扫描外设广播详解

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扫描外设广播详解

一、接口说明

/*!*  @method scanForPeripheralsWithServices:options:**  @param serviceUUIDs A list of <code>CBUUID</code> objects representing the service(s) to scan for.*  @param options      An optional dictionary specifying options for the scan.**  @discussion         Starts scanning for peripherals that are advertising any of the services listed in <i>serviceUUIDs</i>. Although strongly discouraged,*                      if <i>serviceUUIDs</i> is <i>nil</i> all discovered peripherals will be returned. If the central is already scanning with different*                      <i>serviceUUIDs</i> or <i>options</i>, the provided parameters will replace them.*                      Applications that have specified the <code>bluetooth-central</code> background mode are allowed to scan while backgrounded, with two*                      caveats: the scan must specify one or more service types in <i>serviceUUIDs</i>, and the <code>CBCentralManagerScanOptionAllowDuplicatesKey</code>*                      scan option will be ignored.**  @see                centralManager:didDiscoverPeripheral:advertisementData:RSSI:*  @seealso            CBCentralManagerScanOptionAllowDuplicatesKey*    @seealso            CBCentralManagerScanOptionSolicitedServiceUUIDsKey**/
- (void)scanForPeripheralsWithServices:(nullable NSArray<CBUUID *> *)serviceUUIDs options:(nullable NSDictionary<NSString *, id> *)options;

这个方法是支持后台扫描的，前提是工程开启了后台蓝牙模式。然后两个细节：

1. 如果是后台扫描serviceUUIDs需要至少包含一个

2. CBCentralManagerScanOptionAllowDuplicatesKey选项将被忽略

二、Options说明

1、CBCentralManagerScanOptionAllowDuplicatesKey

/*!*  **@const** CBCentralManagerScanOptionAllowDuplicatesKey**  **@discussion** An NSNumber (Boolean) indicating that the scan should run without duplicate filtering. By default, multiple discoveries of the*              same peripheral are coalesced into a single discovery event. Specifying this option will cause a discovery event to be generated* every time the peripheral is seen, which may be many times per second. This can be useful in specific situations, such as making* a connection based on a peripheral's RSSI, but may have an adverse affect on battery-life and application performance.**  **@see**        scanForPeripheralsWithServices:options:**/

这个选项是一个bool值。缺省是false,当发现多个相同的外设时候会合并为一个事件回调。当设置为true的时候，它会将多个相同的的外设单独回调，对设备电池寿命和应用的性能会有影响。但是某些需要通过RSSI来做业务需求的，又需要持续扫描。

2、CBCentralManagerScanOptionSolicitedServiceUUIDsKey

/*!*  **@const** CBCentralManagerScanOptionSolicitedServiceUUIDsKey**  **@discussion** An NSArray of <code>CBUUID</code> objects respresenting service UUIDs. Causes the scan to also look for peripherals soliciting* any of the services contained in the list.**  **@see**        scanForPeripheralsWithServices:options:**/

这个选项是一个bool值。外设建立连接时应用程序挂起，系统会给定外设的连接警报。

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