failedToConnectToHost etc).
For this I would like to be able to use Butterknife to bind the string resources that are used for the different error messages, but I'm not sure if that will be possible.
Would something like this work?
public abstract class NetworkDialog extends BaseDialog implements NetworkDialogView {
#BindString(R.string.global_network_error_internal_server_error)
String mInternalServerErrorString;
#BindString(R.string.global_network_error_no_server_response)
String mNoServerResponseString;
#BindString(R.string.global_network_error_no_network)
String mNoNetworkString;
#BindString(R.string.global_network_error_failed_to_connect_to_host)
String mFailedToConnectToHost;
private Unbinder mUnbinder;
#NonNull
#Override
public Dialog onCreateDialog(#Nullable Bundle savedInstanceState) {
Timber.d("onCreateDialog()");
Timber.d("Binding view using ButterKnife.");
mUnbinder = ButterKnife.bind(this, getView());
Timber.d("View bound");
return super.onCreateDialog(savedInstanceState);
}
#Override
public void onDestroyView() {
Timber.d("onDestroyView() called.");
super.onDestroyView();
mUnbinder.unbind();
}
#Override
public void setNoNetworkError() {
showError(mNoNetworkString);
}
#Override
public void setFailedToConnectToHostError() {
showError(mFailedToConnectToHost);
}
#Override
public void setNoServerResonseError() {
showError(mNoServerResponseString);
}
#Override
public void setInternalServerError() {
showError(mInternalServerErrorString);
}
}
On Last Google IO, Google released a preview of some new arch components, one of which, ViewModel.
In the docs google shows one of the possible uses for this component:
It is very common that two or more fragments in an activity need to
communicate with each other. This is never trivial as both fragments
need to define some interface description, and the owner activity must
bind the two together. Moreover, both fragments must handle the case
where the other fragment is not yet created or not visible.
This common pain point can be addressed by using ViewModel objects.
Imagine a common case of master-detail fragments, where we have a
fragment in which the user selects an item from a list and another
fragment that displays the contents of the selected item.
These fragments can share a ViewModel using their activity scope to
handle this communication.
And shows a implementation example:
public class SharedViewModel extends ViewModel {
private final SavedStateHandle state;
public SharedViewModel(SavedStateHandle state) {
this.state = state;
}
private final MutableLiveData<Item> selected = state.getLiveData("selected");
public void select(Item item) {
selected.setValue(item);
}
public LiveData<Item> getSelected() {
return selected;
}
}
public class MasterFragment extends Fragment {
private SharedViewModel model;
#Override
protected void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
model = new ViewModelProvider(getActivity()).get(SharedViewModel.class);
itemSelector.setOnClickListener(item -> {
model.select(item);
});
}
}
public class DetailFragment extends Fragment {
#Override
protected void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
SharedViewModel model = new ViewModelProvider(getActivity()).get(SharedViewModel.class);
model.getSelected().observe(this, { item ->
// update UI
});
}
}
I was quite excited about the possibility of not needing those interfaces used for fragments to communicate through the activity.
But Google's example does not show exactly how would I call the detail fragment from master.
I'd still have to use an interface that will be implemented by the activity, which will call fragmentManager.replace(...), or there is another way to do that using the new architecture?
Updated on 6/12/2017,
Android Official provide a simple, precise example to example how the ViewModel works on Master-Detail template, you should take a look on it first.Share data between fragments
As #CommonWare, #Quang Nguyen methioned, it is not the purpose for Yigit to make the call from master to detail but be better to use the Middle man pattern. But if you want to make some fragment transaction, it should be done in the activity. At that moment, the ViewModel class should be as static class in Activity and may contain some Ugly Callback to call back the activity to make the fragment transaction.
I have tried to implement this and make a simple project about this. You can take a look it. Most of the code is referenced from Google IO 2017, also the structure.
https://github.com/charlesng/SampleAppArch
I do not use Master Detail Fragment to implement the component, but the old one ( communication between fragment in ViewPager.) The logic should be the same.
But I found something is important using these components
What you want to send and receive in the Middle man, they should be sent and received in View Model only
The modification seems not too much in the fragment class. Since it only change the implementation from "Interface callback" to "Listening and responding ViewModel"
View Model initialize seems important and likely to be called in the activity.
Using the MutableLiveData to make the source synchronized in activity only.
1.Pager Activity
public class PagerActivity extends AppCompatActivity {
/**
* The pager widget, which handles animation and allows swiping horizontally to access previous
* and next wizard steps.
*/
private ViewPager mPager;
private PagerAgentViewModel pagerAgentViewModel;
/**
* The pager adapter, which provides the pages to the view pager widget.
*/
private PagerAdapter mPagerAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_pager);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
mPager = (ViewPager) findViewById(R.id.pager);
mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
pagerAgentViewModel = new ViewModelProvider(this).get(PagerAgentViewModel.class);
pagerAgentViewModel.init();
}
/**
* A simple pager adapter that represents 5 ScreenSlidePageFragment objects, in
* sequence.
*/
private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
...Pager Implementation
}
}
2.PagerAgentViewModel (It deserved a better name rather than this)
public class PagerAgentViewModel extends ViewModel {
private final SavedStateHandle state;
private final MutableLiveData<String> messageContainerA;
private final MutableLiveData<String> messageContainerB;
public PagerAgentViewModel(SavedStateHandle state) {
this.state = state;
messageContainerA = state.getLiveData("Default Message");
messageContainerB = state.getLiveData("Default Message");
}
public void sendMessageToB(String msg)
{
messageContainerB.setValue(msg);
}
public void sendMessageToA(String msg)
{
messageContainerA.setValue(msg);
}
public LiveData<String> getMessageContainerA() {
return messageContainerA;
}
public LiveData<String> getMessageContainerB() {
return messageContainerB;
}
}
3.BlankFragmentA
public class BlankFragmentA extends Fragment {
private PagerAgentViewModel viewModel;
public BlankFragmentA() {
// Required empty public constructor
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
viewModel = new ViewModelProvider(getActivity()).get(PagerAgentViewModel.class);
textView = (TextView) view.findViewById(R.id.fragment_textA);
// set the onclick listener
Button button = (Button) view.findViewById(R.id.btnA);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
viewModel.sendMessageToB("Hello B");
}
});
//setup the listener for the fragment A
viewModel.getMessageContainerA().observe(getViewLifecycleOwner(), new Observer<String>() {
#Override
public void onChanged(#Nullable String msg) {
textView.setText(msg);
}
});
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_blank_a, container, false);
return view;
}
}
4.BlankFragmentB
public class BlankFragmentB extends Fragment {
public BlankFragmentB() {
// Required empty public constructor
}
#Override
public void onViewCreated(#NonNull View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
viewModel = new ViewModelProvider(getActivity()).get(PagerAgentViewModel.class);
textView = (TextView) view.findViewById(R.id.fragment_textB);
//set the on click listener
Button button = (Button) view.findViewById(R.id.btnB);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
viewModel.sendMessageToA("Hello A");
}
});
//setup the listener for the fragment B
viewModel.getMessageContainerB().observe(getViewLifecycleOwner(), new Observer<String>() {
#Override
public void onChanged(#Nullable String msg) {
textView.setText(msg);
}
});
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_blank_b, container, false);
return view;
}
}
As written in the official Google tutorial now you may obtain a shared view model with by activityViewModels()
// Use the 'by activityViewModels()' Kotlin property delegate
// from the fragment-ktx artifact
private val model: SharedViewModel by activityViewModels()
I have found a similar solution as others according to google codelabs example.
I have two fragments where one of them wait for an object change in the other and continues its process with updated object.
for this approach you will need a ViewModel class as below:
import android.arch.lifecycle.MutableLiveData;
import android.arch.lifecycle.ViewModel;
import yourPackage.YourObjectModel;
public class SharedViewModel extends ViewModel {
public MutableLiveData<YourObjectModel> item = new MutableLiveData<>();
public YourObjectModel getItem() {
return item.getValue();
}
public void setItem(YourObjectModel item) {
this.item.setValue(item);
}
}
and the listener fragment should look like this:
public class ListenerFragment extends Fragment{
private SharedViewModel model;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
model.item.observe(getActivity(), new Observer<YourObjectModel>(){
#Override
public void onChanged(#Nullable YourObjectModel updatedObject) {
Log.i(TAG, "onChanged: recieved freshObject");
if (updatedObject != null) {
// Do what you want with your updated object here.
}
}
});
}
}
finally, the updater fragment can be like this:
public class UpdaterFragment extends DialogFragment{
private SharedViewModel model;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
}
// Call this method where it is necessary
private void updateViewModel(YourObjectModel yourItem){
model.setItem(yourItem);
}
}
It is good to mention that the updater fragment can be any form of fragments(not DialogFragment only) and for using these architecture components you should have these lines of code in your app build.gradle file. source
dependencies {
def lifecycle_version = "1.1.1"
implementation "android.arch.lifecycle:extensions:$lifecycle_version"
}
Before you are using a callback which attaches to Activity which is considered as a container.
That callback is a middle man between two Fragments.
The bad things about this previous solution are:
Activity has to carry the callback, it means a lot of work for
Activity.
Two Fragments are coupled tightly, it is difficult to update or change logic later.
With the new ViewModel (with support of LiveData), you have an elegant solution. It now plays a role of middle man which you can attach its lifecycle to Activity.
Logic and data between two Fragments now lay out in ViewModel.
Two Fragment gets data/state from ViewModel, so they do not need to know each other.
Besides, with the power of LiveData, you can change detail Fragment based on changes of master Fragment in reactive approach instead of previous callback way.
You now completely get rid of callback which tightly couples to both Activity and related Fragments.
I highly recommend you through Google's code lab. In step 5, you can find an nice example about this.
I implemented something similar to what you want, my viewmodel contains LiveData object that contains Enum state, and when you want to change the fragment from master to details (or in reverse) you call ViewModel functions that changing the livedata value, and activity know to change the fragment because it is observing livedata object.
TestViewModel:
public class TestViewModel extends ViewModel {
private MutableLiveData<Enums.state> mState;
public TestViewModel() {
mState=new MutableLiveData<>();
mState.setValue(Enums.state.Master);
}
public void onDetail() {
mState.setValue(Enums.state.Detail);
}
public void onMaster() {
mState.setValue(Enums.state.Master);
}
public LiveData<Enums.state> getState() {
return mState;
}
}
Enums:
public class Enums {
public enum state {
Master,
Detail
}
}
TestActivity:
public class TestActivity extends LifecycleActivity {
private ActivityTestBinding mBinding;
private TestViewModel mViewModel;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mBinding=DataBindingUtil.setContentView(this, R.layout.activity_test);
mViewModel=ViewModelProviders.of(this).get(TestViewModel.class);
mViewModel.getState().observe(this, new Observer<Enums.state>() {
#Override
public void onChanged(#Nullable Enums.state state) {
switch(state) {
case Master:
setMasterFragment();
break;
case Detail:
setDetailFragment();
break;
}
}
});
}
private void setMasterFragment() {
MasterFragment masterFragment=MasterFragment.newInstance();
getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout, masterFragment,"MasterTag").commit();
}
private void setDetailFragment() {
DetailFragment detailFragment=DetailFragment.newInstance();
getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout, detailFragment,"DetailTag").commit();
}
#Override
public void onBackPressed() {
switch(mViewModel.getState().getValue()) {
case Master:
super.onBackPressed();
break;
case Detail:
mViewModel.onMaster();
break;
}
}
}
MasterFragment:
public class MasterFragment extends Fragment {
private FragmentMasterBinding mBinding;
public static MasterFragment newInstance() {
MasterFragment fragment=new MasterFragment();
return fragment;
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
mBinding=DataBindingUtil.inflate(inflater,R.layout.fragment_master, container, false);
mBinding.btnDetail.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final TestViewModel viewModel=ViewModelProviders.of(getActivity()).get(TestViewModel.class);
viewModel.onDetail();
}
});
return mBinding.getRoot();
}
}
DetailFragment:
public class DetailFragment extends Fragment {
private FragmentDetailBinding mBinding;
public static DetailFragment newInstance() {
DetailFragment fragment=new DetailFragment();
return fragment;
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
mBinding=DataBindingUtil.inflate(inflater,R.layout.fragment_detail, container, false);
mBinding.btnMaster.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
final TestViewModel viewModel=ViewModelProviders.of(getActivity()).get(TestViewModel.class);
viewModel.onMaster();
}
});
return mBinding.getRoot();
}
}
I end up using the own ViewModel to hold up the listener that will trigger the Activity method. Similar to the old way but as I said, passing the listener to ViewModel instead of the fragment. So my ViewModel looked like this:
public class SharedViewModel<T> extends ViewModel {
private final MutableLiveData<T> selected = new MutableLiveData<>();
private OnSelectListener<T> listener = item -> {};
public interface OnSelectListener <T> {
void selected (T item);
}
public void setListener(OnSelectListener<T> listener) {
this.listener = listener;
}
public void select(T item) {
selected.setValue(item);
listener.selected(item);
}
public LiveData<T> getSelected() {
return selected;
}
}
in StepMasterActivity I get the ViewModel and set it as a listener:
StepMasterActivity.class:
SharedViewModel stepViewModel = ViewModelProviders.of(this).get("step", SharedViewModel.class);
stepViewModel.setListener(this);
...
#Override
public void selected(Step item) {
Log.d(TAG, "selected: "+item);
}
...
In the fragment I just retrieve the ViewModel
stepViewModel = ViewModelProviders.of(getActivity()).get("step", SharedViewModel.class);
and call:
stepViewModel.select(step);
I tested it superficially and it worked. As I go about implementing the other features related to this, I will be aware of any problems that may occur.
For those using Kotlin out there try the following approach:
Add the androidx ViewModel and LiveData libraries to your gradle file
Call your viewmodel inside the fragment like this:
class MainFragment : Fragment() {
private lateinit var viewModel: ViewModel
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
// kotlin does not have a getActivity() built in method instead we use activity, which is null-safe
activity?.let {
viemModel = ViewModelProvider(it).get(SharedViewModel::class.java)
}
}
}
The above method is a good practice since it will avoid crashes due to null pointer exceptions
Edit: As btraas complemented: activity is compiled into getActivity() which is marked as #Nullable in the android SDK. activity and getActivity() are both accessible and equivalent.
You can set values from Detail Fragment to Master Fragment like this
model.selected.setValue(item)
public class FilterFragmentExp extends BaseFragmentFilter implements ListingMVPview{
#Inject PresenterListing presenterExp;
private FilterUtilsModel filterModel;
private ListingModel listingModel,listingModel_tmp;
public static FilterFragmentExp newInstance(FilterUtilsModel filterModel,ListingModel listingModel) {
FilterFragmentExp fragment = new FilterFragmentExp();
Bundle bundle = new Bundle();
bundle.putSerializable("filter",filterModel);
bundle.putSerializable("listing",listingModel);
fragment.setArguments(bundle);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getComponent().inject(this);
presenterExp.attachView(this);
receiveArguments();
filterModel.addOnPropertyChangedCallback(new Observable.OnPropertyChangedCallback() {
#Override
public void onPropertyChanged(Observable observable, int i) {
presenterExp.initialize(filterModel.getExpMap(),TYPE_EXP);
}
});
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return super.onCreateView(inflater, container, savedInstanceState);
}
#Override
public void onDestroy() {
super.onDestroy();
presenterExp.detachView();
}
#Override
protected int getLayout() {
return R.layout.fragment_filter_exp;
}
#Override
protected FilterUtilsModel getFilter() {
}
private void receiveArguments(){
filterModel = (FilterUtilsModel) getArguments().getSerializable("filter");
listingModel = (ListingModel) getArguments().getSerializable("listing");
listingModel_tmp = listingModel;
}
#Override
public void showLoading() {
}
#Override
public void hideLoading() {
}
#Override
public void showRetry() {
}
#Override
public void hideRetry() {
}
#Override
public void showError(String message) {
}
}
When I moved to this fragment for the first time everything works well, but from next time(pressed back and come back again) I am getting a nullpointer exception from this line -
presenterExp.initialize(filterModel.getExpMap(),TYPE_EXP);
I am supposed to get this error only if I wont set any view(MVP view, here its ListingMVPview) to the presenter object(presenterExp), but I already set it on this line
presenterExp.attachView(this);
Here is my Presenter -
public class PresenterListing extends BasePresenter<ListingMVPview> {
private final Context context;
#Inject
public PresenterListing(#ActivityContext Context context) {
this.context = context;
}
#Override
public void attachView(ListingMVPview mvpView) {
super.attachView(mvpView);
}
#Override
public void detachView() {
super.detachView();
}
public void initialize(Map options, String type) {
getMVPView().showLoading();
this.getListing(options,type);
}
....
}
Here in the above code getMVPView() returning null, though I have set MVP view.
I have used Dagger2 for dependency injection and using constructor injection for creating PresenterListing objects and using MVP architecture.
Any clues would be helpful as this problem is happening on when called from onPropertyChanged, if I move the code to some other place(say on some view's onclicklistener) everything works fine
you can add a null judgement
if (null) {...
advise start to use google mvp, good lucky
I am reinventing my app using a classic MVP approach. In order to to this I read many many articles and tutorials, and what I came out with is that the best way is to :
create an interface for the presenter and one for the view
make fragments and activities implements view interfaces
create an implementation of the presenter interface, which takes in the constructor an instance of the the view it manages, and hold a reference to the presenter inside the view's implementation.
So I have created this classes
VIEW INTERFACE
public interface SignupEmailView extends BaseView {
void fillEmail(String email);
void onEmailInvalid(String error);
void onDataValidated();
}
PRESENTER INTERFACE
public interface SignupEmailPresenter {
void initData(Bundle bundle);
void validateData(String email);
}
VIEW IMPLEMENTATION
public class FrSignup_email extends BaseSignupFragmentMVP implements IBackHandler, SignupEmailView {
public static String PARAM_EMAIL = "param_email";
#Bind(R.id.signup_step2_new_scrollview)
ScrollView mScrollview;
#Bind(R.id.signup_step2_new_lblTitle)
SuperLabel mLblTitle;
#Bind(R.id.signup_step2_new_lblSubtitle)
TextView mLblSubtitle;
#Bind(R.id.signup_step2_new_txtEmail)
EditText mTxtEmail;
#Bind(R.id.signup_step2_new_btnNext)
Button mBtnNext;
protected SignupActivityView mActivity;
SignupEmailPresenter mPresenter;
public FrSignup_email() {
// Required empty public constructor
}
public static FrSignup_email newInstance(String email) {
FrSignup_email fragment = new FrSignup_email();
Bundle b = new Bundle();
b.putString(PARAM_EMAIL, email);
fragment.setArguments(b);
return fragment;
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mActivity = (SignupActivityView) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement IResetPasswordBridge");
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = loadView(inflater, container, savedInstanceState, R.layout.fragment_signup_email);
mPresenter = new SignupEmailPresenterImpl(this);
ButterKnife.bind(this, view);
return view;
}
#Override
public final void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
applyCircularReveal();
mPresenter.initData(this.getArguments());
mTxtEmail.setImeOptions(EditorInfo.IME_ACTION_NEXT);
mTxtEmail.setOnEditorActionListener(new TextView.OnEditorActionListener() {
#Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
if (actionId == EditorInfo.IME_ACTION_NEXT) {
mPresenter.validateData(mTxtEmail.getText().toString());
return true;
}
return false;
}
});
mTxtEmail.setOnTouchListener(new OnTouchCompoundDrawableListener_NEW(mTxtEmail, new OnTouchCompoundDrawableListener_NEW.OnTouchCompoundDrawable() {
#Override
public void onTouch() {
mTxtEmail.setText("");
}
}));
mBtnNext.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mPresenter.validateData(mTxtEmail.getText().toString());
}
});
}
#Override
public void fillEmail(String email) {
mTxtEmail.setText(email);
}
#Override
public void onEmailInvalid(String error) {
displayError(error);
}
#Override
public void onDataValidated() {
changeFieldToValid(mTxtEmail);
setEmail(mTxtEmail.getText().toString());
// the activity shows the next fragment
mActivity.onEmailValidated();
}
#Override
public boolean doBack() {
if (!isLoading()) {
mActivity.onEmailBack();
}
return true;
}
#Override
public void displayError(String error) {
changeFieldToInvalid(mTxtEmail);
mLblSubtitle.setText(error);
mLblSubtitle.setTextColor(ContextCompat.getColor(getActivity(), R.color.field_error));
}
}
PRESENTER IMPLEMENTATION
public class SignupEmailPresenterImpl implements SignupEmailPresenter {
private SignupEmailView mView;
public SignupEmailPresenterImpl(SignupEmailView view) {
mView = view;
}
#Override
public void initData(Bundle bundle) {
if (bundle != null) {
mView.fillEmail(bundle.getString(FrSignup_email.PARAM_EMAIL));
}
}
#Override
public void validateData(String password) {
ValidationUtils_NEW.EmailStatus status = ValidationUtils_NEW.validateEmail(password);
if (status != ValidationUtils_NEW.EmailStatus.VALID) {
mView.onEmailInvalid(ValidationUtils_NEW.getEmailErrorMessage(status));
} else {
mView.onDataValidated();
}
}
}
Now the fragment is held by an activity which implements this view interface and has its own presenter
public interface SignupActivityView extends BaseView {
void onEmailValidated();
void onPhoneNumberValidated();
void onPasswordValidated();
void onUnlockCodeValidated();
void onResendCodeClick();
void onEmailBack();
void onPhoneNumberBack();
void onPasswordBack();
void onConfirmCodeBack();
void onSignupRequestSuccess(boolean resendingCode);
void onSignupRequestFailed(String errorMessage);
void onTokenCreationFailed();
void onUnlockSuccess();
void onUnlockError(String errorMessage);
void showTermsAndConditions();
void hideTermsAndConditions();
}
My idea is to have a unit test for each project unit, so for each view and presenter implementation I want a unit test, so I want to unit test my fragment with roboletric, and for example I want to test that if I click the "NEXT" button and the email is correct, the hosting Activity's onEmailValidated()method is called. This is my test class
public class SignupEmailViewTest {
private SignupActivity_NEW mActivity;
private SignupActivity_NEW mSpyActivity;
private FrSignup_email mFragment;
private FrSignup_email mSpyFragment;
private Context mContext;
#Before
public void setUp() {
final Context context = RuntimeEnvironment.application.getApplicationContext();
this.mContext = context;
mActivity = Robolectric.buildActivity(SignupActivity_NEW.class).create().visible().get();
mSpyActivity = spy(mActivity);
mFragment = FrSignup_email.newInstance("");
mSpyFragment =spy(mFragment);
mSpyActivity.getFragmentManager()
.beginTransaction()
.replace(R.id.signupNew_fragmentHolder, mSpyFragment)
.commit();
mSpyActivity.getFragmentManager().executePendingTransactions();
}
#Test
public void testEmailValidation() {
assertTrue(mSpyActivity.findViewById(R.id.signup_step2_new_lblTitle).isShown());
assertTrue(mSpyActivity.findViewById(R.id.signup_step2_new_lblSubtitle).isShown());
mSpyActivity.findViewById(R.id.signup_step2_new_btnNext).performClick();
assertTrue(((SuperLabel) mSpyActivity.findViewById(R.id.signup_step2_new_lblSubtitle)).getText().equals(mContext.getString(R.string.email_empty)));
((EditText) mSpyActivity.findViewById(R.id.signup_step2_new_txtEmail)).setText("aaa#bbb.ccc");
mSpyActivity.findViewById(R.id.signup_step2_new_btnNext).performClick();
verify(mSpyFragment).onDataValidated();
verify(mSpyActivity).onEmailValidated();
}
}
everything works well, is just the last verify which doesn't work. Note that the previous verify works, so onEmailValidated is called for sure.
Aside from this specific case, I have some point to discuss:
If with roboeletric I am forced to use an activity to instantiate a fragment, how can I test the fragment in complete isolation (which would be the unit tests goal)? I mean, if I use Robolectric.setupActivity(MyActivity.class) and the activity instantiates somewhere a fragment, it will load the activity and the fragment, which is good, but what if the activity manages a flow of fragments? How can I test the second or third fragment without manually navigating to it? Someone can say to use a dummy activity and use FragmentTestUtil.startFragment, but what in the fragment's onAttach() method is implemented the bridging with the parent activity? Is it me going on the wrong way or are this problems still unsolved?
thanks
Actually you don't even require Roboelectric to do any of those tests.
If each fragment/activity implements a different view interface you could implement fake views and instantiate those instead of the activity/fragment. In this way you could have isolated tests.
If you don't want to implement all the methods of the view interface you could use Mockito and stub only the ones that your unit test requires.
Let me know if you need sample code.