Android 使用带TabLayout的ViewPager时出现意外行为

大家好

我有一个带有TabLayout的片段，带有to选项卡，我实现了PagerAdapter，一切正常，问题是当我转到其他选项，然后我再次点击该选项，TabLayout显示但为空，我将与您分享我为此功能编写的代码：

适配器：

public class DevicePagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        switch (position){
            case 0:{
                return new fragmentDeviceCategory();
            }
            case 1:{
                return new fragmentDeviceRoom();
            }
            default:{
                return null;
            }
        }
    }

    @Override
    public int getCount() {
        return 2;
    }
}

TabLayout中某个片段的代码：

 public class fragmentDeviceList extends Fragment {

    protected ViewPager viewPager;

    public fragmentDeviceList() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActivity().setTitle(getResources().getString(R.string.title_devices_list));
    }

    @Override
    public void onResume() {
        super.onResume();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_device_list, container, false);
        TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp)));
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp)));
        }
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
        viewPager = (ViewPager) view.findViewById(R.id.pager);
        DevicePagerAdapter adapter = new DevicePagerAdapter(getFragmentManager());
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

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

            }

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

            }
        });
        return view;
    }
}

  public class fragmentDeviceList extends Fragment {

    protected ViewPager viewPager;

    public fragmentDeviceList() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActivity().setTitle(getResources().getString(R.string.title_devices_list));
    }

    @Override
    public void onResume() {
        super.onResume();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_device_list, container, false);
        TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp)));
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp)));
        }
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
        viewPager = (ViewPager) view.findViewById(R.id.pager);
        DevicePagerAdapter adapter = new DevicePagerAdapter(getFragmentManager());
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

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

            }

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

            }
        });
        return view;
    }
}

这是我在主持TabLayout的主片段中使用的代码：

 public class fragmentDeviceList extends Fragment {

    protected ViewPager viewPager;

    public fragmentDeviceList() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActivity().setTitle(getResources().getString(R.string.title_devices_list));
    }

    @Override
    public void onResume() {
        super.onResume();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_device_list, container, false);
        TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp)));
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp)));
        }
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
        viewPager = (ViewPager) view.findViewById(R.id.pager);
        DevicePagerAdapter adapter = new DevicePagerAdapter(getFragmentManager());
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

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

            }

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

            }
        });
        return view;
    }
}

  public class fragmentDeviceList extends Fragment {

    protected ViewPager viewPager;

    public fragmentDeviceList() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getActivity().setTitle(getResources().getString(R.string.title_devices_list));
    }

    @Override
    public void onResume() {
        super.onResume();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_device_list, container, false);
        TabLayout tabLayout = (TabLayout) view.findViewById(R.id.tab_layout);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_category)).setIcon(getResources().getDrawable(R.drawable.ic_category_black_36dp)));
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp, getActivity().getTheme())));
        } else {
            tabLayout.addTab(tabLayout.newTab().setText(getString(R.string.title_tab_by_room)).setIcon(getResources().getDrawable(R.drawable.ic_room_black_36dp)));
        }
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
        viewPager = (ViewPager) view.findViewById(R.id.pager);
        DevicePagerAdapter adapter = new DevicePagerAdapter(getFragmentManager());
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
            }

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

            }

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

            }
        });
        return view;
    }
}

---

注意：当我调试代码时，我注意到'fragmentDeviceList'中的'onCreateView'方法是它托管在TableLayout中的片段，但是'fragmentDeviceCategory'片段的'onCreateView'方法没有被触发。

我得到了问题的解决方案，解决方案非常简单，我认为我可以用作ViewPage FragmentPagerAdapter的适配器，因为我只想显示片段，但是这个类保持片段的状态，所以嵌套片段不会再次初始化，所以我将适配器更改为FragmentStatePagerAdapter，现在可以正常工作了

谢谢大家

要使用片段内的选项卡，您应该使用ChildFragmentManager

该行：

DevicePagerAdapter adapter = new DevicePagerAdapter(getFragmentManager());

应该是：

DevicePagerAdapter adapter = new DevicePagerAdapter(getChildFragmentManager());

FragmentPagerAdapter仅适用于两个片段，因为它将它们保存在内存中。FragmentStatePagerAdapter适用于大量碎片

TabLayout还有一个方法setupWithViewPager，它将： 该方法将：

添加一个ViewPager.OnPageChangeListener，它将事件转发到此TableLayout。 从ViewPager的PagerAdapter填充表格布局的选项卡。 设置TabLayout.ontAbsSelectedListener，它将所选事件转发到ViewPager

---

您可以使用它，而不是手动添加选项卡。

@JoseRaulPerera还可以查看我对ViewPager设置的编辑