Androidの断片は

Question

コンテキスト消える：

Iは、視覚的に問題を説明するための画像を追加した： click for image explanation

Iが活性ならびに5つのフラグメント（件名、コース、AddCourse及び割り当て）を有する

アクティビティでは、下部のナビゲーションバーを使用して、コースの断片と割り当ての断片を切り替えます。

アクティビティを開始すると、コースの断片は最初は画面に表示されます。 コースの断片は科目のリストであることを意図していますが、最初にこの断片には0件の科目があり、科目を追加するボタンがあります。 Add Subjectボタンをクリックすると、AddCourseフラグメントがCoursesを置き換えます。 AddCourseフラグメント内の件名情報を入力して確認をクリックすると、新しいSubjectフラグメントが作成され、AddCourseフラグメントに埋め込まれたすべての情報が埋め込まれた後、インタフェースを介してアクティビティに送信されます。 次に、アクティビティは、科目を科目の断片に送信し、それを画面に表示します（科目の中に科目がある科目の断片）。これは素晴らしいです。しかし、課題の断片に切り替えてコースの断片に戻ったとき、その科目は消えてしまいました。

ここにいくつかのコードです：

Activity.java

import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentTransaction; 
import android.support.annotation.IdRes; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.support.v7.view.menu.SubMenuBuilder; 

import com.roughike.bottombar.BottomBar; 
import com.roughike.bottombar.OnTabSelectListener; 

public class Activity extends AppCompatActivity implements AddCourseInterface { 

    private Subject subject; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity); 

     BottomBar bottomBar = (BottomBar) findViewById(R.id.bottomBar); 
     bottomBar.setOnTabSelectListener(new OnTabSelectListener() { 
      @Override 
      public void onTabSelected(@IdRes int tabId) { 
       swapPage(tabId); 
      } 
     }); 

    } 

    public void swapPage(@IdRes int tabId) 
    { 
     FragmentManager fm = getSupportFragmentManager(); 
     FragmentTransaction ft = fm.beginTransaction(); 

     if (tabId == R.id.tab_courses) { 
      //if (subject != null) subject.print(); 
      ft.replace(R.id.content, Courses.newInstance(subject)); 
      ft.addToBackStack(null); 
      ft.commit(); 
     } 
     else if (tabId == R.id.tab_assignments) { 
      ft.replace(R.id.content, Assignments.newInstance()); 
      ft.addToBackStack(null); 
      ft.commit(); 
     } 
     else if (tabId == R.id.tab_agenda) { 
      ft.replace(R.id.content, Agenda.newInstance()); 
      ft.addToBackStack(null); 
      ft.commit(); 
     } 
     else if (tabId == R.id.tab_exams) { 
      ft.replace(R.id.content, Exams.newInstance()); 
      ft.addToBackStack(null); 
      ft.commit(); 
     } 
     else if (tabId == R.id.tab_grades) { 
      ft.replace(R.id.content, Grades.newInstance()); 
      ft.addToBackStack(null); 
      ft.commit(); 
     } 

    } 

    @Override 
    public void sendCourse(Subject subject) { 
     this.subject = subject; 
     FragmentManager fm = getSupportFragmentManager(); 
     FragmentTransaction ft = fm.beginTransaction(); 
     ft.replace(R.id.content, Courses.newInstance(subject)); 
     ft.addToBackStack(null); 
     ft.commit(); 
    } 
} 

AddCourse.java

import android.content.Context; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.Button; 
import android.widget.CheckBox; 
import android.widget.LinearLayout; 
import android.widget.RadioButton; 
import android.widget.TextView; 

import org.w3c.dom.Text; 

import java.util.ArrayList; 

public class AddCourse extends Fragment implements View.OnClickListener { 

    private View inflatedView; 
    private AddCourseInterface comm; 

    private TextView nameText; 
    private TextView nameGivenText; 
    private TextView codeText; 
    private TextView professorText; 

    private CheckBox additionalCheck; 
    private LinearLayout additionalInfo; 
    private CheckBox monCheck; 
    private LinearLayout monInfo; 
    private TextView monLoc; 
    private TextView monSTime; 
    private TextView monETime; 
    private CheckBox tueCheck; 
    private LinearLayout tueInfo; 
    private TextView tueLoc; 
    private TextView tueSTime; 
    private TextView tueETime; 
    private CheckBox wedCheck; 
    private LinearLayout wedInfo; 
    private TextView wedLoc; 
    private TextView wedSTime; 
    private TextView wedETime; 
    private CheckBox thuCheck; 
    private LinearLayout thuInfo; 
    private TextView thuLoc; 
    private TextView thuSTime; 
    private TextView thuETime; 
    private CheckBox friCheck; 
    private LinearLayout friInfo; 
    private TextView friLoc; 
    private TextView friSTime; 
    private TextView friETime; 

    private RadioButton mon_lec; 
    private RadioButton mon_sem; 
    private RadioButton mon_lab; 

    private RadioButton tue_lec; 
    private RadioButton tue_sem; 
    private RadioButton tue_lab; 

    private RadioButton wed_lec; 
    private RadioButton wed_sem; 
    private RadioButton wed_lab; 

    private RadioButton thu_lec; 
    private RadioButton thu_sem; 
    private RadioButton thu_lab; 

    private RadioButton fri_lec; 
    private RadioButton fri_sem; 
    private RadioButton fri_lab; 

    private Button confirm; 

    private String name = "Subject Name"; 
    private String givenName = "Short Name"; 
    private String code = "Course Code"; 
    private String professor = "Professor"; 

    private ArrayList<String> days = new ArrayList<String>();; 
    private ArrayList<String> locations = new ArrayList<String>(); 
    private ArrayList<String> stimes = new ArrayList<String>(); 
    private ArrayList<String> etimes = new ArrayList<String>(); 
    private ArrayList<String> types = new ArrayList<String>(); 

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

    public static AddCourse newInstance() { 

     return new AddCourse(); 
    } 

    @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 
     inflatedView = inflater.inflate(R.layout.fragment_add_course, container, false); 

     nameText = (TextView) inflatedView.findViewById(R.id.subject_name); 
     nameGivenText = (TextView) inflatedView.findViewById(R.id.short_name); 
     codeText = (TextView) inflatedView.findViewById(R.id.course_code); 
     professorText = (TextView) inflatedView.findViewById(R.id.professor); 

     additionalCheck = (CheckBox) inflatedView.findViewById(R.id.check_additional); 
     additionalCheck.setOnClickListener(this); 

     additionalInfo = (LinearLayout) inflatedView.findViewById(R.id.additional_info); 

     monCheck = (CheckBox) inflatedView.findViewById(R.id.check_mon); 
     monCheck.setOnClickListener(this); 

     tueCheck = (CheckBox) inflatedView.findViewById(R.id.check_tue); 
     tueCheck.setOnClickListener(this); 

     wedCheck = (CheckBox) inflatedView.findViewById(R.id.check_wed); 
     wedCheck.setOnClickListener(this); 

     thuCheck = (CheckBox) inflatedView.findViewById(R.id.check_thu); 
     thuCheck.setOnClickListener(this); 

     friCheck = (CheckBox) inflatedView.findViewById(R.id.check_fri); 
     friCheck.setOnClickListener(this); 

     monInfo = (LinearLayout) inflatedView.findViewById(R.id.monday_info); 
     tueInfo = (LinearLayout) inflatedView.findViewById(R.id.tuesday_info); 
     wedInfo = (LinearLayout) inflatedView.findViewById(R.id.wednesday_info); 
     thuInfo = (LinearLayout) inflatedView.findViewById(R.id.thursday_info); 
     friInfo = (LinearLayout) inflatedView.findViewById(R.id.friday_info); 

     monLoc = (TextView) inflatedView.findViewById(R.id.monday_location); 
     monSTime = (TextView) inflatedView.findViewById(R.id.monday_stime); 
     monETime = (TextView) inflatedView.findViewById(R.id.monday_etime); 

     tueLoc = (TextView) inflatedView.findViewById(R.id.tuesday_location); 
     tueSTime = (TextView) inflatedView.findViewById(R.id.tuesday_stime); 
     tueETime = (TextView) inflatedView.findViewById(R.id.tuesday_etime); 

     wedLoc = (TextView) inflatedView.findViewById(R.id.wednesday_location); 
     wedSTime = (TextView) inflatedView.findViewById(R.id.wednesday_stime); 
     wedETime = (TextView) inflatedView.findViewById(R.id.wednesday_etime); 

     thuLoc = (TextView) inflatedView.findViewById(R.id.thursday_location); 
     thuSTime = (TextView) inflatedView.findViewById(R.id.thursday_stime); 
     thuETime = (TextView) inflatedView.findViewById(R.id.thursday_etime); 

     friLoc = (TextView) inflatedView.findViewById(R.id.friday_location); 
     friSTime = (TextView) inflatedView.findViewById(R.id.friday_stime); 
     friETime = (TextView) inflatedView.findViewById(R.id.friday_etime); 

     mon_lec = (RadioButton) inflatedView.findViewById(R.id.mon_lec); 
     mon_sem = (RadioButton) inflatedView.findViewById(R.id.mon_sem); 
     mon_lab = (RadioButton) inflatedView.findViewById(R.id.mon_lab); 

     tue_lec = (RadioButton) inflatedView.findViewById(R.id.tue_lec); 
     tue_sem = (RadioButton) inflatedView.findViewById(R.id.tue_sem); 
     tue_lab = (RadioButton) inflatedView.findViewById(R.id.tue_lab); 

     wed_lec = (RadioButton) inflatedView.findViewById(R.id.wed_lec); 
     wed_sem = (RadioButton) inflatedView.findViewById(R.id.wed_sem); 
     wed_lab = (RadioButton) inflatedView.findViewById(R.id.wed_lab); 

     thu_lec = (RadioButton) inflatedView.findViewById(R.id.thu_lec); 
     thu_sem = (RadioButton) inflatedView.findViewById(R.id.thu_sem); 
     thu_lab = (RadioButton) inflatedView.findViewById(R.id.thu_lab); 

     fri_lec = (RadioButton) inflatedView.findViewById(R.id.fri_lec); 
     fri_sem = (RadioButton) inflatedView.findViewById(R.id.fri_sem); 
     fri_lab = (RadioButton) inflatedView.findViewById(R.id.fri_lab); 

     mon_lec.setOnClickListener(this); 
     mon_sem.setOnClickListener(this); 
     mon_lab.setOnClickListener(this); 

     tue_lec.setOnClickListener(this); 
     tue_sem.setOnClickListener(this); 
     tue_lab.setOnClickListener(this); 

     wed_lec.setOnClickListener(this); 
     wed_sem.setOnClickListener(this); 
     wed_lab.setOnClickListener(this); 

     thu_lec.setOnClickListener(this); 
     thu_sem.setOnClickListener(this); 
     thu_lab.setOnClickListener(this); 

     fri_lec.setOnClickListener(this); 
     fri_sem.setOnClickListener(this); 
     fri_lab.setOnClickListener(this); 

     confirm = (Button) inflatedView.findViewById(R.id.button_confirm_subject); 
     confirm.setOnClickListener(this); 

     return inflatedView; 
    } 

    @Override 
    public void onClick(View v) { 
     if (v == additionalCheck) 
     { 
      if (additionalCheck.isChecked()) 
      { 
       System.out.println("ADDITIONAL INFO ENABLED <---------------------"); 
       additionalInfo.setVisibility(View.VISIBLE); 
      } 
      else 
      { 
       System.out.println("ADDITIONAL INFO DISABLED <---------------------"); 
       additionalInfo.setVisibility(View.GONE); 
      } 
     } 

     else if (v == monCheck) 
     { 
      if (monCheck.isChecked()) 
      { 
       System.out.println("MONDAY WAS CHECKED <---------------------"); 
       monInfo.setVisibility(View.VISIBLE); 
      } 
      else 
      { 
       System.out.println("MONDAY WAS UNCHECKED <---------------------"); 
       monInfo.setVisibility(View.GONE); 
      } 
     } 

     else if (v == tueCheck) 
     { 
      if (tueCheck.isChecked()) 
      { 
       System.out.println("tueDAY WAS CHECKED <---------------------"); 
       tueInfo.setVisibility(View.VISIBLE); 
      } 
      else 
      { 
       System.out.println("tueDAY WAS UNCHECKED <---------------------"); 
       tueInfo.setVisibility(View.GONE); 
      } 
     } 

     else if (v == wedCheck) 
     { 
      if (wedCheck.isChecked()) 
      { 
       System.out.println("wedDAY WAS CHECKED <---------------------"); 
       wedInfo.setVisibility(View.VISIBLE); 
      } 
      else 
      { 
       System.out.println("wedDAY WAS UNCHECKED <---------------------"); 
       wedInfo.setVisibility(View.GONE); 
      } 
     } 

     else if (v == thuCheck) 
     { 
      if (thuCheck.isChecked()) 
      { 
       System.out.println("thuDAY WAS CHECKED <---------------------"); 
       thuInfo.setVisibility(View.VISIBLE); 
      } 
      else 
      { 
       System.out.println("thuDAY WAS UNCHECKED <---------------------"); 
       thuInfo.setVisibility(View.GONE); 
      } 
     } 

     else if (v == friCheck) 
     { 
      if (friCheck.isChecked()) 
      { 
       System.out.println("friDAY WAS CHECKED <---------------------"); 
       friInfo.setVisibility(View.VISIBLE); 
      } 
      else 
      { 
       System.out.println("friDAY WAS UNCHECKED <---------------------"); 
       friInfo.setVisibility(View.GONE); 
      } 
     } 

     else if (v == mon_lec) { 
      mon_lec.setChecked(true); 
      mon_sem.setChecked(false); 
      mon_lab.setChecked(false); 
     } 

     else if (v == mon_sem) { 
      mon_lec.setChecked(false); 
      mon_sem.setChecked(true); 
      mon_lab.setChecked(false); 
     } 

     else if (v == mon_lab) { 
      mon_lec.setChecked(false); 
      mon_sem.setChecked(false); 
      mon_lab.setChecked(true); 
     } 

     else if (v == tue_lec) { 
      tue_lec.setChecked(true); 
      tue_sem.setChecked(false); 
      tue_lab.setChecked(false); 
     } 

     else if (v == tue_sem) { 
      tue_lec.setChecked(false); 
      tue_sem.setChecked(true); 
      tue_lab.setChecked(false); 
     } 

     else if (v == tue_lab) { 
      tue_lec.setChecked(false); 
      tue_sem.setChecked(false); 
      tue_lab.setChecked(true); 
     } 

     else if (v == wed_lec) { 
      wed_lec.setChecked(true); 
      wed_sem.setChecked(false); 
      wed_lab.setChecked(false); 
     } 

     else if (v == wed_sem) { 
      wed_lec.setChecked(false); 
      wed_sem.setChecked(true); 
      wed_lab.setChecked(false); 
     } 

     else if (v == wed_lab) { 
      wed_lec.setChecked(false); 
      wed_sem.setChecked(false); 
      wed_lab.setChecked(true); 
     } 

     else if (v == thu_lec) { 
      thu_lec.setChecked(true); 
      thu_sem.setChecked(false); 
      thu_lab.setChecked(false); 
     } 

     else if (v == thu_sem) { 
      thu_lec.setChecked(false); 
      thu_sem.setChecked(true); 
      thu_lab.setChecked(false); 
     } 

     else if (v == thu_lab) { 
      thu_lec.setChecked(false); 
      thu_sem.setChecked(false); 
      thu_lab.setChecked(true); 
     } 

     else if (v == fri_lec) { 
      fri_lec.setChecked(true); 
      fri_sem.setChecked(false); 
      fri_lab.setChecked(false); 
     } 

     else if (v == fri_sem) { 
      fri_lec.setChecked(false); 
      fri_sem.setChecked(true); 
      fri_lab.setChecked(false); 
     } 

     else if (v == fri_lab) { 
      fri_lec.setChecked(false); 
      fri_sem.setChecked(false); 
      fri_lab.setChecked(true); 
     } 
     else if (v == confirm) 
     { 

      name = nameText.getText().toString(); 
      givenName = nameGivenText.getText().toString(); 
      code = codeText.getText().toString(); 
      professor = professorText.getText().toString(); 

      if (monCheck.isChecked()) 
      { 
       days.add("monday"); 
       locations.add(monLoc.getText().toString()); 
       stimes.add(monSTime.getText().toString()); 
       etimes.add(monETime.getText().toString()); 
       if (mon_lec.isChecked()) { 
        types.add("lec"); 
       } 
       else if (mon_sem.isChecked()) { 
        types.add("sem"); 
       } 
       else if (mon_lab.isChecked()) { 
        types.add("lab"); 
       } 
      } 
      if (tueCheck.isChecked()) 
      { 
       days.add("tuesday"); 
       locations.add(tueLoc.getText().toString()); 
       stimes.add(tueSTime.getText().toString()); 
       etimes.add(tueETime.getText().toString()); 
       if (tue_lec.isChecked()) { 
        types.add("lec"); 
       } 
       else if (tue_sem.isChecked()) { 
        types.add("sem"); 
       } 
       else if (tue_lab.isChecked()) { 
        types.add("lab"); 
       } 
      } 
      if (wedCheck.isChecked()) 
      { 
       days.add("wednesday"); 
       locations.add(wedLoc.getText().toString()); 
       stimes.add(wedSTime.getText().toString()); 
       etimes.add(wedETime.getText().toString()); 
       if (wed_lec.isChecked()) { 
        types.add("lec"); 
       } 
       else if (wed_sem.isChecked()) { 
        types.add("sem"); 
       } 
       else if (wed_lab.isChecked()) { 
        types.add("lab"); 
       } 
      } 
      if (thuCheck.isChecked()) 
      { 
       days.add("thursday"); 
       locations.add(thuLoc.getText().toString()); 
       stimes.add(thuSTime.getText().toString()); 
       etimes.add(thuETime.getText().toString()); 
       if (thu_lec.isChecked()) { 
        types.add("lec"); 
       } 
       else if (thu_sem.isChecked()) { 
        types.add("sem"); 
       } 
       else if (thu_lab.isChecked()) { 
        types.add("lab"); 
       } 
      } 
      if (friCheck.isChecked()) 
      { 
       days.add("friday"); 
       locations.add(friLoc.getText().toString()); 
       stimes.add(friSTime.getText().toString()); 
       etimes.add(friETime.getText().toString()); 
       if (fri_lec.isChecked()) { 
        types.add("lec"); 
       } 
       else if (fri_sem.isChecked()) { 
        types.add("sem"); 
       } 
       else if (fri_lab.isChecked()) { 
        types.add("lab"); 
       } 
      } 

      /* 
      System.out.println(name); 
      System.out.println(givenName); 
      System.out.println(code); 
      System.out.println(professor); 

      System.out.println(days); 
      System.out.println(locations); 
      System.out.println(stimes); 
      System.out.println(etimes); 
      System.out.println(types); 
      */ 

      Subject subject = Subject.newInstance(name, givenName, code, professor, days, locations, stimes, etimes, types); 
      comm = (AddCourseInterface) getActivity(); 
      comm.sendCourse(subject); 
     } 

    } 
} 

Courses.java

は、

import android.content.Context; 
import android.net.Uri; 
import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.support.v4.app.Fragment; 
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 android.widget.Button; 
import android.widget.TextView; 

import java.util.ArrayList; 

public class Courses extends Fragment implements View.OnClickListener { 

    //private static final String ARG_PARAM1 = "arg1"; 

    private String title; 
    private TextView titleView; 
    private ArrayList<Subject> subjects; 
    private Subject subject; 
    private View inflatedView; 
    private Button addSubject; 

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

    public static Courses newInstance(Subject s) { 
     Courses courses = new Courses(); 

     Bundle bundle = new Bundle(); 
     bundle.putSerializable("sub1", s); 
     courses.setArguments(bundle); 

     return courses; 
    } 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     subjects = new ArrayList<Subject>(); 
    } 

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

     titleView = (TextView) inflatedView.findViewById(R.id.courses_title); 

     addSubject = (Button) inflatedView.findViewById(R.id.add_subject); 
     addSubject.setOnClickListener(this); 

     subject = (Subject) getArguments().getSerializable("sub1"); 

     if (subject != null) addSubject(subject); 

     return inflatedView; 
    } 

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

    public void changeText(String t) 
    { 
     titleView.setText(t); 
    } 

    public void addSubject(Subject s) 
    { 
     subjects.add(s); 
     FragmentManager fm = getActivity().getSupportFragmentManager(); 
     FragmentTransaction ft = fm.beginTransaction(); 
     ft.replace(R.id.sub1, s); 
     ft.addToBackStack(null); 
     ft.commit(); 
     System.out.println("SUBJECT ADDED TO COURSES < ------------------------"); 
     //subject.print(); 
    } 

    @Override 
    public void onClick(View v) { 
     System.out.println("BUTTON CLICKED < -----------------------------------"); 
     FragmentManager fm = getActivity().getSupportFragmentManager(); 
     FragmentTransaction ft = fm.beginTransaction(); 
     ft.replace(R.id.content, AddCourse.newInstance()); 
     ft.addToBackStack(null); 
     ft.commit(); 
    } 
} 

AddCourseで「確認」をクリックすると表示されるように、件名の断片がコースの断片の中に正しく表示されますが、割り当てを受けて戻ってくると、コースの新しいインスタンスを作成していても件名はなくなります。同じ主題（私の活動で保存された参照）。何か案は？

私は視覚的に問題を説明するための画像を追加しました： click for image explanation

Answer 1

コース断片はそのデータが失われた理由を、あなたはsqliteのかsharedpreferenceに日付を保存し、代わりに活動

にデータを渡すので、そこからデータを読み込む必要があります再作成します