视图模型一直在创建实时数据的实例

ViewModel onClick() 方法。

你应该在家里做 onCreate() Activity 或在 onViewCreated 你的碎片的方法。如果你愿意的话,就没必要了 removeObserver Lifecycle 机械装置会帮你盖好的。

yourViewModel.yourList.removeObservers(this)

经过 this 意味着通过你的 活动 ,或者还有第二种方法:

yourViewModel.yourList.removeObserver(observer)

val observer = object : Observer<YourObject> {
    override fun onChanged(t: YourObject?) {
        //todo
    }
}

• Viewmodel的目的是公开可观察对象(Livedata)
• 视图(活动/片段)的目的是获取这些可观察的对象并观察它们
• 每当这些可观察对象(Livedata)发生更改时,更改就会自动发布到活动订阅所有者(Activity/Fragment),因此不需要在onPause/onStop中删除它们,因为这不是必需的

视图模型

public class TicketViewModel extends AndroidViewModel implements IServiceResponse {

    MutableLiveData<String> mObservableResponse = new MutableLiveData<String>();

   public LiveData<String> getResponseLiveData(){
        return mObservableResponse;
        }

    public void AddTicket(String id){

        JsonObject jsonObject= new JsonObject();
        jsonObject.addProperty("id",  id);

        NetworkUtility networkUtility= new NetworkUtility(this, ADD_TICKET);
        networkUtility.hitService(URL, jsonObject, RequestMethods.POST);

    }


     @Override
        public void onServiceResponse(String response, String callType){

        if(serviceTag.equalsIgnoreCase(ADD_TICKET)){    
             mObservableResponse.setValue("success");
        }
    }

}

    onCreate(){
    ticketViewModel = ViewModelProviders.of(this).get(TicketViewModel.class);
    observeForResponse();
    }

    private void observeForResponse(){
       ticketViewModel.getResponseLiveData().observe(this, response ->{
                            //do what has to be updated in UI
    }
    }

public void addTicket(View view){
     ticketViewModel.AddTicket(id);
    }

希望这有帮助:)

observe 有一次,我更喜欢在家里做 onResume removeObserver 在里面 onPause

将给定的观察者添加到观察者列表

我拿了一个现有的代码样本 Fragment 并重命名了所有内容(我希望),这里没有将数据设置到 ViewModel ticketViewModel.AddTicket(id);

public class ListFragment extends Fragment {

    private MyViewModel viewModel;
    private MyRecyclerViewAdapter recyclerViewAdapter;
    private Observer<List<DatabaseObject>> dataObserver;
    private RecyclerView recyclerView;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_layout, container, false);
        initRecyclerView(rootView, getContext());
        initObservers();

        return rootView;
    }

    private void initRecyclerView(View rootView, Context context) {
        recyclerViewAdapter = new MyRecyclerViewAdapter(context);
        recyclerView = rootView.findViewById(R.id.recycler_view);
        recyclerView.setAdapter(recyclerViewAdapter);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(context);
        recyclerView.setLayoutManager(linearLayoutManager);
        recyclerView.addItemDecoration(new DividerNoLastItemDecoration());
    }

    private void initObservers() {
        dataObserver = new Observer<List<DatabaseObject>>() {
            @Override
            public void onChanged(@Nullable final List<DatabaseObject> data) {
                recyclerViewAdapter.setData(data);
            }
        };
    }

    @Override
    public void onResume() {
        super.onResume();
        initViewModel();
    }

    private void initViewModel() {
        FragmentActivity activity = getActivity();
        if (activity != null) {
            viewModel = ViewModelProviders.of(activity).get(MyViewModel.class);
            viewModel.getData().observe(activity, dataObserver);
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        if (viewModel != null) {
            viewModel.getData().removeObserver(dataObserver);
            viewModel = null;
        }
    }

}

我也有类似的问题。你可以试着用 SingleLiveEvent

或者,在我更复杂的情况下,我不得不使用自定义观察者。它看起来是这样的:

public class CustomObserver implements Observer<YourType> {
    private MyViewModel mViewModel;

    public CustomObserver (){}

    public void setViewModel(MyViewModel model) {
        mViewModel = model;
    }

    @Override
    public void onChanged(@Nullable YourType object) {
        mViewModel.AddTicket(id).removeObserver(this); // removing previous 
        mmViewModel.refreshTickets(); // refreshing Data/UI
        // ... do the job here
        // in your case it`s: dismissLoadingAnimation();
    } 
}

使用它就像:

public void addTicket(View view){

     ticketViewModel.AddTicket(id).observe(this, myCustomObserver);
}

LiveData用于包含视图的属性值

在ViewModel中

public class TicketViewModel extends AndroidViewModel implements IServiceResponse {

    private MutableLiveData<Boolean> showLoadingAnimationLiveData = new MutableLiveData<String>();

    public LiveData<Boolean> getShowLoadingAnimationLiveData(){
        return showLoadingAnimationLiveData;
    }

    public void addTicket(String id){

        JsonObject jsonObject= new JsonObject();
        jsonObject.addProperty("id",  id);

        NetworkUtility networkUtility= new NetworkUtility(this, ADD_TICKET);
        networkUtility.hitService(URL, jsonObject, RequestMethods.POST);
        showLoadingAnimationLiveData.setValue(true);
    }


    @Override
    public void onServiceResponse(String response, String callType){
        if(serviceTag.equalsIgnoreCase(ADD_TICKET)){    
            showLoadingAnimationLiveData.setValue(false);
        }
    }

}

在活动/片段的“onCreate”中

ticketViewModel.getShowLoadingAnimationLiveData().observe(this,showLoadingAnimation->{
    if(showLoadingAnimation != null && showLoadingAnimation){
        startLoadingAnimation();
    }else{
        dismissLoadingAnimation();
    }
})

主要概念是划分责任, 活动/片段不需要知道哪个进程正在进行,它们只需要知道这些子视图的当前属性/状态。

活动/片段对流程的唯一责任是触发它并忘记它,ViewModel需要处理所有事情(比如通知存储库执行工作和更改视图属性)。

就你而言, 关于这个过程的活动/片段的唯一责任就是触发它。