片段添加編程消失

Question

我的應用程序使用選項卡，每個選項卡Fragment（從android.app.Fragment）。我想在其中的一箇中使用嵌套片段。

這裏是應該頂層片段包含嵌套片段：

import android.app.Fragment; 
import android.os.Bundle; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentTransaction; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import fr.epitech.test_esi.R; 

public class ReservationCalendarFragment extends Fragment { 
    public static final int stringId = R.string.calendar_tab; 
    public static final String tag = "reservation_calendar_frag"; 

    CalendarFragment t = new CalendarFragment(); 

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

     FragmentManager fm = ((FragmentActivity) getActivity()) 
       .getSupportFragmentManager(); 
     FragmentTransaction ft = fm.beginTransaction(); 
     ft.add(R.id.calendarframelayout, t, CalendarFragment.tag); 
     ft.commit(); 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
      Bundle savedInstanceState) { 
     return inflater.inflate(R.layout.reservation_calendar_layout, null); 
    } 
} 

}

它增加了編程使用FragmentTransaction第一片段。它實際上工作（我的意思是，嵌套的片段被添加，我可以看到它），但每次我切換到另一個選項卡（所以顯示另一個片段）並回到它，嵌套片段已消失。

這裏是CalendarFragment的代碼：

import java.text.SimpleDateFormat; 
import java.util.Calendar; 
import java.util.Locale; 

import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.CalendarView; 
import android.widget.CalendarView.OnDateChangeListener; 
import fr.epitech.test_esi.R; 

public class CalendarFragment extends Fragment { 

    public static final String tag = "calendar_frag"; 

    private SimpleDateFormat _df = new SimpleDateFormat("yyyy-MM-dd", Locale.US); 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
      Bundle savedInstanceState) { 
     View fragView = inflater.inflate(R.layout.calendar_layout, null); 
     CalendarView calendarView = (CalendarView) fragView 
       .findViewById(R.id.calendar); 
     calendarView.setOnDateChangeListener(new OnDateChangeListener() { 

      @Override 
      public void onSelectedDayChange(CalendarView view, int year, 
        int month, int dayOfMonth) { 
       Calendar c = Calendar.getInstance(); 

       c.set(year, month, dayOfMonth); 
       Log.d("DATE", c.getTime().toString()); 
      } 
     }); 
     return fragView; 
    } 

• 嵌套片段CalendarFragment延伸android.support.v4.app.Fragment
• 我的活動是FragmentActivity

我甚至嘗試對這個片段期間，把後臺的活動（使用home按鈕）並恢復它，嵌套的片段仍然顯示。當我在我的應用程序的選項卡之間切換時真的發生。

Answer 1

而不是增加在的onCreate片段一旦創建了片段，它只會被調用，在onCreateView創建它，但檢查片段是你用`getChildFragmentmanager空第一

public class ReservationCalendarFragment extends Fragment { 
    public static final int stringId = R.string.calendar_tab; 
    public static final String tag = "reservation_calendar_frag"; 

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

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
     Bundle savedInstanceState) { 
     CalendarFragment t = (CalendarFragment) getChildFragmentManager() 
      .findFragmentByTag(CalendarFragment.tag); 

     if(t == null) { 
      t = new CalendarFragment(); 
     } 
     FragmentTransaction transaction = getChildFragmentManager() 
       .beginTransaction(); 
     ft.add(R.id.calendarframelayout, t, CalendarFragment.tag); 
     ft.commit(); 
     return inflater.inflate(R.layout.reservation_calendar_layout, null); 
    } 
}