メインアクティビティーにフラグメントが表示されないアクティビティーのフラグメントコンテンツはツールバーをクリックすると表示されます

Question

フラグメント1に進むには、フラグメント2と次のフラグメント1を取得する必要があります。 私のコードに何がありますか？

は、これは私のフラグメント

public class TodaysmemeFragement extends Fragment { 


private RecyclerView recyclerView; 
private DatabaseReference databaseReference; 

private FloatingActionButton sharebutton; 




@Nullable 
@Override 
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) { 




    return inflater.inflate(R.layout.fragment_todaysmeme,container,false); 
} 

@Override 
public void onCreate(@Nullable Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 

} 

@Override 
public void onStart() { 
    super.onStart(); 
    FirebaseRecyclerAdapter<Meme,MemeViewHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Meme, MemeViewHolder>(
      Meme.class, 
      R.layout.meme_row, 
      MemeViewHolder.class, 
      databaseReference 
    ) { 
     @Override 
     protected void populateViewHolder(MemeViewHolder viewHolder, final Meme model, final int position) { 
      viewHolder.setTag(model.getTag()); 
      viewHolder.setDesc(model.getDesc()); 
      viewHolder.setImage(getActivity(),model.getImage()); 

      final String imageurl = model.getImage(); 

      View v = viewHolder.getmViews(); 

      FloatingActionButton f = (FloatingActionButton) v.findViewById(R.id.sharebutton); 

      f.setOnClickListener(new View.OnClickListener() { 
       @Override 
       public void onClick(View v) { 


        URL url = null; 
        Bitmap image = null; 
        try { 
         url = new URL(imageurl); 
        } catch (MalformedURLException e) { 
         e.printStackTrace(); 
        } 



        try { 
         image = BitmapFactory.decodeStream(url.openConnection().getInputStream()); 
        } catch (IOException e) { 
         e.printStackTrace(); 
        } 
        Intent intent = new Intent(Intent.ACTION_SEND); 
        intent.putExtra(Intent.EXTRA_TEXT, model.getDesc()); 
        Uri screenshotUri = null; 
        String path = null; 
        try { 
         path = MediaStore.Images.Media.insertImage(getActivity().getContentResolver(), image, "", null); 
         screenshotUri = Uri.parse(path); 
        } catch (Exception e) { 
         Log.d(e.getLocalizedMessage(),"dfsf"); 
        } 


        intent.putExtra(Intent.EXTRA_STREAM, screenshotUri); 
        intent.setType("image/*"); 
        startActivity(Intent.createChooser(intent, "Share image via...")); 

       } 

      }); 
     } 
    }; 

    recyclerView.setAdapter(firebaseRecyclerAdapter); 

} 

@Override 
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) { 
    super.onViewCreated(view, savedInstanceState); 
    getActivity().setTitle("Today's Meme"); 

    sharebutton = (FloatingActionButton) view.findViewById(R.id.sharebutton); 

    databaseReference = FirebaseDatabase.getInstance().getReference("Today"); 
    recyclerView = (RecyclerView)view.findViewById(R.id.meme_list); 
    recyclerView.setHasFixedSize(true); 
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity())); 


} 


public static class MemeViewHolder extends RecyclerView.ViewHolder{ 
    View mView; 
    public MemeViewHolder(View itemView) 
    { 
     super(itemView); 
     mView = itemView; 
    } 

    public void setTag(String tag) 
    { 
     TextView post_tag = (TextView)mView.findViewById(R.id.post_tag); 
      post_tag.setText(tag); 
    } 
    public void setDesc(String desc) 
    { 
    TextView post_desc = (TextView)mView.findViewById(R.id.post_desc); 
     post_desc.setText(desc); 
    } 
    public void setImage(Context context,String image) { 
     ImageView imageView = (ImageView) mView.findViewById(R.id.post_image); 
     Picasso.with(context).load(image).into(imageView); 

    } 
    public View getmViews() 
    { 
     return this.mView; 
    } 




} 
} 

ですこれは、XMLには問題はありません私のMainActivity

<android> 
public class MainActivity extends AppCompatActivity 
    implements NavigationView.OnNavigationItemSelectedListener { 

DatabaseReference databaseReference; 
FirebaseAuth firebaseAuth; 



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

    setContentView(R.layout.activity_main); 


    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1); 

    Fragment fragment; 
     fragment = new TodaysmemeFragement(); 
     FragmentManager fragmentManager = getFragmentManager(); 
     fragmentManager.beginTransaction() 
       .replace(R.id.content_main, fragment) 
       .commit(); 




    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 
    firebaseAuth = FirebaseAuth.getInstance(); 
    if(firebaseAuth.getCurrentUser() == null) 
    { 
     finish(); 
     startActivity(new Intent(getApplicationContext(),LoginSignupActivity.class)); 
    } 








    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 


    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
      this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
    drawer.setDrawerListener(toggle); 
    toggle.syncState(); 

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
    navigationView.setNavigationItemSelectedListener(this); 
} 

です。しかし、断片の中の何かが置き換えられます。

Answer 1

を開始するFragmentTransactionを追加し、私は問題を把握します。削除する必要がありますrecyclerView.sethasFixedSize(true);

Answer 2

は、トランザクションはすべての後

Fragment fragment; 
fragment = new TodaysmemeFragement(); 
FragmentManager fragmentManager = getFragmentManager(); 
FragmentTransaction ft = fragmentManager.beginTransaction(); 
ft.addToBackStack(null); 

ft.replace(R.id.main_content, fragment); 
ft.commit();