getChildFragmentManager() 无法解析或无法引用

Question

我知道，已经有很多关于这个主题的论坛帖子，但没有一个能解决我的问题

我的代码如下所示：

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);
....

但我收到了Cannot resolve method getChildFragmentManager ()，这似乎会造成很多问题。

我已经尝试了很多东西：

• 我检查了入站支持库的版本是否正确。
• 我尝试将该方法引用为 android.support.v7.app.getChildFragmentManager()，这让我遇到了 Cannot make static reference from non-static context 错误。
• 我重新导入了 v4 支持库

出现了整个问题，因为每当我返回活动时，片段就会变空。如果您有其他想法，请随时回答或发表评论，那么关于 getChildFragmentManager 的整个问题无论如何都解决了

我不知道该怎么办......

ps：这是整个类的实现：

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);
    }
}

如果您需要更多信息，请告诉我。

Answer 1

getChildFragmentManager() 是Fragment 的一个方法。由于您正在继承 AppCompatActivity，因此您无法访问它。如果您使用支持库中的Fragment，您可以使用getSupportFragmentManager()

Answer 2

你应该这样做：

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

Answer 3

我遇到了完全相同的问题，我通过简单地添加来解决它：

viewpager.setOffscreenPageLimit(2);

正如in this post所建议的那样。

Answer 4

这可能不是最优雅的解决方案，但在我的情况下，我需要 viewpager 在其自己的片段中运行，同时工具栏和 tablayout 驻留在 MainAcitivy 中。 唯一的缺点是您必须在其他不使用 Tab/Viewpager 的 Fragment 中手动隐藏 TabLayout。

但是这样你仍然可以从 Fragment 调用 getChildFragmentManager。

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

    viewPager = (ViewPager) v.findViewById(R.id.fm_feed_host_viewpager);

    setupViewPager(viewPager);

    ((MainActivity)getActivity()).mTabLayout.setupWithViewPager(viewPager);

    return v;
}

private void setupViewPager(ViewPager viewPager) {

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

    adapter.addFragment(new YourFragment(), "Title");
    adapter.addFragment(...);
    viewPager.setAdapter(adapter);
}

Answer 5

使用 Kotlin，与我使用的 Fragment 一起使用：

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