我遇到了困扰我好几天的问题.
主活动中有一个ViewPager,它将3个片段作为制表符片段保存.在第一个片段中有一个ListView,它包含一些视图,其中最重要的是另一个ViewPager.我想在子ViewPager中保存一些照片,并在这里使用更多片段.
现在有麻烦:
当第一个Fragment停止时(在屏幕上看到父ViewPager中的第三个片段)并恢复(用户切换到第二个片段),应用程序崩溃,调试器说:
java.lang.IllegalArgumentException: No view found for id 0x7f05008b (com.example.viewpager:id/sub_viewpager) for fragment ScreenSlidePageFragment
我已经使用了getChildFragmentManager(),因为这是nested fragments的情况.
以下是与父ViewPager中第一个片段对应的列表适配器的关键代码:
@Override
public View getView(int position, View convertView, ViewGroup parent) {
int type = getItemViewType(position);
switch (type) {
case TYPE_BANNER:
if (convertView == null) {
convertView = mBannerView.getBannerView(parent);
}
mBannerView.update(convertView);
break;
case TYPE_ITEM:
break;
}
return convertView;
}
这是mBannerView的代码:
public class BannerView {
private static final displayImageOptions IMAGE_OPTIONS_SCALE_stretched =
new displayImageOptions.Builder()
.cacheInMemory()
.cacheOndisc()
.imageScaleType(ImageScaleType.EXACTLY_stretched)
.build();
private FragmentActivity mActivity;
private Fragment mFragment;
private List<Banner> mBanners;
private ScreenSlidePagerAdapter mPagerAdapter;
private ViewPager mViewPager;
public BannerView(FragmentActivity activity, Fragment fragment) {
mActivity = activity;
mFragment = fragment;
}
public void update(View convertView) {
mViewPager = (ViewPager) convertView;
if (mBanners != null && !mBanners.isEmpty()) {
if (mPagerAdapter == null) {
mPagerAdapter = new ScreenSlidePagerAdapter(mFragment.getChildFragmentManager());
mViewPager.setAdapter(mPagerAdapter);
}
}
mViewPager.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mOnBannerClickListener != null) {
mOnBannerClickListener.onBannerClick();
}
}
});
}
class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
public ScreenSlidePagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return new ScreenSlidePageFragment(mBanners.get(position).getimageUrl());
}
@Override
public int getCount() {
return mBanners == null ? 0 : mBanners.size();
}
}
class ScreenSlidePageFragment extends Fragment {
private String mUrl;
ScreenSlidePageFragment(String url) {
super();
mUrl = url;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.item_banner, container, false);
if (view != null) {
ImageView imageView = (ImageView) view.findViewById(R.id.item_banner_image);
imageView.setLayoutParams(new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT));
ImageLoader.getInstance().displayImage(mUrl, imageView, IMAGE_OPTIONS_SCALE_stretched);
}
return view;
}
}
}
这是详细的错误列表:
11-10 18:12:19.217 1444-1444/? E/MessageQueue-JNI﹕ java.lang.IllegalArgumentException: No view found for id 0x7f05008b (com.example.viewpager:id/sub_viewpager) for fragment ScreenSlidePageFragment{428d8ea0 #0 id=0x7f05008b}
at android.support.v4.app.FragmentManagerImpl.movetoState(FragmentManager.java:919)
at android.support.v4.app.FragmentManagerImpl.movetoState(FragmentManager.java:1104)
at android.support.v4.app.FragmentManagerImpl.movetoState(FragmentManager.java:1086)
at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1884)
at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1514)
at android.support.v4.app.FragmentManagerImpl.movetoState(FragmentManager.java:947)
at android.support.v4.app.FragmentManagerImpl.attachFragment(FragmentManager.java:1280)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:672)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
at android.support.v4.view.ViewPager$3.run(ViewPager.java:244)
at android.support.v4.view.ViewPager.completeScroll(ViewPager.java:1761)
at android.support.v4.view.ViewPager.onInterceptTouchEvent(ViewPager.java:1896)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1854)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2211)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1912)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superdispatchTouchEvent(PhoneWindow.java:2228)
at com.android.internal.policy.impl.PhoneWindow.superdispatchTouchEvent(PhoneWindow.java:1471)
at android.app.Activity.dispatchTouchEvent(Activity.java:2424)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2176)
at android.view.View.dispatchPointerEvent(View.java:7571)
at android.view.ViewRootImpl$ViewPostImeInputStage.processpointerEvent(ViewRootImpl.java:3883)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3778)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3483)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3540)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3429)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3398)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3406)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3379)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5419)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5399)
at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5370)
at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5493)
at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:182)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:132)
at android.os.Looper.loop(Looper.java:124)
at android.app.ActivityThread.main(ActivityThread.java:5289)
at java.lang
解决方法:
更新:
我已经阅读了FragmentManager的源代码,最后得到了真正的原因:当viewpager附加到其父级之前,片段想要附加到viewpager时会发生此异常.换句话说,在getView()方法返回之前,片段会膨胀.然后调用ViewPager容器的findViewById()方法,但ViewPager仍处于分离状态,因此找到null并抛出IllegalArgumentException.
public class BannerViewPager extends ViewPager {
PagerAdapter mPagerAdapter;
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
if (mPagerAdapter != null) {
super.setAdapter(mPagerAdapter);
mPageIndicator.setViewPager(this);
}
}
@Override
public void setAdapter(PagerAdapter adapter) {
}
public void storeAdapter(PagerAdapter pagerAdapter) {
mPagerAdapter = pagerAdapter;
}
public BannerViewPager(Context context) {
super(context);
}
public BannerViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
}
在getView()方法中,使用storeAdapter()而不是setAdapter.
以下陈述不正确.上面的话就是实际的原因.
最后我得到了答案.它由两部分组成.
>在父ViewPager中,我使用FragmentPagerAdapter来保存片段,但现在我使用FragmentStatePagerAdapter.这两者之间的区别可以在这里找到:Difference between FragmentPagerAdapter and FragmentStatePagerAdapter.
简单来说,FragmentPagerAdapter将在片段停止时存储更多信息.在这种情况下,父ViewPager中的第一个片段会被停止但不会被销毁,而此片段中的视图将被销毁.恢复后,片段尝试重新膨胀所有视图.但是在调用getView()方法并重新创建子ViewPager之前,子FragmentManager尝试查找子ViewPager以保存先前存储的片段.因此,出现“java.lang.IllegalArgumentException:找不到id的视图”.
>用FragmentStatePagerAdapter替换FragmentPagerAdapter后,出现另一个问题.当父片段(父视图中的第一个片段)被停止,销毁和恢复时,子视图抓取器丢失.当选择第一个片段时很快就会发生这种情况,之后很快就会选择第三个片段,最后重新选择第一个片段.
我认为这是android sdk的一个bug.灵感来自here和here,我使用一些棘手的方法来解决问题.关键是,当一个父片段被销毁时,字段成员— mChildFragmentManager“最终会破坏内部状态”并且不会被彻底清除.重新创建父片段时,mChildFragmentManager不为null,但子片段在被销毁之后已被销毁,该片段由mChildFragmentManager管理.因此,子ViewPager在屏幕上显示一个空视图,该视图响应实际上不存在的假片段.有趣的是,在子ViewPager上直接滑动几次后,子片段和视图再次出现.
这是代码:
父适配器:
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = getBannerView(mParent);
}
mViewPager = (ViewPager) convertView;
if (mBanners != null && !mBanners.isEmpty()) {
if (mPagerAdapter == null) {
FragmentManager childFM = mFragment.getChildFragmentManager();
removeOldFragment(childFM);
mPagerAdapter = new ScreenSlidePagerAdapter(childFM, mBanners);
mViewPager.setAdapter(mPagerAdapter);
}
}
return convertView;
}
关键方法:
private void removeOldFragment(FragmentManager fm) {
try {
Field added = fm.getClass().getDeclaredField("mAdded");
added.setAccessible(true);
added.set(fm, null);
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
} catch (illegalaccessexception e) {
throw new RuntimeException(e);
}
try {
Field active = fm.getClass().getDeclaredField("mActive");
active.setAccessible(true);
active.set(fm, null);
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
} catch (illegalaccessexception e) {
throw new RuntimeException(e);
}
}
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