Android - 使用 FragmentStatePagerAdapter 的 BackStack 问题
Android - Problems with BackStack using FragmentStatePagerAdapter
我正在构建一个 Android 应用程序，它使用 FragmentStatePagerAdapter 用于选项卡式导航和每个选项卡中的动态内容。每个选项卡都有 Fragment 内容，用户输入时会替换内容（例如，第一个选项卡有一个 Fragment 包含书籍列表，点击后，您可以访问该书的详细信息，使用另一个 Fragment
显示
问题：我还没有找到正确处理 onBack 事件和 BackStack 的方法，所以当我查看任何书籍的详细信息时，我可以轻松地按后退按钮返回 - 我的意思是, 从 BackStack 弹出最后一个状态。
我怀疑的是：我切换 Fragment 对象的方式可能不是最好的方式，但除了后退按钮问题外，它工作正常。我怀疑 FragmentStatePagerAdapter 的适配器和 FragmentManager 自己的 Fragment 集合之间存在一些问题；可能这是我没有看到的简单解决方案。
未回答的问题（虽然不是很详细）：Adding Fragment to BackStack using FragmentStatePagerAdapter
代码：
// MAIN ACTIVITY, 就这么简单。
public class MainActivity extends FragmentActivity {
public static final String TAG = "MainActivity";
// Whether the Log Fragment is currently shown
private boolean mLogShown;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
MainTabSliderFragment fragment = new MainTabSliderFragment();
transaction.replace(R.id.sample_content_fragment, fragment);
transaction.commit();
}
}
}
.
// 幻灯片标签片段，成为标签的父视图。
public class MainTabSliderFragment extends Fragment {
static final String LOG_TAG = MainTabSliderFragment.class.getSimpleName();
private SlidingTabLayout mSlidingTabLayout;
private ViewPager mViewPager;
private CustomFragmentStatePageAdapter cfspAdapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_sample, container, false);
return root;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
mViewPager = (ViewPager) view.findViewById(R.id.viewpager);
cfspAdapter = new CustomFragmentStatePageAdapter(getFragmentManager());
List<String> pageTitles = new ArrayList<>();
pageTitles.add(getString(R.string.page_one));
pageTitles.add(getString(R.string.page_two));
pageTitles.add(getString(R.string.page_three));
List<Fragment> pageFragments = new ArrayList<>();
final BookListPageFragment pageOne = BookListPageFragment.newInstance(new CustomFragmentStatePageAdapter.SwitchFragmentListener() {
@Override
public void onSwitchFragments(Class<? extends Fragment> clazz, Map<String, String> ... args) {
cfspAdapter.switchFragment(CustomFragmentStatePageAdapter.PagePosition.POSITION_PAGE_ONE, clazz, this, args);
}
});
CustomerPageFragment pageTwo = CustomerPageFragment.newInstance(...);
ForumPageFragment pageThree = ForumPageFragment.newInstance(...);
pageFragments.add(pageOne);
pageFragments.add(pageTwo);
pageFragments.add(pageThree);
cfspAdapter.addFragments(pageFragments, pageTitles);
mViewPager.setAdapter(cfspAdapter);
mSlidingTabLayout = (SlidingTabLayout) view.findViewById(R.id.sliding_tabs);
mSlidingTabLayout.setViewPager(mViewPager);
}
}
.
// 第一个标签，处于初始状态（初始片段）。
public class BookListPageFragment extends Fragment {
private static final String TAG = BookListPageFragment.class.getSimpleName();
private BookListAdapter bAdapter;
private static CustomFragmentStatePageAdapter.SwitchFragmentListener switchFragmentListener;
public static BookListPageFragment newInstance(CustomFragmentStatePageAdapter.SwitchFragmentListener _switchFragmentListener) {
switchFragmentListener = _switchFragmentListener;
BookListPageFragment f = new BookListPageFragment();
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.page_one_booklist, container, false);
final ListView lv = (ListView) v.findViewById(R.id.list);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
BookRowData bRow = (BookRowData) lv.getItemAtPosition(position);
Log.i(TAG, "Clicked on book " + bRow.getBookId());
Map<String, String> param = new HashMap<>();
param.put("book_id", Long.toString(bRow.getBookId()));
switchFragmentListener.onSwitchFragments(ReviewBookPageFragment.class, new Map[]{param});
}
});
initializeTestList(v, lv); // Just add some books to the list.
return v;
}
.
// PAGE ADAPTER，用于处理tab的Fragment切换。
public class CustomFragmentStatePageAdapter extends FragmentStatePagerAdapter {
private final static String TAG = FragmentStatePagerAdapter.class.getSimpleName();
private FragmentManager fragmentManager;
private List<Fragment> fragmentList = new ArrayList<>();
private List<String> tabTitleList = new ArrayList<>();
public CustomFragmentStatePageAdapter(FragmentManager fm) {
super(fm);
fragmentManager = fm;
}
public void addFragments(List<Fragment> fragments, List<String> titles) {
fragmentList.clear();
tabTitleList.clear();
fragmentList.addAll(fragments);
tabTitleList.addAll(titles);
notifyDataSetChanged();
}
@Override
public int getItemPosition(Object object) {
if (fragmentList.contains(object)) {
return POSITION_UNCHANGED;
}
return POSITION_NONE;
}
@Override
public Fragment getItem(int item) {
if (item >= fragmentList.size()) {
return null;
}
return fragmentList.get(item);
}
@Override
public int getCount() {
return fragmentList.size();
}
@Override
public CharSequence getPageTitle(int position) {
return tabTitleList.get(position);
}
/**
* Switching pages
*
* @param newFragment
*/
public void switchFragment(final PagePosition position, Class<? extends Fragment> newFragment, SwitchFragmentListener sfListener, Map<String, String> ... args) {
final Fragment old = fragmentList.get(position.getPagePosition());
fragmentManager.beginTransaction().remove(old).commit(); //FIRST VERSION: IF HITTING BACK, IT EXITS APP AT ONCE.
//fragmentManager.beginTransaction().addToBackStack("page_one").remove(old).commit(); //SECOND VERSION: NOW I NEED TO HIT BACK TWICE TO EXIT, BUT THE VIEW DOESN'T CHANGE AFTER HITTING THE FIRST TIME.
try {
Fragment f = (Fragment) newFragment.asSubclass(Fragment.class).getMethod("newInstance", SwitchFragmentListener.class, Map[].class).invoke(newFragment, new Object[]{sfListener, args});
fragmentList.set(position.getPagePosition(), f);
} catch (IllegalAccessException iae) {
Log.e(TAG, "Fragment class access exception");
} catch (NoSuchMethodException e) {
Log.e(TAG, "Fragment instantiation exception (reflection)");
} catch (InvocationTargetException e) {
Log.e(TAG, "Fragment instantiation exception (reflection: no public constructor)");
}
notifyDataSetChanged();
}
public interface SwitchFragmentListener {
void onSwitchFragments(Class<? extends Fragment> clazz, Map<String, String> ... args);
}
public enum PagePosition {
POSITION_PAGE_ONE (0),
POSITION_PAGE_TWO (1),
POSITION_PAGE_THREE (2);
private final int position;
PagePosition(int position) {
this.position = position;
}
public int getPagePosition() {
return this.position;
}
}
}
.
// 和 最后是我想从 返回的片段；这是书评片段，当从列表中单击一本书时，它也会显示在第一个选项卡中。第二个和第三个选项卡被省略了。
public class ReviewBookPageFragment extends Fragment {
private static final String TAG = ReviewBookPageFragment.class.getSimpleName();
private CommentsListAdapter cAdapter;
private Long bookId;
private static CustomFragmentStatePageAdapter.SwitchFragmentListener switchFragmentListener;
public static ReviewBookPageFragment newInstance() {
ReviewBookPageFragment f = new ReviewBookPageFragment();
return f;
}
public static ReviewBookPageFragment newInstance(CustomFragmentStatePageAdapter.SwitchFragmentListener _sfListener, Map<String, String> ... args) {
switchFragmentListener = _sfListener;
Bundle b = BundlePacker.packMaps(args); // Custom util class for packing the params into a bundle.
ReviewBookPageFragment f = new ReviewBookPageFragment();
f.setArguments(b);
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.page_review_book, container, false);
Bundle bookIdBundle = this.getArguments();
Long bId = Long.parseLong(bookIdBundle.getString("book_id"));
Log.i(TAG, "Book ID: " + bId);
initializeTestList(v); // Just fill the book's reviews with test data.
return v;
}
}
所以，这就是一堆代码。总而言之，这个想法是在点击列表中的任何一本书时从图书列表视图（显示在选项卡一）切换到该书的评论；评论也显示在第一个选项卡上，我想按返回键返回图书列表。 目前，它会关闭应用程序回击一次，如果我将事务添加到后台堆栈（请参阅我的 CustomFragmentStatePageAdapter），则会关闭两次（但视图在第一次回击后不会改变。
我们将不胜感激任何对此问题的帮助。
要解决弹回问题，您可以在 activity class,
中使用此代码
@Override
public void onBackPressed() {
// if there is a fragment and the back stack of this fragment is not empty,
// then emulate 'onBackPressed' behaviour, because in default, it is not working
FragmentManager fm = getSupportFragmentManager();
for (Fragment frag : fm.getFragments()) {
if (frag.isVisible()) {
FragmentManager childFm = frag.getChildFragmentManager();
if (childFm.getBackStackEntryCount() > 0) {
childFm.popBackStack();
return;
}
}
}
super.onBackPressed();
}
我做了这样的事情：
private View _view;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if(_view==null){
_view = inflater.inflate(R.layout.page_review_book, container, false);
// your_code
}
return _view;
}
我正在构建一个 Android 应用程序，它使用 FragmentStatePagerAdapter 用于选项卡式导航和每个选项卡中的动态内容。每个选项卡都有 Fragment 内容，用户输入时会替换内容（例如，第一个选项卡有一个 Fragment 包含书籍列表，点击后，您可以访问该书的详细信息，使用另一个 Fragment
问题：我还没有找到正确处理 onBack 事件和 BackStack 的方法，所以当我查看任何书籍的详细信息时，我可以轻松地按后退按钮返回 - 我的意思是, 从 BackStack 弹出最后一个状态。
我怀疑的是：我切换 Fragment 对象的方式可能不是最好的方式，但除了后退按钮问题外，它工作正常。我怀疑 FragmentStatePagerAdapter 的适配器和 FragmentManager 自己的 Fragment 集合之间存在一些问题；可能这是我没有看到的简单解决方案。
未回答的问题（虽然不是很详细）：Adding Fragment to BackStack using FragmentStatePagerAdapter
代码：
// MAIN ACTIVITY, 就这么简单。
public class MainActivity extends FragmentActivity {
public static final String TAG = "MainActivity";
// Whether the Log Fragment is currently shown
private boolean mLogShown;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
MainTabSliderFragment fragment = new MainTabSliderFragment();
transaction.replace(R.id.sample_content_fragment, fragment);
transaction.commit();
}
}
}
.
// 幻灯片标签片段，成为标签的父视图。
public class MainTabSliderFragment extends Fragment {
static final String LOG_TAG = MainTabSliderFragment.class.getSimpleName();
private SlidingTabLayout mSlidingTabLayout;
private ViewPager mViewPager;
private CustomFragmentStatePageAdapter cfspAdapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_sample, container, false);
return root;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
mViewPager = (ViewPager) view.findViewById(R.id.viewpager);
cfspAdapter = new CustomFragmentStatePageAdapter(getFragmentManager());
List<String> pageTitles = new ArrayList<>();
pageTitles.add(getString(R.string.page_one));
pageTitles.add(getString(R.string.page_two));
pageTitles.add(getString(R.string.page_three));
List<Fragment> pageFragments = new ArrayList<>();
final BookListPageFragment pageOne = BookListPageFragment.newInstance(new CustomFragmentStatePageAdapter.SwitchFragmentListener() {
@Override
public void onSwitchFragments(Class<? extends Fragment> clazz, Map<String, String> ... args) {
cfspAdapter.switchFragment(CustomFragmentStatePageAdapter.PagePosition.POSITION_PAGE_ONE, clazz, this, args);
}
});
CustomerPageFragment pageTwo = CustomerPageFragment.newInstance(...);
ForumPageFragment pageThree = ForumPageFragment.newInstance(...);
pageFragments.add(pageOne);
pageFragments.add(pageTwo);
pageFragments.add(pageThree);
cfspAdapter.addFragments(pageFragments, pageTitles);
mViewPager.setAdapter(cfspAdapter);
mSlidingTabLayout = (SlidingTabLayout) view.findViewById(R.id.sliding_tabs);
mSlidingTabLayout.setViewPager(mViewPager);
}
}
.
// 第一个标签，处于初始状态（初始片段）。
public class BookListPageFragment extends Fragment {
private static final String TAG = BookListPageFragment.class.getSimpleName();
private BookListAdapter bAdapter;
private static CustomFragmentStatePageAdapter.SwitchFragmentListener switchFragmentListener;
public static BookListPageFragment newInstance(CustomFragmentStatePageAdapter.SwitchFragmentListener _switchFragmentListener) {
switchFragmentListener = _switchFragmentListener;
BookListPageFragment f = new BookListPageFragment();
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.page_one_booklist, container, false);
final ListView lv = (ListView) v.findViewById(R.id.list);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
BookRowData bRow = (BookRowData) lv.getItemAtPosition(position);
Log.i(TAG, "Clicked on book " + bRow.getBookId());
Map<String, String> param = new HashMap<>();
param.put("book_id", Long.toString(bRow.getBookId()));
switchFragmentListener.onSwitchFragments(ReviewBookPageFragment.class, new Map[]{param});
}
});
initializeTestList(v, lv); // Just add some books to the list.
return v;
}
.
// PAGE ADAPTER，用于处理tab的Fragment切换。
public class CustomFragmentStatePageAdapter extends FragmentStatePagerAdapter {
private final static String TAG = FragmentStatePagerAdapter.class.getSimpleName();
private FragmentManager fragmentManager;
private List<Fragment> fragmentList = new ArrayList<>();
private List<String> tabTitleList = new ArrayList<>();
public CustomFragmentStatePageAdapter(FragmentManager fm) {
super(fm);
fragmentManager = fm;
}
public void addFragments(List<Fragment> fragments, List<String> titles) {
fragmentList.clear();
tabTitleList.clear();
fragmentList.addAll(fragments);
tabTitleList.addAll(titles);
notifyDataSetChanged();
}
@Override
public int getItemPosition(Object object) {
if (fragmentList.contains(object)) {
return POSITION_UNCHANGED;
}
return POSITION_NONE;
}
@Override
public Fragment getItem(int item) {
if (item >= fragmentList.size()) {
return null;
}
return fragmentList.get(item);
}
@Override
public int getCount() {
return fragmentList.size();
}
@Override
public CharSequence getPageTitle(int position) {
return tabTitleList.get(position);
}
/**
* Switching pages
*
* @param newFragment
*/
public void switchFragment(final PagePosition position, Class<? extends Fragment> newFragment, SwitchFragmentListener sfListener, Map<String, String> ... args) {
final Fragment old = fragmentList.get(position.getPagePosition());
fragmentManager.beginTransaction().remove(old).commit(); //FIRST VERSION: IF HITTING BACK, IT EXITS APP AT ONCE.
//fragmentManager.beginTransaction().addToBackStack("page_one").remove(old).commit(); //SECOND VERSION: NOW I NEED TO HIT BACK TWICE TO EXIT, BUT THE VIEW DOESN'T CHANGE AFTER HITTING THE FIRST TIME.
try {
Fragment f = (Fragment) newFragment.asSubclass(Fragment.class).getMethod("newInstance", SwitchFragmentListener.class, Map[].class).invoke(newFragment, new Object[]{sfListener, args});
fragmentList.set(position.getPagePosition(), f);
} catch (IllegalAccessException iae) {
Log.e(TAG, "Fragment class access exception");
} catch (NoSuchMethodException e) {
Log.e(TAG, "Fragment instantiation exception (reflection)");
} catch (InvocationTargetException e) {
Log.e(TAG, "Fragment instantiation exception (reflection: no public constructor)");
}
notifyDataSetChanged();
}
public interface SwitchFragmentListener {
void onSwitchFragments(Class<? extends Fragment> clazz, Map<String, String> ... args);
}
public enum PagePosition {
POSITION_PAGE_ONE (0),
POSITION_PAGE_TWO (1),
POSITION_PAGE_THREE (2);
private final int position;
PagePosition(int position) {
this.position = position;
}
public int getPagePosition() {
return this.position;
}
}
}
.
// 和 最后是我想从 返回的片段；这是书评片段，当从列表中单击一本书时，它也会显示在第一个选项卡中。第二个和第三个选项卡被省略了。
public class ReviewBookPageFragment extends Fragment {
private static final String TAG = ReviewBookPageFragment.class.getSimpleName();
private CommentsListAdapter cAdapter;
private Long bookId;
private static CustomFragmentStatePageAdapter.SwitchFragmentListener switchFragmentListener;
public static ReviewBookPageFragment newInstance() {
ReviewBookPageFragment f = new ReviewBookPageFragment();
return f;
}
public static ReviewBookPageFragment newInstance(CustomFragmentStatePageAdapter.SwitchFragmentListener _sfListener, Map<String, String> ... args) {
switchFragmentListener = _sfListener;
Bundle b = BundlePacker.packMaps(args); // Custom util class for packing the params into a bundle.
ReviewBookPageFragment f = new ReviewBookPageFragment();
f.setArguments(b);
return f;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.page_review_book, container, false);
Bundle bookIdBundle = this.getArguments();
Long bId = Long.parseLong(bookIdBundle.getString("book_id"));
Log.i(TAG, "Book ID: " + bId);
initializeTestList(v); // Just fill the book's reviews with test data.
return v;
}
}
所以，这就是一堆代码。总而言之，这个想法是在点击列表中的任何一本书时从图书列表视图（显示在选项卡一）切换到该书的评论；评论也显示在第一个选项卡上，我想按返回键返回图书列表。 目前，它会关闭应用程序回击一次，如果我将事务添加到后台堆栈（请参阅我的 CustomFragmentStatePageAdapter），则会关闭两次（但视图在第一次回击后不会改变。
我们将不胜感激任何对此问题的帮助。
要解决弹回问题，您可以在 activity class,
中使用此代码@Override
public void onBackPressed() {
// if there is a fragment and the back stack of this fragment is not empty,
// then emulate 'onBackPressed' behaviour, because in default, it is not working
FragmentManager fm = getSupportFragmentManager();
for (Fragment frag : fm.getFragments()) {
if (frag.isVisible()) {
FragmentManager childFm = frag.getChildFragmentManager();
if (childFm.getBackStackEntryCount() > 0) {
childFm.popBackStack();
return;
}
}
}
super.onBackPressed();
}
我做了这样的事情：
private View _view;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if(_view==null){
_view = inflater.inflate(R.layout.page_review_book, container, false);
// your_code
}
return _view;
}