Question

我是android studio的新手，我试图在中间创建一个带有菜单选项卡的选项卡式应用程序，

我在我的片段中使用RecyclerView，如tutorial

中所述

我已按照应有的方式完成所有工作，但是在＆＃34;将适配器绑定到RecyclerView＆＃34;第一步我遇到了问题，

findViewById(R.id.my_recycler_id);返回null

以下是代码：

主要活动

public class MainActivity extends AppCompatActivity {


private SectionsPagerAdapter mSectionsPagerAdapter;

private ViewPager mViewPager;
ArrayList<DummyItem> dummies;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(mViewPager);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    RecyclerView rvDummies =(RecyclerView) findViewById(R.id.listdummies);
    // Initialize contacts
    dummies = DummyItem.createDummiesList(20);
    // Create adapter passing in the sample user data
    MyItemRecyclerViewAdapter adapter = new MyItemRecyclerViewAdapter(dummies, this);
    //Log.d("D",fragment.toString());
    // Attach the adapter to the recyclerview to populate items
    rvDummies.setAdapter(adapter);
    // That's all!
}

... (some other code)

}

我的经历

public class ItemFragment extends Fragment {

// TODO: Customize parameter argument names
private static final String ARG_COLUMN_COUNT = "column-count";
// TODO: Customize parameters
private int mColumnCount = 1;
private OnListFragmentInteractionListener mListener;
RecyclerView fragmentchildRecyclerView;

/**
 * Mandatory empty constructor for the fragment manager to instantiate the
 * fragment (e.g. upon screen orientation changes).
 */
public ItemFragment() {
}

// TODO: Customize parameter initialization
@SuppressWarnings("unused")
public static ItemFragment newInstance(int columnCount) {
    ItemFragment fragment = new ItemFragment();
    Bundle args = new Bundle();
    args.putInt(ARG_COLUMN_COUNT, columnCount);
    fragment.setArguments(args);
    return fragment;
}

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

    if (getArguments() != null) {
        mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT);
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_item_list, container, false);
    fragmentchildRecyclerView = (RecyclerView) view.findViewById(R.id.listdummies);
    // Set the adapter
    if (view instanceof RecyclerView) {
        Context context = view.getContext();
        RecyclerView recyclerView = (RecyclerView) view;
        recyclerView.setLayoutManager(new LinearLayoutManager(context));
        recyclerView.setAdapter(new MyItemRecyclerViewAdapter(DummyContent.ITEMS, context));
    }
    return view;
}

public RecyclerView getRecyclerView(){
    return fragmentchildRecyclerView;
}
@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof OnListFragmentInteractionListener) {
        mListener = (OnListFragmentInteractionListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnListFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

/**
 * This interface must be implemented by activities that contain this
 * fragment to allow an interaction in this fragment to be communicated
 * to the activity and potentially other fragments contained in that
 * activity.
 * <p/>
 * See the Android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnListFragmentInteractionListener {
    // TODO: Update argument type and name
    void onListFragmentInteraction(DummyItem item);
}
}

虚拟物品

public static class DummyItem {
    public final String id;
    public final String content;
    public final String details;

    public DummyItem(String id, String content, String details) {
        this.id = id;
        this.content = content;
        this.details = details;
    }

    @Override
    public String toString() {
        return content;
    }
    public static ArrayList<DummyItem> createDummiesList(int numDummies){
        ArrayList<DummyItem> dummies = new ArrayList<DummyItem>();
        for (int i = 1; i <= numDummies; i++) {
            dummies.add(new DummyItem("id "+numDummies,"title "+numDummies,"description "+numDummies));
        }
        return dummies;

    }
}

我搜索了很多，我发现它可能在创建之前调用findViewByID，而其他人则说该片段应该有一个函数返回{{1}所以我可以访问它......

任何建议都会有所帮助。

Answer 1

当组件位于片段中时，您无法引用活动中的组件。相反，添加您的

RecyclerView rvDummies = (RecyclerView) view.findViewById(R.id.listdummies);

在Fragment的OnCreateView方法中

并在那里设置适配器。这里视图对象将是Fragment可能膨胀的布局。

这样做的理由：由于片段将具有单独的布局，因此必须在片段中引用其中包含的组件作为片段膨胀的视图（布局）的子元素。

在Tabbed应用程序的片段中填充recyclerView

1 个答案: