Android ViewPager 第一次后不显示内容

Question

我正在开发一个带有 fragment 的抽屉式应用程序。抽屉中的一个选项调用了一个 fragment ，我在其中设置了一个显示图形的选项卡式 View (带有 fragment )。

当我第一次运行该应用程序时，我的选项卡运行良好，内容、图表和一切看起来都很棒。

只要我点击离开那个 fragment 并转到任何其他 fragment ，然后返回，选项卡就会显示正确的标题，但没有内容，没有图表什么都没有。

这是我设置 viewpager 的主要 fragment :

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;

public class StatsMain extends Fragment {
    private ViewPagerAdapter adapter = null;
    private TabLayout tabLayout = null;
    private ViewPager viewPager = null;

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    return inflater.inflate(R.layout.stats_main, container, false);
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    viewPager = (ViewPager) view.findViewById(R.id.viewpager);
    tabLayout = (TabLayout) view.findViewById(R.id.tabs);

    setupViewPager(viewPager);
    tabLayout.setupWithViewPager(viewPager);

}

private void setupViewPager(ViewPager viewPager) {
    adapter = new ViewPagerAdapter(getFragmentManager());
    adapter.addFragment(new Stats1(), "Stats 1");
    adapter.addFragment(new Stats2(), "Stats 2");
    viewPager.setAdapter(adapter);
}

class ViewPagerAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
    }
}
}

这是我的布局:

<android.support.design.widget.CoordinatorLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:tabMode="fixed"
        app:tabGravity="fill"/>
</android.support.design.widget.AppBarLayout>

<android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"  />

</android.support.design.widget.CoordinatorLayout>

这是我的 Stats() fragment 之一。第二个看起来非常相似:

public class Stats1 extends Fragment {
GraphView graph;
public Stats1 () {
    // Required empty public constructor
}

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {


    return inflater.inflate(R.layout.stats1, container, false);

}

@Override
public void onViewCreated(View view, Bundle savedInstanceState){
    Calendar calendar = Calendar.getInstance();
    Date d1 = calendar.getTime();
    calendar.add(Calendar.DATE, 1);
    Date d2 = calendar.getTime();
    calendar.add(Calendar.DATE, 1);
    Date d3 = calendar.getTime();
    calendar.add(Calendar.DATE, 1);
    Date d4 = calendar.getTime();
    calendar.add(Calendar.DATE, 1);
    Date d5 = calendar.getTime();

    graph = (GraphView) view.findViewById(R.id.graph);
    StaticLabelsFormatter staticLabelsFormatter = new 
StaticLabelsFormatter(graph);

    staticLabelsFormatter.setHorizontalLabels(new String[] {"old", "middle", "new"});

    graph.setTitle("Data History");
    LineGraphSeries<DataPoint> series = new LineGraphSeries<DataPoint>(new DataPoint[] {
            new DataPoint(d1, 145.4),
            new DataPoint(d2, 145.9),
            new DataPoint(d3, 147.2),
            new DataPoint(d4, 146.5),
            new DataPoint(d5, 147.1)
    });

    graph.getViewport().setScalable(true);

    graph.addSeries(series);
// set date label formatter
    //graph.getGridLabelRenderer().setLabelFormatter(new 
DateAsXAxisLabelFormatter(this));
    graph.getGridLabelRenderer().setLabelFormatter(staticLabelsFormatter);

    //graph.getGridLabelRenderer().setNumHorizontalLabels(6); // only 4 because of the space
    series.setDrawDataPoints(true);

// set manual x bounds to have nice steps
    graph.getViewport().setMinX(d1.getTime());
    graph.getViewport().setMaxX(d5.getTime());
    graph.getViewport().setXAxisBoundsManual(true);

// as we use dates as labels, the human rounding to nice readable numbers
// is not necessary
    graph.getGridLabelRenderer().setHumanRounding(false);
}

我使用 appsthatmatter/GraphView 来作图。

我尝试调试它，我发现在我离开选项卡并返回后，功能:

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

不会再被调用了。第一次它会执行两次，但在我正确关闭应用程序并重新启动之前它永远不会执行。

有人能帮我找出我做错了什么吗？

谢谢

Answer 1

我真的修好了。我不得不改变:

adapter = new ViewPagerAdapter(getFragmentManager());

到

adapter = new ViewPagerAdapter(getChildFragmentManager());