android - RecyclerView 在没有 fragment 的情况下工作。当我使用 fragment 时不起作用

Question

我开始学习 Android 并且在使用 fragment 时遇到了一些困难。你能帮我弄清楚问题是什么吗？除了下面提到的内容之外，其他所有内容在两个项目中都是相同的

1. Code without fragments (works totally fine. Gives a simple list with some data):



    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerList);
    LinearLayoutManager llm = new LinearLayoutManager(this);
    llm.setOrientation(LinearLayoutManager.VERTICAL);
    recyclerView.setLayoutManager(llm);
    recyclerView.setAdapter(new MyRecyclerAdapter(generatePalettes()));
}



2. Code with Fragment (doesnt work. Blank Screen):



    MainActivity
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            if (savedInstanceState == null) {
                getSupportFragmentManager().beginTransaction()
                        .add(R.id.container, new MainActivityFragment()).commit();
            }
        }



    MainActivityFragment    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            RecyclerView recyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerList);
            LinearLayoutManager llm = new LinearLayoutManager(getActivity());
            llm.setOrientation(LinearLayoutManager.VERTICAL);
            recyclerView.setLayoutManager(llm);
            recyclerView.setAdapter(new PaletteAdapter(generatePalettes()));
            return rootView;
        }

--------------------------------更新------------ --

代码更改为以下内容:仍然不起作用。显示空白屏幕。尝试将 UI 更新放在 onActivityCreated 和 onViewCreated() 中。代码要点在这里:https://gist.github.com/adityarb88/12f5ccce665afbf58069

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.recyclerList);
        LinearLayoutManager llm = new LinearLayoutManager(getActivity());
        llm.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(llm);
        recyclerView.setAdapter(new PaletteAdapter(generatePalettes()));
    }

Answer 1

在构建 View 后，对于 Fragments 设置适配器:

主要 Activity fragment

此方法应该只膨胀并返回您的 View :

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
    }

然后在onViewCreated(View, Bundle)或onActivityCreated(Bundle)中:

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

      // getView() returns your Fragments root view
      RecyclerView recyclerView = (RecyclerView) getView().findViewById(R.id.recyclerList);
        LinearLayoutManager llm = new LinearLayoutManager(getActivity());
        llm.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(llm);
        recyclerView.setAdapter(new PaletteAdapter(generatePalettes()));

   }