我这里有一个奇怪的情况。我有一个FragmentActivity有TabHost5 个选项卡的。在我拥有的其中两个选项卡中ViewPager。假设这些选项卡是“Tab-A”和“Tab-B”，现在 Tab-A 内部有 3 个片段ViewPager，Tab-B 有 2 个。所有这些片段都是不同的。我正在使用我的自定义FragmentPagerAdapter来填充 ViewPagers。奇怪的是，当我从 Tab-A/Tab-B 切换到另一个选项卡并返回到它时，ViewPager 不再显示片段，或者它显示一个或两个片段但不显示 3.甚至更多，有时片段Tab-A 的 ViewPager 中的（不是全部）显示到 Tab-B 的 ViewPager 中，即使它们使用 2 个不同的适配器。
通过搜索，我了解到这可能是由于片段的嵌套（因为 ViewPager 在片段中，并且它的页面也是片段）。我试过传递 FragmentPagerAdaptergetChildFragmentManager()而不是getFragmentManager(). 但在那种情况下，当我切换到另一个选项卡并返回到 Tab-A/Tab-B 时，应用程序崩溃（请参阅下面的日志）。
我在下面粘贴我的代码。布局为FragmentActivity
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- The main content view -->
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TabHost
android:id="@android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<LinearLayout android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_weight="0"/>
<FrameLayout
android:id="@+android:id/realtabcontent"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1"/>
<TabWidget android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0" />
</LinearLayout>
</TabHost>
</FrameLayout>
<!-- The navigation drawer -->
<ListView android:id="@+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:background="@android:color/darker_gray"/>
</android.support.v4.widget.DrawerLayout>
在活动中，我为每个选项卡维护一个单独的片段堆栈。这是在选项卡开关上添加或显示片段的方式
/*Comes here when user switch tab, or we do programmatically*/
TabHost.OnTabChangeListener listener = new TabHost.OnTabChangeListener() {
public void onTabChanged(String tabId) {
/*Set current tab..*/
mCurrentTab = tabId;
if(mStacks.get(tabId).size() == 0){
/*
* First time this tab is selected. So add first fragment of that tab.
* Dont need animation, so that argument is false.
* We are adding a new fragment which is not present in stack. So add to stack is true.
*/
if(tabId.equals(TABTAGS.MessageTab))
{
FragmentInbox_ MessageFragment=new FragmentInbox_();
pushFragments(tabId, MessageFragment, false,true);
}
else if(tabId.equals(TABTAGS.VIPTab))
{
VIPOffers_ VIPTab=new VIPOffers_();
Bundle b=new Bundle();
b.putInt("mode", 1);
VIPTab.setArguments(b);
pushFragments(tabId, VIPTab, false,true);
}
else if(tabId.equals(TABTAGS.DatingTab))
{
FragmentDating_ datingTab=new FragmentDating_();
pushFragments(tabId, datingTab, false,true);
}
else if(tabId.equals(TABTAGS.VenueTab))
{
Fragment_EventPager_ venueTab=new Fragment_EventPager_();
pushFragments(tabId, venueTab, false,true);
}
}
else
{
/*
* We are switching tabs, and target tab is already has atleast one fragment.
* No need of animation, no need of stack pushing. Just show the target fragment
*/
pushFragments(tabId, mStacks.get(tabId).lastElement(), false,false);
}
}
};
这是在选项卡中添加或删除新片段的方式
public void pushFragments(String tag, Fragment fragment,boolean shouldAnimate, boolean shouldAdd){
if(shouldAdd)
mStacks.get(tag).push(fragment);
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
if(shouldAnimate)
ft.setCustomAnimations(R.anim.slide_in_right, R.anim.slide_out_left);
ft.replace(R.id.realtabcontent, fragment);
ft.commit();
}
public void popFragments(){
/*
* Select the second last fragment in current tab's stack..
* which will be shown after the fragment transaction given below
*/
Fragment fragment = mStacks.get(mCurrentTab).elementAt(mStacks.get(mCurrentTab).size() - 2);
/*pop current fragment from stack.. */
mStacks.get(mCurrentTab).pop();
/* We have the target fragment in hand.. Just show it.. Show a standard navigation animation*/
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
ft.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_right);
ft.replace(R.id.realtabcontent, fragment);
ft.commit();
}
@Override
public void onBackPressed()
{
if(mStacks.get(mCurrentTab).size() == 1){
super.onBackPressed(); // or call finish..
}else{
popFragments();
}
}
这是具有的Fragment布局ViewPager
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/profile_pager"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<android.support.v4.view.PagerTabStrip
android:id="@+id/pager_header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
android:background="@color/bar_back"
android:textColor="@android:color/holo_blue_light" />
</android.support.v4.view.ViewPager>
这就是适配器ViewPager的设置方式。（我使用了 Android Annotation 库）
@AfterViews
void InitiateViews()
{
getActivity().getActionBar().setDisplayShowCustomEnabled(false);
getActivity().getActionBar().setTitle("Dating");
getActivity().getActionBar().setIcon(R.drawable.nav_dating);
setHasOptionsMenu(true);
Pager.setOffscreenPageLimit(2);
SearchPagerAdapter adapter=new SearchPagerAdapter(getFragmentManager());
Pager.setAdapter(adapter);
}
最后FragmentPagerAdapter
public class SearchPagerAdapter extends FragmentPagerAdapter{
ArrayList<Fragment> Fragments;
final int PAGE_COUNT=3;
public SearchPagerAdapter(FragmentManager fm)
{
super(fm);
// TODO Auto-generated constructor stub
Fragments=new ArrayList<Fragment>();
Fragments.add(new FragmentBasicSearch_());
Fragments.add(new FragmentSearchSealed_());
Fragments.add(new Fragment_Username_Search_());
}
@Override
public Fragment getItem(int pos) {
// TODO Auto-generated method stub
if(Fragments==null)
{
Fragments=new ArrayList<Fragment>();
Fragments.add(new FragmentBasicSearch_());
Fragments.add(new FragmentSearchSealed_());
Fragments.add(new Fragment_Username_Search_());
}
if(pos<PAGE_COUNT)
{
Log.d("PF", "get pager fragment");
return Fragments.get(pos);
}
return null;
}
@Override
public CharSequence getPageTitle(int position) {
// TODO Auto-generated method stub
switch (position)
{
case 0:
return "BASIC SEARCH";
case 1:
return "SEALED SECTION SEARCH";
case 2:
return "UERNAME SEARCH";
}
return super.getPageTitle(position);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return PAGE_COUNT;
}
}
下面是Logcat我通过传递得到的输出FragmentPagerAdapter ChildFragmentManager
10-01 17:16:33.103: E/AndroidRuntime(3093): FATAL EXCEPTION: main
10-01 17:16:33.103: E/AndroidRuntime(3093): java.lang.IllegalStateException: No activity
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1091)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1086)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1877)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1492)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1460)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:440)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.os.Handler.handleCallback(Handler.java:605)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.os.Handler.dispatchMessage(Handler.java:92)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.os.Looper.loop(Looper.java:137)
10-01 17:16:33.103: E/AndroidRuntime(3093): at android.app.ActivityThread.main(ActivityThread.java:4441)
10-01 17:16:33.103: E/AndroidRuntime(3093): at java.lang.reflect.Method.invokeNative(Native Method)
10-01 17:16:33.103: E/AndroidRuntime(3093): at java.lang.reflect.Method.invoke(Method.java:511)
10-01 17:16:33.103: E/AndroidRuntime(3093): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-01 17:16:33.103: E/AndroidRuntime(3093): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
10-01 17:16:33.103: E/AndroidRuntime(3093): at dalvik.system.NativeStart.main(Native Method)
任何帮助或建议将不胜感激。