RecyclerView：未连接适配器；跳过布局-主要缺少什么？

Question

在得分中输入-1之前，我告诉你我已阅读所有内容，我在此站点甚至在其他站点中都重复了有关此问题的所有答案，因此，如果可以的话，请帮忙。 / em>

大家好，我的应用程序遇到了这个问题，我在此浪费了太多时间。

我的应用程序由4个片段组成，并且recyclerview的这两个片段（在fragment_fibra和fragment_adsl中）存在问题。

main.java

public class main extends AppCompatActivity implements 
OnFragmentInteractionListener //I HAVE a problem with 
OnFragmentInteractionListener {

private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_homepage);
    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
    mViewPager = findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);
    TabLayout tabLayout = findViewById(R.id.tabs);
    // tabLayout.setupWithViewPager(mViewPager); //aggiunta dopo
    mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));

}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_homepage, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
public static class PlaceholderFragment extends Fragment {
    private static final String ARG_SECTION_NUMBER = "section_number";
    public PlaceholderFragment() {
    }
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = null;
        switch(getArguments().getInt(ARG_SECTION_NUMBER))
        {
            case 1:
                rootView = inflater.inflate(R.layout.fragment_homepage, container, false);
                break;
            case 2:
                rootView = inflater.inflate(R.layout.fragment_fibra, container, false);
                break;
            case 3:
                rootView = inflater.inflate(R.layout.fragment_adsl, container, false);
                break;
            case 4:
                rootView = inflater.inflate(R.layout.fragment_aiuto, container, false);
                break;
        }
        return rootView;
    }
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }
    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return PlaceholderFragment.newInstance(1);
            case 1:
                return PlaceholderFragment.newInstance(2);
            case 2:
                return PlaceholderFragment.newInstance(3);
            case 3:
                return PlaceholderFragment.newInstance(4);
            default: return PlaceholderFragment.newInstance(1);
// here i have other problems, so like this the app still work, but if i change something it crash (and I know it's wrong like this)
        }
        //return PlaceholderFragment.newInstance(position + 1);
    }
    @Override
    public int getCount() {
        return 4;
    }
}
}

activity_homepage.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".homepage">

<android.support.design.widget.AppBarLayout
    android:id="@+id/appbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/appbar_padding_top">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:layout_weight="1"
        android:background="@color/colorPrimaryDark"
        app:layout_scrollFlags="scroll|enterAlways"
        app:popupTheme="@style/PopupOverlay"
        app:title="@string/app_name">

    </android.support.v7.widget.Toolbar>

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary">

        <android.support.design.widget.TabItem
            android:id="@+id/tabItem"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/tab_text_1" />

        <android.support.design.widget.TabItem
            android:id="@+id/tabItem2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/tab_text_2" />

        <android.support.design.widget.TabItem
            android:id="@+id/tabItem3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/tab_text_3" />

        <android.support.design.widget.TabItem
            android:id="@+id/tabItem4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/tab_text_4" />

    </android.support.design.widget.TabLayout>
</android.support.design.widget.AppBarLayout>

<android.support.v4.view.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</android.support.design.widget.CoordinatorLayout>

homepage.java （第一个片段）

public class homepage extends AppCompatActivity {
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_homepage);
    Toolbar toolbar = findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
    mViewPager = findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);
    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
    mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_homepage, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

public static class PlaceholderFragment extends Fragment {
    private static final String ARG_SECTION_NUMBER = "section_number";

    public PlaceholderFragment() {
    }

    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = null;

        switch(getArguments().getInt(ARG_SECTION_NUMBER))
        {
            case 1:
                rootView = inflater.inflate(R.layout.fragment_homepage, container, false);
                break;
            case 2:
                rootView = inflater.inflate(R.layout.fragment_fibra, container, false);
                break;
            case 3:
                rootView = inflater.inflate(R.layout.fragment_adsl, container, false);
                break;
            case 4:
                rootView = inflater.inflate(R.layout.fragment_aiuto, container, false);
                break;
        }
        return rootView;
    }
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }
    @Override
    public Fragment getItem(int position) {
        return PlaceholderFragment.newInstance(position + 1);
    }
    @Override
    public int getCount() {
        return 4;
    }
}
}

fragment_fibra.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".fibra"
android:background="#EFEFEF">

<Button
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:background="#FFFFFF"
  android:drawablePadding="22dp"
  android:gravity="center"
  android:hint="@string/cercasugg"
  android:textColor="#000000"
  android:padding="16dp" />

<android.support.v7.widget.RecyclerView
    android:id="@+id/ListaFibra"
    android:scrollbars="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

</LinearLayout>

fibra.java （第二个片段）

public class fibra extends Fragment {
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
private OnFragmentInteractionListener mListener;
private RecyclerView recyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager layoutManager;

public fibra() {
        }
public static fibra newInstance(String param1, String param2) {
    fibra fragment = new fibra();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;
}

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View V = inflater.inflate(R.layout.fragment_fibra, container, false);
    recyclerView = V.findViewById(R.id.ListaFibra);
    recyclerView.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(getActivity());
    recyclerView.setLayoutManager(layoutManager);
    List<String> input = new ArrayList<>();
    for (int i = 0; i < 100; i++) {
        input.add("Test" + i);
    }
    mAdapter = new adFibra(input);
    recyclerView.setAdapter(mAdapter);
    return V;

    /*View rootView = inflater.inflate(R.layout.fragment_fibra, container, false);
    RecyclerView recyclerView = rootView.findViewById(R.id.ListaFibra);
    recyclerView.setHasFixedSize(true); //per migliorare performance

    LinearLayoutManager llm = new LinearLayoutManager(getActivity());
    recyclerView.setLayoutManager(llm);

    adFibra adapter = new adFibra(new String[]{"Example One"});
    recyclerView.setAdapter(adapter);

    return rootView;*/
    //return inflater.inflate(R.layout.fragment_fibra, container, false);
}
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (context instanceof OnFragmentInteractionListener) {
            mListener = (OnFragmentInteractionListener) context;
        } else {
            throw new RuntimeException(context.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

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

    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

Answer 1

尝试放置

recyclerView.setLayoutManager(llm);

之前

recyclerView.setAdapter(adapter);

所以会是

   LinearLayoutManager llm = new LinearLayoutManager(getActivity());
        recyclerView.setLayoutManager(llm);

 MyAdapter adapter = new MyAdapter(new String[]{"Example One", "Example Two", "Example Three", "Example Four", "Example Five" , "Example Six" , "Example Seven"});
    recyclerView.setAdapter(adapter);

快乐编码：D

Answer 2

您确定您实际上称为纤维碎片吗？

您每次都创建一个PlaceHolderFragment，并且只是夸大不同的布局。您实际上并没有创建纤维碎片，因此不会填充回收站，因此不会显示消息。

在您的SectionsPagerAdapter中，在getItem方法中，返回与该位置相对应的片段实例。

例如：

switch (position) {
   case 0:
      return homepage.newInstance();                
   case 1:
      return fibra.newInstance();
   case 2:
      return adsl.newInstance();
   case 3:
      return aiuto.newInstance();
   default:
      return homepage.newInstance();      
}

从您的主要活动中删除PlaceHolderFragment。主页也不是片段，而是活动。您所有的碎片看起来都像纤维。

并实现所有片段接口，例如：

implements fibra.OnFragmentInteractionListener

并创建一个实现它的方法：

@Override
public void onFragmentInteraction(Uri uri) {
     // your code here...   
}