如何在Android中从MutableLiveData中获取所有结果？

Question

我在我的应用程序中使用LiveData，我有一个Model和一个ViewModel。这是我的Model和ViewModel类。

public class HomeMenuModel {

  String id;
  String title;

  public String getId() {
    return id;
  }

  public void setId(String id) {
    this.id = id;
  }

  public String getTitle() {
    return title;
  }

  public void setTitle(String title) {
    this.title = title;
  }

}

public class DashboardViewModel {

  public MutableLiveData < HomeMenuModel > menuList = new MutableLiveData < > ();
  private List<String> idList = new ArrayList<>();
  private List<String> idLists = new ArrayList<>();
  private List<String> titleList = new ArrayList<>();

  public MutableLiveData < HomeMenuModel > setupMenu(Context mCtx) {

    idList.add("homeData");
    idList.add("homeVoiceAndSMS");
    idList.add("homeRoaming");
    idList.add("homeDigital");

    titleList.add(mCtx.getString(R.string.homeData));
    titleList.add(mCtx.getString(R.string.homeVoiceAndSMS));
    titleList.add(mCtx.getString(R.string.homeRoaming));
    titleList.add(mCtx.getString(R.string.homeDigital));

    HomeMenuModel homeMenuModel = new HomeMenuModel();
    for (int i = 0; i < idList.size(); i++) {
      homeMenuModel.setId(idList.get(i));
      homeMenuModel.setTitle(titleList.get(i));
    }

    menuList.setValue(homeMenuModel);
    return menuList;

  }

}

我试着在setupMenu中添加idList和titleList，并从函数中返回menuList。我在我的Fragment中调用了setupMenu函数，代码如下。

public class HomeFragment extends BaseFragment {

  static final String TAG = "FragmentHome";
  private FragmentHomeBinding mBinding;
  @Inject
  DashboardViewModel dashboardViewModel;
  private Context mCtx;

  @Override
  public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    setHasOptionsMenu(true);
  }

  @Override
  public void onAttach(Context context) {
    super.onAttach(context);
    AndroidSupportInjection.inject(this);
  }

  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
    mBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_home, container, false);
    View v = mBinding.getRoot();
    mCtx = mBinding.getRoot().getContext();
    initEvent();
    return v;
  }

  private void initEvent() {
    mBinding.setDashboardView(dashboardViewModel);
    dashboardViewModel.setupMenu(mCtx).observe(this, data - > {
      Log.e("menuList", data.getTitle());
    });
  }

  @Override
  public String getTagFragment() {
    return TAG;
  }

}

我在一个HomeFragment中记录了menuList，但不幸的是，我只得到了观察到的id或title的最后一项。

我错过了什么？

为什么我只得到最后一项结果，而不是在setupMenu函数中创建的4个结果？我怎样才能得到所有4个结果？

任何帮助都将是非常感激的。

谢谢你的帮助。

Answer 1

你只更新最后的信息 homeMenuModel.要获得所有的项目，你应该创建 MutableLiveData<ArrayList<HomeMenuModel>>. 试试这个

    private MutableLiveData<ArrayList<HomeMenuModel>> menuList = new MutableLiveData<ArrayList<HomeMenuModel>>()

    ArrayList<HomeMenuModel> list = new ArrayList<HomeMenuModel>()
    for (int i = 0; i < idList.size(); i++) {
      HomeMenuModel homeMenuModel = new HomeMenuModel();
      homeMenuModel.setId(idList.get(i));
      homeMenuModel.setTitle(titleList.get(i));
      list.add(homeMenuModel)
    }
    menuList.setValue(list);