My question might be a little awkard:
My scenario:
I have a singleton which contains many references to my objects.
I initialize this singleton in my activity running an UI operation with Realm with realm.where(myobj.class).first();
In my activity I have a ViewPager with many fragments. Those fragments refers to the Singleton's properties.
In my many fragments, I need to update some of my singleton object properties, but I want to do it with an async transaction. Obv it result on a thread realm error.
Relevant code (cutted)
singleton
public class OpenedIntervention {
private static OpenedIntervention openedIntervention;
public static OpenedIntervention getIstance() {
if (openedIntervention == null) {
openedIntervention = new OpenedIntervention();
}
return openedIntervention;
}
public void dispose() {
openedIntervention = null;
}
private Intervention intervention = null;
//getter setter
}
My activity init:
//...
Intervention i = realm.where(Intervention.class).equalTo("ID", intId).findFirst(); //this realm istance has activity-scope
openedIntervention.setIntervention(i);
//...
My fragment, what I would like to do:
realm.executeTransactionAsync(
new Realm.Transaction() {
#Override
public void execute(Realm realm) {
//...
openedIntervention.getIntervention().setTIPOLOGIA_INTERVENTO(etInterventionType.getText().toString());
openedIntervention.getIntervention().setTIPOLOGIA_INTERVENTO_ID(etInterventionType.getTag().toString());
}
},
new Realm.Transaction.OnSuccess() {
#Override
public void onSuccess() {
//...
}
},
new Realm.Transaction.OnError() {
#Override
public void onError(Throwable error) {
//...
}
});
Any Idea about how can I solve this problem? I 'd like to do it async to avoid lag
Related
The structure of my application is as follows:
MainActivity(Activity) containing Bottom Navigation View with three fragments nested below
HomeFragment(Fragment) containing TabLayout with ViewPager with following two tabs
Journal(Fragment)
Bookmarks(Fragment)
Fragment B(Fragment)
Fragment C(Fragment)
I am using Room to maintain all the records of journals. I'm observing one LiveData object each in Journal and Bookmarks fragment. These LiveData objects are returned by my JournalViewModel class.
JournalDatabase.java
public abstract class JournalDatabase extends RoomDatabase {
private static final int NUMBER_OF_THREADS = 4;
static final ExecutorService dbWriteExecutor = Executors.newFixedThreadPool(NUMBER_OF_THREADS);
private static JournalDatabase INSTANCE;
static synchronized JournalDatabase getInstance(Context context) {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(context.getApplicationContext(), JournalDatabase.class, "main_database")
.fallbackToDestructiveMigration()
.build();
}
return INSTANCE;
}
public abstract JournalDao journalDao();
}
JournalRepository.java
public class JournalRepository {
private JournalDao journalDao;
private LiveData<List<Journal>> allJournals;
private LiveData<List<Journal>> bookmarkedJournals;
public JournalRepository(Application application) {
JournalDatabase journalDatabase = JournalDatabase.getInstance(application);
journalDao = journalDatabase.journalDao();
allJournals = journalDao.getJournalsByDate();
bookmarkedJournals = journalDao.getBookmarkedJournals();
}
public void insert(Journal journal) {
JournalDatabase.dbWriteExecutor.execute(() -> {
journalDao.insert(journal);
});
}
public void update(Journal journal) {
JournalDatabase.dbWriteExecutor.execute(() -> {
journalDao.update(journal);
});
}
public void delete(Journal journal) {
JournalDatabase.dbWriteExecutor.execute(() -> {
journalDao.delete(journal);
});
}
public void deleteAll() {
JournalDatabase.dbWriteExecutor.execute(() -> {
journalDao.deleteAll();
});
}
public LiveData<List<Journal>> getAllJournals() {
return allJournals;
}
public LiveData<List<Journal>> getBookmarkedJournals() {
return bookmarkedJournals;
}
}
JournalViewModel.java
public class JournalViewModel extends AndroidViewModel {
private JournalRepository repository;
private LiveData<List<Journal>> journals;
private LiveData<List<Journal>> bookmarkedJournals;
public JournalViewModel(#NonNull Application application) {
super(application);
repository = new JournalRepository(application);
journals = repository.getAllJournals();
bookmarkedJournals = repository.getBookmarkedJournals();
}
public void insert(Journal journal) {
repository.insert(journal);
}
public void update(Journal journal) {
repository.update(journal);
}
public void delete(Journal journal) {
repository.delete(journal);
}
public void deleteAll() {
repository.deleteAll();
}
public LiveData<List<Journal>> getAllJournals() {
return journals;
}
public LiveData<List<Journal>> getBookmarkedJournals() {
return bookmarkedJournals;
}
}
I'm instantiating this ViewModel inside onActivityCreated() method of both Fragments.
JournalFragment.java
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
JournalFactory factory = new JournalFactory(requireActivity().getApplication());
journalViewModel = new ViewModelProvider(requireActivity(), factory).get(JournalViewModel.class);
journalViewModel.getAllJournals().observe(getViewLifecycleOwner(), new Observer<List<Journal>>() {
#Override
public void onChanged(List<Journal> list) {
journalAdapter.submitList(list);
}
});
}
BookmarksFragment.java
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
JournalFactory factory = new JournalFactory(requireActivity().getApplication());
journalViewModel = new ViewModelProvider(requireActivity(), factory).get(JournalViewModel.class);
journalViewModel.getBookmarkedJournals().observe(getViewLifecycleOwner(), new Observer<List<Journal>>() {
#Override
public void onChanged(List<Journal> list) {
adapter.submitList(list);
}
});
}
However, the problem when I use this approach is as I delete make some changes in any of the Fragment like delete or update some Journal some other Journal's date field changes randomly.
I was able to solve this issue by using single LiveData object and observe it in both fragments. The changes I had to make in BookmarkFragment is as follows:
BookmarksFragment.java
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
JournalFactory factory = new JournalFactory(requireActivity().getApplication());
journalViewModel = new ViewModelProvider(requireActivity(), factory).get(JournalViewModel.class);
journalViewModel.getAllJournals().observe(getViewLifecycleOwner(), new Observer<List<Journal>>() {
#Override
public void onChanged(List<Journal> list) {
List<Journal> bookmarkedJournals = new ArrayList<>();
for (int i = 0; i < list.size(); i++) {
if (list.get(i).getBookmark() == 1)
bookmarkedJournals.add(list.get(i));
}
adapter.submitList(bookmarkedJournals);
}
});
}
It works properly now.
However, I want to know why it didn't work using my first approach which was to use two different LiveData objects and observe them in different fragments.
Are multiple LiveData objects not meant to be used in single ViewModel?
OR
Are two instances of same ViewModel not allowed to exist together while making changes and fetching different LiveData objects from the same table simultaneously?
I found out the reason causing this problem.
As I was using LiveData with getViewLifecycleOwner() as the LifecycleOwner, the observer I passed as parameter was never getting removed. So, after switching to a different tab, there were two active observers observing different LiveData objects of same ViewModel.
The way this issue can be solved is by storing the LiveData object in a variable then removing the observer as you switch to different fragment.
In my scenario, I solved this issue by doing the following:
//store LiveData object in a variable
LiveData<List<Journal>> currentLiveData = journalViewModel.getAllJournals();
//observe this livedata object
currentLiveData.observer(observer);
Then remove this observer in a suitable Lifecycle method or anywhere that suits your needs like
#Override
public void onDestroyView() {
super.onDestroyView();
//if you want to remove all observers
currentLiveData.removeObservers(getViewLifecycleOwner());
//if you want to remove particular observers
currentLiveData.removeObserver(observer);
}
I am new to ReactiveX and I have a case where I want my observable to emit data to a late subscriber(whenever the observer subscribes, observable should emit the same data that it emitted previously). I made this Observable class that provide ReplaySubject's same instance to all observers (it is singleton class).
public class AccountsObservable {
private static ConnectableObservable<String> hotObservable;
private static AccountsObservable accountsObservable;
public static AccountsObservable getObject() {
if (accountsObservable == null) {
accountsObservable = new AccountsObservable();
}
return accountsObservable;
}
public ConnectableObservable<String> getObservable() {
if (hotObservable == null) {
Observable<String> observable = ReplaySubject.create(new ObservableOnSubscribe<String>() {
#Override
public void subscribe(ObservableEmitter<String> emitter) throws Exception {
emitter.onNext("XYZ");
emitter.onComplete();
}
});
hotObservable = observable.replay();//publish
}
return hotObservable;
}
}
Similarly, this is the observer class that creates new observer instance.
public class AccountsObserver {
AccountsFetchListener listener;
public AccountsObserver(AccountsFetchListener listener) {
this.listener = listener;
}
public Observer<String> getObserver() {
return new Observer<String>() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onNext(String accounts) {
listener.onSuccess(accounts);
}
#Override
public void onError(Throwable e) {
listener.onFailure();
}
#Override
public void onComplete() {
}
};
}
public interface AccountsFetchListener {
void onSuccess(String accounts);
void onFailure();
}
}
Here is the function where I test these observables
private void testObs() {
ConnectableObservable<String> observable = AccountsObservable.getObject().getObservable();
Observer<String> observer = new AccountsObserver(new AccountsObserver.AccountsFetchListener() {
#Override
public void onSuccess(String accounts) {
Log.e("DATA -> ", accounts);
}
#Override
public void onFailure() {
}
}).getObserver();
observable.subscribe(observer);
observable.connect();
}
I called this function "testObs()" 5 times but it emitted data only 2 times. The problem seems to be in AccountsObservable class where I provide ReplaySUbject's instance. Thanks
Your code runs fine as it is, your logs are being suppressed in logcat as per this:
We declared an application as too chatty once it logs more than 5 lines a second. Please file a bug against the application's owner that is producing this developer-verbose-debug-level class logging spam. The logs are 256KB, that means the application is creating a DOS attack and shortening the logs timepan to 6 seconds(!) making it useless for all others.
You can avoid this behaviour by whitelisting your app for logcat:
adb logcat -P '<pid or uid of your app>'
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 have this method, i want return value when the transaction complete, but i cant. This's my code
public List<Group> getConversations() {
final RealmResults<Group> conversations;
try {
mRealm = Realm.getDefaultInstance();
mRealm.executeTransactionAsync(new Realm.Transaction() {
#Override
public void execute(Realm realm) {
RealmResults<Group> conversations = realm.where(Group.class).findAllSorted("time", Sort.DESCENDING);
cursorConversation(conversations);
}
}, new Realm.Transaction.OnSuccess() {
#Override
public void onSuccess() {
//return conversation
}
});
}
return null;
}
What should i do ?
I am not sure what are you doing in cursorConversation(..) but you can use the same method on returned values from Realm.
give a try
public List<Group> getConversations() {
try (Realm realm = Realm.getDefaultInstance()) {
return realm.copyFromRealm(realm.where(Group.class).findAllSorted("time", Sort.DESCENDING));
}
}
You don't need to run a transaction for getting the conversations. You can run your query on the realm db and add a change listener to the result. When the query completes, it'll call that change listener with the RealmResults<Converstaion>, Check this link for more.
Something like
public void listenToConversations(RealmChangeListener<RealmResults<Conversation>> listener) {
RealmResults<Conversations> conversations = realm.where(Group.class).sort("time", Sort.DESCENDING).findAllAsync();
conversations.addChangeListener(listener);
}
where listener is something like
listener = new RealmChangeListener<RealmResults<Conversations>>() {
\#Override
public void onChange(RealmResults<Conversations> conversations) {
// React to change
}
}
You'll also need to remove listener to avoid any memory leaks.
I already gone through these similar questions for the issue, but could not find the answer
SO question1 , SO question2 and SO question3
My application flow is on button click, network is requested as follows using Volley. Included only relevant code . Error getting in ActivityCustomer in the following line
Object obj = realmObj.where(ExplorerFolderData.class)
.equalTo(Constants.DBPARENTID,"0")
.or()
.equalTo(Constants.DBPARENTID,"-1")
.findAllAsync();
Error:
Caused by: java.lang.IllegalStateException: Realm access from
incorrect thread. Realm objects can only be accessed on the thread
they were created.
1) MyApplication
public class MyApplication extends Application
{
private static Context appContext;
#Override
public void onCreate() {
super.onCreate();
RealmConfiguration realmConfiguration = new RealmConfiguration.Builder(this)
.name(Realm.DEFAULT_REALM_NAME)
.schemaVersion(0)
.deleteRealmIfMigrationNeeded()
.build();
Realm.setDefaultConfiguration(realmConfiguration);
appContext = getApplicationContext();
}
public static Context getAppContext(){
return appContext;
}
}
2) Interface OnAsyncTaskComplition
//This interface will get back the status to Activity/Fragment
public interface OnAsyncTaskComplition {
public void networkResponse(ResultObject responseObject);
}
3) NetworkProcessor
public class NetworkProcessor{
private OnAsyncTaskComplition mCaller;
public NetworkProcessor(Activity activity){
//setting caller Activity/Fragment to get back data
mCaller=(OnAsyncTaskComplition)activity;
processNetworkData();
}
//Method for Volley Network Procesing
public void processNetworkData(){
JsonObjectRequest jsonObjReq = new JsonObjectRequest(methodReq,urlBuffer.toString(),null,
new Response.Listener<JSONObject>(){
#Override
public void onResponse(JSONObject response) {
JsonProcessor jsonProcessor=new JsonProcessor();
mCaller.networkResponse(jsonProcessor.getThingList(response));
}
}, new Response.ErrorListener(){
#Override
public void onErrorResponse(VolleyError error) {
//Handle error also back to caller
}
});
}
}
4) JsonProcessor
public class JsonProcessor {
public status void getThingList(JSONObject response){
boolean status=false;
try{
RealmProcessor realmProcessor=RealmProcessor.with(MyApplication.getAppContext());
Realm realmObj = realmProcessor.getRealm();
//Code for setting values to RealmObject class ExplorerFolderData
realmObj.beginTransaction();
realmObj.copyToRealm(ExplorerFolderData RealmObject which has values populated);
realmObj.commitTransaction();
status=true;
}catch(Exception e){
}
}
}
5) RealmProcessor
public class RealmProcessor {
private static RealmProcessor instance;
private Realm realm;
private RealmProcessor(Context context) {
realm = Realm.getDefaultInstance();
}
public static RealmProcessor with(Context context) {
if (instance == null) {
instance = new RealmProcessor(context);
}
return instance;
}
public Realm getRealm() {
return realm;
}
}
6) Activity class ActivityCustomer
public class ActivityCustomer extends AppBaseActivity implements OnAsyncTaskComplition
{
//Method called on Button click
private void callNetwork(){
new NetworkProcessor(this);
}
#Override
public void networkResponse(ResultObject responseObject) {
new ExplorerDBOperation().execute();
}
class ExplorerDBOperation extends AsyncTask<Void,Boolean,Boolean> {
ProgressDialog dialog;
#Override
protected Boolean doInBackground(Void... params) {
RealmProcessor realmProcessor=RealmProcessor.with(MyApplication.getAppContext());
Realm realmObj = realmProcessor.getRealm();
//ERROR OVER HERE
Object obj = realmObj.where(ExplorerFolderData.class)
.equalTo(Constants.DBPARENTID,"0")
.or()
.equalTo(Constants.DBPARENTID,"-1")
.findAllAsync();
return true;
}
}
I am getting realm object using the same line in Activity as well as JsonProcessor class. What is the mistake I am making over here.
The way you are set up with the singleton you have only 1 Realm instance.
If you call realmProcessor.getRealm(); in thread A, and then call it again in thread B, they get back the same instance. Realm does not allow sharing instances between threads. Since the AsyncTask's doInBackground runs on a separate thread, this is not working.
Changing to this will rid you of the error. However you have some redesigning to do.
#Override
protected Boolean doInBackground(Void... params) {
Realm realmObj = Realm.getDefaultInstance();
try {
Object obj = realmObj.where(ExplorerFolderData.class)
.equalTo(Constants.DBPARENTID,"0")
.or()
.equalTo(Constants.DBPARENTID,"-1")
.findAll();
} catch (Exception ex) {
// handle error
} finally {
realmObj.close();
}
return true;
}
Note that you are responsible for each and every realm instance. This means that you must manually ensure that you close every instance once you're done with it. A common practice for AsyncTasks is that you wrap your doInBackground operations in a try/catch/finally and close the realm instance in the finally block to ensure it gets closed.
See more in the docs
The problem is that your Realm object is created only once on first call to RealmProcessor.with (because it is singleton).Lets say that JsonProcessor::getThingList happen on Thread#1 and ExplorerDBOperation::doInBackground() happens on another Thread#2.
So if JsonProcessor::getThingList call will be prior to ExplorerDBOperation::doInBackground() then Realm object will be bound to Thread#1, and when you try to access it from Thread#2 you will get that error.