每次oncreateView片段时从活动中检索数据

Posted 2023-04-18

【中文标题】每次oncreateView片段时从活动中检索数据

【英文标题】：Retrive data from activity every time oncreateViwe of fragments

【发布时间】：2021-03-30 08:04:54

【问题描述】：

活动

public class GroupesActivity extends BaseActivity 
SelectedBundle selectedBundle;
 @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_groupes);
        sectionsPagerAdapter = new GroupPagerAdapter(this, getSupportFragmentManager());
    viewPager.setAdapter(sectionsPagerAdapter);
    tabs.setupWithViewPager(viewPager);
    

 private void getAllGroup() 
// api call retrive data
        // send data using interface on response     
        //   set data         selectedBundle.onBundleSelect(isVisible,calanderModelList,groupModelList,eventModelList);



  public void setOnBundleSelected(SelectedBundle selectedBundle) 
        this.selectedBundle = selectedBundle;
    

    public interface SelectedBundle 
        void onBundleSelect(boolean isVisible, List<CalanderModel> calanderModelList, List<GroupModel> groupModelList, List<EventModel> eventModelList);
    

片段

    public class FragmentOne extends Fragment 
      @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) 
            // Inflate the layout for this fragment
            View root = inflater.inflate(R.layout.fragment_all_groups_fragments, container, false);

// get data only once on oncreateview 

      ((GroupesActivity) getActivity()).setOnBundleSelected(new GroupesActivity.SelectedBundle() 
                @Override
                public void onBundleSelect(boolean isVisible, List<CalanderModel> calanderModelListtt, List<GroupModel> groupModelList, List<EventModel> eventModelList) 
    
                    Log.e("retrive data","data")
                
            );
    
    return root;
    
    

GroupPagerAdapter

public class GroupPagerAdapter extends FragmentPagerAdapter 
    @StringRes
    private static final int[] TAB_TITLES = new int[]R.string.tab_text_1, R.string.tab_text_2, R.string.tab_text_3;
    private final Context mContext;

    public GroupPagerAdapter(Context context, FragmentManager fm) 
        super( fm);
        this.mContext=context;
    

    @NonNull
    @Override
    public Fragment getItem(int position) 
        switch (position) 
            case 0:
                return new AllGroupsFragments();
            case 1:
                return new HostFragments();
            case 2:
                return new GuestFragments();
        
        return null;
    

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) 
        return mContext.getResources().getString(TAB_TITLES[position]);
    

    @Override
    public int getCount() 
        return 3;
    

问题

当我滑动这个上面的片段时，我在 tabview 中有三个片段 然后在这个没有调用接口的fragmnet中再次出现，我是 没有从活动中获取数据

如何从其父活动中再次获取该数据，我只需要 从片段 oncreateView 的每次活动中检索该数据

提前感谢 ;)

【参考方案1】：

在 Fragment 中使用setMenuVisibility() 方法来解决问题。

//In fragments
@Override
public void setMenuVisibility(final boolean isVisible) 
    super.setMenuVisibility(isVisible);
    if (isVisible) 
        //visible to user- do ur stuff
        ((GroupesActivity) getActivity()).setOnBundleSelected(new 
           GroupesActivity.SelectedBundle() 
            @Override
            public void onBundleSelect(boolean isVisible, List<CalanderModel> 
                calanderModelListtt, List<GroupModel> groupModelList, List<EventModel> 
                eventModelList) 

                Log.e("retrive data","data")
            
        );
    

如果您遇到任何问题，以下链接可能会有所帮助： How to determine when Fragment becomes visible in ViewPager

【讨论】：

感谢您的快速回答，但它给出了 NullPointerException: on interface method with on a null object reference at setOnBundleSelected

可以分享一下logcat日志吗？

问题是当我通过滑动 tabview 继续片段 3 并再次进入片段 1 时它再次创建并且那个时候这个接口方法没有调用

java.lang.NullPointerException：尝试在 com.illumaworks.Whenis 的空对象引用上调用虚拟方法“void com.activity.GroupesActivity.setOnBundleSelected(com.activity.GroupesActivity$SelectedBundle)”。 Fragments.AllGroupsFragments.setMenuVisibility(AllGroupsFragments.java:96)

fragment创建时有没有其他方法可以再次从父activity获取数据？