We need a more reliable way to detect when to destroy activity's presenter.

Here is where the issue that started the discussion: https://github.com/konmik/nucleus/issues/42#issuecomment-204233175

TL/DR: activity's finish() can be called some time after onPause, so this code will leak the activity's presenter: https://github.com/konmik/nucleus/blob/master/nucleus/src/main/java/nucleus/view/NucleusActivity.java#L76

Possible solutions:

a) Leverage retained fragments. This will solve the presenter destruction issue but we will leak background tasks sometimes.

b) Extend PresenterLifecycleDelegate lifecycle to explicitly call onDestroy.

c) Install system-wide lifecycle listener registerActivityLifecycleCallbacks.

Hello Konstantin,

Do your long-term plans for the library include the adoption of RxJava v2? It had recently reached RC1, which means the API should be quite stable by now.

If yes, perhaps there's sense in creating another branch of nucleus containing preparations/adaptations for the new RxJava?

I might be able to help with some crude initial conversion if needed.

Is currently under testing.

I hope that it will be production-ready in the middle of August.

Want to join beta?

compile "info.android15.nucleus:nucleus:2.0.0-beta8"

Primary goals are:

• Make RxPresenter to be completely usable without getView() - 100% done!
• Replace OperatorSemaphore with standard RxJava operators. - 100% done!
• Simplify internal structure: remove manager and helper. - 100% done!
• Move all tests into unit tests to be testable without device. - 80%.

Update: a little note about the new rx.Single. rx.Single is awesome and I'm already playing with it. However, creation of additional methods for it will cause much more confusion than advantage (I already implemented this, but dropped the implementation because it just looks bulky, imagine stranger method names like deliverSingleCache, restartableSingleCache). The right way to handle rx.Single in Nucleus is to cast it to Observable.

Hey, thanks for the library.

Several times I caught the exception from here:

    /**
     * {@link android.app.Activity#onCreate(Bundle)}, {@link android.app.Fragment#onCreate(Bundle)}, {@link android.view.View#onRestoreInstanceState(Parcelable)}.
     */
    public void onRestoreInstanceState(Bundle presenterState) {
        if (presenter != null)
            throw new IllegalArgumentException("onRestoreInstanceState() should be called before onResume()");
        this.bundle = ParcelFn.unmarshall(ParcelFn.marshall(presenterState));
    }

The exception message seems too low-level for any library user. After some source code exploring, I found, that we can't call getPresenter() in any point before onResume(). Thus, for instance, method references like

private SomeView.ClickListener mViewClickListener = getPresenter()::viewClicked;

can crash the app, because getPresenter() is obviously called before onCreate.

Also I caught the crash several times in other callbacks, probably, in FragmentStatePagerAdapter (which can call onRestoreInstanceState before or even without onCreate, sorry, I don't remember a lot of details)

Is it reasonable to:

1. Replace throwing exception to some warning message, leaving developer's responsibility to save/restore state?
2. (more complex) to separate Presenter constructor and onCreate() methods, so that some time, before onCreate call, Presenter can exist without state restored?

If a fragments (PresenterLifecycleDelegates) onSaveInstanceState method gets called before the PresenterFactory is set, it will not save its presenter id in the result bundle.

I have a NucleusSupportFragment for which I set the PresenterFactory in onActivityCreated. When I detach that fragment (without destroying the presenter) and rotate the screen once, the presenter id will be saved in the bundle . After another rotate however the presenter id will not be saved anymore because getPresenter() will not restore the Presenter without a set Factory.

Hi,

I've recently updated my support library to version 26.0.1 which does not include the deprecated ActionBarActivity class. This causes an error while creating a release APK file saying that the NucleusActionBarActivity can't be compiled since it has unknown method references:

Warning:nucleus.view.NucleusActionBarActivity: can't find referenced method 'boolean isChangingConfigurations()' in program class nucleus.view.NucleusActionBarActivity

I've tried removing only this class with gradle's 'exclude', but with no success. So currently I'm adding the sources without the problematic class directly into my app sources...

I think this class should be removed from nucleus since it extends a class that has been removed from the android support library.

I'm attempting to use a NucleusLayout as the base class for my view. Because the view life cycle is not tied to the activity life cycle, Nucleus is creating a new Presenter each time addView() is used, but not destroying it when removeView() is used. Due to the way PresenterHelper and NucleusLayour are implemented I am unsure how to fix this issue without duplicating the classes in their entirety.

Hi there! I don't understand how to implement a case where a data should be delivered without caching (like PublishSubject or EventBus event). For example, I have a UserAddedEvent event. I need to handle it in my presenter only if there is a view attached (I can skip it otherwise).

add(userAdded()
    .compose(deliverLatestCache()) 
    .subscribe(split(View::addUser)));

This moves the logic of reflectively creating the presenter into a presenter factory, so that that functionality can be customized.

In my case, I'm using Dagger to inject dependencies, and using a presenter factory allows me to inject the dependencies through the presenter constructor, without having to use a pseudo-singleton injector class.

The superclasses include the default ReflectionPresenterFactory, so they have the same out of the box functionality, but by extracting that logic out of the PresenterHelper, the user is offered much more flexibility.

Note: I'm not sure how you're handling versioning, so I changed the dependencies in the support libraries and the examples to point to the snapshot version that I made and installed locally. I didn't include that in this PR since that's a change that shouldn't go into production.

This is simply a question, please label it as such.

I understand getView() is deprecated. The docs comments on the method mention the following:

/**
 * Please, use restartableXX and deliverXX methods for pushing data from RxPresenter into View.
 */

What if an Android Context is needed, in cases like parsing a local .json file from assets?

For example:

InputStream is = getView().getAssets().open("data.json");

What is the best practice for this particular case?

I'm a RxJava newbie. In my opinion, Retrofit, RxJava and this library is the best practice to implement a client-server communication in Android. Retrofit and RxJava makes easily to call and handle (asynchronous) HTTP requests, Nucleus makes safety to implement the callback in the life circle of Activity or Fragment. Data could come from either remote server or local data base. In remote server side, I have an awesome Retrofit library. In local data base, I could use SQLite Database and ContentProvider. I haven't found the best way to make an asynchronous query to ContentProvider that use RxJava and implement callback with Nucleus yet. Would you mind suggesting me?

I tried with extending AppCompactActivity it works. But with nucleusappcompactactivity crashes.

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dayanithi.supercamping/com.dayanithi.supercamping.activities.admin.AdminLoginClass}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2760) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2821) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1541) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:181) at android.app.ActivityThread.main(ActivityThread.java:6295) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:793) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference at android.content.ContextWrapper.getResources(ContextWrapper.java:86) at android.view.ContextThemeWrapper.getResourcesInternal(ContextThemeWrapper.java:127) at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:121) at android.support.v7.app.AppCompatActivity.getResources(AppCompatActivity.java:542) at android.view.Window.getDefaultFeatures(Window.java:1627) at android.view.Window.(Window.java:668) at com.android.internal.policy.PhoneWindow.(PhoneWindow.java:333) at com.android.internal.policy.PhoneWindow.(PhoneWindow.java:341) at android.app.Activity.attach(Activity.java:6797)

Is there a way to clear the delivery cache used by deliverReply etc - for example if the underlying data query has changed and we want to forget the history?

I'm either confused on the wording of the Javadocs, or restartable is not behaving how I would expect. I'm using restartableLatestCache, which from dissecting the Javadocs indicates that it will emit the last onNext value each time it is started, plus any new onNext values if they are emitted in the future. A restartable will re-subscribe after a "process restart". I'm unsure exactly what entails a process restart, but I assumed that meant when an activity is being recreated for whatever reason.

However, a simple pause/resume of the activity via backgrounding the app and bringing it back to the foreground triggers the restartable to fire off its cached value without a subsequent call to start. I didn't think that would qualify as a "process restart".

So if someone would be so kind, could you explain to me if this is working as intended, and if so, qualify what a "process restart" means so I know what behavior to expect in the future? How could I achieve a "latestCache"-like result, but only if the Activity has been re-created (destroy/create)?

Hi.

DeliverLatest completes automatically when the source observable is done.

In my case I have a Repository which emits data from Cache, DB and API. I can emit from Cache first, then from DB and API. It's a sequence of distinct items.

Why I'm not using deliveryLatestCache?

• to avoid keeping subscription to viewObservable
• to avoid getting the last cache from observable, cause it can be incorrect (old)

Why I'm not using deliveryFirst?

• it will emit only first item (from Cache)

Why I'm not using deliveryReplay?

• the item sequence in ReplaySubject might be outdated and I want just to get the new sequence from Repository (it's already got own cache)

Hello, first thanks for great looking library, I would like to ask if you still maintain this library? Because I plan start using nucleus, but at the same time I am little curious. Most of work you did was done last year and first months of this year. So that's why I have some doubts.

Thank you for your answer! Seidak

Hi!

I'm working on an app I want to use Nucleus for MVP+Rx.

I have some doubts, and I couldn't find any solution in the documentation/wiki. Could you please help me?:

1. How can I use two instances of the same view, and make each of them have their own instances of their presenters? Is it possible by telling the PresenterStorage with ID to use? Or by any other way?

2. Why is the presenter being destroyed and pointed to null in the onPause method instead of doing so in onDestroy? The documentation seems to be out of date. What if I want to stack several activities of the same type, and want them to keep their presenters while not destroyed by the system? Is that working because you pass isFinishing() to the delegate?

3. I think we need more documentation about the restartable* methods in RxPresenter. I know that it is documented in the code with Javadoc, but I think it would be great to add some explanation in the wiki. Something like the deliver* methods documentation (btw, some of them seem to be out of date since you released version 2.0.1).

Thank you very much. Your library is great. Cheers, M.