更改碎片時Android碎片UI元素消失了嗎？

Question

我正在創建一個具有多個片段的android應用程序，每個功能一個。我目前使用抽屜來訪問每個功能，在一個特定功能中，我使用FragmentPagerAdapter至switch between fragments within that fragment。當我創建第一個打開應用程序以訪問我的片段時，我的layout.xml文件中定義的UI元素按預期加載。但是，當我使用抽屜切換到其他片段並返回到原始片段時，原始UI元素消失。

抽屜在基本活動切換代碼來訪問不同的特徵的片段

public class BaseActivity extends AppCompatActivity 
     implements NavigationView.OnNavigationItemSelectedListener, ValueEventListener { 
    FragmentManager fm; 
    ArrayList<String> listOfAvailableRooms=new ArrayList<>(); 
    String timing=""; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_base); 
     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     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); 

     // start of own code 
     fm = getSupportFragmentManager(); 
    } 

    @Override 
    public void onBackPressed() { 
     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     if (drawer.isDrawerOpen(GravityCompat.START)) { 
      drawer.closeDrawer(GravityCompat.START); 
     } else { 
      super.onBackPressed(); 
     } 
    } 

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

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     return super.onOptionsItemSelected(item); 
    } 

    @SuppressWarnings("StatementWithEmptyBody") 
    @Override 
    public boolean onNavigationItemSelected(MenuItem item) { 
     Fragment fragment; 

     int id = item.getItemId(); 

     if (id == R.id.f_map) { 
      fragment = new MapFragment(); 
     } else if (id == R.id.f_booking) { 
      fragment = new CalendarFragment(); 
     } else if (id == R.id.f_roomSearch) { 
      fragment = new RoomSearchFragment(); 
     } else if (id == R.id.f_authentication) { 
      fragment = new AuthenticationFragment(); 
     } else if (id == R.id.nav_send) { 
      fragment = new MapFragment().newInstance(3, new LatLng(-53.965623629921105, -5.974991060793399)); 
     } else { 
      fragment = new MapFragment(); 
     } 

     fm.beginTransaction().replace(R.id.main_container, fragment).commit(); 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     drawer.closeDrawer(GravityCompat.START); 
     return true; 
    } 

    public class SectionsPagerAdapter extends FragmentPagerAdapter { 

     public SectionsPagerAdapter(FragmentManager fm) { 
      super(fm); 
     } 

     @Override 
     public Fragment getItem(int position) { 
      if (position == 0) return new MapFragment(); 
      return new MapFragment(); 
     } 

     @Override 
     public int getCount() { 
      // Show 4 total pages. 
      return 4; 
     } 

     @Override 
     public CharSequence getPageTitle(int position) { 
      switch (position) { 
       case 0: 
        return "Client"; 
       case 1: 
        return "Server"; 
      } 
      return null; 
     } 
    } 
} 

爲特徵

public class AuthenticationFragment extends Fragment { 
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER 
    private static final String ARG_PARAM1 = "param1"; 
    private static final String ARG_PARAM2 = "param2"; 

    FragmentPagerAdapter adapterViewPager; 

    private OnFragmentInteractionListener mListener; 

    public AuthenticationFragment() { 
     // Required empty public constructor 
    } 

    public static AuthenticationFragment newInstance(String param1, String param2) { 
     AuthenticationFragment fragment = new AuthenticationFragment(); 
     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) { 
     // Inflate the layout for this fragment 
     View view = inflater.inflate(R.layout.fragment_authentication, container, false); 
     ViewPager vpPager = (ViewPager) view.findViewById(R.id.vpPager); 
     adapterViewPager = new MyPagerAdapter(getFragmentManager()); 
     vpPager.setAdapter(adapterViewPager); 
     return view; 
    } 

    @Override 
    public void onResume() { 
     super.onResume(); 
    } 

    @Override 
    public void onPause() { 
     super.onPause(); 
    } 

    public void onButtonPressed(Uri uri) { 
     if (mListener != null) { 
      mListener.onFragmentInteraction(uri); 
     } 
    } 

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

    public static class MyPagerAdapter extends FragmentPagerAdapter { 
     private static int NUM_ITEMS = 2; 

     public MyPagerAdapter(FragmentManager fragmentManager){ 
      super(fragmentManager); 
     } 

     // Returns total number of pages 
     @Override 
     public int getCount() { 
      return NUM_ITEMS; 
     } 

     // Returns the fragment to display for that page 
     @Override 
     public Fragment getItem(int position){ 
      switch (position){ 
       case 0: //CurrentBookings Fragment 
        return CurrentBookings.getInstance("Current"); 
       case 1: //UpcomingBookings Fragment 
        return UpcomingBookings.newInstance("Upcoming"); 
       default: 
        return null; 
      } 
     } 

     // Returns page title for the top indicator 
     @Override 
     public CharSequence getPageTitle(int position){ 
      switch (position){ 
       case 0: //CurrentBookings Fragment 
        return "Current"; 
       case 1: //UpcomingBookings Fragment 
        return "Upcoming"; 
       default: 
        return null; 
      } 
     } 
    } 

} 

片段與消失的UI元素總體片段

public class CurrentBookings extends Fragment { 
    private Button myButton; 

    // newInstance constructer for creating fragment with arguments 
    public static CurrentBookings newInstance(String title){ 
     CurrentBookings currentBookings = new CurrentBookings(); 
     Bundle args = new Bundle(); 
     args.putString("title",title); 
     currentBookings.setArguments(args); 
     return currentBookings; 
    } 

    // Store instance variables based on arguments passed 
    @Override 
    public void onCreate(Bundle savedInstanceState){ 
     super.onCreate(savedInstanceState); 
     title = getArguments().getString("title"); 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){ 
     View view = inflater.inflate(R.layout.fragment_current_bookings,container,false); 

     myButton = (Button) view.findViewById(R.id.button1); 
     return view; 
    } 
} 

當重溫片段時，應用程序的首開段

截圖

的UI元素只再次出現在手機方向變化時的App

截圖。我怎麼解決這個問題？

Answer 1

是的，

您需要手動刪除您的AuthenticationFragment的子片段。

當您設置適配器時，您必須將這兩個片段添加到您的parentFragment的arraylist中，以便您可以獲取片段的完整列表，以便您可以輕鬆地除去父片段的onDestroyView（）上的片段。

private class AuthenticationFragment extends Fragment{ 

private Arraylist fragmentList = new ArrayList<>(); 


private void setAdapter(){ 
    fragmentList.add(new FirstFragment()); 
    fragmentList.add(new SecondFragment()); 
............. code of adapter 


} 



    @Override 
    public void onDestroyView() { 
     super.onDestroyView(); 

     final FragmentManager fragmentManager = getFragmentManager(); 
     final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); 

     for (Fragment fragment : fragmentList) { 
      fragmentTransaction.remove(fragment); 
     } 
     fragmentTransaction.commit(); 

    } 

} 

因爲您在AuthenticationFragment中使用了FragmentPagerAdapter。