Question

当应用程序启动时，viewPager会正确显示，但是当我更改片段然后切换回来时，viewPager什么都不显示。我该如何解决这个问题？

结构是FragmentActivity＆gt; Fragment＆gt;（ViewPager with PagerAdapter）

应用启动时 before

切换到其他片段并返回后。 after

这是代码。

public class BuyFragment extends Fragment {

private final Float REFRESH_TRIGGER_DISTANCE = 100f; //pixel
private final Float iMAGE_HW_RATE = 0.4f;

ViewPager viewPager;
CustomPagerAdapter pagerAdapter;
ArrayList<String> adPaths;
DisplayMetrics metric;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    inflater.inflate(R.layout.fragment_buy, container);
    metric = new DisplayMetrics();
    getActivity().getWindowManager().getDefaultDisplay().getMetrics(metric);
    return super.onCreateView(inflater, container, savedInstanceState);
}
@Override
public void onResume() {
    initViewPager();
    initScrollView();
    super.onResume();
}
private void initViewPager() {
    viewPager = (ViewPager) getActivity().findViewById(R.id.viewpager_buy);
    adPaths = EntityUtil.getADPaths();
    pagerAdapter = new CustomPagerAdapter(getActivity(), adPaths);
    viewPager.setAdapter(pagerAdapter);
    int width  = metric.widthPixels;
    int height = Integer.parseInt(new java.text.DecimalFormat("0").format(width * iMAGE_HW_RATE));
    RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(width, height);
    viewPager.setLayoutParams(params);
    params.setMargins(0, 10, 0, 0);
    params.addRule(RelativeLayout.BELOW, R.id.layout_buy_category);
    CirclePageIndicator pageIndicator = (CirclePageIndicator) getActivity().findViewById(R.id.viewpagerindicator_buy);
    pageIndicator.setViewPager(viewPager);
}
private void initScrollView() {
    final PullToRefreshScrollView pullToRefreshScrollView = (PullToRefreshScrollView) getActivity().findViewById(R.id.layout_buy_refresh);
    pullToRefreshScrollView.setOnRefreshListener(new OnRefreshListener<ScrollView>() {
        @Override
        public void onRefresh(PullToRefreshBase<ScrollView> refreshView) {
            pagerAdapter.clearPicassoCache(adPaths);
            refreshView.onRefreshComplete();
        }
    });
}

}

fragment_buy.xml文件。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/grey_200"
    tools:context=".activity.MainActivity" xmlns:app="http://schemas.android.com/apk/res/com.liuchang">

    <LinearLayout
        android:id="@+id/layout_buy_titlebar"
        android:layout_width="fill_parent"
        android:layout_height="50dip"
        android:layout_alignParentTop="true"
        android:background="@color/teal_500"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btn_localize"
            android:layout_width="0dip"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@color/teal_500"
            android:onClick="toLocalizeActivity"
            android:text="城市"
            android:textColor="@color/white" />

        <TextView
            android:layout_width="0dip"
            android:layout_height="match_parent"
            android:layout_marginBottom="12dip"
            android:layout_marginLeft="20dip"
            android:layout_marginRight="20dip"
            android:layout_marginTop="12dip"
            android:layout_weight="3"
            android:background="@drawable/corner_bg"
            android:clickable="true"
            android:gravity="center"
            android:onClick="toSearchActivity"
            android:text="请输入药店或药品名称"
            android:textColor="@color/black" />
    </LinearLayout>

    <com.handmark.pulltorefresh.library.PullToRefreshScrollView
        xmlns:ptr="http://schemas.android.com/apk/res-auto"
        android:id="@+id/layout_buy_refresh"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_below="@id/layout_buy_titlebar" >

        <ScrollView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" >

            <RelativeLayout
                android:layout_width="fill_parent"
                android:layout_height="wrap_content" >

                <LinearLayout
                    android:id="@+id/layout_buy_category"
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical" >

            ...several buttons...

                </LinearLayout>

                <android.support.v4.view.ViewPager
                    android:id="@+id/viewpager_buy"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:layout_below="@id/layout_buy_category" />

                <com.viewpagerindicator.CirclePageIndicator
                    android:id="@+id/viewpagerindicator_buy"
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:layout_below="@id/viewpager_buy"
                    android:layout_marginTop="5dip"
                    app:fillColor="@color/teal_500" />
            </RelativeLayout>
        </ScrollView>
    </com.handmark.pulltorefresh.library.PullToRefreshScrollView>

</RelativeLayout>

Answer 1

更改onCreateView＆amp; onResume方法没有设置布局＆amp;适配器相关。

在OnCreateView您错过了返回虚增的视图。这里我在浏览视频通话onCreateView＆amp;之后更新了initScrollView();方法。 initViewPager();

您也可以在Fragment的onViewCreated方法中调用这两种方法。但在这里，我用onCreateView

给出答案

尝试以下代码＆amp;如果有的话，请告诉我

public class BuyFragment extends Fragment {

        private final Float REFRESH_TRIGGER_DISTANCE = 100f; //pixel
        private final Float iMAGE_HW_RATE = 0.4f;
        private View fragmentView;
        ViewPager viewPager;
        CustomPagerAdapter pagerAdapter;
        ArrayList<String> adPaths;
        DisplayMetrics metric;

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

        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            if (fragmentView == null)
                fragmentView = inflater.inflate(R.layout.fragment_buy, container, false);
            metric = new DisplayMetrics();
            getActivity().getWindowManager().getDefaultDisplay().getMetrics(metric);
            initViewPager();
            initScrollView();
            return fragmentView;
        }

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

        private void initViewPager() {
            if (fragmentView != null) {
                viewPager = (ViewPager) fragmentView.findViewById(R.id.viewpager_buy);
                adPaths = EntityUtil.getADPaths();
                pagerAdapter = new CustomPagerAdapter(getActivity(), adPaths);
                viewPager.setAdapter(pagerAdapter);
                int width = metric.widthPixels;
                int height = Integer.parseInt(new java.text.DecimalFormat("0").format(width * iMAGE_HW_RATE));
                RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(width, height);
                viewPager.setLayoutParams(params);
                params.setMargins(0, 10, 0, 0);
                params.addRule(RelativeLayout.BELOW, R.id.layout_buy_category);
                CirclePageIndicator pageIndicator = (CirclePageIndicator) fragmentView.findViewById(R.id.viewpagerindicator_buy);
                pageIndicator.setViewPager(viewPager);
            }
        }

        private void initScrollView() {
            if (fragmentView != null) {
                final PullToRefreshScrollView pullToRefreshScrollView = (PullToRefreshScrollView) fragmentView.findViewById(R.id.layout_buy_refresh);
                pullToRefreshScrollView.setOnRefreshListener(new OnRefreshListener<ScrollView>() {
                    @Override
                    public void onRefresh(PullToRefreshBase<ScrollView> refreshView) {
                        pagerAdapter.clearPicassoCache(adPaths);
                        refreshView.onRefreshComplete();
                    }
                });
            }
        }
    }

Answer 2

由于您的ViewPager位于Fragment而非活动内，因此您应该在适配器或适配器参考中尽可能使用getChildFragmentManager()而不是getActivity().getSupportFragmentManager();。

当onRusume时，ViewDeager与Fragr中的PagerAdapter消失

2 个答案: