使用 RxAndroidBle 编写多个特性的正确方法是什么？

Question

我是 Rx 的新手，仍在尝试弄清楚如何正确处理可观察对象。我想知道是否有比使用 RxAndroidBle 一次编写一个特性更好的方法来编写多个特性？目前我正在使用下面的代码一次一个地完成它们。

Observable<RxBleConnection> mConnectionObservable;

private void saveChanges(String serialNumber, Date date, MachineTypeEnum machineType, MachineConfig machineConfig) {
    mWriteSubscription = mConnectionObservable
            .flatMap(rxBleConnection -> Observable.merge(
                    getWrites(rxBleConnection, serialNumber, machineType, machineConfig, date)
            ))
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(bytes -> {
                Toast.makeText(getContext(), "Saved Changes", Toast.LENGTH_SHORT).show();
                ((MainActivity)getActivity()).back();
            }, BleUtil::logError);
}

private Iterable<? extends Observable<? extends byte[]>> getWrites(RxBleConnection rxBleConnection,
                                                                   String serialNumber,
                                                                   MachineTypeEnum machineType,
                                                                   MachineConfig machineConfig,
                                                                   Date date) {
    List<Observable<byte[]>> observables = new ArrayList<>();


    observables.add(rxBleConnection.writeCharacteristic(
            Constants.Bluetooth.Services.DrainCleaner.Characteristics.UUID_WRITE_SERIAL_NUMBER,
            Utf8Util.nullPad(serialNumber, 16).getBytes()).doOnError(throwable -> Log.e("Write", "serial failed", throwable)));

    observables.add(rxBleConnection.writeCharacteristic(
            Constants.Bluetooth.Services.DrainCleaner.Characteristics.UUID_MACHINE_TYPE,
            new byte[]{(byte) machineType.val()}).doOnError(throwable -> Log.e("Write", "machine type failed", throwable)));

    observables.add(rxBleConnection.writeCharacteristic(
            Constants.Bluetooth.Services.DrainCleaner.Characteristics.UUID_CHARACTERISTIC,
            MachineConfigBitLogic.toBytes(machineConfig)).doOnError(throwable -> Log.e("Write", "machine config failed", throwable)));

    observables.add(rxBleConnection.writeCharacteristic(
            Constants.Bluetooth.Services.CurrentTime.Characteristics.UUID_CURRENT_TIME,
            TimeBitLogic.bytesFor(date)).doOnError(throwable -> Log.e("Write", "date failed", throwable)));

    return observables;
}

所以我将我的旧代码更改为上面的代码，现在使用合并，但现在似乎只有一个特性更新了。

Answer 1

我会使用 merge 运算符：

mConnectionObservable
        .flatMap(rxBleConnection -> 
        Observable.merge(
        rxBleConnection.writeCharacteristic(
            Constants.Bluetooth.Services.DeviceInformation.Characteristics.UUID_SERIAL_NUMBER,
            Utf8Util.nullPad(serialNumber, 16).getBytes()
        ),
        rxBleConnection.writeCharacteristic(
            Constants.Bluetooth.Services.DrainCleaner.Characteristics.UUID_MACHINE_TYPE,
            new byte[]{(byte) machineType.val()}
        ))
        .subscribe(bytes -> {/* do something*/}, BleUtil::logError);

您还可以将可观察对象列表传递给该运算符：

Instead of passing multiple Observables (up to nine) into merge, you could also pass in a List<> (or other Iterable) of Observables, an Array of Observables, or even an Observable that emits Observables, and merge will merge their output into the output of a single Observable

Answer 2

RxAndroidBle 库在后台序列化任何 BLE 请求，因为 Android 上的 BLE 实现大部分是同步的（尽管 Android vanilla API 表明它是不是）。

尽管您需要了解合并运算符的作用，但合并写入是一种很好的方法：

 * You can combine the items emitted by multiple Observables so that they appear as a single Observable, by
 * using the {@code merge} method.

So I changed my old code to what is above which now uses merge but only one of the characteristics seems to update now.

此行为的原因可能是您使用流的方式：

        .subscribe(bytes -> {
            Toast.makeText(getContext(), "Saved Changes", Toast.LENGTH_SHORT).show();
            ((MainActivity)getActivity()).back();
        }, BleUtil::logError);

每当发出 bytes 时，您就在调用 Activity.back()。 .merge() 运算符确实会为执行的每个写入命令发出 bytes。如果您取消订阅 Subscription in 即 .onPause() ，那么它将在第一次写入完成后立即取消订阅。您可以让您的流程等待所有写入完成，如下所示：

private void saveChanges(String serialNumber, Date date, MachineTypeEnum machineType, MachineConfig machineConfig) {
    mWriteSubscription = mConnectionObservable
        .flatMap(rxBleConnection -> 
            Observable.merge(
                getWrites(rxBleConnection, serialNumber, machineType, machineConfig, date)
            )
            .toCompletable() // we are only interested in the merged writes completion
            .andThen(Observable.just(new byte[0])) // once the merged writes complete we send a single value that will be reacted upon (ignored) in .subscribe()
        )
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(ignored -> {
            Toast.makeText(getContext(), "Saved Changes", Toast.LENGTH_SHORT).show();
            ((MainActivity)getActivity()).back();
        }, BleUtil::logError);
}

使用 RxAndroidBle 编写多个特性的正确方法是什么？

What is the proper way to write multiple characteristics with RxAndroidBle?

android

rx-android

rxandroidble