我是 Android 开发和并发方面的新手，我正在尝试构建一个 Kotlin 应用程序，它连接到 BLE 设备并使用
readCharacteristicreadCharacteristic目前所有 BLE 操作都放入队列中，以便一次只有一个操作可以工作。队列的实现如下。
object ConnectionManager {
private val deviceGattMap = ConcurrentHashMap<BluetoothDevice, BluetoothGatt>()
private val operationQueue = ConcurrentLinkedQueue<BleOperationType>()
private var pendingOperation: BleOperationType? = null
private var connecting = false
@Synchronized
private fun enqueueOperation(operation: BleOperationType) {
operationQueue.add(operation)
if (pendingOperation == null) {
doNextOperation()
}
}
@Synchronized
private fun signalEndOfOperation() {
pendingOperation = null
if (operationQueue.isNotEmpty()) {
doNextOperation()
}
}
@SuppressLint("MissingPermission")
@Synchronized
private fun doNextOperation() {
if (pendingOperation != null) {
Log.e(
"ConnectionManager",
"doNextOperation() called when an operation is pending! Aborting."
)
return
}
val operation = operationQueue.poll() ?: run {
Log.i("ConnectionManager", "Operation queue empty, returning")
return
}
pendingOperation = operation
if (operation is Connect) {
connecting = true
operation.device.connectGatt(operation.context, false, gattCallback)
while (connecting) {
}
return
}
val gatt = deviceGattMap[operation.device]
?: [email protected] {
Log.e(
"ConnectionManager",
"Not connected to ${operation.device.address}! Aborting $operation operation."
)
signalEndOfOperation()
return
}
when (operation) {
is Disconnect -> {
gatt.close()
deviceGattMap.remove(operation.device)
signalEndOfOperation()
}
is CharacteristicWrite -> {
gatt.findCharacteristic(operation.characteristicUuid)?.let { characteristic ->
characteristic.value = operation.value
characteristic.writeType = operation.writeType
gatt.writeCharacteristic(characteristic)
} ?: run {
Log.e(
"ConnectionManager",
"Characteristic ${operation.characteristicUuid} not found!"
)
signalEndOfOperation()
}
}
is CharacteristicRead -> {
gatt.findCharacteristic(operation.characteristicUuid)?.let { characteristic ->
gatt.readCharacteristic(characteristic)
} ?: [email protected] {
Log.e(
"ConnectionManager",
"Characteristic ${operation.characteristicUuid} not found!"
)
signalEndOfOperation()
}
}
is WriteDescriptor -> {
.......
}
} is ......
}
}
这是GATT回调：
@SuppressLint("MissingPermission")
private val gattCallback = object : BluetoothGattCallback() {
override fun onConnectionStateChange(gatt: BluetoothGatt, status: Int, newState: Int) {
Log.w("BluetoothGattCallback", "Connection state changed: $status")
if (status == BluetoothGatt.GATT_SUCCESS) {
if (newState == BluetoothProfile.STATE_CONNECTED) {
deviceGattMap[gatt.device] = gatt
Handler(Looper.getMainLooper()).post {
deviceGattMap[gatt.device]?.discoverServices()
}
connecting = false
} else if (newState == BluetoothProfile.STATE_DISCONNECTING) {
disconnect(gatt.device)
}
} else {
connecting = false
Log.w("BluetoothGattCallback", "Error $status")
if (pendingOperation is Connect) {
signalEndOfOperation()
}
//disconnect(gatt.device)
} // Todo handle errors
}
override fun onServicesDiscovered(gatt: BluetoothGatt, status: Int) {
with(gatt) {
if (status == BluetoothGatt.GATT_SUCCESS) {
Log.w("BluetoothGattCallback", "Discovered ${services.size} services")
if (services.isEmpty()) {
Log.i(
"PrintGattTable",
"No services characteristics available, Call DiscoverServices() first?"
)
return
}
else {
services.forEach { service ->
val characteristicsTable = service.characteristics.joinToString(
separator = "\n | --",
prefix = "| --"
) {
it.uuid.toString()
}
Log.i(
"PrintGattTable",
"\n Services ${service.uuid} \n Characteristics ${characteristicsTable}"
)
}
}
ConnectionManager.requestMtu(gatt.device, 517)
} else {
Log.e("BluetoothGattCallback", "Service discovery failed with status $status")
disconnect(device)
}
}
if (pendingOperation is Connect) {
signalEndOfOperation()
}
}
override fun onMtuChanged(gatt: BluetoothGatt?, mtu: Int, status: Int) {
Log.i("MTU", "ATT MTU changed to $mtu, success ${status == BluetoothGatt.GATT_SUCCESS}")
if (pendingOperation is MtuRequest) {
signalEndOfOperation()
}
}
override fun onCharacteristicRead(
gatt: BluetoothGatt,
characteristic: BluetoothGattCharacteristic,
status: Int
) {
with(characteristic) {
when (status) {
BluetoothGatt.GATT_SUCCESS -> {
if (characteristic.uuid.toString() == BatteryCharacteristicUUID) {
Log.i("BluetoothGattCallback", "Read characteristic $uuid:\n${
value.joinToString(
separator = " ",
prefix = "0x"
) { String.format("%02X", it) }
} and \n ${value[0].toUInt()}"
)
}
else {
var light : MutableList<UInt> = mutableListOf()
for (i in 0..value.size-1 step 4) {
light.add(
((value[i].toUInt() and 0xFFu) shl 24) or
((value[i + 1].toUInt() and 0xFFu) shl 16) or
((value[i + 2].toUInt() and 0xFFu) shl 8) or
(value[i+ 3].toUInt() and 0xFFu))
}
Log.i("BluetoothGattCallback", "Read characteristic $uuid:\n${
value.joinToString(
separator = " ",
prefix = "0x"
) { String.format("%02X", it) }
}" +
" and \n ${light}"
)
}
}
BluetoothGatt.GATT_READ_NOT_PERMITTED -> {
}
else -> {
Log.e("BluetoothGattCallback", "Characteristic read failed for $uuid, error: $status")
}
}
}
if (pendingOperation is CharacteristicRead) {
signalEndOfOperation()
}
}
}
何时读取特征，我调用
ConnectionManager.readCharacteristic()打电话时
ConnectionManager.readCharacteristic(device, char)
Log.i("Tag", $char.value)
输出为 null，因为 Log 语句是在执行读取回调之前执行的。
有没有办法在没有时间延迟的情况下阻塞线程，或者阻塞可能不是一个好主意，应该研究涉及 future 或 Promise 的解决方案？如果是的话，欢迎任何建议！