RecyclerView 不显示来自 Firestore 的数据

Question

recyclerView = findViewById(R.id.companyFeed_RecyclerView_CompanyList);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        ArrayList<Company> myCompanyData = new ArrayList<>();
        myCompanyData.add(new Company("Company marc","trustworthy",null));
        db.getFirestore().collection("companies").addSnapshotListener((value, error) -> {
            assert value !=null;
            for (QueryDocumentSnapshot snapshot : value) {
                Company c = Deserialization.deserializeCompany(snapshot);
                myCompanyData.add(new Company(c.getName(),c.getDescription(),null));
                System.out.println("company: " + myCompanyData.get(1).getName());
            }
        });
        CompanyAdapter myCompanyAdapter = new CompanyAdapter(myCompanyData, CompanyFeedActivity.this);
        recyclerView.setAdapter(myCompanyAdapter);

我的 RecyclerView 仅在 snapshotListener 之前显示元素“公司标记”。我的数据库工作得很好。 System.out.println 向我展示了具有正确名称的正确元素。

有没有更好的方法来访问元素还是我做错了什么？

这就是我的数据库的样子：

Firestore-root
  |
  --- companies (collection)
        |
        --- company 1 (document)
             |
             --- name: Marc
             |
             --- description: test
        |
        --- company 2 (document)
             |
             --- name: Lucas
             |
             --- description: test2

Answer 1

我认为问题是在创建和设置适配器后触发了侦听器。数据列表修改后需要显式调用myCompanyAdapter.notifyDataSetChanged。

请尝试以下代码

 recyclerView = findViewById(R.id.companyFeed_RecyclerView_CompanyList);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        ArrayList<Company> myCompanyData = new ArrayList<>();

        CompanyAdapter myCompanyAdapter = new CompanyAdapter(myCompanyData, CompanyFeedActivity.this);
        recyclerView.setAdapter(myCompanyAdapter);
        myCompanyData.add(new Company("Company marc","trustworthy",null));
        db.getFirestore().collection("companies").addSnapshotListener((value, error) -> {
            assert value !=null;
            for (QueryDocumentSnapshot snapshot : value) {
                Company c = Deserialization.deserializeCompany(snapshot);
                myCompanyData.add(new Company(c.getName(),c.getDescription(),null));
                System.out.println("company: " + myCompanyData.get(1).getName());
            }
            myCompanyAdapter.notifyDataSetChanged()
        });