在动态 viewpager 片段中创建 recyclerviews

Question

我的布局中有一个 tablayout+viewpager。

片段及其选项卡是从我的数据库中的类别动态创建的，因此当用户创建或删除新类别时它们会更新。

然后我希望能够在每个选项卡中将相应类别的项目显示为 recyclerview 项目。我已经在创建/编辑它们的常规 recyclerviews 的其他地方显示了这些项目，因此只需让它们在此 viewpager 中以相同的方式显示，按选项卡排序。项目也将使用日历视图按日期过滤。

到目前为止，我有一个 DynamicFragmentAdapter：

package com.example.navgraphtest;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentStatePagerAdapter;

import org.jetbrains.annotations.NotNull;


public class DynamicFragmentAdapter extends FragmentStatePagerAdapter {
    private int mNumOfTabs;

    DynamicFragmentAdapter(FragmentManager fm, int NumOfTabs) {
        super(fm);
        this.mNumOfTabs = NumOfTabs;
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        Bundle b = new Bundle();
        b.putInt("position", position);
        Fragment frag = DynamicFragment.newInstance();
        frag.setArguments(b);
        return frag;
    }

    @Override
    public int getCount() {
        return mNumOfTabs;
    }
}

DynamicFragment 本身，目前只显示与其类别相关的索引

package com.example.navgraphtest;

import android.content.Context;
import android.os.Bundle;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;

import org.jetbrains.annotations.NotNull;

import java.util.ArrayList;


public class DynamicFragment extends Fragment {
    ArrayList<CategoryModel> arrayList;


    public static DynamicFragment newInstance() {
        return new DynamicFragment();
    }

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

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.dynamic_fragment_layout, container, false);
        initViews(view);
        return view;
    }

    private void initViews(View view) {

        DatabaseHelper databaseHelper = new DatabaseHelper(getActivity());
        arrayList = new ArrayList<CategoryModel>(databaseHelper.getCategories());

        TextView textView=view.findViewById(R.id.commonTextView);
         {
            textView.setText(String.valueOf("Category :  "+getArguments().getInt("position")));
        }
    }

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

    @Override
    public void onAttach(@NotNull Context context) {
        super.onAttach(context);
    }

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

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

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

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

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

在主片段内

package com.example.navgraphtest;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.viewpager.widget.ViewPager;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.google.android.material.tabs.TabLayout;
import com.prolificinteractive.materialcalendarview.CalendarDay;
import com.prolificinteractive.materialcalendarview.MaterialCalendarView;
import com.prolificinteractive.materialcalendarview.OnDateSelectedListener;

import org.threeten.bp.LocalDate;

import java.util.ArrayList;

import static android.content.ContentValues.TAG;

public class CalendarViewFragment extends Fragment {

    private MaterialCalendarView mCalendarView;
    private CalendarDay currentDate;
    private TextView mTextViewCurrentDate;
    private ViewPager mViewPager;
    private TabLayout mTabLayout;
    ArrayList<CategoryModel> arrayList;

    @Override
    public void onResume() {
        Log.d(TAG, "onResume: ");
        super.onResume();
        // Update ActionBar titles in MainActivity to reflect current fragment
        // Actionbar is in main layout not the fragments.
        ((MainActivity) getActivity()).setActionBarTitle("Calendar View");
        ((MainActivity) getActivity()).getSupportActionBar().setSubtitle("View your consumption history");

        // Open fragment with today's date selected on calendarview.
        mCalendarView.setSelectedDate(CalendarDay.today());

        // initViews for category tabs
        initViews();


    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Log.d(TAG, "onCreateView: ");


        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_calendar_view, container, false);



    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        Log.d(TAG, "onViewCreated: ");

        mTextViewCurrentDate = getActivity().findViewById(R.id.currentDateTextView);
        mCalendarView = getActivity().findViewById(R.id.calendarView);
        mCalendarView.setOnDateChangedListener(new OnDateSelectedListener(){
            @Override
            public void onDateSelected(@NonNull MaterialCalendarView widget, @NonNull CalendarDay date, boolean selected) {
                mTextViewCurrentDate.setText(String.valueOf(date));
            }

        });

        final NavController navController = Navigation.findNavController(view);
    }

    private void initViews(){
        Log.d(TAG, "initViews: ");

        mViewPager = getActivity().findViewById(R.id.viewPagerCalendarView);
        mTabLayout =  getActivity().findViewById(R.id.tabLayoutCalendarView);
        mViewPager.setOffscreenPageLimit(5);
        mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(mTabLayout));
        mTabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                mViewPager.setCurrentItem(tab.getPosition());
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });

        setDynamicFragmentToTabLayout();

    }

    private void setDynamicFragmentToTabLayout() {
        DatabaseHelper databaseHelper = new DatabaseHelper(getActivity());
        arrayList = new ArrayList<CategoryModel>(databaseHelper.getCategories());

        Log.d(TAG, "setDynamicFragmentToTabLayout: ");

        for (int i = 0; i < arrayList.size() ; i++) {

            mTabLayout.addTab(mTabLayout.newTab().setText(arrayList.get(i).getCategoryTitle()));
        }



        DynamicFragmentAdapter mDynamicFragmentAdapter = new DynamicFragmentAdapter(getActivity().getSupportFragmentManager(), mTabLayout.getTabCount());
        mViewPager.setAdapter(mDynamicFragmentAdapter);
        mViewPager.setCurrentItem(0);
    }
}

我真的不知道如何实现这一点，没有取消用户创建类别的选项并且只有一个固定的数字，但是我不知道如何获得这些项目在 tablayout/viewpager 中显示。

Answer 1

那么你的 dynamicFragmentAdapter 应该是这样的

    public class DynamicFragmentAdapter extends FragmentStatePagerAdapter {
    private int mNumOfTabs;
    Fragment fragment = null;
    ViewPager viewPager;
    ArrayList<Menu> fragDataList=new ArrayList<>();
    private List<String> tabNameList;
    Context context;

    public DynamicFragmentAdapter (Context  context,FragmentManager fm, int mNumOfTabs, List<String> tabNameList, ArrayList<Menu> fragDataList,ViewPager viewPager) {

        super(fm);
        this.mNumOfTabs = mNumOfTabs;
        this.tabNameList = tabNameList;
        this.fragDataList=fragDataList;
        this.context=context;
        this.viewPager=viewPager;


    }

    @Override
    public Fragment getItem(final int position) {
    
        for (int i = 0; i < mNumOfTabs ; i++) {
            
               fragment = GenericFragment.newInstance( fragDataList,position);
               Log.i("info",String.valueOf(position));

                break;


        }
        return fragment;
    }
    @Override
    public int getCount() {
        return mNumOfTabs;
    }

    @Override
    public CharSequence getPageTitle(int position) {
       return tabNameList.get(position);
      //  return super.getPageTitle(position);
    }
}

你的主要片段通过你可以从数据库中获取数据，viewpager和tablayout会是这样的

      //this method is used to set number of tabs dynamically
    private void sendData(int /*sizeof tabNames list*/ size, final List<String> tabName, final ArrayList<Menu> fragArrayList, List<Menu> positioncheck) {
        Log.d("My Msg", "Tab countert check = " + size);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            int pos = 0;

            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                Bundle bundle = new Bundle();
                bundle.putInt("position", position);

            }

            @Override
            public void onPageSelected(int position) {
                pos = position;


            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

        final DynamicFragmentAdapter dynamicFragmentAdapter = new DynamicFragmentAdapter (getApplicationContext(), getSupportFragmentManager(), size, tabName, fragArrayList, viewPager);
        viewPager.setAdapter(dynamicFragmentAdapter );
        //viewPager.setOffscreenPageLimit(5);
        // viewPager.setCurrentItem(tabLayout.getSelectedTabPosition());
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));

        tabLayout.addOnTabSelectedListener(new TabLayout.BaseOnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });
        tabLayout.setupWithViewPager(viewPager);

    }

你的 dynamicFragment 会得到数据

`public class DynamicFragment extends Fragment {
    static List<fragDAta> fragDataList;
    static int loopsize = 0;
    int mnum = 0;


   public static DynamicFragment newInstance(ArrayList<fragData> fragDataList, int position) {
        DynamicFragment.fragDataList = fragDataList;
        DynamicFragment f = new DynamicFragment ();

        // Supply num input as an argument.
        Bundle args = new Bundle();
        args.putInt("position", position);
        f.setArguments(args);
        DynamicFragment.loopsize = loopsize;
        return f;


    }

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

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mnum = getArguments() != null ? getArguments().getInt("position") : 1;
    }
  @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment


        return inflater.inflate(R.layout.fragment_dynamic, container, false);
    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);

    }

 @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

// here is your data
        Log.d("MYMSG", "DATA CHECK = " + fragDataList.size());


    }

    @Override
    public void onResume() { 
Log.d("MYMSG", "DATA CHECK = " + fragDataList.size());
super.onResume(); }

  
}`