[英]Why onChange() called twice when fragment recreated
我正在嘗試使用新的android體系結構組件,但是一時我很困惑。
我創建了一個ViewModel類
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中觀察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,當我用另一個片段替換該片段並切換回該片段時,方法onChange
被調用了兩次,並在rvAdapter
添加了相同數據的兩部分。
我解決了這個!!! 當我創建ViewModel類時,我將“ this” 1st參數傳遞給方法
buyViewModel = ViewModelProviders.of(**this**, viewModelFactory).get(BuyViewModel.class);
但是我需要傳遞“ getActivity()”,代碼看起來像這樣
buyViewModel = ViewModelProviders.of(**getActivity()**,viewModelFactory).get(BuyViewModel.class);
當您在片段內部傳遞“ this”時-它采用片段的實例。 更改配置后,片段的onDestroy()將不會調用(應取消訂閱),而只會調用onDestroyView()。 因此,當您傳遞活動實例時,該實例將不再存在,因為調用了活動的onDestroy()。
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