android - 片段无故失去对活动的引用

问题描述

在我的一个片段中，我有时会遇到一个异常，指出 myContext为空。

目前，我无法重现该问题，因为我尝试以多种不同方式访问崩溃代码，但没有一致的结果。

这是我得到的崩溃日志：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: eu.side.aurora, PID: 12940
    java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
        at android.widget.Toast.<init>(Toast.java:101)
        at android.widget.Toast.makeText(Toast.java:258)
        at eu.side.aurora.views.fragments.StepStock.lambda$onCreateView$2$StepStock(StepStock.java:161)

以及如果引用的代码

    InterventionsViewModel interventionsViewmodel = ViewmodelProviders.of(getActivity()).get(InterventionsViewModel)
    interventionsViewmodel.getExceptions().observe(getActivity(), exception ->{
        if(exception instanceof QuantityOverflowException){
            Toast.makeText(getActivity(), "No you just can't add more stock than there is available!", Toast.LENGTH_SHORT).show();
        }
        if(exception instanceof ScannedArticleNotFoundException){
            Toast.makeText(getActivity(), "This article doesn't even exist! Get your shit together please!²", Toast.LENGTH_SHORT).show();
        }
     });

奇怪的是，我几乎在我的片段中的任何地方都引用了 getActivty()onCreateView并且它只在那里崩溃。

要使用下面的视图访问代码，我只需按+或-按钮从我的列表中添加或删除文章。当它达到最大值时，它会发送一个Toast通知用户。

当点击加号或减号按钮时，它们会通知ViewModel，这将改变我之前观察到的可观察对象。

有谁知道这是从哪里来的？我假设它来自我的片段与我的片段分离，Activity但我无法弄清楚它是如何做到这一点的，因为我在创建片段后再也没有碰过我的片段。

在此先感谢，马蒂厄

编辑：根据要求，这里是完整片段的代码包 eu.side.aurora.views.fragments；

public class StepStock extends Fragment {
    private INextStep nextStep;

    @BindView(R.id.articles_autocomplete)
    AutoCompleteTextView articlesAutocomplete;
    @BindView(R.id.articles_recycler)
    RecyclerView articleRecycler;


    private AccountManager accountManager;
    private Account account;
    private ArrayList<DetailedArticle> articles;
    private ArrayList<Article> stockedArticles;
    private StockRecyclerAdapter stockAdapter;
    private InterventionsViewModel interventionViewModel;

    public StepStock() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @return A new instance of fragment StepStock.
     */
    // TODO: Rename and change types and number of parameters
    public static StepStock newInstance() {
        return new StepStock();
    }

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

    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view =  inflater.inflate(R.layout.fragment_step_stock, container, false);
        ButterKnife.bind(this, view);

        interventionViewModel = ViewModelProviders.of(getActivity()).get(InterventionsViewModel.class);

        /* UI Intialization */
        articleRecycler.setLayoutManager(new LinearLayoutManager(getContext(), LinearLayoutManager.VERTICAL, false));


        /**
         * Stock recycler view
         * Used to keep track of stock used in an intervention
         * OnPlus -> Add one from article
         * OnMinus -> Remove one from article
         * */
        stockedArticles = new ArrayList<>();
        stockAdapter = new StockRecyclerAdapter(stockedArticles, new StockRecyclerAdapter.OnArticleClickListener() {
            @Override
            public void onArticleClicked(int position) {
                //new intent
            }

            @Override
            public void onPlusClicked(int position) {
                interventionViewModel.addOneToStockAtArticle(stockAdapter.getData().get(position));
            }

            @Override
            public void onMinusClicked(int position) {
                interventionViewModel.minusOneOrRemoveAtArticle(stockAdapter.getData().get(position));
            }
        });

        interventionViewModel.getCurrentIntervention().observe(getActivity(), intervention -> {
            if(intervention!= null && intervention.getArticles() != null)
                stockAdapter.putData(intervention.getArticles());
        });

        interventionViewModel.getExceptions().observe(getActivity(), exception ->{
            if(exception instanceof QuantityOverflowException){
                Toast.makeText(getActivity(), "No you just can't add more stock than there is available!", Toast.LENGTH_SHORT).show();
            }
            if(exception instanceof ScannedArticleNotFoundException){
                Toast.makeText(getActivity(), "This article doesn't even exist! Get your shit together please!²", Toast.LENGTH_SHORT).show();
            }
        });
        return view;
    }


    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if(context instanceof INextStep){
            nextStep = (INextStep) context;
        }
        else{
            throw new  RuntimeException(context.toString() + " must implement INextStep");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        nextStep = null;
    }
}

标签： androidandroid-fragmentsandroid-context

android - 片段无故失去对活动的引用

问题描述

解决方案

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