为什么片段重新创建时onChange（）调用了两次

Question

我正在尝试使用新的android体系结构组件，但是一时我很困惑。

我创建了一个ViewModel类

public class BuyViewModel extends ViewModel {

private BuyRepository buyRepository;
private LiveData<Adverts> advertsLiveData;
private boolean isLoading;
private int currentPage;

@Inject
public BuyViewModel(BuyRepository buyRepository) {
    this.buyRepository = buyRepository;
}

public void init(int currentPage) {
    this.currentPage = currentPage;
    if (this.advertsLiveData != null) {
        return;
    }
    Timber.tag("logi").d("BuyViewModel > init -> ");
    advertsLiveData = buyRepository.getAdverts(currentPage);
}

public LiveData<Adverts> getAdvertsLiveData() {
    return advertsLiveData;
}
}

在我的LifeCycleFragment中观察LiveData

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    buyViewModel = ViewModelProviders.of(this, viewModelFactory).get(BuyViewModel.class);
    buyViewModel.init(1);
    buyViewModel.getAdvertsLiveData().observe(this, adverts -> {
        Timber.tag("logi").d("BuyFragment > onActivityCreated -> ");
        assert adverts != null;
        adapter.addMoreAdverts(adverts.getResults());
    });

    setupViews();
}

但是，当我用另一个片段替换该片段并切换回该片段时，该方法onChange被调用了两次，并在中添加了相同数据的两部分rvAdapter。

Answer 1

我解决了这个！！！当我创建ViewModel类时，我将“ this” 1st参数传递给方法

buyViewModel = ViewModelProviders.of(**this**, viewModelFactory).get(BuyViewModel.class);

但是我需要传递“ getActivity（）”，代码看起来像这样

buyViewModel = ViewModelProviders.of(**getActivity()**,viewModelFactory).get(BuyViewModel.class);