Develop Reference

RXJAVA ROOM android

Trying to learn Room and RXJAVA.
I have about 80% of this understood but I'm getting stuck on figuring the rest out.
Here is the error I get on the insert data.
java.lang.NullPointerException: Attempt to invoke interface method
'void
com.example.learnroom.EntityDao.insert(com.example.learnroom.Entitys)'
on a null object reference
If I don't run the try catch I get the following error which seems to be related.
java.lang.RuntimeException: Unable to start activity
ComponentInfo{com.example.learnroom/com.example.learnroom.MainActivity}:
java.lang.NullPointerException: Attempt to invoke interface method
'io.reactivex.Maybe
com.example.learnroom.EntityDao.getEntity(java.lang.String)' on a null
object reference
How do I fix this?
I have tried to simplify from the tutorials all over the web most using recyclerviews to just 2 text fields. They say this is 3 pieces but it doesn't seem like it, as the DB was never set up so I ran it in a method to run the code. Maybe someone can help explain to me how this really works.
my code
Dao
public interface EntityDao {
#Query("SELECT * FROM Entitys WHERE ID = :ID LIMIT 1")
Maybe<List<Entitys>> getEntity(String ID);
#Insert(onConflict = OnConflictStrategy.REPLACE)
void insert(Entitys entitys);
#Query("DELETE FROM Entitys")
void deleteAllEntity();
}
Entity
public class Entitys {
#PrimaryKey
#NonNull
public String ID;
public String ts;
public String tss;
public Entitys(#NonNull String ID, String ts, String tss) {
this.ID = ID;
this.ts = ts;
this.tss = tss;
}
public String getTss() {
return tss;
}
public void setTss(String tss) {
this.tss = tss;
}
public void setID(String ID) {
this.ID = ID;
}
public void setTs(String ts) {
this.ts = ts;
}
public String getID() {
return ID;
}
public String getTs() {
return ts;
}
}
database
#Database(entities = {Entitys.class}, version = 1)
public abstract class PathwaysDB extends RoomDatabase {
private static volatile PathwaysDB INSTANCE;
public static EntityDao entityDao() {
return null;
}
public static PathwaysDB getInstance(Context context) {
if (INSTANCE == null) {
synchronized (PathwaysDB.class) {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
PathwaysDB.class, "Pathwaysdb")
.build();
}
}
}
return INSTANCE;
}
}
MainActivity
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private static final String TAG = MainActivity.class.getSimpleName();
Button tb;
EditText te, tes;
String ts, tss, ID;
CompositeDisposable compositeDisposable = new CompositeDisposable();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ID ="test";
te = findViewById(R.id.te);
tb = findViewById(R.id.tb);
tb.setOnClickListener(this);
tes = findViewById(R.id.tes);
Builddb();
try{
getData();}catch (Exception e){}
}
private void Builddb() {
Completable.fromAction(() -> PathwaysDB.getInstance(this))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new CompletableObserver() {
#Override
public void onSubscribe(Disposable d) {
compositeDisposable.add(d);
}
#Override
public void onComplete() {
// action was completed successfully
}
#Override
public void onError(Throwable e) {
// something went wrong
}
});
}
private void getData() {
Maybe<List<Entitys>> single = entityDao().getEntity(ID);
single.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new MaybeObserver<List<Entitys>>() {
#Override
public void onSubscribe(Disposable d) {
// add it to a CompositeDisposable
}
#Override
public void onSuccess(List<Entitys> entity) {
te.setText(entity.indexOf(ts));
tes.setText(entity.indexOf(tss));
}
#Override
public void onError(Throwable e) {
// show an error message
}
#Override
public void onComplete() {
}
});
compositeDisposable.add((Disposable) single);
}
#Override
protected void onDestroy() {
super.onDestroy();
compositeDisposable.dispose();
}
private void updateUserName() {
ts = te.getText().toString();
tss = tes.getText().toString();
Entitys entitys = new Entitys(ID, ts, tss);
Completable.fromAction(() -> entityDao().insert(entitys))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new CompletableObserver() {
#Override
public void onSubscribe(Disposable d) {
compositeDisposable.add(d);
}
#Override
public void onComplete() {
// action was completed successfully
}
#Override
public void onError(Throwable e) {
// something went wrong
}
});
}
#Override
public void onClick(View view) {
updateUserName();
Intent forward = new Intent(this, secondpage.class);
startActivity(forward);
}
}

Reason for crash is this line in your PathwaysDB class
public static EntityDao entityDao() {
return null;
}
it is returning null. It should be like
public abstract EntityDao entityDao()

You forget to add #Dao annonation to your EntityDao interface class.
also you need to change below method :
public static EntityDao entityDao() {
return null;
}
To
public abstract EntityDao entityDao();

How can I make connection between retrofit and RxJava in different classes?

I have some classes as presenter and in these classes I use retrofit for some methods. But some methods are duplicated. So I want to use a class for all retrofit and connect to server methods and call them when I want.
But when I created that class it has NullpointerException Error
I will be very thankful if you help me
this is presenter codes:
public class DefinitionPresenter implements DefinitionContract.Presenter {
private KalaBeanDataSource kalaBeanDataSource;
private DefinitionContract.View view;
private CompositeDisposable compositeDisposable = new CompositeDisposable();
private DatabaseMethods databaseMethods;
private ActivityKindList activityKindList;
public DefinitionPresenter(KalaBeanDataSource kalaBeanDataSource){
this.kalaBeanDataSource = kalaBeanDataSource;
databaseMethods = new DatabaseMethods(kalaBeanDataSource,compositeDisposable);
activityKindList = new ActivityKindList();
}
#Override
public void attachView(DefinitionContract.View view) {
this.view = view;
}
#Override
public void detachView() {
view = null;
if(compositeDisposable != null && compositeDisposable.size() > 0){
compositeDisposable.clear();
}
}
#Override
public void activityKind() {
activityKindList = databaseMethods.getActivityKind();
if(activityKindList.getItems().size() > 0){
view.getActivityKind(activityKindList);
}else{
view.showMessage(databaseMethods.message);
}
}
}
And this is a class that I created for get data from server with retrofit and RxJava
public class DatabaseMethods {
private KalaBeanDataSource kalaBeanDataSource;
private CompositeDisposable compositeDisposable;
private ActivityKindList activityKindListResult;
public String message = null;
public DatabaseMethods(KalaBeanDataSource kalaBeanDataSource,CompositeDisposable compositeDisposable){
this.kalaBeanDataSource = kalaBeanDataSource;
this.compositeDisposable = compositeDisposable;
activityKindListResult = new ActivityKindList();
}
public ActivityKindList getActivityKind(){
kalaBeanDataSource.getActivityKind().subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new SingleObserver<ActivityKindList>() {
#Override
public void onSubscribe(Disposable d) {
compositeDisposable.add(d);
}
#Override
public void onSuccess(ActivityKindList activityKindList) {
activityKindListResult = activityKindList;
}
#Override
public void onError(Throwable e) {
message = e.toString();
}
});
if(message == null && activityKindListResult.getItems().size() > 0){
return activityKindListResult;
}else{
return null;
}
}

this method always returns null:
public ActivityKindList getActivityKind(){
kalaBeanDataSource.getActivityKind().subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new SingleObserver<ActivityKindList>() {
#Override
public void onSubscribe(Disposable d) {
compositeDisposable.add(d);
}
#Override
public void onSuccess(ActivityKindList activityKindList) {
activityKindListResult = activityKindList;
}
#Override
public void onError(Throwable e) {
message = e.toString();
}
});
if(message == null && activityKindListResult.getItems().size() > 0){
return activityKindListResult;
}else{
return null;
}
}
1) make this method void
2) create an interface and call it in onSuccess() and onError()
3) implement interface in your presenter

How to notify activity when repository class gets the data?

I'm new in android architecture component. this is my code , i'm at the point that I don't know how to notify my activity and get the results back
these are my codes:
Activity:
private void iniViewModels() {
Observer<List<User>>usersObserver=new Observer<List<User>>() {
#Override
public void onChanged(#Nullable List<User> users) {
Log.v("this","LiveData: ");
for (int i=0;i<users.size();i++){
Log.v("this",users.get(i).getName());
}
}
};
mViewModel = ViewModelProviders.of(this)//of-->name of act or fragment
.get(AcActivityViewModel.class);///get -->the name of viewModelClass
mViewModel.mUsers.observe(this,usersObserver);
}
this is my viewModel Class:
public class IpStaticViewModel extends AndroidViewModel {
public LiveData<List<Ipe>> ips;
private AppRepository repository;
public IpStaticViewModel(#NonNull Application application) {
super(application);
repository=AppRepository.getInstance(application.getApplicationContext());
}
public void getIpStatics() {
repository.getStaticIps();
}
}
this is my repository class:
public class AppRepository {
private static AppRepository ourInstance ;
private Context context;
private IpStaticInterface ipInterface;
public static AppRepository getInstance(Context context) {
if (ourInstance == null) {
ourInstance=new AppRepository(context);
}
return ourInstance;
}
private AppRepository(Context context) {
this.context=context;
}
public void getStaticIps() {
ipInterface= ApiConnection.getClient().create(IpStaticInterface.class);
ipInterface.getIpes()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribeWith(new SingleObserver<IpStaticList>() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onSuccess(IpStaticList ipStaticList) {
List<Ipe>ips=ipStaticList.getIpes();
}
#Override
public void onError(Throwable e) {
Log.v("this","Eror "+ e.getMessage());
}
});
}
}
I'm using retrofit for fetching the data ,it fetch the data successfully but I don't know how to notify my activity
can you help me?

Have a MutableLiveData
final MutableLiveData<List<Ipe>> data = new MutableLiveData<>();
In onSucess
public MutableLiveData<List<Ipe>> getStaticIps() {
ipInterface= ApiConnection.getClient().create(IpStaticInterface.class);
ipInterface.getIpes()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribeWith(new SingleObserver<IpStaticList>() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onSuccess(IpStaticList ipStaticList) {
List<Ipe>ips=ipStaticList.getIpes();
data.setValue(ips);
}
#Override
public void onError(Throwable e) {
Log.v("this","Eror "+ e.getMessage());
}
});
return data;
}
In repository expose this to viewmodel
public LiveData<List<Ipe>> getIpStatics() {
return repository.getStaticIps();
}
In Activity you observe the livedata
IpStaticViewModel viewmodel = ViewModelProviders.of(this
.get(IpStaticViewModel.class)
viewModel.getIpStatics().observe(this, new Observer<List<Ipe>>() {
#Override
public void onChanged(#Nullable List<Ipe> ipes) {
if (ipes != null) {
// dosomething
}
}
});
If you want to generalize your response in case you have a error or something have a look at https://github.com/googlesamples/android-architecture-components/blob/master/GithubBrowserSample/app/src/main/java/com/android/example/github/vo/Resource.kt

Change Observable List to Hashmap Singleton

I have a singleton to cache objects, from here I create an observable from a List, this List is a response from the API which is filled with objects. (JSON)
private static BehaviorSubject<List<Model>> observableModelsList;
private static Observable<List<Model>> observable = myAPI.loadModelsRx();
private static Subscription subscription;
private PoiSingleton() {
}
public static PoiSingleton getInstance() {
return ourInstance;
}
public static void resetObservable() {
observablePoisList = BehaviorSubject.create();
if (subscription != null && !subscription.isUnsubscribed()) {
subscription.unsubscribe();
}
subscription = observable.subscribe(new Subscriber<List<Model>>() {
#Override
public void onCompleted() {
// do nothing
}
#Override
public void onError(Throwable e) {
observablePoisList.onError(e);
}
#Override
public void onNext(List<Model> models) {
observablePoisList.onNext(models);
}
});
}
public static Observable<List<Poi>> getPoisObservable() {
if (observablePoisList == null) {
resetObservable();
}
return observablePoisList;
}
What I want to achieve is create a HashMap from the List, the key should be the ID of the object and the value the object itself.
I am new to Android and Retrofit/RxJava so in what method/stage is it responsible to create the HashMap?

OnCompleted calls not tidy

i'm new in Rx programming (and I'm having a lot of fun so far ^^).
I'm trying to transform a AsyncTask call into an Rx function.
My function :
Get all the installed apps
normalize the labels
sort everything alphabetically
arrange them by group of letter (it was a Multimap(letter, list of apps)) and pass the result to an adapter to display everything.
Here is how I'm doing so far with Rx :
Observable.from(getInstalledApps(getActivity(), false))
.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.map(new Func1<ResolvedActivityInfoWrapper, ResolvedActivityInfoWrapper>() {
#Override
public ResolvedActivityInfoWrapper call(ResolvedActivityInfoWrapper act) {
// Normalize labels
act.setLabel(Normalizer.normalize(act.getLabel(getPackageManager()).replace(String.valueOf((char) 160), "").trim(), Normalizer.Form.NFD).replaceAll("\\p{M}", ""));
return act;
}
})
.toList()
.subscribe(new Observer<List<ResolvedActivityInfoWrapper>>() {
List<ResolvedActivityInfoWrapper> list;
#Override
public void onCompleted() {
Observable.from(list).groupBy(new Func1<ResolvedActivityInfoWrapper, String>() {
#Override
public String call(ResolvedActivityInfoWrapper input) {
//Get groups by letter
String label = input.getLabel(getPackageManager());
if (!TextUtils.isEmpty(label)) {
String firstChar = label.substring(0, 1);
if (pattern.matcher(firstChar).matches()) {
return firstChar.toUpperCase();
}
}
return "#";
}
}).subscribe(this); // implementation below
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(List<ResolvedActivityInfoWrapper> list) {
Collections.sort(list, new Comparator<ActivityInfoWrapper>() {
#Override
// Sort all the apps in the list, not sure it's a good way to do it
public int compare(ActivityInfoWrapper info1, ActivityInfoWrapper info2) {
return info1.getLabel(getPackageManager()).compareToIgnoreCase(info2.getLabel(getPackageManager()));
}
});
this.list = list;
}
});
Once I groupedBy letters, on complete I subscribe with this :
#Override
public void onCompleted() {
//display the apps
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(GroupedObservable<String, ResolvedActivityInfoWrapper> input) {
//For each list of apps by letter i subscribe with an observer that will handle those apps (observer code below)
input.subscribe(new TestObserver(input.getKey()));
}
Observer :
private class TestObserver implements Observer<ResolvedActivityInfoWrapper> {
List<ResolvedActivityInfoWrapper> list;
String letter;
public TestObserver(String letter) {
list = new ArrayList<>();
this.letter = letter;
}
#Override
public void onCompleted() {
adapter.addData(letter, list);
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(ResolvedActivityInfoWrapper input) {
list.add(input);
}
}
Everything works correctly excpets for one problem : the observer's onCompleted are called not in the right order. So I got all my apps, sorted by letter, but the groups are nots displayed in the right order (C first, then Y, then M etc ...).
I guess there are plenty of errors in the code, can you help me with this probleme and maybe understanding how all this works please ?
Thanks
UPDATE :
Following the advices in the commentary section (thanks people), here is what I'm trying after normalizing the labels :
Observable.from(list).groupBy(new Func1<ResolvedActivityInfoWrapper, String>() {
#Override
public String call(ResolvedActivityInfoWrapper input) {
String label = input.getLabel(getPackageManager());
if (!TextUtils.isEmpty(label)) {
String firstChar = label.substring(0, 1);
if (pattern.matcher(firstChar).matches()) {
return firstChar.toUpperCase();
}
}
return "#";
}
})
.toSortedList(new Func2<GroupedObservable<String, ResolvedActivityInfoWrapper>, GroupedObservable<String, ResolvedActivityInfoWrapper>, Integer>() {
#Override
public Integer call(GroupedObservable<String, ResolvedActivityInfoWrapper> obs1, GroupedObservable<String, ResolvedActivityInfoWrapper> obs2) {
return obs1.getKey().compareToIgnoreCase(obs2.getKey());
}
})
.subscribe(new Observer<List<GroupedObservable<String, ResolvedActivityInfoWrapper>>>() {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(List<GroupedObservable<String, ResolvedActivityInfoWrapper>> input) {
String test = input.get(0).getKey();
}
});
But it never goes into the Compare function.