Can LiveData have multiple observers?

Can LiveData have multiple observers?

You can extend a LiveData object using the singleton pattern to wrap system services so that they can be shared in your app. The LiveData object connects to the system service once, and then any observer that needs the resource can just watch the LiveData object.

How do I fix serious problems in LiveData?

Solution

1. First, we need to create a class with the name Event to wrap the data that the livedata is exposing.
2. Now we need to create another class with name EventObserver that extends Observer .
3. While observing livedata , we need to use EventObserver instead of regular Observer so that handling is simplified.

What is SingleLiveEvent?

SingleLiveEvent is a subclass of MutableLiveData with a single Observer Observing it at a time, hence it is aware of view’s lifecycle.

How do I remove live data observer?

To remove a single observer, call removeObserver() on the LiveData . @MrVasilev: That might be an issue with Kotlin SAM support for lambdas or something. You may need to use object : Observer and create a “real” Observer instance, in order to get the correct this from inside that Observer ‘s onChanged() function.

Why LiveData Observer is being triggered twice?

As you are using getActivity() this retains your NoteViewModel while the scope of MainActivity is alive so is your trashedNotesLiveData. If your observer for a LiveData<*> is getting called multiple times then it means you are calling livedata. observe(…) multiple times.

Is LiveData deprecated?

LiveData is officially deprecated in kotlin-only apps.

How do you observe live data in Viewmodel?

Use Kotlin coroutines with Architecture components. You can use the liveData builder function to call a suspend function, serving the result as a LiveData object. You can also emit multiple values from the block. Each emit() call suspends the execution of the block until the LiveData value is set on the main thread.

What is the difference between LiveData and MutableLiveData?

By using LiveData we can only observe the data and cannot set the data. MutableLiveData is mutable and is a subclass of LiveData. In MutableLiveData we can observe and set the values using postValue() and setValue() methods (the former being thread-safe) so that we can dispatch values to any live or active observers.

What is MutableLiveData?

MutableLiveData. MutableLiveData is just a class that extends the LiveData type class. MutableLiveData is commonly used since it provides the postValue() , setValue() methods publicly, something that LiveData class doesn’t provide.

What is mediator live data android?

android.arch.lifecycle.MediatorLiveData LiveData subclass which may observe other LiveData objects and react on OnChanged events from them. This class correctly propagates its active/inactive states down to source LiveData objects.

How do I get rid of observer?

If you are using block based observers you must still manually remove the observers. The best general way to do this is to capture the tokens in an array, append them when you add the observer and use them for removal when you deinit/dealloc or otherwise need to remove observer behavior for your object.

How do I know if LiveData is empty?

1 Answer

1. Make sure you have an Observer for changes to the LiveData.
2. You need to call observeForever(Observer observer) unless you are using a LiveCyclerOwner then use that instead with: observe (LifecycleOwner owner, Observer observer)
3. Finally, there is an interesting note on getValue() :

Why is livedata observer being triggered twice for a newly created object?

Upon this LiveData object it calls LiveData::postValue (T value) which then calls LiveData::setValue (T value). LiveData::setValue (T value) calls LiveData::dispatchingValue (@Nullable ObserverWrapper initiator). This calls LiveData::considerNotify (ObserverWrapper observer) with the observer wrapper as parameter.

When does onchange get called multiple times in Android?

In Problem is when i back from new Fragment (BlankFragment) and click on button again and type “0” again and click, onchange () is called multiple times so Fragment is get created multiple times

What do you need to know about the observer in Minecraft?

An observer is a block that emits a redstone signal when the block or fluid it faces experiences a change. An observer requires a pickaxe to be mined. When mined without a pickaxe, it drops nothing. ↑ Times are for unenchanted tools as wielded by players with no status effects, measured in seconds.

Why does observer keep alive even if you kill your fragment?

So observer will keep alive even if you kill your fragment. So when livedata postvalue, it will send data to all the observers, as there are too many observers observing livedata, then all will get notified.