基于结果链接可观察对象

Question

我是rx-java和rx-android的完全初学者。我听说学习曲线在一开始是相当陡峭的。

我试图通过使用rx-android将所有基于Eventbus的代码替换为更类型安全的替代方案。

我已经设置了这个代码片段来创建可观察的编辑文本文本更改事件:

MainActivity

RxUtils.createEditTextChangeObservable(txtInput).throttleLast(200, TimeUnit.MILLISECONDS, AndroidSchedulers.mainThread()).subscribe(new Action1<EditText>() {
            @Override
            public void call(EditText editText) {
                searchStopResultFragment.query(editText.getText().toString());
            }
        });

RxUtils:

public static Observable<EditText> createEditTextChangeObservable(final EditText editText){
        return Observable.create(new Observable.OnSubscribe<EditText>() {
            @Override
            public void call(final Subscriber<? super EditText> subscriber) {
                editText.addTextChangedListener(new TextWatcher() {
                    @Override
                    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                    }
                    @Override
                    public void onTextChanged(CharSequence s, int start, int before, int count) {
                    }
                    @Override
                    public void afterTextChanged(Editable s) {
                        if (subscriber.isUnsubscribed()) return;
                        subscriber.onNext(editText);
                    }
                });
            }
        });
    }

SearchStopResultFragment:

public void query(String query){
        lastQuery = query;
        resultObservable = StopProvider.getStopResultObservable(getActivity().getContentResolver(),query);
        subscription = resultObservable.subscribeOn(Schedulers.newThread())
                    .observeOn(AndroidSchedulers.mainThread()).subscribe(new Observer<List<Stop>>() {
            @Override
            public void onCompleted() {
            }
            @Override
            public void onError(Throwable e) {
            }
            @Override
            public void onNext(List<Stop> stops) {
                if(!lastQuery.equals("")) {
                    if(stops.size()>0) {
                        ArrayList<AdapterItem> items = adapter.getItems();
                        items.clear();
                        for (Stop stop : stops) {
                            SearchResultStopItem item = new SearchResultStopItem(stop, SearchResultStopItem.STOP);
                            items.add(item);
                        }
                        adapter.setItems(items);
                        adapter.notifyDataSetChanged();
                    }else{
                      //DO A NOTHER ASYNC QUERY TO FETCH RESULTS
                    }
                }else{
                    showStartItems();
                }
            }
        });
    }

感觉我做错了。我在每个文本更改事件上从我的片段中的查询方法创建新的可观察对象。我还想根据StopProvider.getStopResultObservable中的结果创建一个新的异步查找操作(参见注释)

有什么想法吗?

Answer 1

我是这么想的:

RxUtils.createEditTextChangeObservable(txtInput)
.throttleLast(200, TimeUnit.MILLISECONDS, AndroidSchedulers.mainThread())
.map(EXTRACT_STRING)
.filter(STRING_IS_NOT_EMPTY)
.concatMap(new Func1<EditText, Observable<Pair<String,List<Stop>>>>() {
    @Override
    public Observable<Pair<String, List<Stop>>> call(final String query) {
        return StopProvider.getStopResultObservable(getContentResolver(), query)
        .map(new Func1<List<Stop>, Pair<String, List<Stop>>>() {
            // I think this map is a bit more readable than the 
            // combineLatest, and since "query" should not be changing 
            // anyway, the result should be the same (you have to 
            // declare it as final in the method signature, though
            @Override
            public Pair<String, List<Stop>> call(List<Stop> stops) {
                return new Pair(query, stops);
            }
        });
    }
)
.concatMap(new Func1<Pair<String, List<Stop>>, Observable<List<Stop>>>() {
    @Override
    public Observable<List<Stop>> call(Pair<String, List<Stop>> queryAndStops) {
        if (queryAndStops.second.size() == 0) {
            return RestClient.service().locationName(queryAndStops.first)
                       .map(new Func1<LocationNameResponse, List<Stop>>() {
                            @Override
                            public List<Stop> call(LocationNameResponse locationNameResponse) {
                                // since there was no if-else in your original code (you were always
                                // just wrapping the List in an Observable) I removed that, too
                                return locationNameResponse.getAddresses();
                            }
            });
        } else {
            return Observable.just(queryAndStops.second);
        }
    }
)
.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.compose(this.<List<Stop>>bindToLifecycle())
.subscribe(new Action1<List<Stop>>() {
    @Override
    public void call(List<Stop> stops) {
        // since I don't know what your API is returning I think
        // it's saver to keep this check in:
        if (stops != null) {
            searchStopResultFragment.showStops(stops);
        } else {
            searchStopResultFragment.showStartItems();
        }
    }
},
new Action1<Throwable>() {
    @Override
    public void call(Throwable throwable) {
        showError(throwable);
    }
});

地点:

public static final Func1<EditText, String> EXTRACT_STRING = new Func1<EditText, String>() {
    @Override
    public void String call(EditText editText) {
        return editText.getText().toString();
    }
};
public static final Func1<String, Boolean> STRING_IS_NOT_EMPTY = new Func1<String, Boolean>() {
    @Override
    public void String call(String string) {
        return !string.isEmpty();
    }
};

因此，这至少消除了返回Observable.just(null)的需要，然后检查该链。

Answer 2

您可以将第二个concatMap移动到您需要的唯一位置-在combinellatest之后

    RxUtils.createEditTextChangeObservable(txtInput)
            .throttleLast(200, TimeUnit.MILLISECONDS, AndroidSchedulers.mainThread())
            .concatMap(new Func1<EditText, Observable<Pair<String, List<Stop>>>>() {
                @Override
                public Observable<Pair<String, List<Stop>>> call(EditText editText) {
                    String query = editText.getText().toString();
                    //searchStopResultFragment.setLastQuery(query);
                    if (query.isEmpty()) {
                        return Observable.just(null);
                    }
                    return Observable
                            .combineLatest(StopProvider.getStopResultObservable(getContentResolver(), query), Observable.just(query), new Func2<List<Stop>, String, Pair<String, List<Stop>>>() {
                                @Override
                                public Pair<String, List<Stop>> call(List<Stop> stops, String s) {
                                    return new Pair(s, stops);
                                }
                            })
                            .concatMap(new Func1<R, Observable<? extends Pair<String, List<Stop>>>>() {
                                @Override
                                public Observable<? extends Pair<String, List<Stop>>> call(R r) {
                                    if (queryAndStops.second.size() == 0) {
                                        return RestClient.service().locationName(queryAndStops.first).concatMap(new Func1<LocationNameResponse, Observable<? extends List<Stop>>>() {
                                            @Override
                                            public Observable<? extends List<Stop>> call(LocationNameResponse locationNameResponse) {
                                                return Observable.just(locationNameResponse.getAddresses());
                                            }
                                        });
                                    } else {
                                        return Observable.just(queryAndStops.second);
                                    }
                                }
                            });
                }
            })
            .subscribeOn(Schedulers.newThread())
            .observeOn(AndroidSchedulers.mainThread()).compose(this.<List<Stop>>bindToLifecycle())
            .subscribe(new Action1<List<Stop>>() {
                @Override
                public void call(List<Stop> stops) {
                    if (stops != null) {
                        searchStopResultFragment.showStops(stops);
                    } else {
                        searchStopResultFragment.showStartItems();
                    }
                }
            }, new Action1<Throwable>() {
                @Override
                public void call(Throwable throwable) {
                    showError(throwable);
                }
            });

Answer 3

使用concatmap和combine解决:

 RxUtils.createEditTextChangeObservable(txtInput).throttleLast(200, TimeUnit.MILLISECONDS, AndroidSchedulers.mainThread()).concatMap(new Func1<EditText, Observable<Pair<String,List<Stop>>>>() {
            @Override
            public Observable<Pair<String, List<Stop>>> call(EditText editText) {
                String query = editText.getText().toString();
                //searchStopResultFragment.setLastQuery(query);
                if(query.isEmpty()){
                    return Observable.just(null);
                }
                return Observable.combineLatest(StopProvider.getStopResultObservable(getContentResolver(), query), Observable.just(query), new Func2<List<Stop>, String, Pair<String, List<Stop>>>() {
                    @Override
                    public Pair<String, List<Stop>> call(List<Stop> stops, String s) {
                        return new Pair(s,stops);
                    }
                });
            }
        }).concatMap(new Func1<Pair<String, List<Stop>>, Observable<List<Stop>>>() {
            @Override
            public Observable<List<Stop>> call(Pair<String, List<Stop>> queryAndStops) {
                if(queryAndStops!=null) {
                    if (queryAndStops.second.size() == 0) {
                        return RestClient.service().locationName(queryAndStops.first).concatMap(new Func1<LocationNameResponse, Observable<? extends List<Stop>>>() {
                            @Override
                            public Observable<? extends List<Stop>> call(LocationNameResponse locationNameResponse) {
                                return Observable.just(locationNameResponse.getAddresses());
                            }
                        });
                    } else {
                        return Observable.just(queryAndStops.second);
                    }
                }
                return Observable.just(null);
            }
        }).subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread()).compose(this.<List<Stop>>bindToLifecycle()).subscribe(new Action1<List<Stop>>() {
            @Override
            public void call(List<Stop> stops) {
                if (stops != null) {
                    searchStopResultFragment.showStops(stops);
                }else{
                    searchStopResultFragment.showStartItems();
                }
            }
        }, new Action1<Throwable>() {
            @Override
            public void call(Throwable throwable) {
                showError(throwable);
            }
        });

然而，有没有更好的方法来打破链而不发送Observable.just(null)和检查null在下一次调用?