在 RxJava 2 中，如何使一个 Observable 发出另一个 Observable 发出的组合项？

Question

I have an Observable that emits random bits/booleans. I need to make another Observable that combines those random bits to create and emit random integers. Every time the underlying Observable emits a bit, this Observable appends that bit to a bit string, once that bit string reaches a specific length, this Observable converts it to an integer and emits it.

Here's the illustration:

Here's how I implement it using Android LiveData:

final StringBuilder bitStringBuilder = new StringBuilder();
final MediatorLiveData<Integer> integerLiveData = new MediatorLiveData<>();
integerLiveData.addSource(
        randomSource.getBooleanLiveData(),
        new Observer<Boolean>() {
            @Override
            public void onChanged(Boolean b) {
                bitStringBuilder.append(b ? '1' : '0');
                if (bitStringBuilder.length() == 31) {
                    integerLiveData.setValue(Integer.parseInt(bitStringBuilder.toString(), 2));
                    bitStringBuilder.setLength(0); // clear the bit string builder
                }
            }
        }
);

How to achieve this using RxJava 2?

Answer 1

Buffer bits:

source
.buffer(31)
.map(bits -> {
    int result = 0;
    for (int b : bits) {
        result = (result << 1) | (b ? 1 : 0);
    }
    return result;
})