即使收到数据,RecyclerView也不会显示任何内容

时间:2018-08-29 21:11:19

标签: android android-recyclerview rx-java2 android-room android-mvp

我正在尝试在RecyclerView上填充一些数据。数据是通过以下一种方式获取的:

  1. 如果存在互联网(使用RetrofitRxJava2从API请求数据,将数据持久保存到本地数据库(使用Room),将数据发送到{{1 }}(在我的情况下是View)。
  2. 如果没有互联网,则从本地数据库获取数据并将其发送到Fragment

我正在使用MVP作为应用程序体系结构,并且正在使用View处理UI的数据处理。我正在使用ViewModels进行视图查找。

ButterKnife调用Presenter,它根据上面指定的条件获取数据,然后数据由Repository发送到Views,其中{ {1}}截取数据,并执行必要的步骤以将数据传递到UI元素(Presenter适配器更新)。

我的问题是:

  1. 即使在调试器中看到数据达到ViewModel时,屏幕还是空白。没有显示数据。
  2. 本地数据库的结果抛出RecyclerView,表示无法从主线程访问本地db,即使在我调用函数从本地db返回数据的RecyclerViewAdapter时也是如此,它返回IllegalStateException

我的代码如下:
资料库:

subscribeOn(Schedulers.io())

Maybe<>

public class CountriesListApiRepository {
    private final IRestServiceDataFetcher restServiceDataFetcher; // Retrofit interface to get data from API

    @Inject
    public CountriesListApiRepository(IRestServiceDataFetcher restServiceDataFetcher) {
        this.restServiceDataFetcher = restServiceDataFetcher;
    }

    public Maybe<List<CountriesFullEntity>> getCountriesFromApi() {
        return restServiceDataFetcher
                .getListOfCountriesData()
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeOn(Schedulers.io());
    }
}


我的演示者:

public class CountriesListLocalDbRepository {
    private final CountriesLocalDb countriesLocalDb;

    @Inject
    CountriesListLocalDbRepository(CountriesLocalDb countriesLocalDb) {
        this.countriesLocalDb = countriesLocalDb;
    }

    Maybe<List<CountriesFullEntity>> getCountriesFromLocalDb() {
        return this.countriesLocalDb
                .getCountriesLocalDbDAO()
                .getCountriesList()
                .observeOn(Schedulers.io())
                .subscribeOn(Schedulers.io());
    }

    void updateLocalDb(List<CountriesFullEntity> updatedCountriesList) {
        countriesLocalDb.getCountriesLocalDbDAO().insertAllCountries(updatedCountriesList);

    }
}

public class CountriesListRepository {
    private final CountriesListApiRepository countriesListApiRepository;
    private final CountriesListLocalDbRepository countriesListLocalDbRepository;
    private static final String TAG_CountriesListRepository = "CountriesListRepository";

    @Inject
    public CountriesListRepository(CountriesListApiRepository countriesListApiRepository,
                                   CountriesListLocalDbRepository countriesListLocalDbRepository) {
        this.countriesListApiRepository = countriesListApiRepository;
        this.countriesListLocalDbRepository = countriesListLocalDbRepository;
    }

    public Maybe<List<CountriesFullEntity>> getCountries() {
        return this.countriesListApiRepository
                .getCountriesFromApi()
                .doOnSuccess(this.countriesListLocalDbRepository::updateLocalDb)
                .doOnError(throwable -> {
                    Log.d(TAG_CountriesListRepository,throwable.getMessage());
                    throwable.printStackTrace(); })
                .onErrorResumeNext(this.countriesListLocalDbRepository.getCountriesFromLocalDb());
    }
}  


我的观点:

public class BasePresenter<T extends BaseView> {
    @Inject
    T injectedView;

    private static final String TAG_BASE_PRESENTER = "BasePresenter";

    T getInjectedView() {
        return injectedView;
    }

    <V> void subscribeToObserver(Maybe<V> flowable, MaybeObserver<V> maybeObserver) {
        flowable.subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .doOnSubscribe(subscription -> Log.d(TAG_BASE_PRESENTER,"Subscribed"))
                .doOnSuccess(v -> Log.d(TAG_BASE_PRESENTER,"onNext() completed"))
                .subscribe(maybeObserver);
    }
}  

public class CountriesListPresenter extends BasePresenter<CountriesListView>
        implements MaybeObserver<List<CountriesFullEntity>> {

    private static final String TAG_ListPresenter = "CountriesListPresenter";

    private final CountriesListRepository countriesListRepository;

    private Disposable disposable;

    @Inject
    public CountriesListPresenter(CountriesListRepository countriesListRepository) {
        this.countriesListRepository = countriesListRepository;
    }

    public void getCountries() {
        Maybe<List<CountriesFullEntity>> listOfCountriesData = this.countriesListRepository
                .getCountries();
        subscribeToObserver(listOfCountriesData, this);
    }

    public void updateCountriesList(@NonNull Boolean isInternetThere) {
        Maybe<List<CountriesFullEntity>> newCountriesFullData = this.countriesListRepository
                .updateCountriesList(isInternetThere);
        subscribeToObserver(newCountriesFullData,this);
    }

    @Override
    public void onSubscribe(Disposable d) {
        this.disposable = d;
    }

    @Override
    public void onSuccess(List<CountriesFullEntity> countriesFullEntities) {
        Log.d(TAG_ListPresenter,"Executing onNext()");
        getInjectedView().onLoadCountriesDataFull(countriesFullEntities);
    }

    @Override
    public void onError(Throwable e) {
        Log.d(TAG_ListPresenter,"Executing onError()",e);
        getInjectedView().onErrorEncountered(e.getMessage());
    }

    @Override
    public void onComplete() {
        if(!disposable.isDisposed()) disposable.dispose();
    }
}  

public class MainActivity extends AppCompatActivity implements IFragmentToFragmentMediator, SwipeRefreshLayout.OnRefreshListener {

    public static final String TAG_MAIN_ACTIVITY = "MainActivity";

    public static final String TAG_LIST_FRAGMENT = "COUNTRY_LIST";
    public static final String TAG_DETAILS_FRAGMENT = "COUNTRY_DETAILS";

    @BindView(R.id.MainActSwipeRefreshLayout)
    SwipeRefreshLayout swipeRefreshLayout;

    private Unbinder unbinder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        unbinder = ButterKnife.bind(this);
        swipeRefreshLayout.setOnRefreshListener(this);
        Configuration config = getResources().getConfiguration();
        Log.d(TAG_MAIN_ACTIVITY,"Main Activity View Created");
        if(config.smallestScreenWidthDp<600){
            CountriesListFrag countriesListFrag = new CountriesListFrag();
            conductFragmentTransaction(countriesListFrag,TAG_LIST_FRAGMENT, false, true);
            Log.d(TAG_MAIN_ACTIVITY,"Main Activity < 600 and portrait");
        }
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        FragmentManager fm = getSupportFragmentManager();
        if(getSupportFragmentManager().getBackStackEntryCount() > 1) {
            Fragment f = fm.findFragmentByTag(TAG_DETAILS_FRAGMENT);
            if (f instanceof  CountryDetailsFrag) fm.popBackStack();
            else this.finish();
        }
    }

    @Override
    public void onRefresh() {
        // TODO : Code the refreshing data callback here
        Fragment countryListFragment = returnNonNullRunningFragmentByTagName(TAG_LIST_FRAGMENT);
        Fragment countryDetailsFragment = returnNonNullRunningFragmentByTagName(TAG_DETAILS_FRAGMENT);
        makeViewsSignalUpdateOfData((CountriesListFrag)countryListFragment);
        makeViewsSignalUpdateOfData((CountryDetailsFrag)countryDetailsFragment);
    }

    @Override
    public void invokeDetailsFragmentOnListItemCLickedInListFragment(CountriesFullEntity countriesFullEntity) {
        CountryDetailsFrag countryDetailsFrag = CountryDetailsFrag.newInstance();
        Bundle data = new Bundle();
        data.putSerializable("data",countriesFullEntity);
        countryDetailsFrag.setArguments(data);
        conductFragmentTransaction(countryDetailsFrag, TAG_DETAILS_FRAGMENT, false, true);
    }

    @Override
    public void invokeDetailsFragmentOnListItemClickedInListFragmentViewModel() {

        CountryDetailsFrag countryDetailsFrag =
                (CountryDetailsFrag) getSupportFragmentManager().findFragmentByTag(TAG_DETAILS_FRAGMENT);

        if(countryDetailsFrag!=null && countryDetailsFrag.isVisible())
        conductFragmentTransaction(countryDetailsFrag, TAG_DETAILS_FRAGMENT, true, true);
    }

    private void makeViewsSignalUpdateOfData(BaseView view) {
        if(view != null) view.onPerformUpdateAction();
    }

    private Fragment returnNonNullRunningFragmentByTagName(String tagName) {
        Fragment fragmentForProcessing = getSupportFragmentManager().findFragmentByTag(tagName);
        if(fragmentForProcessing!=null && fragmentForProcessing.isVisible()) return fragmentForProcessing;
        return null;
    }

    private void conductFragmentTransaction(Fragment targetFragment, String tag, boolean addOrReplaceFlag, boolean backStackFlag) {
        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        if(addOrReplaceFlag)fragmentTransaction.replace(R.id.fragmentCanvas,targetFragment,tag);
        else fragmentTransaction.add(R.id.fragmentCanvas,targetFragment,tag);
        if(backStackFlag)fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbinder.unbind();
    }
}  


我的DAO:

public class CountriesListFrag extends Fragment implements CountriesListView {

    public static final String TAG_LIST_FRAGMENT = "ListFragment";

    @Inject
    Picasso picasso;
    @Inject
    CountriesListPresenter countriesListPresenter;

    private IFragmentToFragmentMediator listeningActivity;
    private Frag2FragCommViewModel frag2FragCommViewModel;

    @BindView(R.id.CountriesEntireHolderRV)
    RecyclerView countriesEntireHolderRV;
    private CountriesListRecyclerViewAdapter countriesListRecyclerViewAdapter;
    private Unbinder unbinder;

    public CountriesListFrag() {
    }

    @Override
    public void onAttach(Context context) {
        DaggerCountryComponents
                .builder()
                .appComponents(((CentralApplication)context.getApplicationContext())
                        .getAppComponents())
                .countryModule(new CountryModule(this))
                .build()
                .inject(this);
        super.onAttach(context);
        try{
            this.listeningActivity = (MainActivity) context;

            this.frag2FragCommViewModel = ViewModelProviders
                    .of((MainActivity) context)
                    .get(Frag2FragCommViewModel.class);
        } catch (ClassCastException e) {
            throw new ClassCastException(context.toString() + " must implement IFragmentToFragmentMediator");
        }
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_countries_list, container, false);
        if(v!=null) this.unbinder = ButterKnife.bind(this,v);

        // Inflate the layout for this fragment
        initialize();
        this.countriesListPresenter.getCountries();
        setUpListItemClickListener();

        frag2FragCommViewModel
                .getLiveDataListOfCountriesData()
                .observe(this,countriesFullEntities ->
                        countriesListRecyclerViewAdapter.setCountriesFullEntityList(countriesFullEntities));
        Log.d(TAG_LIST_FRAGMENT,"List Fragment View Created");

        return v;
    }

    @Override
    public void onLoadCountriesDataFull(List<CountriesFullEntity> countriesFullData) {
//        this.countriesListRecyclerViewAdapter.setCountriesFullEntityList(countriesFullData);
        Log.d(TAG_LIST_FRAGMENT,"Data Received in List Fragment");
        Log.d(TAG_LIST_FRAGMENT,countriesFullData.get(0).getName());
        this.frag2FragCommViewModel.setListOfCountriesData(countriesFullData);
    }

    @Override
    public void onErrorEncountered(String errorMessage) {
        Toast.makeText(getContext(), errorMessage,Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onPerformUpdateAction() {
        callToPresenterToUpdateListOfCountriesOnInternetPresent(this.getContext());
    }

    private void initialize() {
        this.countriesEntireHolderRV = new RecyclerView(this.getContext());
        this.countriesListRecyclerViewAdapter = new CountriesListRecyclerViewAdapter(new ArrayList<>(),
                LayoutInflater.from(this.getContext()), this.picasso);

        this.countriesEntireHolderRV.setLayoutManager(new LinearLayoutManager(this.getContext()));
        this.countriesEntireHolderRV
                .addItemDecoration(new DividerItemDecoration(this.countriesEntireHolderRV.getContext()
                        ,DividerItemDecoration.VERTICAL));
        this.countriesEntireHolderRV.setAdapter(this.countriesListRecyclerViewAdapter);
        Log.d(TAG_LIST_FRAGMENT,"List Fragment init");
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        this.unbinder.unbind();
    }
}  

public class CountriesListRecyclerViewAdapter extends RecyclerView.Adapter<CountriesListRecyclerViewAdapter.CountriesListViewHolder>{
    private List<CountriesFullEntity> countriesFullEntityList;
    private final LayoutInflater layoutInflater;
    private final Picasso picasso;
    private CountriesListRVClickListener countriesListRVClickListener;
    private int currentPosition;

    CountriesListRecyclerViewAdapter(List<CountriesFullEntity> countriesFullEntityList, LayoutInflater layoutInflater, Picasso picasso) {
        this.countriesFullEntityList = countriesFullEntityList;
        this.layoutInflater = layoutInflater;
        this.picasso = picasso;
        this.currentPosition = 0;
    }

    @NonNull
    @Override
    public CountriesListViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new CountriesListViewHolder(this.layoutInflater.inflate(R.layout.countries_list_layout,parent,false));
    }

    @Override
    public void onBindViewHolder(@NonNull CountriesListViewHolder holder, int position) {
        CountriesFullEntity countriesFullEntity = countriesFullEntityList.get(position);
        picasso.load(countriesFullEntity.getFlag()).into(holder.countryIcon);
        holder.nameOfCountry.setText(countriesFullEntity.getName());
    }

    @Override
    public int getItemCount() {
        return this.countriesFullEntityList.size();
    }

    void setItemClickListener(CountriesListRVClickListener itemClickListener) {
        this.countriesListRVClickListener = itemClickListener;
    }

    CountriesFullEntity getCountriesFullEntityAtPosition(int position) {
        return this.countriesFullEntityList.get(position);
    }

    void setCountriesFullEntityList(List<CountriesFullEntity> countriesFullEntityList) {
        this.countriesFullEntityList = countriesFullEntityList;
        notifyDataSetChanged();
    }

    int getCurrentPosition() {
        return currentPosition;
    }

    void setCurrentPosition(int currentPosition) {
        this.currentPosition = currentPosition;
    }

    class CountriesListViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        @BindView(R.id.NameOfCountry)
        TextView nameOfCountry;
        @BindView(R.id.CountryIcon)
        ImageView countryIcon;
        CountriesListViewHolder(View itemView) {
            super(itemView);
        }

        @Override
        public void onClick(View v) {
            countriesListRVClickListener.onListItemClicked(v,getAdapterPosition());
        }
    }
}  


我的布局:

ActivityMainLayout:

@Dao
public interface CountriesLocalDbDAO {
    @Query("SELECT * FROM Countries")
    Maybe<List<CountriesFullEntity>> getCountriesList();

    @Query("SELECT * FROM Countries WHERE name LIKE :countryName")
    Maybe<CountriesFullEntity> getCountryByName(String countryName);

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insertAllCountries(List<CountriesFullEntity> countryList);

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insertSingleCountry(CountriesFullEntity singleCountry);

    @Delete
    void deleteSingleCountry(CountriesFullEntity singleCountry);

    @Delete
    void endOfTheWorld(List<CountriesFullEntity> theWorld);
}  

FragmentListLayout:

public interface IRestServiceDataFetcher {
    @GET("all")
    Maybe<List<CountriesFullEntity>> getListOfCountriesData();
    @GET("name/{name}")
    Maybe<CountriesFullEntity> getParticularCountry(@Path("name") String name);
}

RecyclerViewViewHolderLayout:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
android:id="@+id/fragmentCanvas"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.MainActivity">
    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/MainActSwipeRefreshLayout"
        android:layout_height="20dp"
        android:layout_width="match_parent">
    </android.support.v4.widget.SwipeRefreshLayout>
</FrameLayout>


我的应用程序build.gradle:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".ui.countrieslist.CountriesListFrag">

    <!-- TODO: Update blank fragment layout -->


    <android.support.v7.widget.RecyclerView
        android:id="@+id/CountriesEntireHolderRV"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>  

更新:

我按照@ Ben-P的建议做了。但是现在我的RecycleViewAdapter给了我错误。
我在此行上收到<?xml version="1.0" encoding="utf-8"?> <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent"> <ImageView android:id="@+id/CountryIcon" android:layout_width="80dp" android:layout_height="80dp" android:layout_marginEnd="8dp" android:layout_marginLeft="8dp" android:layout_marginRight="8dp" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:contentDescription="@string/app_name" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" app:srcCompat="@drawable/ic_launcher_background" /> <TextView android:id="@+id/NameOfCountry" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginEnd="8dp" android:layout_marginLeft="8dp" android:layout_marginRight="8dp" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:text="@string/app_name" android:textSize="40sp" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toEndOf="@+id/CountryIcon" app:layout_constraintTop_toTopOf="parent" /> </android.support.constraint.ConstraintLayout> apply plugin: 'com.android.application' android { compileSdkVersion 27 defaultConfig { applicationId "shankhadeepghoshal.org.countrieslistapp" minSdkVersion 14 //noinspection OldTargetApi targetSdkVersion 27 multiDexEnabled true versionCode 1 versionName "1.0" vectorDrawables.useSupportLibrary = true testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner" javaCompileOptions { annotationProcessorOptions { includeCompileClasspath = true } } externalNativeBuild { cmake { cppFlags "-std=c++14 -frtti -fexceptions" } } // multiDexEnabled true } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' } } externalNativeBuild { cmake { path "CMakeLists.txt" } } compileOptions { targetCompatibility JavaVersion.VERSION_1_8 sourceCompatibility JavaVersion.VERSION_1_8 } buildToolsVersion '27.0.3' } dependencies { implementation fileTree(include: ['*.jar'], dir: 'libs') implementation 'com.google.dagger:dagger:2.16' annotationProcessor 'com.google.dagger:dagger-compiler:2.16' implementation 'com.google.dagger:dagger-android:2.16' implementation 'com.google.dagger:dagger-android-support:2.16' annotationProcessor 'com.google.dagger:dagger-android-processor:2.16' implementation 'io.reactivex.rxjava2:rxandroid:2.1.0' implementation 'io.reactivex.rxjava2:rxjava:2.2.0' implementation 'com.squareup.picasso:picasso:2.71828' implementation( [group: 'com.fasterxml.jackson.core', name: 'jackson-core', version: '2.9.6'], [group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.9.6'], [group: 'com.fasterxml.jackson.core', name: 'jackson-annotations', version: '2.9.6'] ) implementation 'com.squareup.retrofit2:retrofit:2.4.0' implementation 'com.squareup.retrofit2:converter-jackson:2.4.0' implementation 'com.squareup.retrofit2:adapter-java8:2.4.0' implementation 'com.squareup.retrofit2:adapter-rxjava2:2.4.0' implementation 'com.squareup.okhttp3:logging-interceptor:3.5.0' compileOnly 'org.projectlombok:lombok:1.18.2' annotationProcessor 'org.projectlombok:lombok:1.18.2' def room_version = "1.1.1" implementation "android.arch.persistence.room:runtime:$room_version" annotationProcessor "android.arch.persistence.room:compiler:$room_version" implementation "android.arch.persistence.room:rxjava2:$room_version" implementation "android.arch.persistence.room:guava:$room_version" testImplementation "android.arch.persistence.room:testing:$room_version" def lifecycle_version = "1.1.1" implementation "android.arch.lifecycle:extensions:$lifecycle_version" implementation "android.arch.lifecycle:runtime:$lifecycle_version" implementation "android.arch.lifecycle:common-java8:$lifecycle_version" implementation "android.arch.lifecycle:reactivestreams:$lifecycle_version" testImplementation "android.arch.core:core-testing:$lifecycle_version" implementation 'com.jakewharton:butterknife:8.8.1' annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1' implementation 'com.android.support:design:27.1.1' implementation 'com.android.support:appcompat-v7:27.1.1' implementation 'com.android.support.constraint:constraint-layout:1.1.2' implementation 'com.android.support:recyclerview-v7:27.1.1' implementation 'com.android.support:support-compat:27.1.1' implementation 'com.android.support:exifinterface:27.1.1' implementation 'com.android.support:multidex:1.0.3' testImplementation 'junit:junit:4.12' androidTestImplementation 'com.android.support.test:runner:1.0.2' androidTestImplementation 'com.android.support.test:rules:1.0.2' androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2' }

中的IllegalArgumentException - Target must be null

1 个答案:

答案 0 :(得分:1)

在您的片段中,您具有以下代码:

private void initialize() {
    this.countriesEntireHolderRV = new RecyclerView(this.getContext());
    ...
}

之前,在onCreateView()中,您调用ButterKnife.bind() ...,这意味着上述代码将countriesEntireHolderRV重新分配给新引用。这个新的RecyclerView永远不会添加到您的Fragment的视图中(而且无论如何都不会可见,因为LinearLayout已经有一个孩子占据了所有可见空间),因此您的所有操作都可以与用户无法使用的RecyclerView一起使用见。

只需从initialize()中删除该行。然后,您将在布局文件中使用RecyclerView,一切都会出现。