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这一节解释ConnectableObservable 和它的子类以及它们的操作符:

一个可连接的Observable与普通的Observable差不多,除了这一点:可连接的Observable在被订阅时并不开始发射数据,只有在它的connect()被调用时才开始。用这种方法,你可以等所有的潜在订阅者都订阅了这个Observable之后才开始发射数据。

publishConnect

The following example code shows two Subscribers subscribing to the same Observable. In the first case, they subscribe to an ordinary Observable; in the second case, they subscribe to a Connectable Observable that only connects after both Subscribers subscribe. Note the difference in the output: 下面的示例代码展示了两个订阅者订阅同一个Observable的情况。第一种情形,它们订阅一个普通的Observable;第二种情形,它们订阅一个可连接的Observable,并且在两个都订阅后再连接。注意输出的不同:

示例 #1:

def firstMillion  = Observable.range( 1, 1000000 ).sample(7, java.util.concurrent.TimeUnit.MILLISECONDS);

firstMillion.subscribe(
   { println("Subscriber #1:" + it); },       // onNext
   { println("Error: " + it.getMessage()); }, // onError
   { println("Sequence #1 complete"); }       // onCompleted
);

firstMillion.subscribe(
    { println("Subscriber #2:" + it); },       // onNext
    { println("Error: " + it.getMessage()); }, // onError
    { println("Sequence #2 complete"); }       // onCompleted
);
Subscriber #1:211128
Subscriber #1:411633
Subscriber #1:629605
Subscriber #1:841903
Sequence #1 complete
Subscriber #2:244776
Subscriber #2:431416
Subscriber #2:621647
Subscriber #2:826996
Sequence #2 complete

示例 #2:

def firstMillion  = Observable.range( 1, 1000000 ).sample(7, java.util.concurrent.TimeUnit.MILLISECONDS).publish();

firstMillion.subscribe(
   { println("Subscriber #1:" + it); },       // onNext
   { println("Error: " + it.getMessage()); }, // onError
   { println("Sequence #1 complete"); }       // onCompleted
);

firstMillion.subscribe(
   { println("Subscriber #2:" + it); },       // onNext
   { println("Error: " + it.getMessage()); }, // onError
   { println("Sequence #2 complete"); }       // onCompleted
);

firstMillion.connect();
Subscriber #2:208683
Subscriber #1:208683
Subscriber #2:432509
Subscriber #1:432509
Subscriber #2:644270
Subscriber #1:644270
Subscriber #2:887885
Subscriber #1:887885
Sequence #2 complete
Sequence #1 complete

参见:

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