I am trying to follow Android architecture guidelines to make this app. I have a MovieRepository which is responsible for fetching JSON (data layer), and I have a ViewModel that supplies data to the UI in my MainActivity. I am using retrofit 2 for my networking task.
MovieRespository code:
public class MovieRepository {
private static final String TAG = MovieRepository.class.getSimpleName();
public LiveData<ReturnMovie> search(String term) {
final MutableLiveData<ReturnMovie> data = new MutableLiveData<>();
MovieService service = ServiceGenerator.createService(MovieService.class);
Call<ReturnMovie> call = service.requestMovie(term, MovieAPIUtils.KEY);
call.enqueue(new Callback<ReturnMovie>() {
#Override
public void onResponse(Call<ReturnMovie> call, Response<ReturnMovie> response) {
ReturnMovie movie = response.body();
data.setValue(movie);
Log.d(TAG, data.getValue().getPage().toString());
}
#Override
public void onFailure(Call<ReturnMovie> call, Throwable t) {
Log.d(TAG, t.toString());
}
});
return data;
}
}
MovieService:
public interface MovieService {
#GET(MovieAPIUtils.Path.MOVIE_PATH + "/{param}")
Call<ReturnMovie> requestMovie (#Path("param") String endpoints,
#Query(MovieAPIUtils.Query.API_QUERY) String key);
}
ViewModel:
public class MainActivityMovieViewModel extends ViewModel {
private static final String TAG = MainActivityMovieViewModel.class.getSimpleName();
private LiveData<ReturnMovie> movie;
private MovieRepository repo = new MovieRepository();
public LiveData<ReturnMovie> getMovie(String searchTerm) {
if (movie == null) {
movie = repo.search(searchTerm);
}
return movie;
}
}
MainActivity:
public class MainActivity extends AppCompatActivity implements MovieAdapter.MovieOnClickListener {
private RecyclerView mRecyclerView;
private MovieAdapter mMovieAdapter;
private MainActivityMovieViewModel viewModel;
private static final String TAG = MainActivity.class.getSimpleName();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewModel = ViewModelProviders.of(this).get(MainActivityMovieViewModel.class);
initRecyclerViewWithMovies();
ReturnMovie movie = viewModel.getMovie(MovieAPIUtils.Endpoints.POPULAR_ENDPOINT).getValue();
// other code....
}
In the onResponse(new Callback<ReturnMovie>) I was able to retrieve the movie object and I proved it by logging one of its property values, so there IS a valid ReturnMovie object. However, in my MainActivity, the method ReturnMovie movie = viewModel.getMovie(MovieAPIUtils.Endpoints.POPULAR_ENDPOINT).getValue(); gives me a null. I checked everywhere is just cannot see where the problem is.
The rest of the code is on my Github:
https://github.com/brendoncheung/PopularMovie/tree/mvvm_approach
You use android architecture components, which uses observable pattern in live data. If you are just getting the current value of livedata, you are not sure it has been processed yet.
Instead of
ReturnMovie movie = viewModel.getMovie(MovieAPIUtils.Endpoints.POPULAR_ENDPOINT).getValue(); i think you should use
viewModel.getMovie(MovieAPIUtils.Endpoints.POPULAR_ENDPOINT).observe(this, new Observer<ReturnMovie>() {
#Override
public void onChanged(#Nullable ReturnMovie movie) {
//do stuff with the movie
doSomething(movie);
}
});
You don't have to manage unsubscription since architecture component manages unsubscription for activities itself
Take a look on : https://developer.android.com/topic/libraries/architecture/livedata
Related
Even though I am using ViewModel, whenever the device is rotated, the data in the Recyclerview disappears. I had to put the makeSearch() method inside the onClick() method because I need to get the text that the button grabs and use it as the search parameter. Is there a better way I can handle this to avoid this problem? My code is right here:
SearchActivity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
// What happens when the search button is clicked
materialButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (Objects.requireNonNull(textInputEditText.getText()).toString().isEmpty()) {
textInputEditText.setError("Type a search query");
} else {
mSearchInput = Objects.requireNonNull(textInputEditText.getText()).toString();
textInputEditText.setText("");
makeSearch();
}
}
});
}
// Gets the ViewModel, Observes the Question LiveData and delivers it to the Recyclerview
private void makeSearch() {
final SearchAdapter searchAdapter = new SearchAdapter();
SearchViewModel mSearchViewModel = new ViewModelProvider(this,
new CustomSearchViewModelFactory(new SearchRepository())).get(SearchViewModel.class);
mSearchViewModel.setQuery(mSearchInput);
mSearchViewModel.getQuestionLiveData().observe(this, new Observer<List<Question>>() {
#Override
public void onChanged(List<Question> questions) {
mQuestions = questions;
searchAdapter.setQuestions(questions);
}
});
mRecyclerView.setAdapter(searchAdapter);
searchAdapter.setOnClickListener(mOnClickListener);
}
SearchViewModel:
public class SearchViewModel extends ViewModel {
private SearchRepository mSearchRepository;
private MutableLiveData<String> mSearchLiveData = new MutableLiveData<>();
private LiveData<List<Question>> mQuestionLiveData = Transformations.switchMap(mSearchLiveData, (query) -> {
return mSearchRepository.getQuestions(query);
});
SearchViewModel(SearchRepository searchRepository) {
this.mSearchRepository = searchRepository;
}
public LiveData<List<Question>> getQuestionLiveData() {
return mQuestionLiveData;
}
public void setQuery(String query) {
mSearchLiveData.setValue(query);
}
}
SearchRepository:
public class SearchRepository {
//private String inTitle;
private MutableLiveData<List<Question>> mQuestions = new MutableLiveData<>();
public SearchRepository() {
//getQuestionsWithTextInTitle();
}
private void getQuestionsWithTextInTitle(String inTitle) {
ApiService apiService = RestApiClient.getApiService(ApiService.class);
Call<QuestionsResponse> call = apiService.getQuestionsWithTextInTitle(inTitle);
call.enqueue(new Callback<QuestionsResponse>() {
#Override
public void onResponse(Call<QuestionsResponse> call, Response<QuestionsResponse> response) {
QuestionsResponse questionsResponse = response.body();
if (questionsResponse != null) {
mQuestions.postValue(questionsResponse.getItems());
//shouldShowData = true;
} else {
Log.d("SearchRepository", "No matching question");
//shouldShowData = false;
}
}
#Override
public void onFailure(Call<QuestionsResponse> call, Throwable t) {
//shouldShowData = false;
t.printStackTrace();
}
});
}
public LiveData<List<Question>> getQuestions(String inTitle) {
getQuestionsWithTextInTitle(inTitle);
return mQuestions;
}
}
Your approach of passing the search input in through your CustomSearchViewModelFactory and into the constructor for the ViewModel and into the constructor for your SearchRepository isn't going to work in any case. While the first time you search your CustomSearchViewModelFactory creates the ViewModel, the second time you hit search, your SearchViewModel is already created and your factory is not invoked a second time, meaning you never get the second query.
Instead, you should file the ViewModel Overview documentation, and use Transformations.switchMap() to convert your input (the search string) into a new LiveData<List<Question>> for that given query.
This means that your ViewModel would look something like
public class SearchViewModel extends ViewModel {
private SearchRepository mSearchRepository;
private MutableLiveData<String> mSearchLiveData = new MutableLiveData<String>();
private LiveData<List<Question>> mQuestionLiveData =
Transformations.switchMap(mSearchLiveData, (query) -> {
return mSearchRepository.getQuestions(query);
});
public SearchViewModel() {
mSearchRepository = new SearchRepository();
}
public void setQuery(String query) {
mSearchLiveData.setValue(query);
}
public LiveData<List<Question>> getQuestionLiveData() {
return mQuestionLiveData;
}
}
You'd then update your Activity to:
Always observe the getQuestionLiveData() (note that you won't get a callback to your Observer until you actually set the first query)
Call setQuery() on your SearchViewModel in your makeSearch()
Remove your CustomSearchViewModelFactory entirely (it would no longer be needed).
I have a doubt.If i have a method that make asynchronous call to an api and converts the results of it to livedata object and in another place i am updating my recyclerview when data changes, then every time call to this method will update recyclerview or ,for eg:if url stays same then it won't update the recyclerview;Pls help.
Here is the code for observing data in Mainactivity onCreate method.
JsonViewModel model = new ViewModelProvider(this).get(JsonViewModel.class);
model.getData("top_rated").observe(this, data -> {
mRecyclerView.setAdapter(new MovieRecyclerViewAdapter(this,data));
});
Here is the JsonViewModel class
public class JsonViewModel extends AndroidViewModel {
private JsonLivedata data;
public JsonViewModel(#NonNull Application application) {
super(application);
data=new JsonLivedata();
}
public LiveData<List<Movie>> getData(String path) {
data.loadData(path);
return data;
}
}
Here is the JsonLivedata class
public class JsonLivedata extends LiveData<List<Movie>> {
private static final String TAG = "JsonLivedata";
public JsonLivedata() {
}
public void loadData(String path){
Log.d(TAG, "loadData: Called");
new AsyncTask<String,Void,List<Movie>>(){
#Override
protected List<Movie> doInBackground(String... path) {
List<Movie> allTopMovies= JsonResponseFetcher.makeAsyncQueryForMovies(path[0]);
return allTopMovies;
}
#Override
protected void onPostExecute(List<Movie> movies) {
setValue(movies);
}
}.execute(path);
}
}
And here is the method that call livedata loaddata method
changeBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
model.getData("popular");
}
});
Or I am doing things wrongly.Can anyone suggest
First create adapter instance & set to RecyclerView
JsonViewModel model = new ViewModelProvider(this).get(JsonViewModel.class);
MovieRecyclerViewAdapter movieRecyclerViewAdapter = new MovieRecyclerViewAdapter(this, dataList)
mRecyclerView.setAdapter(movieRecyclerViewAdapter);
Then do this on data changes
model.getData("top_rated").observe(this, data -> {
dataList.clear();
dataList.addAll(data);
movieRecyclerViewAdapter.notifyDataSetChanged();
});
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();
}
});
}
}
So according to android developers: "Architecture Components provides ViewModel helper class for the UI controller that is responsible for preparing data for the UI. ViewModel objects are automatically retained during configuration changes so that data they hold is immediately available to the next activity or fragment instance."
In the code below there is an asynchronous class that gets called in deleteItem function. My question is this: Does ViewModel also handles the asynchronous calls made inside it or will cause memory leaks?
Thank you
public class BorrowedListViewModel extends AndroidViewModel {
private final LiveData<List<BorrowModel>> itemAndPersonList;
private AppDatabase appDatabase;
public BorrowedListViewModel(Application application) {
super(application);
appDatabase = AppDatabase.getDatabase(this.getApplication());
itemAndPersonList = appDatabase.itemAndPersonModel().getAllBorrowedItems();
}
public LiveData<List<BorrowModel>> getItemAndPersonList() {
return itemAndPersonList;
}
public void deleteItem(BorrowModel borrowModel) {
new deleteAsyncTask(appDatabase).execute(borrowModel);
}
private static class deleteAsyncTask extends AsyncTask<BorrowModel, Void, Void> {
private AppDatabase db;
deleteAsyncTask(AppDatabase appDatabase) {
db = appDatabase;
}
#Override
protected Void doInBackground(final BorrowModel... params) {
db.itemAndPersonModel().deleteBorrow(params[0]);
return null;
}
}
}
I would provide an example, probably you need to modify the code.
First you need a live data change and subscribe to that in your view. Then in the controller you post the value telling the subscriber that something appends. This way asynchronously the view would get alerted.
private MutableLiveData<String> databaseLiveData = new MutableLiveData<>();
...
And in the deleteAsyncTask class you can add:
protected void onPostExecute(Void result) {
databaseLiveData.postValue("some data deleted");
}
And in the BorrowedListViewModel class this method to access from the view add this method:
public LiveData<String> getChanger() {
return databaseLiveData;
}
In the view e.g.Activity add this:
private BorrowedListViewModel mBorrowedListViewModel;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//...
BorrowedListViewModel = ViewModelProviders.of(this).get(BorrowedListViewModel.class);
subscribe();
}
private void subscribe() {
final Observer<String> liveDataChange = new Observer<String>() {
#Override
public void onChanged(#Nullable final String message) {
Log.d("Activity", message);
}
};
liveDataChange.getChanger().observe(this, liveDataChange);
}
Hope this help.
I have an web api which gives me array of partners and it looks like this:
[
"partner1",
"partner2",
"partner3",
"....",
"parner222"
]
I have Table partners (ActiveAndroid) in which I would like to save all partners from api.
#Table(name = "Partners")
public class Partners extends Model {
#Column(name = "Name")
String name;
public Partners() {}
public Partners(String name) {
this.name = name;
}
}
Here is my Pojo model class:
public class Partners {
#SerializedName("name")
#Expose
private List<String> name = new ArrayList<String>();
public List<String> getName() {
return name;
}
public void setName(List<String> name) {
this.name = name;
}
}
This is my interface
public interface APIService {
#GET("Partners")
Call<Partners> getPartners();
}
And this is my APIHelper with api url
public class APIHelper {
public static APIService apiService;
public static APIService getApiService() {
if (apiService == null) {
Retrofit retrofit = new Retrofit.Builder().baseUrl("https://part-oflink.domain.com/partners.json/")
.addConverterFactory(GsonConverterFactory.create()).build();
apiService = retrofit.create(APIService.class);
}
return apiService;
}
}
And this is Fragment where I have an Button on which I would like to implement onClick method to get data from API and save it into Partners table.
public class DownloadMain extends Fragment implements Callback<Partners> {
private Button dloadPartners;
private Call<Partners> callPartners;
public static APIService apiService;
public DownloadMain() {}
public DownloadMain newInstance() { return new DownloadMain(); }
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.download_main, container, false);
dloadPartners = (Button) view.findViewById(R.id.downloadPartners);
dloadPartners.setOnClickListener(btnListener);
callPartners = APIHelper.getApiService().getPartners();
callPartners.enqueue(this);
return view;
}
Button.OnClickListener btnListener = (new View.OnClickListener() {
#Override
public void onClick(View v) {
//here I need to implement that on click downloads me data
// and save it into my Partners table
}
});
#Override
public void onResponse(Call<Partners> call, Response<Partners> response) {
//here I'm trying to put api response into array list
if (response.body() != null) {
ArrayList<String> partnersList = new ArrayList<>();
partnersList = response.body();
}
}
#Override
public void onFailure(Call<Partners> call, Throwable t) {
}
}
And now I have stuck. I would like to implement onClick Button method to get data from API. In onResponse() method I'm trying to put data into ArrayList to check if data is recieved. And also I would like to save this data into my table partners.
I would be grateful if someone could help me or guide me to fix this. This is first time I'm doing with retrofit and api.
Can somebody help me or guide me to successfully get data from API and save it into table Partners?
The way you are trying to parse the JSON string(array of partners) is not the appropriate. Your JSON should like this:
{
"partners":
["partner1", "partner2", "partner3", ...]
}
And the POJO model class should be:
class Partners{
private List<String> partners;
public Partners(){}
public void setList(List<String> partners) {
this.partners = partners;
}
public List<String> getList() {
return this.partners;
}
//setter and getter methods
}
If the response is not empty then for printing the values:
for(Partner partner: response){
Log.d("Partner Name",partner.name);
}
And if you are using any ORM for the database, then call its DAO and pass the values to save in the DB.