android - RecyclerView 使用 RxJava 无限滚动

Question

我想使用 RxJava 在 RecyclerView 上实现 Endless Scrolling 功能。

我想要什么:我想从 API 调用中获取前 10 个数据并将其显示在 RecyclerView 中。用户向下滚动这 10 个数据后，我想进行另一个 API 调用并提取另外 10 个数据。再次当用户在这些最新的 10 个数据之后向下滚动时，我必须为另外 10 个数据进行 API 调用。这将一直持续到 API 调用提供所有数据为止。

我尝试使用 take 运算符，但没有得到想要的结果。我搜索了不同的运营商，但没有找到单个运营商或运营商的任何组合来实现这一目标。任何帮助将不胜感激。

我的代码如下。

SalesDashboardActivity.java

    public class SalesDashboardActivity2 extends BaseActivity implements SalesDashboardView {

    List<DashboardStatusBean> inProgressList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sales_dashboard2);
        ButterKnife.bind(this);
        setSupportActionBar(mToolbar);
        mSalesDashboardPresenter.attachView(this);
        getDashboardData();
    }

    private void getDashboardData() {

        SearchLoansInput searchLoansInput = new SearchLoansInput();
        searchLoansInput.setUserName(sessionManager.getMobileNumber());

        if (Util.isInternetConnection(this)) {
            mSalesDashboardPresenter.handleSalesInquiryRequest(searchLoansInput);
        } else {
            displayToastMessage("Internet is not available! Check your internet connection.");
        }
    }

    @Override
    public void handleSalesInquiryResponse(SearchLoansOutput searchLoansOutputData) {

        if (searchLoansOutputData.isSuccess()) {

            Util.SALES_IN_PROGRESS_LIST.clear();

            for (int i = 0; i < searchLoansOutputData.getLoanDetailList().size(); i++) {
                DashboardStatusBean dashboardStatusBean = new DashboardStatusBean();
                SimpleDateFormat sdf = new SimpleDateFormat("dd MMM yyyy");
                String approveDate = null;
                String createdDate = null;

                if (searchLoansOutputData.getLoanDetailList().get(i).getCreatedDate() != null) {
                    createdDate = String.valueOf(sdf.format(searchLoansOutputData.getLoanDetailList().get(i).getCreatedDate()));
                }
                if (searchLoansOutputData.getLoanDetailList().get(i).getApprovedDate() != null) {
                    approveDate = String.valueOf(sdf.format(searchLoansOutputData.getLoanDetailList().get(i).getApprovedDate()));
                }

                String loanNumber = searchLoansOutputData.getLoanDetailList().get(i).getLoanNumber();
                String firstName = searchLoansOutputData.getLoanDetailList().get(i).getFirstName();
                String lastName = searchLoansOutputData.getLoanDetailList().get(i).getLastName();
                String mobileNumber = searchLoansOutputData.getLoanDetailList().get(i).getMobileNumber();
                String status = searchLoansOutputData.getLoanDetailList().get(i).getStatus().getDisplayName();
                String loanAmount = String.valueOf(searchLoansOutputData.getLoanDetailList().get(i).getLoanAmount().setScale(0, BigDecimal.ROUND_UP));
                String loanAppId = searchLoansOutputData.getLoanDetailList().get(i).getId();
                BigDecimal productAmount = searchLoansOutputData.getLoanDetailList().get(i).getTotalProductAmount();
                BigDecimal downPayment = searchLoansOutputData.getLoanDetailList().get(i).getDownPayment();
                BigDecimal processingFee = searchLoansOutputData.getLoanDetailList().get(i).getProcessingFee();
                String tenure = searchLoansOutputData.getLoanDetailList().get(i).getDesiredItemPaybackTenure();
                String sourceAcquisition = searchLoansOutputData.getLoanDetailList().get(i).getSourceAcquisition();
                List<SingleDocumentOuput> documentUpdatedList = searchLoansOutputData.getLoanDetailList().get(i).getDocOutputList();

                dashboardStatusBean.setCreatedDate(createdDate);
                dashboardStatusBean.setApproveDate(approveDate);
                dashboardStatusBean.setLoanNumber(loanNumber);
                dashboardStatusBean.setFirstName(firstName);
                dashboardStatusBean.setLastName(lastName);
                dashboardStatusBean.setMobileNumber(mobileNumber);
                dashboardStatusBean.setStatus(status);
                dashboardStatusBean.setLoanAppId(loanAppId);
                dashboardStatusBean.setProductAmount(productAmount);
                dashboardStatusBean.setDownPayment(downPayment);
                dashboardStatusBean.setProcessingFee(processingFee);
                dashboardStatusBean.setTenure(tenure);
                dashboardStatusBean.setLoanAmount(loanAmount);
                dashboardStatusBean.setDocumentUpdatedList(documentUpdatedList);

                if (status.equals(LoanApplicationStatus.STILL_FILLING.getDisplayName()) ||
                        status.equals(LoanApplicationStatus.ONBOARDIN_IN_PROG.getDisplayName()) ||
                        status.equals(LoanApplicationStatus.INITIATED.getDisplayName()) ||
                        status.equals(LoanApplicationStatus.ADDITIONAL_DATA_REQ.getDisplayName()) ||
                        status.equals(LoanApplicationStatus.UPLOAD_IN_PROG.getDisplayName()) ||
                        status.equals(LoanApplicationStatus.VERIFIED.getDisplayName()) ||
                        status.equals(LoanApplicationStatus.LEAD.getDisplayName())) {
                    inProgressList.add(dashboardStatusBean);
                }

                Util.SALES_IN_PROGRESS_LIST = inProgressList;
            }

        } else {
            displayMessage(searchLoansOutputData.getErrorCode(), searchLoansOutputData.getErrorMessage());
        }
    }
}

SalesLoginDashboardPresenter.java

    public class SalesLoginDashboardPresenter implements Presenter {

    private SalesDashboardView mView;
    private final SalesLoginInquiryUseCase mSalesInquiryUseCase;

    @Inject
    public SalesLoginDashboardPresenter(SalesLoginInquiryUseCase salesLoginInquiryUseCase) {
        mSalesInquiryUseCase = salesLoginInquiryUseCase;
    }

    @Override
    public void attachView(View v) {
        mView = (SalesDashboardView) v;
    }

    public void handleSalesInquiryRequest(SearchLoansInput searchLoansInput) {
        mView.displayLoadingScreen();
        mSalesInquiryUseCase.setSalesLoginInquiryBody(searchLoansInput);
        mSalesInquiryUseCase.execute()
                .subscribe(this::onSalesInquiryReceived, this::onSalesInquiryError);
    }

    private void onSalesInquiryError(Throwable throwable) {
        mView.hideLoadingScreen();
        mView.displayErrorMessage("Error fetching data");
        throwable.printStackTrace();
    }

    private void onSalesInquiryReceived(SearchLoansOutput searchLoansOutput) {
        mView.hideLoadingScreen();
        mView.handleSalesInquiryResponse(searchLoansOutput);
    }
}

SalesLoginInquiryUseCase.java

    public class SalesLoginInquiryUseCase extends Usecase<SearchLoansOutput> {

    private final MerchantRepository mRepository;
    private final Scheduler mUiThread;
    private final Scheduler mExecutorThread;
    private SearchLoansInput mSearchLoansInput;
    private String mCookie;

    @Inject
    public SalesLoginInquiryUseCase(
            MerchantRepository repository,
            @Named("ui_thread") Scheduler uiThread,
            @Named("executor_thread") Scheduler executorThread) {

        mRepository = repository;
        mUiThread = uiThread;
        mExecutorThread = executorThread;
    }

    public void setSalesLoginInquiryBody(SearchLoansInput searchLoansInput){
        mSearchLoansInput = searchLoansInput;
    }

    @Override
    public Observable<SearchLoansOutput> buildObservable() {
        return mRepository.postSalesLoginDetailsInquiryBody(mSearchLoansInput)
                .observeOn(mUiThread)
                .subscribeOn(mExecutorThread);
    }
}

Answer 1

我正在做一个关于在应用程序上无限滚动和学习 RxJava 的练习。

我在 StackOverflow 和其他网站上gandalfing，寻找好的示例和指南。

到目前为止我找到了this one ，我也在这里报告(当然，版权属于要点所有者)。

ApiService.class

public static Observable<List<String>> paginatedThings(final Observable<Void> onNextObservable) {
        return Observable.create(new Observable.OnSubscribe<List<String>>() {
            @Override
            public void call(final Subscriber<? super List<String>> subscriber) {

            onNextObservable.subscribe(new Observer<Void>() {
                int latestPage = -1;
                @Override
                public void onCompleted() {
                    subscriber.onCompleted();
                }

                @Override
                public void onError(Throwable e) {
                    subscriber.onError(e);
                }

                @Override
                public void onNext(Void aVoid) {
                    latestPage++;
                    List<String> pageItems = new ArrayList<String>();
                    for (int i = 0; i < 10; i++) {
                        pageItems.add("page " + latestPage + " item " + i);
                    }
                    subscriber.onNext(pageItems);
                }
            });
        }
    });
}

ReactiveList.java

import android.app.Activity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.example.rxandroid.api.RepresentativeApi;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;

import butterknife.ButterKnife;
import butterknife.InjectView;
import rx.Observable;
import rx.Observer;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.subscriptions.CompositeSubscription;
import timber.log.Timber;

import static rx.android.app.AppObservable.bindActivity;

/**
 * Created by Dustin on 2/14/15.
 */
public class ReactiveList extends Activity {

    @InjectView(R.id.reactiveList)
    RecyclerView reactiveList;

    private ReactiveRecyclerAdapter adapter = new ReactiveRecyclerAdapter();
    private LinearLayoutManager layoutManager;

    private CompositeSubscription subscriptions = new CompositeSubscription();

    private List<String> mockItems = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.reactive_list);
        ButterKnife.inject(this);

        for (int i = 0; i < 100; i++) {
            mockItems.add(String.valueOf(i));
        }

        reactiveList.setHasFixedSize(true);
        reactiveList.setAdapter(adapter);
        layoutManager = new LinearLayoutManager(this);
        reactiveList.setLayoutManager(layoutManager);

        adapter.addAll(mockItems);

        Observable<Void> pageDetector = Observable.create(new Observable.OnSubscribe<Void>() {
            @Override
            public void call(final Subscriber<? super Void> subscriber) {
                reactiveList.setOnScrollListener(new RecyclerView.OnScrollListener() {
                    int pastVisibleItems, visibleItemCount, totalItemCount;
                    @Override
                    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                        visibleItemCount = layoutManager.getChildCount();
                        totalItemCount = layoutManager.getItemCount();
                        pastVisibleItems = layoutManager.findFirstVisibleItemPosition();

                        if ((visibleItemCount+pastVisibleItems) >= totalItemCount) {
                            subscriber.onNext(null);
                        }
                    }
                });
            }
        }).debounce(400, TimeUnit.MILLISECONDS);

        bindActivity(this, pageDetector);
        Observable<List<String>> listItemObservable = RepresentativeApi.paginatedThings(pageDetector);
        bindActivity(this, listItemObservable);
        subscriptions.add(listItemObservable.observeOn(AndroidSchedulers.mainThread()).subscribe(new Observer<List<String>>() {
            @Override
            public void onCompleted() {
                Timber.d("completed");
            }

            @Override
            public void onError(Throwable e) {
                Timber.e("error: " + e.getMessage());
            }

            @Override
            public void onNext(List<String> strings) {
                adapter.addAll(strings);
            }
        }));
    }

    public static class ReactiveRecyclerAdapter extends RecyclerView.Adapter<ReactiveRecyclerAdapter.ReactiveViewHolder> {

        private List<String> items = new ArrayList<>();

        public void addAll(List<String> moreItems) {
            items.addAll(moreItems);
            notifyDataSetChanged();
        }

        @Override
        public ReactiveViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View v = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1,parent,false);
            ReactiveViewHolder vh = new ReactiveViewHolder(v);
            return vh;
        }

        @Override
        public void onBindViewHolder(ReactiveViewHolder holder, int position) {
            String item = items.get(position);
            holder.label.setText(item);
        }

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

        public static class ReactiveViewHolder extends RecyclerView.ViewHolder {

            TextView label;
            public ReactiveViewHolder(View itemView) {
                super(itemView);
                label = (TextView) itemView.findViewById(android.R.id.text1);
            }
        }
    }
}

如果您对其他工具感兴趣，请查看 Google Architecture .

目标是简化应用程序代码(为什么不呢，程序员的生活):你会发现 Paging library你可以用它来解决无尽的滚动(我目前也在研究这个)。顺便说一下，它使用 RxJava2。

如果你愿意，这个GitHub repo上有一个例子这是用 Kotlin(!) 完成的。

结论:无限滚动可能非常棘手，我强烈建议您花时间学习和理解它的工作原理，无论是否使用库。