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前言
本文總結專案中常用的 Rxjava2 操作符。
使用RxJava2原因
- ★★★★★ 封裝了執行緒切換，不用自己封裝執行緒池、Handler了
- ★★★★☆ 鏈式呼叫，一氣呵成
單值發射
Single：大多數場景都是單值發射，所以使用 Single 即可覆蓋大部分場景。
Case1. 在非UI執行緒執行且不關注結果
- fromCallable
Single.fromCallable(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
Logger.d(TAG, "test: fromCallable() invoked on %s", Thread.currentThread().getName());
return generateRandom();
}
}).subscribeOn(Schedulers.io()).subscribe();
複製程式碼從名字 Callable 就能看出，這是個回撥函式，在 io 執行緒執行
- defer
Single.defer(new Callable<SingleSource<Integer>>() {
@Override
public SingleSource<Integer> call() throws Exception {
Logger.d(TAG, "test: defer() invoked on %s", Thread.currentThread().getName());
return Single.just(generateRandom());
}
}).subscribeOn(Schedulers.io()).subscribe();
複製程式碼注意，不能直接使用 Single.just(generateRandom()).subscribeOn(Schedulers.io()).subscribe()，這麼寫將直接在當前執行緒呼叫 generateRandom() ，無法實現在 io 執行緒執行的效果。
Case2. 在非UI執行緒執行並關注結果
需要關注結果的場景，建議都訂閱 Consumer<Throwable>，因為 RxJava 內部捕獲了 Exception，導致外部無感知
Single.fromCallable(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
return generateRandom();
}
}).subscribeOn(Schedulers.io()).subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
Logger.d(TAG, "test: accept(Integer integer) invoked on %s", Thread.currentThread().getName());
}
}, new Consumer<Throwable>() {
@Override
public void accept(Throwable throwable) throws Exception {
Logger.d(TAG, "test: accept(Throwable throwable) invoked on %s", Thread.currentThread().getName());
}
});
複製程式碼Case3. 在非UI執行緒執行但在UI執行緒關注結果
Single.fromCallable(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
return generateRandom();
}
}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<Integer>() {
@Override
public void accept(Integer integer) throws Exception {
Logger.d(TAG, "test: accept(Integer integer) invoked on %s", Thread.currentThread().getName());
}
}, new Consumer<Throwable>() {
@Override
public void accept(Throwable throwable) throws Exception {
Logger.d(TAG, "test: accept(Integer integer) invoked on %s", Thread.currentThread().getName());
}
});
複製程式碼Case4. 變換返回值
Single.fromCallable(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
return generateRandom();
}
}).map(new Function<Integer, String>() {
@Override
public String apply(Integer integer) throws Exception {
return String.valueOf(integer + "_mapped");
}
}).subscribe(new Consumer<String>() {
@Override
public void accept(String s) throws Exception {
Logger.d(TAG, "test: " + s);
}
});
複製程式碼Case5. 按順序做某事且下一件事依賴上一件事的結果[常用於網路請求介面依賴時]
Single.defer(new Callable<SingleSource<String>>() {
@Override
public SingleSource<String> call() throws Exception {
return getUserId();
}
}).flatMap(new Function<String, SingleSource<UserInfo>>() {
@Override
public SingleSource<UserInfo> apply(String userId) throws Exception {
return getUserInfo(userId);
}
}).subscribeOn(Schedulers.io()).subscribe(new Consumer<UserInfo>() {
@Override
public void accept(UserInfo userInfo) throws Exception {
Logger.d(TAG, "test: get userInfo success: " + userInfo);
}
}, new Consumer<Throwable>() {
@Override
public void accept(Throwable throwable) throws Exception {
Logger.e(TAG, "test: get userInfo error.", throwable);
}
});
複製程式碼Case6. 併發讀取不同資料來源，轉換成同型別後，合併
Single<IBook> novel = Single.fromCallable(new Callable<Novel>() {
@Override
public Novel call() throws Exception {
return getNovel();
}
}).map(new Function<Novel, IBook>() {
@Override
public IBook apply(Novel novel) throws Exception {
return new NovelAdapter(novel);
}
}).subscribeOn(Schedulers.io());
Single<IBook> rxJava2Tutorial = Single.fromCallable(new Callable<RxJava2Tutorial>() {
@Override
public RxJava2Tutorial call() throws Exception {
return getRxJava2Tutorial();
}
}).map(new Function<RxJava2Tutorial, IBook>() {
@Override
public IBook apply(RxJava2Tutorial rxJava2Tutorial) throws Exception {
return new RxJava2TutorialAdapter(rxJava2Tutorial);
}
}).subscribeOn(Schedulers.io());
Single.zip(novel, rxJava2Tutorial, new BiFunction<IBook, IBook, List<IBook>>() {
@Override
public List<IBook> apply(IBook iBook, IBook iBook2) throws Exception {
List<IBook> books = new ArrayList<>(2);
books.add(iBook);
books.add(iBook2);
return books;
}
}).subscribe(new Consumer<List<IBook>>() {
@Override
public void accept(List<IBook> iBooks) throws Exception {
Logger.d(TAG, "test: books are " + iBooks);
}
}, new Consumer<Throwable>() {
@Override
public void accept(Throwable throwable) throws Exception {
Logger.d(TAG, "test: get books error.", throwable);
}
});
複製程式碼多值發射
Observable：使用場景較少，比如搜尋功能需要不斷髮射搜尋關鍵字。
Case1. 搜尋頻率限制
Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(final ObservableEmitter<String> emitter) throws Exception {
mEditText.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 (!emitter.isDisposed()) {
emitter.onNext(s.toString().trim());
}
}
});
}
}).debounce(200, TimeUnit.MILLISECONDS).observeOn(AndroidSchedulers.mainThread())
.subscribe(new Consumer<String>() {
@Override
public void accept(String keyword) throws Exception {
mTextView.setText(search(keyword));
}
}, new Consumer<Throwable>() {
@Override
public void accept(Throwable throwable) throws Exception {
Logger.e(TAG, "test: emitter keyword error.", throwable);
}
});
複製程式碼背壓
Flowable：使用場景最少，目前僅發射下載進度時可以用上。
Demo 地址
總結
陳康肅公善射，當世無雙 ，公亦以此自矜。嘗射於家圃，有賣油翁釋擔而立，睨之久而不去。見其發矢十中八九，但微頷之。 康肅問曰：”汝亦知射乎？吾射不亦精乎？”翁曰：”無他， 但手熟爾。”康肅忿然曰：”爾安敢輕吾射！”翁曰：”以我酌油知之。”乃取一葫蘆置於地，以錢覆其口，徐以杓酌油瀝之，自錢孔入，而錢不溼。因曰：”我亦無他，惟手熟爾。”康肅笑而遣之。