android - Navigation Drawer + ViewPager + Fragments，ViewPager 不会破坏嵌套的 fragment

Question

我的应用有带两个项目的抽屉导航:ViewPager(在 Fragment 内)和 SupportMapFragment。

ViewPager 使用 FragmentStatePagerAdapter 和 getItem(int position) 返回两个 fragment 。

当我打开抽屉导航并选择“item 1”(SupportMapFragment)时，另一个 Fragment(ViewPager 在其中)执行 onDestroy() 方法 但是这个方法不会破坏适配器创建的 fragment ，因此当我再次选择“item 0”时，我的应用程序创建了 ViewPager 及其两个项目和 ViewPager 未删除的其他两个 fragment 。

当我选择“item 1”然后选择“item 0”时，这个问题会创建相同的 fragment ...所以 fragment 的数量会增加。

ViewPager 如何在其容器 fragment 执行 onDestroy 时删除这些 fragment ？

我的代码

主要 Activity

public class Main extends SherlockFragmentActivity {

//Nombre de los elementos de la lista
private String[] mTitles;   
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mDrawerToggle;
private ListView mDrawerList;

private int currentPosition;

@Override
public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_navigation_drawer);

    //Inicialmente no hay ninguna opcion
    currentPosition = -1;

    mDrawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
    mDrawerList = (ListView)findViewById(R.id.left_drawer);
    mDrawerToggle = new ActionBarDrawerToggle(
            this, 
            mDrawerLayout,
            R.drawable.ic_drawer, 
            R.string.drawer_open, 
            R.string.drawer_close) {

        /** Called when a drawer has settled in a completely closed state. */
        public void onDrawerClosed(View view) {
            // creates call to onPrepareOptionsMenu()
            supportInvalidateOptionsMenu();
        }

        /** Called when a drawer has settled in a completely open state. */
        public void onDrawerOpened(View drawerView) {             
            // creates call to onPrepareOptionsMenu()
            supportInvalidateOptionsMenu();
        }
    };

    mTitles = getResources().getStringArray(R.array.navigation_drawer_options);

    //Asignamos el Adapter
    mDrawerList.setAdapter(new ArrayAdapter<String>(this,R.layout.drawer_list_item, mTitles));
    //Asignamos el listener
    mDrawerList.setOnItemClickListener(new DrawerItemClickListener());

    mDrawerLayout.setDrawerListener(mDrawerToggle);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeButtonEnabled(true);

    if (savedInstanceState == null) {
        selectItem(0);
    }
}

@Override
protected void onPostCreate(Bundle savedInstanceState) {
    super.onPostCreate(savedInstanceState);
    // Sync the toggle state after onRestoreInstanceState has occurred.
    mDrawerToggle.syncState();
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    mDrawerToggle.onConfigurationChanged(newConfig);
}

private class DrawerItemClickListener implements ListView.OnItemClickListener {

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        selectItem(position);
    }
}

/** Swaps fragments in the main content view */
private void selectItem(int position) {
    // Create a new fragment and specify the planet to show based on position

    if(currentPosition != position){
        //Solo hacemos remplazo de fragment si la opcion selecionada no es la misma
        //que la que esta ya en pantalla
        Fragment fragment = null;
        String fragmentName = "";
        boolean attach = true;

        switch (position) {
            case 0:
                fragmentName = PagerFragment.class.getSimpleName();
                fragment = getSupportFragmentManager().findFragmentByTag(fragmentName);
                if(fragment == null) {
                    fragment = new PagerFragment();
                    attach = false;
                }
                break;
            case 1:
                fragmentName = Map1Fragment.class.getSimpleName();
                fragment = getSupportFragmentManager().findFragmentByTag(fragmentName);
                if(fragment == null) {
                    fragment = new Map1Fragment();
                    attach = false;
                }
                break;      
            default:
                throw new IllegalArgumentException("Posicion no valida");
        }

        // Insert the fragment by replacing any existing fragment
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        if(!attach){
            transaction.replace(R.id.content_frame, fragment);
        }else{
            transaction.attach(fragment);
        }
        transaction.commit();
    }
    currentPosition = position;
    // Highlight the selected item, update the title, and close the drawer
    mDrawerList.setItemChecked(position, true);     
    mDrawerLayout.closeDrawer(mDrawerList);
}

带有 ViewPager 的 fragment

public class PagerFragment extends SherlockFragment{

private ViewPager viewPager;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
    Log.d("PagerFragment", "onCreateView");
    return inflater.inflate(R.layout.application_tus, container, false);
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        Log.d("PagerFragment", "onViewCreated");
        viewPager = (ViewPager) view.findViewById(R.id.viewpager);
        viewPager.setAdapter(new ViewPagerAdapter(getSherlockActivity(), getFragmentManager()));

        TitlePageIndicator titleIndicator = (TitlePageIndicator)view.findViewById(R.id.titles_viewpager);
        titleIndicator.setViewPager(viewPager,0);

}
}

FragmentStatePagerAdapter

public class ViewPagerAdapter extends FragmentStatePagerAdapter{

public static final int NUM_PAGES = 2;
public static final int [] titles = { R.string.st1, R.string.st2};

private Context context;

public ViewPagerAdapter(Context context, FragmentManager fragmentManager) {
    super(fragmentManager);
    this.context = context;
}

@Override
public Fragment getItem(int position) {
    Log.d("ViewPagerAdapter", "GetItem(" + position+")");
    switch (position) {
        case 0:
            return new FavoritesFragment();         
        case 1:
            return new LinesFragment();     
        default:
            throw new IllegalArgumentException("Error");
    }
}

@Override
public int getCount() {
    return NUM_PAGES;
}

@Override
public CharSequence getPageTitle(int position) {
    return context.getString(titles[position]);
}

}

Answer 1

我终于解决了我的问题。

当我创建 FragmentStatePagerAdapter 时，我使用了 new ViewPagerAdapter(getSherlockActivity(), getFragmentManager())。我终于使用了 getChildFragmentManager() 并且成功了!