您的應用程式可使用與訂閱鄰近裝置發布訊息相同的機制,訂閱藍牙低功耗 (BLE) 信標訊息。
根據預設,只有在應用程式於前景運作時,信標訂閱才能運作。應用程式進入背景時,訂閱項目會自動停止掃描信標。如要進一步瞭解如何啟用背景掃描,請參閱「背景掃描」。
如要訂閱信標,請將訂閱參數中的 deviceTypesToDiscover
參數設為 kGNSDeviceBLEBeacon
。下列程式碼片段說明如何執行這項作業:
Objective-C
id<GNSSubscription> beaconSubscription = [messageManager
subscriptionWithMessageFoundHandler:myMessageFoundHandler
messageLostHandler:myMessageLostHandler
paramsBlock:^(GNSSubscriptionParams *params) {
params.deviceTypesToDiscover = kGNSDeviceBLEBeacon;
}];
Swift
let beaconSubscription = messageManager.subscriptionWithMessageFoundHandler(
myMessageFoundHandler, messageLostHandler: myMessageLostHandler,
paramsBlock: { (params: GNSSubscriptionParams!) in
params.deviceTypesToDiscover = .BLEBeacon
})
上述訂閱項目只會探索專案擁有的信標,並接收來自這些信標的所有訊息。如果您想接收來自以不同命名空間註冊信標的訊息,可以在訂閱參數中傳遞命名空間。同樣地,如果您想要特定類型的訊息,也可以傳送訊息類型來篩選。下列程式碼片段說明如何執行此操作:
Objective-C
id<GNSSubscription> beaconSubscription = [messageManager
subscriptionWithMessageFoundHandler:myMessageFoundHandler
messageLostHandler:myMessageLostHandler
paramsBlock:^(GNSSubscriptionParams *params) {
params.deviceTypesToDiscover = kGNSDeviceBLEBeacon;
params.messageNamespace = @"com.mycompany.mybeaconservice";
params.type = @"mybeacontype";
}];
Swift
let beaconSubscription = messageManager.subscriptionWithMessageFoundHandler(
myMessageFoundHandler, messageLostHandler: myMessageLostHandler,
paramsBlock: { (params: GNSSubscriptionParams!) in
params.deviceTypesToDiscover = .BLEBeacon
params.messageNamespace = "com.mycompany.mybeaconservice"
params.type = "mybeacontype"
})
根據預設,信標訂閱會掃描 Eddystone 和 iBeacon 這兩種信標。啟用 iBeacon 掃描功能時,系統會提示使用者授予應用程式使用其位置資料的權限。應用程式的 Info.plist
必須包含 NSLocationWhenInUseUsageDescription
鍵,且簡述如何使用位置資訊。詳情請參閱 Apple 說明文件。
如果只想掃描 Eddystone 信標,可以在 GNSBeaconStrategy
中停用 iBeacon 掃描功能,這樣一來,iOS 就不會要求使用者授予位置使用權限。下列程式碼片段說明如何為上述原始訂閱項目停用 iBeacon 掃描功能:
Objective-C
id<GNSSubscription> beaconSubscription = [messageManager
subscriptionWithMessageFoundHandler:myMessageFoundHandler
messageLostHandler:myMessageLostHandler
paramsBlock:^(GNSSubscriptionParams *params) {
params.deviceTypesToDiscover = kGNSDeviceBLEBeacon;
params.beaconStrategy =
[GNSBeaconStrategy strategyWithParamsBlock:^(GNSBeaconStrategyParams *params) {
params.includeIBeacons = NO;
};
}];
Swift
let beaconSubscription = messageManager.subscriptionWithMessageFoundHandler(
myMessageFoundHandler, messageLostHandler: myMessageLostHandler,
paramsBlock: { (params: GNSSubscriptionParams!) in
params.deviceTypesToDiscover = .BLEBeacon
params.beaconStrategy =
GNSBeaconStrategy(paramsBlock: { (params: GNSBeaconStrategyParams!) in
params.includeIBeacons = false
})
})
預設會啟用低功耗掃描,在尋找 Eddystone 信標時,有時可能會發生嚴重延遲。低耗電模式停用時,系統會使用 iBeacon 掃描來尋找 Eddystone 信標,從而減少這些延遲。不過,這會導致電池用量增加,而 iOS 會要求使用者授予位置資訊使用權限。
下列程式碼片段說明如何在掃描 Eddystone 信標時停用低耗電模式。
Objective-C
id<GNSSubscription> beaconSubscription = [messageManager
subscriptionWithMessageFoundHandler:myMessageFoundHandler
messageLostHandler:myMessageLostHandler
paramsBlock:^(GNSSubscriptionParams *params) {
params.deviceTypesToDiscover = kGNSDeviceBLEBeacon;
params.beaconStrategy =
[GNSBeaconStrategy strategyWithParamsBlock:^(GNSBeaconStrategyParams *params) {
params.includeIBeacons = NO;
params.lowPowerPreferred = NO;
};
}];
Swift
let beaconSubscription = messageManager.subscriptionWithMessageFoundHandler(
myMessageFoundHandler, messageLostHandler: myMessageLostHandler,
paramsBlock: { (params: GNSSubscriptionParams!) in
params.deviceTypesToDiscover = .BLEBeacon
params.beaconStrategy =
GNSBeaconStrategy(paramsBlock: { (params: GNSBeaconStrategyParams!) in
params.includeIBeacons = false
params.lowPowerPreferred = false
})
})
掃描 iBeacon 時,系統會先顯示「鄰近分享」權限對話方塊,然後顯示 iOS 位置存取權對話方塊。如要覆寫這個對話方塊 (例如提供「預檢」對話方塊,說明需要位置存取權的原因),請將 permissionRequestHandler
設為訂閱參數中的自訂區塊。下列程式碼片段說明如何執行此操作:
Objective-C
id<GNSSubscription> beaconSubscription = [messageManager
subscriptionWithMessageFoundHandler:myMessageFoundHandler
messageLostHandler:myMessageLostHandler
paramsBlock:^(GNSSubscriptionParams *params) {
params.deviceTypesToDiscover = kGNSDeviceBLEBeacon;
params.permissionRequestHandler = ^(GNSPermissionHandler permissionHandler) {
// Show your custom dialog here, and don't forget to call permissionHandler after it is dismissed
permissionHandler(userGavePermission);
};
}];
Swift
let beaconSubscription = messageManager.subscriptionWithMessageFoundHandler(
myMessageFoundHandler, messageLostHandler: myMessageLostHandler,
paramsBlock: { (params: GNSSubscriptionParams!) in
params.deviceTypesToDiscover = .BLEBeacon
params.permissionRequestHandler = { (permissionHandler: GNSPermissionHandler!) in
// Show your custom dialog here, and don't forget to call permissionHandler after it is dismissed
permissionHandler(userGavePermission);
}
})
背景掃描
信標掃描功能採用 BLE,因此可在背景運作。決定使用背景模式時,請注意下列幾點:
- 背景 BLE 會增加電池成本。雖然成本很低,但建議您在決定使用背景模式前就先行衡量。
- 在啟用 iBeacon 掃描功能或停用低耗電模式時,iOS 會要求使用者授予在背景使用位置資訊的權限。
如要在背景啟用信標掃描功能,請採取下列額外步驟:
傳入正確設定的
GNSBeaconStrategy
物件,為訂閱項目啟用背景模式。下列程式碼片段說明如何執行這項作業:Objective-C
id<GNSSubscription> beaconSubscription = [messageManager subscriptionWithMessageFoundHandler:myMessageFoundHandler messageLostHandler:myMessageLostHandler paramsBlock:^(GNSSubscriptionParams *params) { params.deviceTypesToDiscover = kGNSDeviceBLEBeacon; params.beaconStrategy = [GNSBeaconStrategy strategyWithParamsBlock:^(GNSBeaconStrategyParams *params) { params.allowInBackground = YES; }]; }];
Swift
let beaconSubscription = messageManager.subscriptionWithMessageFoundHandler( myMessageFoundHandler, messageLostHandler: myMessageLostHandler, paramsBlock: { (params: GNSSubscriptionParams!) in params.deviceTypesToDiscover = .BLEBeacon params.beaconStrategy = GNSBeaconStrategy(paramsBlock: { (params: GNSBeaconStrategyParams!) in params.allowInBackground = true }) })
在應用程式的
Info.plist
中加入必要的項目:UIBackgroundModes
個項目:bluetooth-central
代表在背景掃描 BLE。location
可透過高耗電模式在背景掃描 iBeacon。 如果您只針對 Eddystone 信標進行低功耗掃描,可以省略此功能。
NSLocationAlwaysUsageDescription
字串,說明您將在背景追蹤使用者位置的原因。例如:「需要您的位置,才能在背景掃描信標。」詳情請參閱 Apple 說明文件。如果只掃描 Eddystone 信標,可以省略此功能。
使用者是否可以在應用程式中啟用或停用背景掃描功能?如果是的話,請將背景模式值儲存至
NSUserDefaults
,因為 iOS 在背景執行應用程式時可以隨時終止應用程式。應用程式應執行以下操作:- 每當使用者進行變更時,將背景模式值儲存至
NSUserDefaults
。 - 在啟動時從
NSUserDefaults
讀取,並在已啟用背景模式的情況下還原信標訂閱。
- 每當使用者進行變更時,將背景模式值儲存至