如何从使用视图寻呼机创建的选项卡片段转移到另一个片段

Question

我使用视图寻呼机创建了三个带有三个片段的选项卡。单击类别片段中定义的列表项（使用视图寻呼机创建的选项卡片段）后，我想跳转到鼓舞人心的片段。当我单击列表项时发生错误。我想要从类别片段（在视图寻呼机中定义的片段）跳转到鼓舞人心的片段。 类别（使用视图分页器创建的选项卡片段）

 public class Categories extends Fragment {

    private RecyclerView recyclerView;
    private List<CategoriesDataModel> list;
    private String[] categories={"Inspiring","Feelings","Strength","Hard Work","Success"};

    public Categories() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

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

        recyclerView = (RecyclerView) view.findViewById(R.id.categoriesList_Id);

        list = new ArrayList<>();

        for (int i = 0; i < categories.length; i++) {
            CategoriesDataModel dataModel = new CategoriesDataModel();

            dataModel.cat_name = categories[i];

            list.add(dataModel);
        }

        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        recyclerView.setHasFixedSize(true);
        CategoryRecyclerViewAdapter adapter = new CategoryRecyclerViewAdapter(list,getContext());
        adapter.setOnItemClickListener(new CategoryRecyclerViewAdapter.ClickListener() {
            @Override
            public void onItemClick(int position, View v) {
                switch (position){
                    case 0:
                        getFragmentManager().beginTransaction().replace(R.id.frameLayout_inspiring,new Inspiring()).addToBackStack(null).commit();

                }
            }
        });
        recyclerView.setAdapter(adapter);
        return view;
    }
}

鼓舞人心：-

public class Inspiring extends Fragment {


    public Inspiring() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        return inflater.inflate(R.layout.fragment_inspiring, container, false);
    }
}

寻呼机适配器：-

public class Pager extends FragmentStatePagerAdapter {
    int tabCount=0;

    public Pager(FragmentManager fm,int tabCount) {
        super(fm);
        this.tabCount=tabCount;
    }


    //this will return tab selected
    @Override
    public Fragment getItem(int i) {
        switch(i) {
            case 0:
                return new Recents();

            case 1:
                return new Top();

            case 2:
                return new Categories();

            default:
                return null;
        }
    }

    @Override
    public int getCount() {
        return tabCount;
    }
}

Answer 1

您可能会发现在这种情况下使用 AndroidViewModel。

您正在做的是尝试维护应用不同部分之间的状态。

如果您有一个AndroidViewModel 附加到 Activity 生命周期，您可以在您的 Activity 中观察该状态并向FragmentManager 进行交易以代表您的选择。

一个例子

视图模型

此 ViewModel 包含您所在导航项的状态数据（在本例中用整数表示 Fragment）并使用整数表示灵感行的索引。

public class NavigationViewModel extends AndroidViewModel {
    private MutableLiveData<Integer> navigationLiveData = new MutableLiveData<>();
    private MutableLiveData<Integer> inspirationLiveData = new MutableLiveData<>();

    public NavigationViewModel(@NonNull Application application) {
        super(application);
    }

    public LiveData<Integer> getNavigation() {
        return navigationLiveData;
    }

    public void setNavigation(Integer id) {
        navigationLiveData.postValue(id);
    }

    public LiveData<Integer> getInspiration() {
        return inspirationLiveData;
    }

    public void setInspiration(Integer id) {
        inspirationLiveData.postValue(id);
    }
}

活动

Activity 将观察LiveData 由我们的AndroidViewModel 实现提供的导航。这将在进行导航更改时立即通知它。

public class NavigationActivity extends AppCompatActivity {

    private NavigationViewModel navigationViewModel;

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

        navigationViewModel = ViewModelProviders.of(this).get(NavigationViewModel.class);

        navigationViewModel.getNavigation().observe(this, id -> {
            switch(id) {
                case R.id.recents:
                    // TODO: Load recent fragment here with a transaction
                    break;
                case R.id.top:
                    // TODO: Load top fragment here with a transaction
                    break;
                case R.id.categories:
                    // TODO: Load categories fragment here with a transaction
                    break;
                case R.id.inspiring:
                    // TODO: Load inspiring fragment here with a transaction
                    break;
            }
        });
    }
}

灵感片段

这个Fragment 将观察我们实现AndroidViewModel 提供的灵感索引。这让它知道需要显示哪些内容。这可以从 ANYWHERE 进行设置。

public class InspiringFragment extends Fragment {

    private NavigationViewModel navigationViewModel;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_inspiring, container, false);

        navigationViewModel = ViewModelProviders.of(this).get(NavigationViewModel.class);

        navigationViewModel.getInspiration().observe(getViewLifecycleOwner(), inspiration -> {
            // TODO: Update the root view UI with data gleaned using the inspiration index given here
        });

        return root;
    }
}

设置

一旦你有了，你需要做的就是打电话：

navigationViewModel.setInspiration(1);
navigationViewModel.setNavigation(R.id.inspiration);

这应该会给你一个很好的开始。