getChildFragmentManager () cannot be resolved or cannot be referenced

Question

I know, there are many forum posts on this topic already, but none did solve my issue

My code looks like this:

private SectionsPagerAdapter myAdapt;
private ViewPager myPager;
....

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    if (mSectionsPagerAdapter == null) {
        mSectionsPagerAdapter = new SectionsPagerAdapter(getChildFragmentManager());
    }
    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);
....

But I get the Cannot resolve method getChildFragmentManager () which seems to make many problems.

I already tried a pretty whole lot of things:

• I checked the inbound support library for the correct version.
• I tried to reference the method as android.support.v7.app.getChildFragmentManager() which got me the Cannot make static reference from non-static context error.
• I reimported the v4 support library

The whole issue arose because the Fragments turn empty whenever I return to the activity. If you have another idea, feel free to answer or comment it, then the whole issue regarding the getChildFragmentManager is solved anyway

I have no clue what to do...

ps: here is the whole class implementation:

import android.support.v4.app.FragmentManager;
import android.content.Intent;
import android.os.AsyncTask;
import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;


public class HomeScreen extends AppCompatActivity {

    int index = 0;
    int semIndex = 0;

    public static final String GROUP_EXTRA = "Group";
    public static final String HOME_SCREEN_LOG = "HomeScreen Activity";

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link 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}.
     */
    private SectionsPagerAdapter mSectionsPagerAdapter;

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

    LayoutInflater inflater;

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        if (mSectionsPagerAdapter == null) {
            mSectionsPagerAdapter = new SectionsPagerAdapter(getChildFragmentManager());
        }
        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);

        final Bundle b;
        if ((b =this.getIntent().getExtras()) != null) {
            AsyncTask at = new AsyncTask() {
                @Override
                protected Object doInBackground(Object[] params) {

                    String  groupName = b.getString(HomeScreen.GROUP_EXTRA),
                            desc = b.getString(NewEditGroupActivity.DESC_EXTRA),
                            time = b.getString(NewEditGroupActivity.TIME_EXTRA),
                            date = b.getString(NewEditGroupActivity.DATE_EXTRA);

                    int numOfPart = b.getInt(NewEditGroupActivity.NUM_EXTRA);

                    boolean regular = b.getBoolean(NewEditGroupActivity.IS_NEW);

                    ExpandListChild elc = new ExpandListChild(desc,String.valueOf(numOfPart),date,time,regular);
                    ExpandListGroup elg = new ExpandListGroup(groupName);

                    MyLgFragment lf = (MyLgFragment) mSectionsPagerAdapter.getItem(0);
                    AllLgFragment af = (AllLgFragment) mSectionsPagerAdapter.getItem(1);

                    af.add(elc,elg);
                    lf.add(elc,elg);
                    return null;
                }
            };
        }

        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);    
        inflater = getLayoutInflater();
    }


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

Let me know if you need further information.

Answer 1

getChildFragmentManager() is a method of a Fragment. Since you are subclassing AppCompatActivity, you can't access it. If you are using the Fragment from the support library you can use getSupportFragmentManager()

Answer 2

Using Kotlin, used with my Frgament I used:

//using this.childFragmentManager
//not as this.childFragmentManager()
val sectionsPagerAdapter = CameraTabLayoutAdapter(this.childFragmentManager)

Answer 3

you should do like:

adapter = new ViewPagerAdapter(this.getChildFragmentManager());

Answer 4

I had exactly same issue and I managed to resolve it by simply adding:

viewpager.setOffscreenPageLimit(2);

As was suggested in this post.