[英]How can I write to a BLE GATT characteristic using RxAndroidBle in Kotlin?
[英]How to Read BLE GATT characterstics in chunks form GATT server using RxAndroidBLE
我正在使用RxAndroidBle庫來處理BLE連接以及從我的android gatt客戶端應用讀取/寫入GATT服務器。 我遵循了github提供的示例應用程序。
我面臨的問題是我的GATT服務器在Intel Edison上運行,並且僅支持80的MTU大小。它以塊的形式發送數據,我應該多次讀取特征值,直到遇到特殊字符,例如`` /結束' 。 我嘗試了“自定義讀取”操作示例,該示例應該每250毫秒讀取5次。
private static class CustomReadOperation implements RxBleRadioOperationCustom<byte[]> {
private RxBleConnection connection;
private UUID characteristicUuid;
CustomReadOperation(RxBleConnection connection, UUID characteristicUuid) {
this.connection = connection;
this.characteristicUuid = characteristicUuid;
}
/**
* Reads a characteristic 5 times with a 250ms delay between each. This is easily achieve without
* a custom operation. The gain here is that only one operation goes into the RxBleRadio queue
* eliminating the overhead of going on & out of the operation queue.
*/
@NonNull
@Override
public Observable<byte[]> asObservable(BluetoothGatt bluetoothGatt,
RxBleGattCallback rxBleGattCallback,
Scheduler scheduler) throws Throwable {
return connection.getCharacteristic(characteristicUuid)
.flatMap(characteristic -> readAndObserve(characteristic, bluetoothGatt, rxBleGattCallback))
.subscribeOn(scheduler)
.takeFirst(readResponseForMatchingCharacteristic())
.map(byteAssociation -> byteAssociation.second)
.repeatWhen(notificationHandler -> notificationHandler.take(5).delay(250, TimeUnit.MILLISECONDS));
}
@NonNull
private Observable<ByteAssociation<UUID>> readAndObserve(BluetoothGattCharacteristic characteristic,
BluetoothGatt bluetoothGatt,
RxBleGattCallback rxBleGattCallback) {
Observable<ByteAssociation<UUID>> onCharacteristicRead = rxBleGattCallback.getOnCharacteristicRead();
return Observable.create(emitter -> {
Subscription subscription = onCharacteristicRead.subscribe(emitter);
emitter.setCancellation(subscription::unsubscribe);
try {
final boolean success = bluetoothGatt.readCharacteristic(characteristic);
if (!success) {
throw new BleGattCannotStartException(bluetoothGatt, BleGattOperationType.CHARACTERISTIC_READ);
}
} catch (Throwable throwable) {
emitter.onError(throwable);
}
}, Emitter.BackpressureMode.BUFFER);
}
private Func1<ByteAssociation<UUID>, Boolean> readResponseForMatchingCharacteristic() {
return uuidByteAssociation -> uuidByteAssociation.first.equals(characteristicUuid);
}
}
我這樣稱呼它
public void customRead()
{
if (isConnected()) {
connectionObservable
.flatMap(rxBleConnection -> rxBleConnection.queue(new CustomReadOperation(rxBleConnection, UUID_READ_CHARACTERISTIC)))
.observeOn(AndroidSchedulers.mainThread())
.subscribe(bytes -> {
configureMvpView.showList(bytes);
}, this::onRunCustomFailure);
}
}
而且我沒有使用此代碼從服務器獲取任何數據。 但是,如果我嘗試這樣的簡單讀取操作
public void readInfo() {
if (isConnected()) {
connectionObservable
.flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(UUID_READ_CHARACTERISTIC))
.observeOn(AndroidSchedulers.mainThread())
.subscribe(bytes -> {
// parse data
configureMvpView.showWifiList(bytes);
}, this::onReadFailure);
}
}
我得到了第一批數據,但是我需要讀取其余數據。
我對RxJava不太了解。 因此,可能有一種簡單的方法來執行此操作,但是任何建議或幫助都會很好。
這是我的prepareConnectionObservable
private Observable<RxBleConnection> prepareConnectionObservable() {
return bleDevice
.establishConnection(false)
.takeUntil(disconnectTriggerSubject)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.doOnUnsubscribe(this::clearSubscription)
.compose(this.bindToLifecycle())
.compose(new ConnectionSharingAdapter());
}
我打電話
connectionObservable.subscribe(this::onConnectionReceived, this::onConnectionFailure);
和onConnectionReceived我叫CustomRead。
您沒有顯示如何創建connectionObservable
,並且我不知道在執行上述代碼之前對該連接是否進行了其他操作。
我的猜測是,如果您查看應用程序的日志,您會看到無線電處理隊列在連接后的第一個操作中開始執行CustomReadOperation
。 在自定義操作中,您正在調用RxBleConnection.getCharacteristic(UUID)
,該嘗試嘗試執行.discoverServices()
(在無線電隊列上安排RxBleRadioOperationDiscoverServices
)。 問題在於,無線電隊列已經在執行CustomReadOperation
並且在完成之前不會發現服務。
還有就是為什么一個原因RxBleConnection
沒有傳遞到RxBleRadioOperationCustom.asObservable()
-大部分的功能將不會在那個時候工作。
您可以做的是在安排CustomReadOperation
之前執行RxBleConnection.discoverServices()
並在構造函數中傳遞從RxBleDeviceServices
檢索到的BluetoothGattCharacteristic
。 所以不要這樣:
public void customRead()
{
if (isConnected()) {
connectionObservable
.flatMap(rxBleConnection -> rxBleConnection.queue(new CustomReadOperation(rxBleConnection, UUID_READ_CHARACTERISTIC)))
.observeOn(AndroidSchedulers.mainThread())
.subscribe(bytes -> {
configureMvpView.showList(bytes);
}, this::onRunCustomFailure);
}
}
您將有類似以下內容:
public void customRead()
{
if (isConnected()) {
connectionObservable
.flatMap(RxBleConnection::discoverServices, (rxBleConnection, services) ->
services.getCharacteristic(UUID_READ_CHARACTERISTIC)
.flatMap(characteristic -> rxBleConnection.queue(new CustomReadOperation(characteristic)))
)
.flatMap(observable -> observable)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(bytes -> {
configureMvpView.showList(bytes);
}, this::onRunCustomFailure);
}
}
編輯(說明):
而且CustomReadOperation
的構造函數應如下所示:
CustomReadOperation(BluetoothGattCharacteristic characteristic) {
this.characteristic = characteristic;
}
因此,您不必在CustomReadOperation
內部使用this.rxBleConnection.getCharacteristic(UUID)
並直接使用bluetoothGatt.readCharacteristic(this.characteristic)
。
編輯2:更改這兩行:
return connection.getCharacteristic(characteristicUuid)
.flatMap(characteristic -> readAndObserve(characteristic, bluetoothGatt, rxBleGattCallback))
對此(其余部分相同):
return readAndObserve(this.characteristic, bluetoothGatt, rxBleGattCallback)
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