Android片段更新问题

Question

我有三个片段使用tablayout。问题是我将数据保存在片段1中，并希望显示第二片段中的数据，但第二片段在单击或滑动到第二片段时未更新，因为片段由于默认偏移限制1而未再次创建。当我再次重新启动应用程序时，显示数据。任何解决方案高度赞赏

//我的MainActivity代码在这里

public class MainActivity extends AppCompatActivity 
{ 
    private Toolbar toolbar; 
    private TabLayout tabLayout; 
    private ViewPager viewPager; 
    private int[] tabIcons = { 
      R.drawable.calender, 
      R.drawable.favourite, 
      R.drawable.setting_icon 
    }; 

    PagerAdapter pagerAdapter; 

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

     toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     getSupportActionBar().setDisplayShowTitleEnabled(false); 

     viewPager = (ViewPager) findViewById(R.id.viewpager); 
     pagerAdapter = new PagerAdapter(getSupportFragmentManager(), MainActivity.this); 
     viewPager.setAdapter(pagerAdapter); 
     // viewPager.setOffscreenPageLimit(0); 

     tabLayout = (TabLayout) findViewById(R.id.tab_layout); 
     tabLayout.setupWithViewPager(viewPager); 
     tabLayout.getTabAt(0).setIcon(R.drawable.calender_hover); 


     for (int i = 0; i < tabLayout.getTabCount(); i++) 
     { 
      TabLayout.Tab tab = tabLayout.getTabAt(i); 
      tab.setCustomView(pagerAdapter.getTabView(i)); 
     } 

    } 

    class PagerAdapter extends FragmentStatePagerAdapter 
    { 

     String tabTitles[] = new String[] { "Tab One", "Tab Two", "Tab Three", }; 

     private int[] tabIcons = { R.drawable.tab_selector_calendar, R.drawable.tab_selector_favorite, R.drawable.tab_selector_settings 
     }; 

     Context context; 

     public PagerAdapter(FragmentManager fm, Context context) { 
      super(fm); 
      this.context = context; 
     } 

     @Override 
     public int getCount() { 
      return tabTitles.length; 
     } 

     @Override 
     public Fragment getItem(int position) { 

      switch (position) { 
       case 0: 
        return new FragmentAyah(); 
       case 1: 
        return new FragmentFavorite(); 
       case 2: 
        return new FragmentSettings(); 
      } 

      return null; 
     } 

     @Override 
     public CharSequence getPageTitle(int position) { 
      // Generate title based on item position 
      // return tabTitles[position]; 
      return null; 
     } 

     public View getTabView(int position) { 
      View tab = LayoutInflater.from(MainActivity.this).inflate(R.layout.custom_tab, null); 
      ImageView imgView = (ImageView) tab.findViewById(R.id.imgView); 

      imgView.setBackgroundResource(tabIcons[position]); 


      // TextView tv = (TextView) tab.findViewById(R.id.custom_text); 
      // tv.setText(tabTitles[position]); 
      return tab; 
     } 

    } 

} 
and Fragment code 

//标签1 FragmentAyah代码在这里在这里

public class FragmentAyah extends Fragment 
{ 
    private RecyclerView recyclerView; 
    private List<Ayat> ayatList = new ArrayList<>(); 
    private AyatAdapter ayatAdapter; 
    DBHelper dbHelperA; 
    List<AyatVariables> datalist = new ArrayList<AyatVariables>(); 
    String formattedDate = ""; 
    SimpleDateFormat df; 
    private Calendar c; 

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

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

     recyclerView = (RecyclerView) root.findViewById(R.id.recycler_view); 
     ayatAdapter = new AyatAdapter(ayatList,getActivity()); 

     dbHelperA = new DBHelper(getActivity()); 

     c = Calendar.getInstance(); 
     df = new SimpleDateFormat("yyyy-MM-dd"); 
     formattedDate = df.format(c.getTime()); 

     getAllValuesFromDB(); 

     RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity()); 
     recyclerView.setLayoutManager(mLayoutManager); 
     recyclerView.setItemAnimator(new DefaultItemAnimator()); 
     recyclerView.addItemDecoration(new SimpleDividerItemDecoration(getActivity())); 
     recyclerView.setAdapter(ayatAdapter); 
     ayatAdapter.notifyDataSetChanged(); 

     return root; 
    } 

    private void prepareMovieData() { 
     // AyatVariables ayat = new AyatVariables("Surah Al-Fatiha","Ayat","1",":11","Translation11"); 
for (int i = 0; i < datalist.size(); i++) { 
        Ayat ayat = new Ayat(datalist.get(i).getID(), datalist.get(i).getSURAH_NAME(), 
          datalist.get(i).getTEXTS(), datalist.get(i).getSURAH(), 
          datalist.get(i).getAYA(), datalist.get(i).getEN_TRANSLATION(), 
          datalist.get(i).getDATES()); 

        ayatList.add(ayat); 

       ayatAdapter.notifyDataSetChanged(); 
     } 
    } 

    @Override 
    public void onDestroyView() 
    { 
     super.onDestroyView(); 
     Log.e("onDestroyView======>","onDestroyView"); 
     ayatAdapter.notifyDataSetChanged(); 
     ayatList.clear(); 
    } 

    public void getAllValuesFromDB() 
    { 
     try { 
      dbHelperA.createDataBase(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 

     datalist.clear(); 
     datalist = dbHelperA.getDataWithAllTranslation(formattedDate); 
     // Log.e("datasize=========>",""+datalist.size()); 
     dbHelperA.close(); 

     prepareMovieData(); 
    } 

} 

//标签2 FragmentFavorite代码

public class FragmentFavorite extends Fragment { 

    private RecyclerView recyclerView; 
    private List<FAyat> ayatList = new ArrayList<>(); 
    private AyatFAdapter ayatAdapter; 
    DBHelper dbHelperA; 
    DBHelper2 dbHelperF; 
    List<AyatVariables> datalist = new ArrayList<AyatVariables>(); 
    List<FavVariables> fVar = new ArrayList<FavVariables>(); 
    String formattedDate = ""; 
    SimpleDateFormat df; 
    private Calendar c; 

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

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     ViewGroup root = (ViewGroup) inflater.inflate(R.layout.fragment_favorits, null); 
     recyclerView = (RecyclerView) root.findViewById(R.id.frecycler_view); 
     ayatAdapter = new AyatFAdapter(ayatList, getActivity()); 

     dbHelperA = new DBHelper(getActivity()); 
     dbHelperF = new DBHelper2(getActivity()); 

     c = Calendar.getInstance(); 
     df = new SimpleDateFormat("yyyy-MM-dd"); 
     formattedDate = df.format(c.getTime()); 

     getAllValuesFromDB(); 

     RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity()); 
     recyclerView.setLayoutManager(mLayoutManager); 
     recyclerView.setItemAnimator(new DefaultItemAnimator()); 
     recyclerView.setAdapter(ayatAdapter); 
     ayatAdapter.notifyDataSetChanged(); 

     return root; 
    } 

    private void prepareMovieData() { 
     // AyatVariables ayat = new AyatVariables("Surah Al-Fatiha","Ayat","1",":11","Translation11"); 

     for (int i = 0; i < datalist.size(); i++) { 
        FAyat ayat = new FAyat(datalist.get(i).getID(), datalist.get(i).getSURAH_NAME(), 
          datalist.get(i).getTEXTS(), datalist.get(i).getSURAH(), 
          datalist.get(i).getAYA(), datalist.get(i).getEN_TRANSLATION(), 
          datalist.get(i).getDATES()); 

        ayatList.add(ayat); 

          ayatAdapter.notifyDataSetChanged(); 
     } 
    } 

    @Override 
    public void onDestroyView() { 
     super.onDestroyView(); 
     ayatList.clear(); 
    } 

    public void getAllValuesFromDB() 
    { 
     getIDfromFav(); 

     try { 
      dbHelperA.createDataBase(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 

     for (int i = 0; i<fVar.size();i++) { 
      // datalist = dbHelperA.getAllDataForFav(fVar.get(i).getFavID()); 
      datalist.add(dbHelperA.getAllDataForFav(fVar.get(i).getFavID())); 

      Log.e("datasize=========>",""+datalist.size()); 
     } 
     dbHelperA.close(); 

     prepareMovieData(); 
    } 

    public void getIDfromFav() 
    { 
     fVar.clear(); 
     fVar = dbHelperF.getAllFav(); 
     Log.e("fVar--size",""+fVar.size()); 
     dbHelperF.close(); 
    } 

} 

Answer 1

你可以像非与数据更改使用多种方式耦合类。下面是一个示例代码与广播接收器：

在你的片段1，当有一些数据发生变化，为此，

Intent intent = new Intent("my-event"); 
// add data 
intent.putExtra("message", "data"); // This data can be anything which is changed. You can also use SharedPreference and can remove that after using it 
LocalBroadcastManager.getInstance(this).sendBroadcast(intent); 

现在，在片段2，首先，你必须注册该片段一个接收器，

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

// Register mMessageReceiver to receive messages. 
LocalBroadcastManager.getInstance(this).registerReceiver(mMessageReceiver, new IntentFilter("my-event")); 
} 

现在，注册后，你必须处理接收意图

// handler for received Intents for the "my-event" event 
private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() { 
@Override 
public void onReceive(Context context, Intent intent) { 
// Extract data included in the Intent or from SharedPreference in that case 
String message = intent.getStringExtra("message"); 
Log.d("receiver", "Got message: " + message); 
// In your case, you have to update the views or values in this method 
} 
}; 

并暂停监听onPause以避免null上下文

@Override 
protected void onPause() { 
// Unregister since the fragment is not visible 
LocalBroadcastManager.getInstance(this).unregisterReceiver(mMessageReceiver); 
super.onPause(); 
}