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Как использовать FragmentPagerAdapter, чтобы иметь вкладки с различным содержанием?

Я хочу иметь разные вкладки, где вы можете пролистывать, как на рынке Android. Каждая вкладка должна использовать один фрагмент и использовать один метод для него.

Это мой класс FragmentPagerAdapter:

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        Fragment fragment =null;
        switch (position) {
            case 0:
                fragment = new ConnectionFragment();
                break;
            case 1:
                fragment = new DataFragment();
                break;              
            case 2:
                fragment = new GraphFragment();
                break;          }
        return fragment;    
    }
    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }
}

И у меня есть три класса для каждого типа фрагмента/вкладки:

public static class ConnectionFragment extends Fragment {
    public static final String ARG_SECTION_NUMBER = "section_number";
    public String stringConnectionStatus = "Offline";
    public String stringWiflyIp = "0.0.0.0";

    public ConnectionFragment() {}

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View connectionView = inflater.inflate(R.layout.fragment_connection,
                container, false);
        TextView statusView = (TextView) connectionView.findViewById(R.id.status_label);
        statusView.setText("Connection status: " + stringConnectionStatus);
        TextView ipView = (TextView) connectionView.findViewById(R.id.ip_label);
        ipView.setText("WiFly IP: " + stringWiflyIp);
        /**TextView sectionBarView = (TextView) connectionView
                .findViewById(R.id.section_label);
        sectionBarView.setText("pups");"*/

        return connectionView;
    }
}

public static class DataFragment extends Fragment {

    public DataFragment() {}

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View dataView = inflater.inflate(R.layout.fragment_data,
                container, false);
        TextView sectionBarView = (TextView) dataView
                .findViewById(R.id.section_label);
        sectionBarView.setText("pups2");
        return dataView;
    }
}

public static class GraphFragment extends Fragment {

    public GraphFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_graph,
                container, false);
        TextView sectionBarView = (TextView) rootView
                .findViewById(R.id.section_label);
        sectionBarView.setText("pups3");
        return rootView;
    }
}

Каждый фрагмент должен быть настраиваемым, поэтому у меня есть три класса. 

Тем не менее приложение вылетает в методе getItem. Есть идеи? Спасибо!

Правка: полный MainActivity.Java:

import ...
public class MainActivity extends FragmentActivity {

    /**
     * The {@link Android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link Android.support.v4.app.FragmentPagerAdapter} derivative, which
     * will keep every loaded fragment in memory. If this becomes too memory
     * intensive, it may be best to switch to a
     * {@link Android.support.v4.app.FragmentStatePagerAdapter}.
     */
    SectionsPagerAdapter mSectionsPagerAdapter;
    public List<String> fragments = new Vector<String>();

    /**
     * The {@link ViewPager} that will Host the section contents.
     */
    ViewPager mViewPager;

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

        // Create the adapter that will return a fragment for each of the three
        // primary sections of the app.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.pager); //pager
        mViewPager.setAdapter(mSectionsPagerAdapter);


    }

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

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */


    public class SectionsPagerAdapter extends FragmentPagerAdapter {


        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
            fragments.add(ConnectionFragment.class.getName());
            fragments.add(DataFragment.class.getName());
            fragments.add(GraphFragment.class.getName());
            //fragmentsA = "fragments";

        }

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a DummySectionFragment (defined as a static inner class
            // below) with the page number as its lone argument.
            /*Fragment fragment =null;
            switch (position) {
                case 0:
                    fragment = new ConnectionFragment();
                    break;
                case 1:
                    fragment = new DataFragment();
                    break;              
                case 2:
                    fragment = new GraphFragment();
                    break;          }
            return fragment;*/
            return Fragment.instantiate(getBaseContext(), fragments.get(position));

        }
        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            Locale l = Locale.getDefault();
            switch (position) {
            case 0:
                return getString(R.string.title_section1).toUpperCase(l);
            case 1:
                return getString(R.string.title_section2).toUpperCase(l);
            case 2:
                return getString(R.string.title_section3).toUpperCase(l);
            }
            return null;
        }
    }


    /**
     * A dummy fragment representing a section of the app, but that simply
     * displays dummy text.
     */
    public static class ConnectionFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        public static final String ARG_SECTION_NUMBER = "section_number";
        public String stringConnectionStatus = "Offline";
        public String stringWiflyIp = "0.0.0.0";

        public ConnectionFragment() {}

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View connectionView = inflater.inflate(R.layout.fragment_connection,container, false);
            TextView statusView = (TextView) connectionView.findViewById(R.id.status_label);
            statusView.setText("Connection status: " + stringConnectionStatus);
            TextView ipView = (TextView) connectionView.findViewById(R.id.ip_label);
            ipView.setText("WiFly IP: " + stringWiflyIp);
            /**TextView sectionBarView = (TextView) connectionView
                    .findViewById(R.id.section_label);
            sectionBarView.setText("pups");"*/

            return connectionView;
        }
    }
    public static class DataFragment extends Fragment {

        public DataFragment() {}

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View dataView = inflater.inflate(R.layout.fragment_data,
                    container, false);
            //TextView sectionBarView = (TextView) dataView.findViewById(R.id.section_label);
            //sectionBarView.setText("pups2");
            return dataView;
        }
    }
    public static class GraphFragment extends Fragment {

        public GraphFragment() {}

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_graph,
                    container, false);
            //TextView sectionBarView = (TextView) rootView.findViewById(R.id.section_label);
            //sectionBarView.setText("pups3");
            return rootView;
        }
    }
}
19
timolemow

Создайте адаптер:

class MyPagerAdapter extends FragmentPagerAdapter {
        public List<String> fragmentsA; 

        public MyPagerAdapter(FragmentManager fm) {
            super(fm);
            fragmentsA = fragments;
        }

        @Override
        public Fragment getItem(int position) {
            //return MyFragment.newInstance();
            return Fragment.instantiate(context, fragmentsA.get(position));

        }

        @Override
        public CharSequence getPageTitle(int position) {
            //return CONTENT[position % CONTENT.length].toUpperCase();
            return mEntries.get(position % CONTENT.length).toUpperCase();
        }

        @Override
        public int getCount() {
           // return CONTENT.length;
            return mEntries.size();
        }

        @Override
        public int getItemPosition(Object object) {
            return POSITION_NONE;
        }
    }

Каждый фрагмент принадлежит к разным классам.

Таким образом, вы должны определить список фрагментов (они идут к основной FragmentActivity):

static MyPagerAdapter adapter;

и заполните его фрагментами:

fragments.add(ConnectionFragment.class.getName());
fragments.add(DataFragment.class.getName());
fragments.add(Tab3.class.getName());
//..etc

Затем вы должны добавить фрагменты к адаптеру следующим образом:

 pager = (ViewPager)findViewById(R.id.viewpager);
 adapter = new MyPagerAdapter(getSupportFragmentManager());
 pager.setAdapter(adapter);

MyPagerAdaper проверит все фрагменты, содержащиеся в списке fragments, а затем создаст экземпляр каждого из них.

15
Jani Bela

В своем методе FragmentPagerAdapter # getItem не создавайте объект фрагментов. Вам необходимо вернуть фрагмент следующим образом - 

return Fragment.instantiate(context, ConnectionFragment.class.getName());

Это означает, что метод будет выглядеть так - 

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

  @Override
  public Fragment getItem(int position) {
    Fragment fragment =null;
    switch (position) {
        case 0:
            fragment = Fragment.instantiate(context, ConnectionFragment.class.getName());
            break;
        case 1:
            fragment = Fragment.instantiate(context, DataFragment.class.getName());
            break;              
        case 2:
            fragment = Fragment.instantiate(context, GraphFragment.class.getName());
            break;          }
    return fragment;    
  }

  @Override
  public int getCount() {
    // Show 3 total pages.
    return 3;
  }
}
11
jaibatrik

Смотрите этот пример:

 public static class MyPagerAdapter extends FragmentPagerAdapter {
    private static int NUM_ITEMS = 3;

    public MyPagerAdapter(FragmentManager fragmentManager) {
        super(fragmentManager);
    }

    // Returns total number of pages
    @Override
    public int getCount() {
        return NUM_ITEMS;
    }

    // Returns the fragment to display for that page
    @Override
    public Fragment getItem(int position) {
        switch (position) {
        case 0: // Fragment # 0 - This will show FirstFragment
            return FirstFragment.newInstance(0, "Page # 1");
        case 1: // Fragment # 0 - This will show FirstFragment different title
            return FirstFragment.newInstance(1, "Page # 2");
        case 2: // Fragment # 1 - This will show SecondFragment
            return SecondFragment.newInstance(2, "Page # 3");
        default:
            return null;
        }
    }

    // Returns the page title for the top indicator
    @Override
    public CharSequence getPageTitle(int position) {
        return "Page " + position;
    }        
}
0
Iman Marashi