如何从Observable更新数据，而不必重新订阅/添加可处理对象，而我可以在可以加载数据的情况下延迟layout.xml的渲染？

Question

My ViewModel is returning nullfields for current User how to fix ?

Say I had the following Disposable. getUserProfile calls a Retrofit 2 API that returns Observable<Response<GetUserProfileResponseBody> when the Activity is started in onStart . Is this a one-time call to the Retrofit 2 API? Say the user profile has a bunch of posts and user details which is retrievable in the Response<GetUserProfileResponseBody> . I want the user profile to automatically update when stuff changes or gets added, and if it doesn't, I would just swipe down and call onRefresh . For example, say in onStart I call the following code:

public void load(String userId) {
GetUserProfileRequest request = new GetUserProfileRequest(userId);
    Disposable disposable = mViewModel
            .getUserProfile(request)
            .subscribe((Response<GetUserProfileResponseBody> response) -> {
                if (response.body() != null) {
                    mViewModel.setCurrentUser(response.body().getCurrentUser());
                }
            }, (Throwable ex) -> {
            });
    mCompositeDisposable.addDisposable(disposable);
}

and then I go ahead and edit my profile (in the same activity so mCompositeDisposable.clear() is not called). Afterwards, I expect the changes to reflect immediately in the user profile. Do I have to call load(userId ) one more time, which in turns adds another disposable to composite disposable, or will Observable automatically detect the changes from the Retrofit 2 API to update the UI? I want the Observable that I'm subscribing to to get updated so I don't have to resubscribe.

Similarly, everytime I swipe refresh, I don't want to call all of load which add another disposable either, I just want the thing I'm subscribing to to call the Retrofit 2 API again so I can have updated data in the SAME disposable.

Update

In subscribe I'm setting current user in viewmodel. At the same time, in a Fragment of this activity, I am accessing the viewmodel field in the layout.xml, but that field is null, because mViewModel.setCurrentUser has not yet been called when the layout.xml is rendered.

    <variable
        name="viewModel"
        type="com.skoolar.viewmodels.GetUserProfileViewModel" />

                <ImageView
                android:id="@+id/image_user_avatar"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:adjustViewBounds="true"
                android:scaleType="fitCenter"

How do I delay the rendering of the layout.xml until mViewModel.currentUser is rednerred?

Answer 1

You can use background polling to automatically refresh the user posts on the profile every X seconds. Lets say you have a postService to retrieve user wall feed.

Observable.interval(30, TimeUnit.SECONDS, Schedulers.io())
      .map(tick -> postService.getRecentPost())
      .subscribe(posts -> {
        // the subscriber is called with List<Message> every time
        // the remote service is polled
        for (Post post : posts) {
          log.info(post.toString())
        }
      })