Question

当我添加viewpager片段时，一切都很顺利，但当我移动到另一个应用程序并返回到我的应用程序时，我有一个奇怪的问题，getView或inflated是null。它显示了视图，但我无法访问它。

以下是将在ViewPager中使用的片段：

public class FragmentRestauranteBandejao extends Fragment {

JSONObject dados;
View inflated;
ExpandableListView cardapio;
List<String> refeicoes;
List<String> pratos_almoco;
List<String> pratos_janta;
Map<String, List<String>> bandejao = null;
ExpandableListAdapter adapter;

public static FragmentRestauranteBandejao newInstance(String restaurante){
    FragmentRestauranteBandejao frag = new FragmentRestauranteBandejao();

    Bundle args = new Bundle();
    args.putString("restaurante", restaurante);
    frag.setArguments(args);
    return frag; 
}

public void getDados(){
    if(dados == null){
        if(USPRestaurantes.getDados()){
            dados = USPRestaurantes.getCardapioByRestaurante(getArguments().getString("restaurante"));
        }else{
            Log.d("debug", "Dados ainda não estão prontos");
            return;
        }   
    }

    if(inflated == null){
        Log.d("debug", "inflated eh null");
        if(inflated == null){
            return;
        }
    }
    //... some code here that deals with the data that comes from a request made at USPRestaurantes.
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    inflated = inflater.inflate(R.layout.fragment_cardapio, container, false);

    return inflated;
}


@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    inflated = view;
    prepararCardapio();
    getDados();
}

public void prepararCardapio(){

    cardapio = (ExpandableListView) getView().findViewById(R.id.cardapio);
    cardapio.setClickable(true);

    refeicoes = new ArrayList<String>(Arrays.asList("Almoço","Jantar"));
    pratos_almoco = new ArrayList<String>();
    pratos_janta = new ArrayList<String>();
    pratos_almoco.add("");
    pratos_janta.add("");

    bandejao = new LinkedHashMap<String, List<String>>();

    bandejao.put(refeicoes.get(0), pratos_almoco);
    bandejao.put(refeicoes.get(1), pratos_janta);

    adapter = new ExpandableListViewAdapter(getActivity(), refeicoes, bandejao);
    cardapio.setAdapter(adapter);
}

ViewPager片段：

public class FragmentBandejoes extends Fragment{

private String[] tabs = {"Central", "Química", "Física"};

private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ArrayList<Fragment> paginasBandeco;
public int dia_semana = 0;
ProgressDialog dialog;

private TabPageIndicator mIndicator;
int number = 0;


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

    paginasBandeco = new ArrayList<Fragment>();
    paginasBandeco.add(FragmentRestauranteBandejao.newInstance("central"));
    paginasBandeco.add(FragmentRestauranteBandejao.newInstance("quimica"));
    paginasBandeco.add(FragmentRestauranteBandejao.newInstance("fisica"));

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View inflated = inflater.inflate(R.layout.fragment_bandejoes, container, false);
    return inflated;    
}

public void notifyFragments(){

    for(int i=0; i<3; i++){     
        ((FragmentRestauranteBandejao) mAdapter.getItem(i)).getDados();
    }

    if(dialog != null){
        dialog.dismiss();
    }

}

public void getCardapios(boolean update){
    if(!USPRestaurantes.getDados() || update){

        boolean request_made = USPRestaurantes.getCardapio(getActivity());
    }
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {

    getCardapios(false);

    viewPager = (ViewPager) getView().findViewById(R.id.pager_bandejoes);

    mAdapter = new TabsPagerAdapter(((MainActivity) getActivity()).fragmentManager, paginasBandeco, tabs);

    viewPager.setAdapter(mAdapter);
    mIndicator = (TabPageIndicator) getActivity().findViewById(R.id.indicator);
    mIndicator.setViewPager(viewPager);

    mIndicator.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int position) {
            mIndicator.setCurrentItem(position);
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
        }

        @Override
        public void onPageScrollStateChanged(int arg0) {                
        }
    });     
}

最后是FragmentStatePagerAdapter：

public class FragmentBandejoes extends Fragment{

private String[] tabs = {"Central", "Química", "Física"};

private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ArrayList<Fragment> paginasBandeco;
public int dia_semana = 0;
ProgressDialog dialog;

private TabPageIndicator mIndicator;
int number = 0;


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

    paginasBandeco = new ArrayList<Fragment>();
    paginasBandeco.add(FragmentRestauranteBandejao.newInstance("central"));
    paginasBandeco.add(FragmentRestauranteBandejao.newInstance("quimica"));
    paginasBandeco.add(FragmentRestauranteBandejao.newInstance("fisica"));

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View inflated = inflater.inflate(R.layout.fragment_bandejoes, container, false);
    return inflated;    
}

public void notifyFragments(){

    for(int i=0; i<3; i++){     
        ((FragmentRestauranteBandejao) mAdapter.getItem(i)).getDados();
    }

    if(dialog != null){
        dialog.dismiss();
    }

}

public void getCardapios(boolean update){
    if(!USPRestaurantes.getDados() || update){

        boolean request_made = USPRestaurantes.getCardapio(getActivity());
    }
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {

    getCardapios(false);

    viewPager = (ViewPager) getView().findViewById(R.id.pager_bandejoes);

    mAdapter = new TabsPagerAdapter(((MainActivity) getActivity()).fragmentManager, paginasBandeco, tabs);

    viewPager.setAdapter(mAdapter);
    mIndicator = (TabPageIndicator) getActivity().findViewById(R.id.indicator);
    mIndicator.setViewPager(viewPager);

    mIndicator.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int position) {
            mIndicator.setCurrentItem(position);
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
        }

        @Override
        public void onPageScrollStateChanged(int arg0) {                
        }
    });     
}

其他信息：当我滑动到其他选项卡时，视图会重新创建，然后显示数据。提前致谢

Answer 1

据我所知，阅读你的代码就是你没有考虑fragment's lifecycle。

片段，作为活动，具有您应该使用的生命周期方法，以便它们正确呈现。我建议使用onResume回调，并检查是否有任何数据要显示。如果您确实在片段中显示它们。如果您在创建fragmet时没有执行此操作

创建的视图后，viewpager的膨胀布局为null

1 个答案: