Android 从表3返回时碎片消失

我有一个带有包含片段的ViewPager的活动。 第一个片段（书本）在单击按钮时创建嵌套片段（singlebook）。 问题是，当我从fragment3回来时，第一个片段及其组件已经不见了。我认为这与萨维斯塔或onDestroy有关

我尝试过重写onDestroy并在父片段（book）上使用childFragmentManager，但它并没有添加到后堆栈中

MainActivity.java:

public class MainActivity extends FragmentActivity {

ViewPager viewPager;
MyPagerAdapter adapter;
public FragmentManager fragmentManager = getSupportFragmentManager();

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TabLayout tabLayout = (TabLayout) findViewById(R.id.tl_tabs);
    viewPager = (ViewPager) findViewById(R.id.vp_12);

    Fragment[] fragments = new Fragment[3];
    fragments[0] = new Book();
    fragments[1] = new Search();
    fragments[2] = new Study();
    adapter = new MyPagerAdapter(fragmentManager, fragments);
    viewPager.setAdapter(adapter);
    tabLayout.setupWithViewPager(viewPager);
}
}

class MyPagerAdapter extends FragmentStatePagerAdapter {

    private Fragment[] fragments;

    public MyPagerAdapter(FragmentManager fm, Fragment[] fragments) {
        super(fm);
        this.fragments = fragments;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return fragments[0];
            case 1:
                return fragments[1];
            case 2:
                return fragments[2];
            default:
                return fragments[0];
        }
    }

    @Override
    public int getCount() {
        return fragments.length;
    }

    @Override
    public CharSequence getPageTitle(int position) {

        switch (position) {
            case 0:
                return "단어장";
            case 1:
                return "단어 검색";
            case 2:
                return "내 정보";
            default:
                return "";
        }
    }
}

public class Book extends Fragment {

FragmentManager fragmentManager;
private Button btn;
private EditText editText;

public Book() {
    // Required empty public constructor
}
@Override
public View onCreateView( LayoutInflater inflater,  ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_book, container, false);
    btn = (Button) view.findViewById(R.id.btn_toQuiz);
    editText =(EditText) view.findViewById(R.id.edit_text);
    ViewPager viewPager = (ViewPager) container;

    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            fragmentManager = getChildFragmentManager();

            fragmentManager.beginTransaction()
                    .add(R.id.fl_BookContainer,new singleBook(),"TAG")
                    .addToBackStack(null)
                    .commit();

        }
    });
    return view;
}

}

Book.java:

public class MainActivity extends FragmentActivity {

ViewPager viewPager;
MyPagerAdapter adapter;
public FragmentManager fragmentManager = getSupportFragmentManager();

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TabLayout tabLayout = (TabLayout) findViewById(R.id.tl_tabs);
    viewPager = (ViewPager) findViewById(R.id.vp_12);

    Fragment[] fragments = new Fragment[3];
    fragments[0] = new Book();
    fragments[1] = new Search();
    fragments[2] = new Study();
    adapter = new MyPagerAdapter(fragmentManager, fragments);
    viewPager.setAdapter(adapter);
    tabLayout.setupWithViewPager(viewPager);
}
}

class MyPagerAdapter extends FragmentStatePagerAdapter {

    private Fragment[] fragments;

    public MyPagerAdapter(FragmentManager fm, Fragment[] fragments) {
        super(fm);
        this.fragments = fragments;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0:
                return fragments[0];
            case 1:
                return fragments[1];
            case 2:
                return fragments[2];
            default:
                return fragments[0];
        }
    }

    @Override
    public int getCount() {
        return fragments.length;
    }

    @Override
    public CharSequence getPageTitle(int position) {

        switch (position) {
            case 0:
                return "단어장";
            case 1:
                return "단어 검색";
            case 2:
                return "내 정보";
            default:
                return "";
        }
    }
}

public class Book extends Fragment {

FragmentManager fragmentManager;
private Button btn;
private EditText editText;

public Book() {
    // Required empty public constructor
}
@Override
public View onCreateView( LayoutInflater inflater,  ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_book, container, false);
    btn = (Button) view.findViewById(R.id.btn_toQuiz);
    editText =(EditText) view.findViewById(R.id.edit_text);
    ViewPager viewPager = (ViewPager) container;

    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            fragmentManager = getChildFragmentManager();

            fragmentManager.beginTransaction()
                    .add(R.id.fl_BookContainer,new singleBook(),"TAG")
                    .addToBackStack(null)
                    .commit();

        }
    });
    return view;
}

}

---

默认情况下，FragmentStatePagerAdapter只能创建两个片段，当您转到第三个片段时，它将删除第一个片段。因此，解决方案是您需要调用setOffscreenPageLimit方法，保存在将适配器设置为查看寻呼机时添加到寻呼机适配器中的所有片段

Fragment[] fragments = new Fragment[3];
fragments[0] = new Book();
fragments[1] = new Search();
fragments[2] = new Study();
adapter = new MyPagerAdapter(fragmentManager, fragments);
viewPager.setAdapter(adapter);
viewPager.setOffscreenPageLimit(fragments.size());
tabLayout.setupWithViewPager(viewPager);

---

默认情况下，FragmentStatePagerAdapter只能创建两个片段，当您转到第三个片段时，它将删除第一个片段。因此，解决方案是您需要调用setOffscreenPageLimit方法，保存在将适配器设置为查看寻呼机时添加到寻呼机适配器中的所有片段

Fragment[] fragments = new Fragment[3];
fragments[0] = new Book();
fragments[1] = new Search();
fragments[2] = new Study();
adapter = new MyPagerAdapter(fragmentManager, fragments);
viewPager.setAdapter(adapter);
viewPager.setOffscreenPageLimit(fragments.size());
tabLayout.setupWithViewPager(viewPager);

到

到

---

您是否尝试使用父FragmentManager添加新片段？您是否尝试过viewPager.setOffscreenPageLimit（3）；其中3是你的页面数，请点击这里！多谢各位@MrazJason如果您发现此评论有帮助，请标记为向上投票。这也会帮助其他人如何提高投票率？我对这个网站很新。我真的再次感谢你。我在哪里可以找到upvote mark？…您是否尝试使用父FragmentManager添加新片段？您是否尝试过viewPager.setOffscreenPageLimit（3）；其中3是你的页面数，请点击这里！多谢各位@MrazJason如果您发现此评论有帮助，请标记为向上投票。这也会帮助其他人如何提高投票率？我对这个网站很新。我真的再次感谢你。我在哪里可以找到upvote mark？。。。