获取菜单按项并将其传递给回收站视图以设置变量

Question

我有一个导航抽屉设置不同的类别。我还有一个回收站视图，它从firestore获取帖子（已经按类别隔离）并加载并显示它们。我的问题是我想要它，所以当用户按下该菜单项时，它会在firestore中加载该类别的帖子并显示它们。我试图使用捆绑包但尚未弄清楚如何成功加载它

适配器：

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

        blog_list = new ArrayList<>();
        blog_list_view = view.findViewById(R.id.blog_list_view);

        // blogRecyclerAdapter = new BlogRecyclerAdapter(blog_list);
        blogRecyclerAdapter = new BlogRecyclerAdapter(getContext(),blog_list);
        blog_list_view.setLayoutManager(new LinearLayoutManager(getActivity()));
        blog_list_view.setAdapter(blogRecyclerAdapter);



        firebaseFirestore = FirebaseFirestore.getInstance();
        firebaseFirestore.collection("politics").addSnapshotListener(new EventListener<QuerySnapshot>() {
            @Override
            public void onEvent(@javax.annotation.Nullable QuerySnapshot queryDocumentSnapshots, @javax.annotation.Nullable FirebaseFirestoreException e) {

                for(DocumentChange doc: queryDocumentSnapshots.getDocumentChanges())
                    if (doc.getType() == DocumentChange.Type.ADDED) {

                        BlogPost blogPost = doc.getDocument().toObject(BlogPost.class);
                        blog_list.add(blogPost);

                        blogRecyclerAdapter.notifyDataSetChanged();
                    }

            }
        });

        return view;

    }

}

你可以在这里看到它说“政治”是我需要得到适当的菜单项加载的地方

导航抽屉：

    @Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
    switch (item.getItemId()) {
        case R.id.nav_home:
            getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                    new HomeFragment()).commit();
            break;
        case R.id.nav_profile:
            Intent profileIntent = new Intent(MainActivity.this, user_profile.class);
            startActivity(profileIntent);
            break;
        case R.id.nav_settings:
            getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                    new SettingsFragment()).commit();
            break;
        case R.id.nav_sign_out:
            Toast.makeText(this, "SIGNED OUT TEST", Toast.LENGTH_SHORT).show();
            FirebaseAuth.getInstance().signOut();
            sendToStart();
            break;
        case R.id.nav_new_post:
            Intent postIntent = new Intent(MainActivity.this, NewPost.class);
            startActivity(postIntent);
            break;
        case R.id.nav_politics:
            getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                    new CategoriesFragment()).commit();
            break;

适配器工作正常我只是无法弄清楚如何将数据传递给适配器以根据选择的菜单项加载指定类别

Answer 1

首先，在你的onNavigationItemSelected里面，通过一个包将信息添加到你的CategoriesFragment：

case R.id.nav_politics:
    CategoriesFragment fragment = new CategoriesFragment();
    Bundle args = new Bundle();
    args.putString("collection", "politics");
    fragment.setArguments(args);
    getSupportFragmentManager()
       .beginTransaction()
       .replace(R.id.fragment_container, fragment)
       .commit();
    break;

接下来，在你的片段里面的onCreate或onStart（不确定onCreateView）从包中获取字符串：

Bundle bundle = this.getArguments();
if (bundle != null) {
    String collection = bundle.getString("collection", "");
}

然后，您可以将其用于Firestore集合。

未来的改进是将politics提取为静态变量。另一个（如果为collection传递不同的值）将创建一个辅助函数，您只需传递collection值，以便多个导航项可以使用它而无需代码重复。