android - 选项卡 fragment 内的 Cardview

Question

我正在研究带有滑动选项卡的 Material 设计抽屉导航，我已经实现了同样的功能。现在我想在其中一个选项卡 fragment 中添加 cardview 和 recycler view 但不知道该怎么做。

有人可以帮我解决这个问题吗？

这是我的Tab fragment 代码:-

    public class TabFragment extends Fragment {

    public static TabLayout tabLayout;
    public static ViewPager viewPager;
    public static int int_items = 2 ;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        /**
         *Inflate tab_layout_tens and setup Views.
         */
        View x =  inflater.inflate(R.layout.tab_layout_tens,null);
        tabLayout = (TabLayout) x.findViewById(R.id.tabs);
        viewPager = (ViewPager) x.findViewById(R.id.viewpager);

        /**
         *Set an Apater for the View Pager
         */
        viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));

        /**
         * Now , this is a workaround ,
         * The setupWithViewPager dose't works without the runnable .
         * Maybe a Support Library Bug .
         */

        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                tabLayout.setupWithViewPager(viewPager);
            }
        });

        return x;

    }

    class MyAdapter extends FragmentPagerAdapter{

        public MyAdapter(FragmentManager fm) {
            super(fm);
        }

        /**
         * Return fragment with respect to Position .
         */

        @Override
        public Fragment getItem(int position)
        {
            switch (position){
                case 0 : return new CurrentFragment();
                case 1 : return new FavouriteFragment();

            }
            return null;
        }

        @Override
        public int getCount() {

            return int_items;

        }

        /**
         * This method returns the title of the tab according to the position.
         */

        @Override
        public CharSequence getPageTitle(int position) {

            switch (position){
                case 0 :
                    return "Current";
                case 1 :
                    return "Favourite";

            }
            return null;
        }
    }
}

这是我的 fragment 类，我在其中添加了回收器 View ，但它在设置适配器时给出了NULL Point exception。

 public class FavouriteFragment extends Fragment {
    private List<Person> persons;
    private RecyclerView rv;

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

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.favourite_layout,container,false);

        RecyclerView rv = (RecyclerView)rootView.findViewById(R.id.rv);
        final LinearLayoutManager llm = new LinearLayoutManager(getActivity());
        rv.setLayoutManager(llm);

        initializeData();
        initializeAdapter();
        return rootView;
    }
    private void initializeData(){
        persons = new ArrayList<>();
        persons.add(new Person("XYZ", "jhxdjksd", R.drawable.profilepic));
        persons.add(new Person("ABC", "bsxhbs", R.drawable.profilepic));
        persons.add(new Person("PQR", "bsahxb", R.drawable.profilepic));
    }

    private void initializeAdapter(){
        RVAdapter adapter = new RVAdapter(persons);
        rv.setAdapter(adapter);
    }
}

主 Activity

    public class Tens extends AppCompatActivity {

    DrawerLayout mDrawerLayout;
    NavigationView mNavigationView;
    FragmentManager mFragmentManager;
    FragmentTransaction mFragmentTransaction;

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

        /**
         *Setup the DrawerLayout and NavigationView
         */

        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
        mNavigationView = (NavigationView) findViewById(R.id.shitstuff) ;

        /**
         * Lets inflate the very first fragment
         * Here , we are inflating the TabFragmentTens as the first Fragment
         */

        mFragmentManager = getSupportFragmentManager();
        mFragmentTransaction = mFragmentManager.beginTransaction();
        mFragmentTransaction.replace(R.id.containerView,new TabFragmentTens()).commit();
        /**
         * Setup click events on the Navigation View Items.
         */

        mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {

                Fragment fragment = null;

                Class fragmentClass = null;
                switch(menuItem.getItemId()) {
                    case R.id.nav_item_tracker:
                        Intent intent = new Intent(
                        Tens.this, Tracker.class);
                startActivity(intent);
                        break;
                    case R.id.nav_item_clinic:
                        fragmentClass = ClinicFragment.class;
                        break;
                    case R.id.nav_item_about:
                        Intent intent0 = new Intent(
                                Tens.this, AboutFragment.class);
                        startActivity(intent0);
                        break;
                    case R.id.nav_item_settings:
                        Intent intent1 = new Intent(
                                Tens.this, SettingsFragment.class);
                        startActivity(intent1);
                        break;

                    case R.id.nav_item_logout:
                        Intent intent2 = new Intent(
                                Tens.this, MainActivity.class);
                        startActivity(intent2);

                        break;
                }

                try {
                    fragment = (Fragment) fragmentClass.newInstance();
                } catch (Exception e) {
                    e.printStackTrace();
                }

                FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
                    xfragmentTransaction.replace(R.id.containerView, new TabFragmentTens()).commit();

                mDrawerLayout.closeDrawers();


                return false;
            }

        });


        android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
        ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout, toolbar,R.string.app_name,
                R.string.app_name);

        mDrawerLayout.setDrawerListener(mDrawerToggle);

        mDrawerToggle.syncState();

    }
}

这是我的recyclerview 类:-

 public class RVAdapter extends RecyclerView.Adapter<RVAdapter.PersonViewHolder> {

    public static class PersonViewHolder extends RecyclerView.ViewHolder {

        CardView cv;
        TextView personName;
        TextView personAge;
        ImageView personPhoto;

        PersonViewHolder(View itemView) {
            super(itemView);
            cv = (CardView)itemView.findViewById(R.id.cv);
            personName = (TextView)itemView.findViewById(R.id.person_name);
            personAge = (TextView)itemView.findViewById(R.id.person_age);
            personPhoto = (ImageView)itemView.findViewById(R.id.person_photo);
        }
    }

    List<Person> persons;

    RVAdapter(List<Person> persons){
        this.persons = persons;
    }

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);
    }

    @Override
    public PersonViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
        View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.card_view_tens_fvrt, viewGroup, false);
        PersonViewHolder pvh = new PersonViewHolder(v);
        return pvh;
    }

    @Override
    public void onBindViewHolder(PersonViewHolder personViewHolder, int i) {
        personViewHolder.personName.setText(persons.get(i).name);
        personViewHolder.personAge.setText(persons.get(i).age);
        personViewHolder.personPhoto.setImageResource(persons.get(i).photoId);
    }

    @Override
    public int getItemCount() {
        return persons.size();
    }

我想在 Favourite fragment 中添加 cardview 和 recycler view。我知道如何实现 cardview 但无法在 fragment 中实现它。

Answer 1

首先在您的主要 Activity 中进行更改。在这里，我在 mainactivity 中添加了一个抽屉导航和 tablayout。

public class HomeActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        TabLayout tabLayout1 = (TabLayout) findViewById(R.id.tab_layout1);
        tabLayout1.addTab(tabLayout1.newTab().setIcon(R.drawable.tab_ic_home));
        tabLayout1.addTab(tabLayout1.newTab().setIcon(R.drawable.tab_ic_map));
        tabLayout1.addTab(tabLayout1.newTab().setIcon(R.drawable.tab_ic_login));

        tabLayout1.setTabGravity(TabLayout.GRAVITY_FILL);

        final ViewPager viewPager1 = (ViewPager) findViewById(R.id.pager1);
        final PagerAdapter1 adapter = new PagerAdapter1
                (getSupportFragmentManager(), tabLayout1.getTabCount());
        viewPager1.setAdapter(adapter);
        viewPager1.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout1));
        tabLayout1.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager1.setCurrentItem(tab.getPosition());
            }

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

            }

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

            }
        });
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.home, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        // Handle navigation view item clicks here.
        int id = item.getItemId();
        RelativeLayout mainLayout=(RelativeLayout)findViewById(R.id.main_layout);

           if (id == R.id.nav_project) {
            ProjectFragment fragment = new ProjectFragment();
            fragmentTransaction.replace(R.id.mainlayout, fragment);
            fragmentTransaction.addToBackStack(null).commit();
            }
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

然后创建一个寻呼机适配器。在这里你可以为你的标签添加 fragment ..我将其命名为 PagerAdapter1.java。

  import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;

public class PagerAdapter1 extends FragmentStatePagerAdapter {
    int mNumOfTabs;

    public PagerAdapter1(FragmentManager fm, int NumOfTabs) {
        super(fm);
        this.mNumOfTabs = NumOfTabs;
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                HomeTabFragment1 tab1 = new HomeTabFragment1();
                return tab1;
            case 1:
                HomeTabFragment2 tab2 = new HomeTabFragment2();
                return tab2;
            case 2:
                HomeTabFragment3 tab3 = new HomeTabFragment3();
                return tab3;
            default:
                return null;
        }
    }

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

我只想在第一个选项卡中显示 Recycler View 。所以我在 HomeTabFragment1.java 中添加了 recyclerview 的代码。

public class HomeTabFragment1 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v=inflater.inflate(R.layout.home_tab_fragment_1, container, false);
        RecyclerView rv = (RecyclerView)v.findViewById(R.id.home_recyclerview);
        setupRecyclerView(rv);
        return v;

我希望你能做剩下的事..