PageKeyedDataSource loadAfter 没有起火

在我的片段中，我集成了 android jetpack 分页库和我使用的数据源页面键控数据源带有改造 API 回调。

代码以异常方式运行并将数据加载到回收者视图但当我滚动到底部后，它应该通过触发加载更多数据加载后数据源类中的函数，但没有

我也切换到项目键控数据源仍然无法执行

是我的代码错误还是插件有问题！但在我发现 GitHub 上的一些演示应用程序运行良好时，我遵循了那里的代码。如果有人遇到此问题并已修复，请告诉我 编辑：使用AndroidX

public class ReportsDataSource extends PageKeyedDataSource<Integer, ReportItemModel> {

    MutableLiveData<NetworkState> networkState = new MutableLiveData<>();
    MutableLiveData<NetworkState> initialLoad = new MutableLiveData<>();

    private UserService getUserService;
    private List<Call<?>> compositeDisposable;
    private CompositeDisposable compositeDisposableData;
    private SchedulerProvider schedulerProvider;
    private Completable retryCompletable = null;

    public ReportsDataSource(UserService getUserService, List<Call<?>> compositeDisposable, CompositeDisposable compositeDisposableData, SchedulerProvider schedulerProvider) {
        this.getUserService = getUserService;
        this.compositeDisposable = compositeDisposable;
        this.compositeDisposableData = compositeDisposableData;
        this.schedulerProvider = schedulerProvider;
    }


    @Override
    public void loadInitial(@NonNull LoadInitialParams<Integer> params, @NonNull LoadInitialCallback<Integer, ReportItemModel> callback) {

        networkState.postValue(NetworkState.LOADING);
        initialLoad.postValue(NetworkState.LOADING);

        loadPage(1, new callback() {
            @Override
            public void get(ReportListModel list) {
                setRetry(null);
                networkState.postValue(NetworkState.LOADED);
                initialLoad.postValue(NetworkState.LOADED);
                callback.onResult(list.data.items, 1, list.data.next);
            }

            @Override
            public void failure(Throwable t) {
                setRetry(() -> loadInitial(params, callback));
                NetworkState error = NetworkState.error(t.getMessage());
                networkState.postValue(error);
                initialLoad.postValue(error);
            }
        });
    }

    @Override
    public void loadBefore(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, ReportItemModel> callback) {

    }

    @Override
    public void loadAfter(@NonNull LoadParams<Integer> params, @NonNull LoadCallback<Integer, ReportItemModel> callback) {

        networkState.postValue(NetworkState.LOADING);

        loadPage(params.key, new callback() {
            @Override
            public void get(ReportListModel list) {
                setRetry(null);
                networkState.postValue(NetworkState.LOADED);
                callback.onResult(list.data.items, list.data.next != params.key ? null : list.data.next);
            }

            @Override
            public void failure(Throwable t) {
                setRetry(() -> loadAfter(params, callback));
                networkState.postValue(NetworkState.error(t.getMessage()));
            }
        });
    }


    public static void log(String msg) {
        boolean threadMain = Looper.getMainLooper().getThread() == Thread.currentThread();
        Timber.tag("Thread_finder_" + (threadMain ? "ui" : "none")).d(Thread.currentThread().getId() + " " + msg);
    }

    private void loadPage(int i, callback callback) {
        log("loadPage");
        Call<ReportListModel> call = getUserService.getReportsList(i);
        compositeDisposable.add(call);
        try {
            Response<ReportListModel> response = call.execute();
            log("onResponse");
            if (RetrofitHelper.isSuccessful(response)) {
                callback.get(response.body());
            } else {
                callback.failure(new Throwable("Model verification is failed"));
            }
        } catch (IOException e) {
            callback.failure(e);
            //e.printStackTrace();
        }
    }

    public void retry() {
        if (retryCompletable != null) {
            compositeDisposableData.add(retryCompletable.subscribeOn(schedulerProvider.io()).observeOn(schedulerProvider.ui()).subscribe(() -> {
            }, Timber::d));
        }
    }

    private void setRetry(Action action) {
        if (action == null) {
            this.retryCompletable = null;
        } else {
            this.retryCompletable = Completable.fromAction(action);
        }
    }

    @NonNull
    public MutableLiveData<NetworkState> getNetworkState() {
        return networkState;
    }

    @NonNull
    public MutableLiveData<NetworkState> getInitialLoad() {
        return initialLoad;
    }


    public interface callback {
        void get(ReportListModel list);

        void failure(Throwable t);
    }
}

视图模型

public class ReportsListViewModel extends ViewModel {

    private static final int PAGE_SIZE = 10;
    private Executor executor = Executors.newFixedThreadPool(5);
    public LiveData<PagedList<ReportItemModel>> list;
    private List<Call<?>> compositeDisposable = new ArrayList<>();
    private CompositeDisposable compositeDisposableData = new CompositeDisposable();
    private ReportsDataSourceFactory sourceFactory;


    public final ObservableBoolean isErrorMessageVisible;
    public final ObservableBoolean isRetryButtonVisible;
    public final ObservableBoolean isLoadingProgressBarVisible;
    public final ObservableBoolean isSwipeRefreshLayoutEnable;
    public final ObservableField<String> errorMessage;


    public ReportsListViewModel(UserService userService, SchedulerProvider schedulerProvider) {
        sourceFactory = new ReportsDataSourceFactory(userService, compositeDisposable, compositeDisposableData, schedulerProvider);
        PagedList.Config config = new PagedList.Config.Builder()
                .setPageSize(PAGE_SIZE)
                .setEnablePlaceholders(false)
                .build();

        list = new LivePagedListBuilder<>(sourceFactory, config).build();

        isErrorMessageVisible = new ObservableBoolean(false);
        errorMessage = new ObservableField<>("");
        isRetryButtonVisible = new ObservableBoolean(false);
        isLoadingProgressBarVisible = new ObservableBoolean(true);
        isSwipeRefreshLayoutEnable = new ObservableBoolean(true);
    }


    @Override
    protected void onCleared() {
        super.onCleared();
        RetrofitStatic.clearRetrofitList(compositeDisposable);
        compositeDisposableData.clear();
    }

    public void retry() {
        sourceFactory.getDataSourceLiveData().getValue().retry();
    }

    public void refresh() {
        sourceFactory.getDataSourceLiveData().getValue().invalidate();
    }

    public LiveData<NetworkState> getNetworkState() {
        return Transformations.switchMap(sourceFactory.getDataSourceLiveData(), ReportsDataSource::getNetworkState);
    }

    public LiveData<NetworkState> getRefreshState() {
        return Transformations.switchMap(sourceFactory.getDataSourceLiveData(), ReportsDataSource::getInitialLoad);
    }

    public void setInitialLoadingState(NetworkState networkState) {
        isErrorMessageVisible.set((networkState.getMessage() != null));
        errorMessage.set(networkState.getMessage());

        isRetryButtonVisible.set(networkState.getStatus() == NetworkStateStatus.FAILED);
        isLoadingProgressBarVisible.set(networkState.getStatus() == NetworkStateStatus.RUNNING);
        isSwipeRefreshLayoutEnable.set(networkState.getStatus() == NetworkStateStatus.SUCCESS);
    }
}

页列表适配器

public class ReportListAdapter extends PagedListAdapter<ReportItemModel, RecyclerView.ViewHolder> {

    public static final DiffUtil.ItemCallback<ReportItemModel> DIFF_CALLBACK = new DiffUtil.ItemCallback<ReportItemModel>() {

        @Override
        public boolean areItemsTheSame(@NonNull ReportItemModel oldItem, @NonNull ReportItemModel newItem) {
            return oldItem.reportId == newItem.reportId;
        }

        @Override
        public boolean areContentsTheSame(@NonNull ReportItemModel oldItem, @NonNull ReportItemModel newItem) {
            return oldItem.equals(newItem);
        }
    };
    private NetworkState networkState = null;
    private RetryCallback retryCallback;

    public ReportListAdapter(RetryCallback retryCallback) {
        super(DIFF_CALLBACK);
        this.retryCallback = retryCallback;
    }

    @Override
    public int getItemViewType(int position) {
        if (hasExtraRow() && position == getItemCount() - 1) {
            return R.layout.item_network_state;
        } else {
            return R.layout.recycler_report_item;
        }
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view;
        switch (viewType) {
            case R.layout.recycler_report_item:
            default:
                view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_report_item, parent, false);
                return new ViewHolder(view);
            case R.layout.item_network_state:
                view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_network_state, parent, false);
                return new NetWorkStateHolder(view);
        }
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof ViewHolder) {
            bindView((ViewHolder) holder, position, holder.itemView.getContext());
        } else if (holder instanceof NetWorkStateHolder) {
            bindNetworkView((NetWorkStateHolder) holder, position, holder.itemView.getContext());
        }
    }

    private void bindNetworkView(NetWorkStateHolder holder, int position, Context context) {
        NetworkStateItemViewModel mNetworkStateItemViewModel = new NetworkStateItemViewModel(networkState, retryCallback);
        if (holder.binding != null) {
            holder.binding.setViewModel(mNetworkStateItemViewModel);
            holder.binding.executePendingBindings();
        }
    }

    @Override
    public int getItemCount() {
        return super.getItemCount() + (hasExtraRow() ? 1 : 0);
    }

    private void bindView(ViewHolder holder, int position, Context context) {
        holder.binding.reportId.setText( "Report ID: "+position);
    }

    private boolean hasExtraRow() {
        return networkState != null && networkState != NetworkState.LOADED;
    }

    public void setNetworkState(NetworkState newNetworkState) {
        if (getCurrentList() != null) {
            if (getCurrentList().size() != 0) {
                NetworkState previousState = this.networkState;
                boolean hadExtraRow = hasExtraRow();
                this.networkState = newNetworkState;
                boolean hasExtraRow = hasExtraRow();
                if (hadExtraRow != hasExtraRow) {
                    if (hadExtraRow) {
                        notifyItemRemoved(super.getItemCount());
                    } else {
                        notifyItemInserted(super.getItemCount());
                    }
                } else if (hasExtraRow && previousState != newNetworkState) {
                    notifyItemChanged(getItemCount() - 1);
                }
            }
        }
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        private final RecyclerReportItemBinding binding;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            binding = DataBindingUtil.bind(itemView);
        }
    }

    public class NetWorkStateHolder extends RecyclerView.ViewHolder {
        private final ItemNetworkStateBinding binding;
        private final NetworkStateItemViewModel mNetworkStateItemViewModel;

        public NetWorkStateHolder(@NonNull View itemView) {
            super(itemView);
            mNetworkStateItemViewModel = new NetworkStateItemViewModel(networkState, retryCallback);
            binding = DataBindingUtil.bind(itemView);
            binding.setViewModel(mNetworkStateItemViewModel);
            binding.executePendingBindings();
        }
    }
}

分段：

public class ReportsFragment extends ParentFragment implements RetryCallback {

    private ReportsFragment.callback callback;
    private FragmentReportsListBinding binding;
    private ReportsListViewModel reportViewModel;
    private ReportListAdapter adapter;


    public void setup(callback callback) {
        this.callback = callback;
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        binding = DataBindingUtil.inflate(inflater, R.layout.fragment_reports_list, container, false);
        reportViewModel = ViewModelProviders.of(this, mViewModelFactory).get(ReportsListViewModel.class);
        binding.setViewModel(reportViewModel);
        binding.executePendingBindings();
        initAdapter();
        initSwipeToRefresh();
        return binding.getRoot();
    }

    private void initSwipeToRefresh() {
        reportViewModel.getRefreshState().observe(this, networkState -> {
            if (adapter.getCurrentList() != null) {
                if (adapter.getCurrentList().size() > 0) {
                    binding.usersSwipeRefreshLayout.setRefreshing(networkState != null && networkState.getStatus() == NetworkState.LOADING.getStatus());
                } else {
                    setInitialLoadingState(networkState);
                }
            } else {
                setInitialLoadingState(networkState);
            }
        });
    }

    private void setInitialLoadingState(NetworkState networkState) {
        reportViewModel.setInitialLoadingState(networkState);
    }

    private void initAdapter() {
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext());
        adapter = new ReportListAdapter(this);
        binding.recycler.setLayoutManager(linearLayoutManager);
        binding.recycler.setAdapter(adapter);
        reportViewModel.list.observe(this,  adapter::submitList);
        reportViewModel.getNetworkState().observe(this, adapter::setNetworkState);
    }

    @Override
    public void retry() {
        reportViewModel.retry();
    }

    public interface callback {

    }
}

XML

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <import type="android.view.View" />

        <variable
            name="viewModel"
            type="dasarahalli.portal.adapters.paging.reports.ReportsListViewModel" />
    </data>


    <androidx.coordinatorlayout.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
            android:id="@+id/usersSwipeRefreshLayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:enabled="@{viewModel.isSwipeRefreshLayoutEnable}"
            app:onRefreshListener="@{viewModel::refresh}">

            <androidx.recyclerview.widget.RecyclerView
                android:id="@+id/recycler"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />
        </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:orientation="vertical"
            android:padding="8dp">

            <TextView
                android:id="@+id/errorMessageTextView"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_horizontal"
                android:text="@{viewModel.errorMessage}"
                android:visibility="@{viewModel.isErrorMessageVisible ? View.VISIBLE : View.GONE}" />

            <ProgressBar
                android:id="@+id/loadingProgressBar"
                style="?android:attr/progressBarStyle"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:visibility="@{viewModel.isLoadingProgressBarVisible ? View.VISIBLE : View.GONE}" />

            <Button
                android:id="@+id/retryLoadingButton"
                style="@style/Widget.AppCompat.Button.Colored"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:onClick="@{() -> viewModel.retry()}"
                android:text="RETRY"
                android:visibility="@{viewModel.isRetryButtonVisible ? View.VISIBLE : View.GONE}" />

        </LinearLayout>

    </androidx.coordinatorlayout.widget.CoordinatorLayout>
</layout>

在上面的代码中你可以看到我没有调用getitem under 绑定视图持有者但一旦我请求 getItem(itemPostion) 后，一切都开始工作了，它应该是

演示项目：

androidx-paging-library-demo-java https://bitbucket.org/falconro/androidx-paging-library-demo-java