查看片段內部的null

Question

我已經為此工作了幾個小時。 找不到任何原因。 我無法在此處發布整個片段，但以下內容應使其清楚。

@BindView(R.id.acService) AutoCompleteTextView autocompleteService;
@BindView(R.id.acAddress) AutoCompleteTextView autocompleteAddress;

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

    initialize();
    loadSkillsData();

    return view;
}

private void initialize()
{
    context = getActivity();
    util = new Util(context);
    requestService = new RequestService();
    geoDataClient = Places.getGeoDataClient(context, null);

    autocompleteAdapter = new PlaceAutocompleteAdapter(context, geoDataClient, BOUNDS_ONTARIO, null);
    autocompleteAddress.setAdapter(autocompleteAdapter);

    mapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.mapFragment);
    mapFragment.getMapAsync(this);
}

private void loadSkillsData()
{
    Realm realm = getRealm();
    UserModel user = realm.where(UserModel.class).findFirst();

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(RestAPI.ENDPOINT)
            .addConverterFactory(MoshiConverterFactory.create())
            .build();
    RestAPI restApi = retrofit.create(RestAPI.class);
    Call<ResponseSkills> loginCall = restApi.getSkills(user.getServerUserId());
    loginCall.enqueue(new Callback<ResponseSkills>()
    {
        @Override
        public void onResponse(Call<ResponseSkills> call, final Response<ResponseSkills> response)
        {
            if (response.isSuccessful())
            {
                if (response.body().getStatus())
                {
                    skillList = response.body().getSkillList();
                    ArrayAdapter<SkillModel> skillAdapter = new ArrayAdapter<>(context, android.R.layout.simple_list_item_1, skillList);
                    autocompleteService.setAdapter(skillAdapter);
                }
                else
                {
                    switch (response.body().getError())
                    {
                        default:
                            Toasty.error(context, response.body().getError());
                            break;
                    }
                }
            } else
            {
                Toasty.error(context, getString(R.string.toast_experienced_a_problem)).show();
            }
        }

        @Override
        public void onFailure(Call<ResponseSkills> call, Throwable t)
        {
            Toasty.error(context, getString(R.string.toast_experienced_a_problem)).show();
            t.printStackTrace();
        }
    });
}

布局：

在行上autocompleteService.setAdapter（skillAdapter）; ，我得到一個NPE說我正在對一個空對象調用setAdapter。 調試告訴我，此時autocompleteService確實為null。

為什么此視圖為空？ 在此之前調用Butterknife.bind。 為什么不初始化視圖？

這是確切的錯誤：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.AutoCompleteTextView.setAdapter(android.widget.ListAdapter)' on a null object reference
                                                            at com.xyz.controllers.HomeFragment$3.onResponse(HomeFragment.java:183)
                                                            at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:70)
                                                            at android.os.Handler.handleCallback(Handler.java:739)
                                                            at android.os.Handler.dispatchMessage(Handler.java:95)
                                                            at android.os.Looper.loop(Looper.java:148)
                                                            at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                            at java.lang.reflect.Method.invoke(Native Method)
                                                            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

覆蓋onViewCreated並移動您的

    unbinder = ButterKnife.bind(this, view);
    initialize();
    loadSkillsData();

進入那里

Answer 2

使用ViewTreeObserver.onGlobalLayoutListener可以確保在嘗試更改視圖之前將其完全布局。 這是使用全局布局偵聽器的loadSkillsData函數，該函數應解析您的NPE：

private void loadSkillsData()
{
    Realm realm = getRealm();
    UserModel user = realm.where(UserModel.class).findFirst();

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(RestAPI.ENDPOINT)
            .addConverterFactory(MoshiConverterFactory.create())
            .build();
    RestAPI restApi = retrofit.create(RestAPI.class);
    Call<ResponseSkills> loginCall = restApi.getSkills(user.getServerUserId());
    loginCall.enqueue(new Callback<ResponseSkills>()
    {
        @Override
        public void onResponse(Call<ResponseSkills> call, final Response<ResponseSkills> response)
        {
            if (response.isSuccessful())
            {
                if (response.body().getStatus())
                {
                    skillList = response.body().getSkillList();
                    ArrayAdapter<SkillModel> skillAdapter = new ArrayAdapter<>(context, android.R.layout.simple_list_item_1, skillList);
                    autocompleteService.viewTreeObserver.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
                        @Override
                        public void onGlobalLayout() {
                            autocompleteService.setAdapter(skillAdapter);
                        }
                    }
                }
                else
                {
                    switch (response.body().getError())
                    {
                        default:
                        Toasty.error(context, response.body().getError());
                        break;
                    }
                }
            } else
            {
                Toasty.error(context, getString(R.string.toast_experienced_a_problem)).show();
            }
        }

        @Override
        public void onFailure(Call<ResponseSkills> call, Throwable t)
        {
            Toasty.error(context, getString(R.string.toast_experienced_a_problem)).show();
            t.printStackTrace();
        }
    });
}

除了NPE的問題之外，您還將遇到使用領域的方式的問題。 領域需要在其自己的線程上進行訪問，如果您像在上面的代碼中那樣從UI線程訪問它，則將導致應用程序崩潰。

Answer 3

您必須在onCreateView方法中調用ButterKnife.bind

     // bind the view using butterknife
    ButterKnife.bind(this);