在 ViewModel 中加载已在 SplashActvity 中检索到的数据

Question

我是 ViewModel 的新手，我知道它是一种与片段通信的强大而简单的方式。

我的问题如下： 如何加载在 mainActivity 的 ViewModel 中的 SplashActivity 中检索到的数据？

我的应用程序架构如下：

1. SplashActivity：通过改造检索数据并将其存储到列表中
2. 主要活动：包含两个以不同方式显示数据的片段

这是一段代码，显示了我的实现。

飞溅活动

public class SplashActivity extends AppCompatActivity {

    private final String TAG = "TAG.SplashActivity";
    public static List<Toilet> toiletList = new ArrayList<>(); // HERE IS THE DATA I WANT TO 
    RETRIEVE IN THE MAIN ACTIVITY

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        /*Create handle for the RetrofitInstance interface*/
        GetDataService service = ...;
        // MY STUFF RETROFIT including
        Intent intent = new Intent(getApplicationContext(), MainActivity.class);
        intent.putExtra("toiletList", (Serializable) toiletList);
        startActivity(intent);
        finish();
    }
}

主要活动

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

    private final String TAG = getClass().getName();
    private List<Toilet> toiletList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Intent intent= getIntent();
        Serializable s = intent.getSerializableExtra("toiletList");
        // Check type and cast
        if (s instanceof List<?>) {
            for (Object o : (List<?>) s) {
                if (o instanceof Toilet) {
                    toiletList.add((Toilet) o);
                }
            }
        }

        // SETTING UP FRAGMENTS
    }
}

片段示例

public class MainFragment extends Fragment {

    public static List<Toilet> toiletArrayList = new ArrayList<>();
    private final String TAG = this.getClass().getName();

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_main, container, false);

       // SETTING UP UI
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        ToiletListViewModel model = ViewModelProviders.of(this).get(ToiletListViewModel.class);
        model.getToiletList().observe(this, new Observer<List<Toilet>>() {
            @Override
            public void onChanged(@Nullable List<Toilet> toilets) {
                //  update UI
            }
        });
    }
}

厕所列表视图模型

public class ToiletListViewModel extends ViewModel {

    private final String TAG = getClass().getName();
    private MutableLiveData<List<Toilet>> toiletList;

    public LiveData<List<Toilet>> getToiletList() {
        if (toiletList == null) {
            toiletList = new MutableLiveData<>();
            loadToilets();
        }
        return toiletList;
    }

    private void loadToilets() {
        // asynchronously fetch toilets
        // HERE IS MY PROBLEM : How to access the toiletList retrieved
        in the SplashActivity ?
        toiletList.setValue(SplashActivity.toiletList);
    }

    @Override
    protected void onCleared() {
        super.onCleared();
        Log.d(TAG, "onCleared() called");
    }
}

我希望这很清楚。如果您想了解更多信息，请随时询问！

最好的事物

Answer 1

您可以在 the和 its之间共享您的。ToiletListViewModelMainActivityFragment

所以你需要的是提供你ViewModel的MainActivity范围（这意味着你将你的生命周期绑定ViewModel到你的活动）并调用initToilets然后子片段可以轻松地检索它ViewModel并观察它的LiveData.

厕所列表视图模型：

public class ToiletListViewModel extends ViewModel {

    private MutableLiveData<List<Toilet>> toiletList = new MutableLiveData();

    public LiveData<List<Toilet>> getToiletList() {
        return toiletList;
    }

    private void initToilets(List<Toilet> toilets) {
        toiletList.setValue(toilets);
    }


}

主要活动：

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

    private final String TAG = getClass().getName();
    private List<Toilet> toiletList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Intent intent= getIntent();
        Serializable s = intent.getSerializableExtra("toiletList");
        // Check type and cast
        if (s instanceof List<?>) {
            for (Object o : (List<?>) s) {
                if (o instanceof Toilet) {
                    toiletList.add((Toilet) o);
                }
            }
        }
     ToiletListViewModel vm = ViewModelProviders.of(this).get(ToiletListViewModel.class);
     vm.initToilets(toiletList);
        // SETTING UP FRAGMENTS
    }
}

因此，当setValue被调用时，toiletList会通知监听实时数据的Fragment 。

笔记：

您可以在ViewModel不提供的情况下创建共享MainActivity，而不是调用

ViewModelProviders.of(this).get(ToiletListViewModel.class);

在你的片段中做

ViewModelProviders.of(getActivity()).get(ToiletListViewModel.class);