Android ViewPager首次不显示内容

Question

我正在处理带有片段的抽屉应用程序。抽屉中的一个选项称为片段，在该片段中，我设置了一个标签视图(带有片段(，显示图形。

当我第一次运行该应用程序时，我的标签正常工作，内容，图形和所有内容看起来都很棒。

我一旦单击该片段就转到任何其他片段，然后回来，选项卡以正确的标题显示，但没有内容，没有图形。

这是设置ViewPager的主要片段：

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((片段之一。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appthatmatter/GraphView用于绘图目的。

我尝试调试它，发现在远离选项卡并返回后，功能：

之后，我发现：

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

不会再被打电话了。它是第一次进行两倍，但是直到我正确关闭应用并重新启动之前，它永远不会。

任何人都可以帮助我找出我做的不对吗？

谢谢

Answer 1

我实际上修复了它。我必须更改：

adapter = new ViewPagerAdapter(getFragmentManager());

to

adapter = new ViewPagerAdapter(getChildFragmentManager());