android - 旋转时未调用 fragment onCreateView 和 onActivityCreated

Question

我正在处理 fragment 并将新 fragment 推送到后台堆栈，但是当我将设备旋转两次时， fragment 的 onCreateView、onActivityCreated 等等在 fragment 生命周期中永远不会调用方法而留下​​空白屏幕。这仅在 fragment 已添加到后台堆栈或返回到后台堆栈中的第一个 fragment 时发生。

这是我的 Activity 的 fragment 处理方法:

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

    // Injection
    MormonChannel.injectActivity(this);

    setDrawerIndicatorEnabled(true);

    // Do not set currentNavigationItem here.
    NavigationItemSelectedEvent.NavigationItem navItem = null;
    Intent intent = getIntent();
    if (intent != null) {
        navItem = (NavigationItemSelectedEvent.NavigationItem)
        intent.getSerializableExtra(EXTRA_NAV_ITEM);
    }

    if (savedInstanceState == null) {
        FragmentManager fm = getSupportFragmentManager();
        fm.beginTransaction().replace(R.id.container, new FeatureListFragment()).commit();
        if (navItem != null) {
            onNavigationItemSelected(new NavigationItemSelectedEvent(navItem));
        } else {
            currentNavigationItem = NavigationItemSelectedEvent.NavigationItem.FEATURES;
        }
    }

}

@Subscribe
public void onNavigationItemSelected(NavigationItemSelectedEvent event) {

    if (currentNavigationItem == event.getNavigationItem()) {
        return;
    }
    FragmentManager fragmentManager = getSupportFragmentManager();
    fragmentManager.popBackStack();
    NavigationItemSelectedEvent.NavigationItem navigationItem = event.getNavigationItem();
    String name = navigationItem.getName();
    switch (navigationItem) {
        default:
        case FEATURES:
            // Nothing needs to be done it is already there.
            break;
        case AUDIO:
            fragmentManager.beginTransaction().replace(R.id.container,
                    CollectionListFragment.newInstance(prefs.getLanguageId(), prefs.getAudioCollectionId()))
                    .addToBackStack
                            (name).commit();
            break;
        case VIDEO:
            fragmentManager.beginTransaction().replace(R.id.container,
                    CollectionListFragment.newInstance(prefs.getLanguageId(), prefs.getVideoCollectionId()))
                    .addToBackStack(name).commit();
            break;
        case RADIO:
            fragmentManager.beginTransaction().replace(R.id.container,
                    CollectionListFragment.newInstance(prefs.getLanguageId(), prefs.getRadioCollectionId()))
                    .addToBackStack(name).commit();
            break;
        case HISTORY:
            fragmentManager.beginTransaction().replace(R.id.container, new HistoryFragment()).addToBackStack(name).commit();
            break;
        case DOWNLOADS:
            fragmentManager.beginTransaction().replace(R.id.container, new DownloadsFragment()).addToBackStack(name).commit();
            break;
        case PLAYLISTS:
            fragmentManager.beginTransaction().replace(R.id.container, new PlaylistFragment()).addToBackStack(name).commit();
            break;
    }
    currentNavigationItem = navigationItem;
}

这是我的 CollectionListFragment 代码:

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.collection_list_fragment, container, false);
    ButterKnife.inject(this, v);
    return v;
}

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

    listView.setDividerHeight(0);
    listView.setFastScrollEnabled(true);


    Bundle args = getArguments();
    if (args != null) {
        languageId = args.getLong(ARG_LANGUAGE_ID, -1L);
        collectionId = args.getLong(ARG_COLLECTION_ID, -1L);
        if (args.containsKey(ARG_SORT)) {
            sort = (Sort) args.getSerializable(ARG_SORT);
        }
    }

    if (collectionId == -1L || languageId == -1L) {
        // TODO Implement Empty Collection Text
    } else {
        collection = collectionManager.findByCollectionId(languageId, collectionId);
        getLoaderManager().initLoader(LOADER_ID, null, this);
    }

    titleEvent = new TitleChangeEvent(collection != null ? collection.getTitle() : getString(R.string.app_name));
    bus.post(titleEvent);
}

Activity list :

<activity
    android:name=".activity.MainActivity"
    android:launchMode="singleTask">
    <meta-data
        android:name="android.app.default_searchable"
        android:value=".activity.SearchActivity"/>
</activity>

Answer 1

在您的 CollectionListFragment 代码中，在 onCreate() 方法中添加对 setRetainInstance() 方法的调用，并将 true 作为其参数:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRetainInstance(true);
    MormonChannel.injectFragment(this);

}

使用 setRetainInstance(true) 确保当配置更改发生时，activity 将被终止，但 android 不会破坏它托管的 fragment 。

相反，android 将保存 fragment 状态并将 fragment 与 Activity 分离。此外，它不会破坏 fragment ，因此稍后在创建托管 Activity 时不会创建它。因此 fragment 将不会收到对其 onDestroy() 和 onCreate() 方法的调用。