ViewPager没有显示内部片段

Question

MainFragment包含一个加载多个IndexFragment实例的mViewPager。但是，viewpager没有显示片段，虽然使用调试器，整个代码执行成功没有问题

这是我的代码

MainFragment

//MainFragment.java
public class MainFragment extends Fragment {

    private SlidingTabLayout mSlidingTabLayout;
    private ViewPager mViewPager;
    private List<SamplePagerItem> mTabs = new ArrayList<SamplePagerItem>();

    private int tabSepColor;
    private int tabSelColor;

    private String[] mResources;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        tabSepColor = getResources().getColor(R.color.tab_separator);
        tabSelColor = getResources().getColor(R.color.tab_selector);

        mResources = getResources().getStringArray(R.array.sources);

        for (String resource : mResources) {
            mTabs.add(new SamplePagerItem(
                    resource, // Title
                    tabSelColor, // Indicator color
                    tabSepColor // Divider color
            ));
        }

    }



    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_main, container, false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {

        mViewPager = (ViewPager) view.findViewById(R.id.viewpager);
        mViewPager.setAdapter(new SamplePagerAdapter(getChildFragmentManager()));

        mSlidingTabLayout = (SlidingTabLayout) view.findViewById(R.id.sliding_tabs);
        mSlidingTabLayout.setViewPager(mViewPager);

        mSlidingTabLayout.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {

            @Override
            public int getIndicatorColor(int position) {
                return mTabs.get(position).getIndicatorColor();
            }

            @Override
            public int getDividerColor(int position) {
                return mTabs.get(position).getDividerColor();
            }

        });
    }

    static class SamplePagerItem {
        private final CharSequence mTitle;
        private final int mIndicatorColor;
        private final int mDividerColor;

        SamplePagerItem(CharSequence title, int indicatorColor, int dividerColor) {
            mTitle = title;
            mIndicatorColor = indicatorColor;
            mDividerColor = dividerColor;
        }

        Fragment createFragment() {
            return IndexFragment.newInstance(mTitle, mIndicatorColor, mDividerColor);
        }

        CharSequence getTitle() {
            return mTitle;
        }

        int getIndicatorColor() {
            return mIndicatorColor;
        }

        int getDividerColor() {
            return mDividerColor;
        }
    }

    class SamplePagerAdapter extends FragmentPagerAdapter {

        SamplePagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int i) {
            return mTabs.get(i).createFragment();
        }

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

        @Override
        public boolean isViewFromObject(View view, Object o) {
            return o == view;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return getResources().getStringArray(R.array.sources)[position];
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View) object);

        }

    }
}

IndexFragment

//IndexFragment.java
public class IndexFragment extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String KEY_TITLE = "title";
    private static final String KEY_INDICATOR_COLOR = "indicator_color";
    private static final String KEY_DIVIDER_COLOR = "divider_color";


    private int mBank;
    private int mQId;

    private Question question;
    private Context context;

    private CardView qCardView;
    private CardView expCardView;

    private CardListView ansCardView;

    public static IndexFragment newInstance(CharSequence title, int indicatorColor,
                                            int dividerColor) {
        Bundle bundle = new Bundle();
        bundle.putCharSequence(KEY_TITLE, title);
        bundle.putInt(KEY_INDICATOR_COLOR, indicatorColor);
        bundle.putInt(KEY_DIVIDER_COLOR, dividerColor);

        IndexFragment fragment = new IndexFragment();
        fragment.setArguments(bundle);

        return fragment;
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Bundle args = getArguments();

        if (args != null) {
            TextView title = (TextView) view.findViewById(R.id.item_title);
            title.setText("Title: " + args.getCharSequence(KEY_TITLE));

            int indicatorColor = args.getInt(KEY_INDICATOR_COLOR);
            TextView indicatorColorView = (TextView) view.findViewById(R.id.item_indicator_color);
            indicatorColorView.setText("Indicator: #" + Integer.toHexString(indicatorColor));
            indicatorColorView.setTextColor(indicatorColor);

            int dividerColor = args.getInt(KEY_DIVIDER_COLOR);
            TextView dividerColorView = (TextView) view.findViewById(R.id.item_divider_color);
            dividerColorView.setText("Divider: #" + Integer.toHexString(dividerColor));
            dividerColorView.setTextColor(dividerColor);
        }
    }

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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_index, container, false);
    }



}

布局

FragmentMain.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.hadiyazdi.orthopaedicmcqs.widgets.SlidingTabLayout
        android:id="@+id/sliding_tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:color="@color/White"
        android:background="@color/tab_background"/>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="0px"
        android:layout_weight="1"
        android:background="@color/Blue"/>

</LinearLayout>

FragmentIndex.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/ForestGreen"
    android:gravity="center">

    <TextView
        android:id="@+id/item_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TEST" />

    <TextView
        android:id="@+id/item_indicator_color"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/item_divider_color"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="TEST" />

</LinearLayout>