通过底部导航显示片段时应用程序崩溃

如何解决通过底部导航显示片段时应用程序崩溃

嗨，我正在制作一个带有底部导航的简单应用程序来显示一些片段。它在显示吐司时效果很好，但在尝试显示片段时崩溃了。这是我的代码。

MainActivity.java

public class MainActivity extends AppCompatActivity
         {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getwindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.content_main);

        BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);
        bottomNavigationView.setonNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {

                Fragment fragment;
                switch (item.getItemId()) {
                    case R.id.action_recents:
                        Toast.makeText(MainActivity.this,"Recents",Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.action_favorites:     
                        //Toast.makeText(MainActivity.this,"Favorites",Toast.LENGTH_SHORT).show();
                        fragment = new FavFragment();
                        loadFragment(fragment); // i think there's something wrong with these lines but found no way to resolve it.
                        break;
                }
                return true;
            }
        });

    }

             private void loadFragment(android.support.v4.app.Fragment fragment) {
                 // load fragment
                 FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
                 transaction.replace(R.id.frame_container,fragment);
                 transaction.addToBackStack(null);
                 transaction.commit();
             }

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.frg.myapp.MainActivity"
    >  

    <FrameLayout
        android:id="@+id/frame_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        app:itemBackground="@color/colorPrimary"
        app:itemIconTint="@android:color/white"
        app:itemTextColor="@android:color/white"        
        app:menu="@menu/bottom_nav_menu" />

</android.support.constraint.ConstraintLayout>

FavFragment.java。这些是由 android studio 默认创建的，所以我认为这些没有问题。

public class FavFragment extends Fragment {
    
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    public FavFragment() {
        // required empty public constructor
    }

    
    public static FavFragment newInstance(String param1,String param2) {
        FavFragment fragment = new FavFragment();
        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);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_ParaM1);
            mParam2 = getArguments().getString(ARG_ParaM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_fav,container,false);
    }

    // Todo: Rename method,update argument and hook method into UI event
    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);
    }
}

fragment_fav.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.frg.myapp.FavFragment">

    <!-- Todo: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment" />

</FrameLayout>

bottom_nav_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/action_recents"
        android:enabled="true"
        android:icon="@drawable/ic_recent"
        android:title="Recent"
        app:showAsAction="ifRoom" />

    <item
        android:id="@+id/action_favorites"
        android:enabled="true"
        android:icon="@drawable/ic_fav"
        android:title="favorite"
        app:showAsAction="ifRoom" />

</menu>

解决方法

我自己解决了这个问题。有人感兴趣吗？