Question

What I want to achieve: I am loading data from some web service in recyclerView. I want to load first 10 data and display it in recyclerView. When User scrolls, call web service for another 10 data to display it.

What I have done: For above aim, I'm using .take operator of RxJava. But It seems not working for me or else I'm doing some mistake.

What issue I'm having: I'm getting all the data instead of first 5 data. There might be something that I'm missing it.

My code is like below.

MainActivity.java

    public class MainActivity extends AppCompatActivity {

    private final String TAG = MainActivity.class.getSimpleName();

    private RecyclerView recyclerView;
    private ProgressDialog mProgressDialog;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        recyclerView = findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        setupProgressDialog();

        ApiEndPoints apiEndPoints = ApiClient.getClient().create(ApiEndPoints.class);

        mProgressDialog.show();

        apiEndPoints.fetchAllUsers()
                .take(5)
                .subscribeOn(Schedulers.io()) //Background Thread
                .observeOn(AndroidSchedulers.mainThread()) //UI Thread
                .subscribe(new Observer<List<Pojo>>() {
                               @Override
                               public void onSubscribe(Disposable d) {

                               }

                               @Override
                               public void onNext(List<Pojo> pojoList) {

                                   recyclerView.setAdapter(new RVAdapter(pojoList));

                                   Log.e(TAG, "List Size: " + pojoList.size());
                               }

                               @Override
                               public void onError(Throwable e) {

                               }

                               @Override
                               public void onComplete() {
                                   mProgressDialog.dismiss();
                               }
                           }
                );
    }

    private void setupProgressDialog() {
        mProgressDialog = new ProgressDialog(this);
        mProgressDialog.setMessage("Loading . . . ");
        mProgressDialog.setIndeterminate(true);
        mProgressDialog.setCancelable(false);
    }
}

Ask me if anything required. Thanks in advance.

Answer 1

如果使用Take运算符，它将发出前5个项目，然后onCompleted函数将触发。因此，您需要可观察的来源。

我在github上找到了示例应用程序，该应用程序使用rxjava进行更多操作。

Answer 2

您会收到一个列表，该列表被视为对象。您需要对其进行迭代，先获取5个，然后再将其作为列表返回：

apiEndPoints.fetchAllUsers()
            // iterate users
            .concatMap(new Func1<List<Pojo>, Observable<Pojo>>() {
                @Override
                public Observable<Pojo> call(List<Pojo> pojos) {
                    return Observable.from(pojos);
                }
            })
            // take 5 from iteration
            .take(5)
            // put all 5 users back to a list
            .toList()
            .subscribeOn(Schedulers.io()) //Background Thread
            .observeOn(AndroidSchedulers.mainThread()) //UI Thread

如果您有一个数组（Pojos[] users）take()运算符应该没有迭代地工作。

RxJava Take operator is not working

2 个答案: