Question

我正在尝试构建一个以纵向和横向模式显示图书的应用。很明显，有1页以肖像方式显示，2页以横向方式显示。每个模式都工作得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... 实际上 FragmentStatePagerAdapter会保留以纵向方式创建的2个片段，并在为横向模式创建2个双页之前使用它们。如果我再次以纵向模式切换，FragmentStatePagerAdapter使用以前在横向模式下创建的2个片段，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，我得到一个OutOfMemoryError，因为FragmentStatePagerAdapter永远不会在方向改变时冲洗它的碎片。

以下是2个用例，以便于理解：

我以纵向模式启动viewPager
我看到第1页好了
我向右滑动，我看到第2页确定
我向右滑动，我看到第3页确定
我将屏幕旋转为横向模式
我看到第3页错误
我向右滑动，我看到第4页错误
我向右滑动，我看到第5页和第6页确定
我以纵向模式启动viewPager
我看到第1页好了
我向右滑动，我看到第2页确定
我向右滑动，我看到第3页确定
我向右滑动，我看到第4页确定
我向右滑动，我看到第5页确定
我将屏幕旋转为横向模式
我看到第5页错误
我向左滑动，我看到第4页错误

我向左滑动，我看到第2页和第3页确定

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;
}
}

我已经读过框架中的FragmentManager负责保存状态并恢复寻呼机所做的任何活动片段。所以我想当方向改变时，FragmentManager会说

嘿！我已经创建了2个项目，所以我不需要创建新闻，让我们来吧

但实际上它从旧的定位模式获得了2个项目（页面/双页）。因此，当发生方向更改时，我需要找到一种方法来删除FragmentManager保存的片段。

我也测试了this method。问题似乎与this one

有关

祝你好运

Answer 1

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视图寻呼机。

使用FragmentActivity中的viewPager更改方向

1 个答案: