我正在尝试构建一个以纵向和横向模式显示图书的应用。所以很明显有 1 页纵向显示，2 页横向显示。每种模式都很好，但是当我将方向从纵向更改为横向时，viewPager 尝试从纵向模式获取 2 页，而不是尝试从横向模式获取 2 个双页 ... 事实上，FragmentStatePagerAdapter 保留了纵向创建的 2 个 fragment ，并在为横向模式创建 2 个双页之前使用它们。如果我在纵向模式下再次切换，FragmentStatePagerAdapter 使用之前在横向模式下创建的 2 个 fragment ，所以我再次看到 1 个双页而不是 1 个单页等。如果我继续切换方向，我会得到一个 OutOfMemoryError，因为 FragmentStatePagerAdapter 从不在方向改变时刷新它的 fragment 。

为了便于理解，这里有 2 个用例:

• 我以纵向模式启动 viewPager
• 我看到第 1 页了
• 我向右滑动，我看到第 2 页了
• 我向右滑动，我看到第 3 页 ok
• 我将屏幕旋转到横向模式
• 我看错了第 3 页
• 我向右滑动，我看到第 4 页错了

• 我向右滑动，可以看到第 5 页和第 6 页

• 我以纵向模式启动 viewPager

• 我看到第 1 页了
• 我向右滑动，我看到第 2 页了
• 我向右滑动，我看到第 3 页 ok
• 我向右滑动，看到第 4 页 ok
• 我向右滑动，我看到第 5 页 ok
• 我将屏幕旋转到横向模式
• 我看错了第 5 页
• 我向左滑动，我看到第 4 页错了

• 我向左滑动，我看到第 2 页和第 3 页正常

  public class PlayerFragmentActivity extends FragmentActivity {
  private Intent mIntent;
  private ViewPager mPortraitPager;
  private ViewPager mLandscapePager;
  private Boolean mIsLandscape;
  private String mKey;
  private int mNbPages;
  private int mNbDoublePages;
  private PageFactory mPageFactory;
  private DoublePageFactory mDoublePageFactory;
  private PagerAdapter mPagerAdapter;
  
  @Override
  protected void onStop(){
      super.onStop();
      mPagerAdapter = null;
      mDoublePageFactory = null;
      mPageFactory = null; 
  }
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.fragment_activity_player);
      mIntent = getIntent();
      mKey = mIntent.getStringExtra("key");
      mNbPages = mIntent.getIntExtra("nbPages", 0);
      mNbDoublePages = DoublePageFactory.getDoublePageNumFromPageNum(mNbPages);
  
      Resources res = getResources();
      mIsLandscape = (res.getConfiguration().orientation == 1) ? false : true;
      mPortraitPager = (ViewPager) findViewById(R.id.portraitPager);
      mLandscapePager = (ViewPager) findViewById(R.id.landscapePager);
  
      mPagerAdapter = new MyPagerAdapter(getSupportFragmentManager());
  
      if (mIsLandscape) {
          mDoublePageFactory = new DoublePageFactory(this, mKey, mNbPages, res.getInteger(R.integer.nb_page_columns), res.getInteger(R.integer.nb_page_columns));
          mPortraitPager.setVisibility(View.GONE);
          mLandscapePager.setAdapter(mPagerAdapter);
          mPortraitPager.setAdapter(null);
      } else {
          mPageFactory = new PageFactory(this, mKey, this.mNbPages, res.getInteger(R.integer.nb_page_columns), res.getInteger(R.integer.nb_page_columns));
          mLandscapePager.setVisibility(View.GONE);
          mPortraitPager.setAdapter(mPagerAdapter);
          mLandscapePager.setAdapter(null);
      }
  }
  
  
  public class MyPagerAdapter extends FragmentStatePagerAdapter {
  
      public MyPagerAdapter(FragmentManager fm) {
          super(fm);
      }
  
      @Override
      public Fragment getItem(int position) {
          Bundle args = new Bundle();
          if(mIsLandscape){
              Fragment doublePageFragment = new DoublePageFragment();
              args.putInt(DoublePageFragment.ARG_DOUBLEPAGE_NUM, position + 1);
              doublePageFragment.setArguments(args);
              return doublePageFragment;
          }else{
              Fragment pageFragment = new PageFragment();
              args.putInt(PageFragment.ARG_PAGE_NUM, position + 1);
              pageFragment.setArguments(args);
              return pageFragment;
          }
      }
  
      @Override
      public int getCount() {
          return (mIsLandscape) ? mNbDoublePages:mNbPages;
  
      }
  
              /* j'ai essayé cette méthode mais ça ne fonctionne pas :( */
      @Override
      public void destroyItem(ViewGroup container, int position, Object object) {
              FragmentManager manager = ((Fragment) object).getFragmentManager();
              FragmentTransaction trans = manager.beginTransaction();
              trans.remove((Fragment) object);
              trans.commit();
  
          super.destroyItem(container, position, object);
      }
  
      @Override
      public int getItemPosition(Object object){
          return PagerAdapter.POSITION_NONE;
      }
  
      @Override
      public CharSequence getPageTitle(int position) {
          return "p." + position + 1;
      }
  }
  
  public boolean isLandscape() {
      return mIsLandscape;
  }
  
  public ImageView getSinglePage(int position) {
      return mPageFactory.getPage(position);
  }
  
  
  public LinearLayout getDoublePage(int position) {
      return mDoublePageFactory.getDoublePage(position);
  }
  }
  
  
  public class PageFragment extends Fragment {    
  private PlayerFragmentActivity mPlayerFragmentActivity;
  public static final String ARG_PAGE_NUM = "page_number";
  public static final String ARG_WOBOOK_DIRECTORY = "book_directory";
  public static final String ARG_NB_PAGE_COLUMNS = "nb_page_columns";
  public static final String ARG_NB_PAGE_ROWS = "nb_page_rows";
  
  @Override
  public ImageView onCreateView(LayoutInflater inflater, ViewGroup container,
          Bundle savedInstanceState) {
      mPlayerFragmentActivity = ((PlayerFragmentActivity) getActivity());
      return mPlayerFragmentActivity.getSinglePage(getArguments().getInt(ARG_PAGE_NUM));
  }
  
  @Override
  public void onStop(){
      super.onStop();
      mPlayerFragmentActivity = null;
  }
  

  public class DoublePageFragment extends Fragment {
  private PlayerFragmentActivity mPlayerFragmentActivity;
  public static final String ARG_DOUBLEPAGE_NUM = "double_page_number";
  public static final String ARG_WOBOOK_DIRECTORY = "book_directory";
  public static final String ARG_NB_PAGE_COLUMNS = "nb_page_columns";
  public static final String ARG_NB_PAGE_ROWS = "nb_page_rows";
  
  @Override
  public LinearLayout onCreateView(LayoutInflater inflater, ViewGroup container,
          Bundle savedInstanceState) {
      mPlayerFragmentActivity = ((PlayerFragmentActivity) getActivity());
      return mPlayerFragmentActivity.getDoublePage(getArguments().getInt(ARG_DOUBLEPAGE_NUM));
  }
  
  @Override
  public void onStop(){
      super.onStop();
      mPlayerFragmentActivity = null;
  }
  }
  

我读到框架中的 FragmentManager 负责保存状态并恢复寻呼机创建的任何 Activity fragment 。所以我想当方向改变时，FragmentManager 说

Hey ! I already have 2 items created so i don't need to create news, lets get them

但实际上它从旧的方向模式中获取了 2 个项目(页面/双页)。所以我需要找到一种方法来在方向发生变化时删除 FragmentManager 保存的 fragment 。

我还测试了 this method .问题似乎与 this one 有关

最好的问候

最佳答案

尝试将方向限制为纵向或横向模式。因为我们只能在精确模式下使用 View 寻呼机。

关于android - 在 FragmentActivity 中使用 viewPager 改变方向，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15141363/