ios - 在核心蓝牙框架中创建可写特性的问题

Question

我是核心蓝牙框架的新手。我正在开发一个充当外围设备的应用程序。我需要应用程序将特征值通知订阅的中心，并通过连接的中心写入特征值。我在创建特性时设置特性的值。问题是当我设置特性的属性以通知或写入它时显示错误“具有缓存值的特性必须是只读的”。谁能帮帮我？

 var charValue = characteristicDetail["value"] as String
 var charProperties:CBCharacteristicProperties = getProperty(characteristicDetail["properties"] as String )
 let data = charValue.dataUsingEncoding(NSUTF8StringEncoding)
 var characteristic = CBMutableCharacteristic(type: charId, properties: charProperties, value: data, permissions: CBAttributePermissions.Readable)



func getProperty(string:String) -> CBCharacteristicProperties
    {
    var propertyString:CBCharacteristicProperties?
    switch string{
    case "r","R":
        propertyString = CBCharacteristicProperties.Read
    case "w","W":
        propertyString = CBCharacteristicProperties.Write
    case "n","N":
        propertyString = CBCharacteristicProperties.Notify
    case "i","I":
        propertyString = CBCharacteristicProperties.Indicate
    case "rw","wr","WR","RW":
        propertyString = CBCharacteristicProperties.Read|CBCharacteristicProperties.Write
    case "rn","nr","NR","RN":
        propertyString = CBCharacteristicProperties.Read|CBCharacteristicProperties.Notify
    case "wn","nw","NW","WN":
        propertyString = CBCharacteristicProperties.Write|CBCharacteristicProperties.Notify
    default:
        propertyString = CBCharacteristicProperties.Read
    }
    return propertyString!

}

Answer 1

如果您在创建 CBMutableCharacteristic 时指定了一个非 nil value，那么它就是一个“缓存特征”，正如错误消息所说，您不能更改该值稍后。

来自 CBMutableCharacteristic init 方法的文档 -

value - The characteristic value to be cached. If nil, the value is dynamic and will be requested on demand.

在创建 CBMutableCharacteristic 时指定 nil - 在 didReceiveReadRequest CBPeripheralManagerDelegate 方法中请求时提供值.

如果您有订阅该特征的中心，那么只要值发生变化，您还应该在 CBPeripheralManager 上调用 updateValue。

请务必阅读 Core Bluetooth Programming Guide 中的执行常见外设角色任务部分