CTTelephonyNetworkInfo的currentRadioAccessTechnology模糊响应
我在我的一个应用程序中有一个场景，我应该允许用户仅在连接至少为4G or LTE.时才将某些数据同步到服务器4G or LTE. 下面是我使用的源代码，它可以正常工作，直到下面解释的场景发生/发生。
if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyGPRS]) { self.currentCellularDataConnectionType = kGPRS; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyWCDMA]) { self.currentCellularDataConnectionType = kWCDMA; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyEdge]) { self.currentCellularDataConnectionType = kEDGE; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyLTE]) { self.currentCellularDataConnectionType = kLTE; self.cellularConnectionFast = YES; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMA1x]) { self.currentCellularDataConnectionType = (NSString *)currentCellularAccessTechnology; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyHSDPA] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyeHRPD]) { self.currentCellularDataConnectionType = [NSString stringWithFormat:@"%@ ~= %@",currentCellularAccessTechnology,k4G]; self.cellularConnectionFast = YES; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyHSUPA] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORev0] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORevA] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORevB]) { self.currentCellularDataConnectionType = [NSString stringWithFormat:@"%@ ~= %@",currentCellularAccessTechnology,k3G]; self.cellularConnectionFast = NO; } else { self.currentCellularDataConnectionType = (NSString *)currentCellularAccessTechnology; self.cellularConnectionFast = NO; }
currentCellularDataConnectionType保持当前的无线接入技术，而cellularConnectFast属性确定连接是否足够快。
问题出现在以下方案中，
如果用户通过按下睡眠/电源按钮将iPad置于睡眠模式，则CTRadioAccessTechnologyDidChangeNotification通知有时会将“ currentRadioAccessTechnology ”属性值指定为NULL or NIL 。 并且在此之后我们将不会获得具有正确数据连接类型（ RadioAccessTechnology ）的第二通知。 所以我无法在该条件下设置“ cellularConnectionFast ”属性值。
我试图实现一个逻辑，只有当CTTelephonyNetworkInfo.currentRadioAccessTechnology值不是NULL或NIL时才设置“ currentCellularDataConnectionType ”和“ cellularConnectionFast ”属性值，如下所示，
if ((NSNull *)currentCellularAccessTechnology == [NSNull null] || currentCellularAccessTechnology == nil) { DDLogInfo(@"From %s, New Cellular Connection Type recieved as: %@, so sticking with the previous Cellular Connection Type: %@",__PRETTY_FUNCTION__,currentCellularAccessTechnology,self.currentCellularDataConnectionType); } else { if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyGPRS]) { self.currentCellularDataConnectionType = kGPRS; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyWCDMA]) { self.currentCellularDataConnectionType = kWCDMA; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyEdge]) { self.currentCellularDataConnectionType = kEDGE; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyLTE]) { self.currentCellularDataConnectionType = kLTE; self.cellularConnectionFast = YES; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMA1x]) { self.currentCellularDataConnectionType = (NSString *)currentCellularAccessTechnology; self.cellularConnectionFast = NO; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyHSDPA] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyeHRPD]) { self.currentCellularDataConnectionType = [NSString stringWithFormat:@"%@ ~= %@",currentCellularAccessTechnology,k4G]; self.cellularConnectionFast = YES; } else if ([currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyHSUPA] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORev0] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORevA] || [currentCellularAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORevB]) { self.currentCellularDataConnectionType = [NSString stringWithFormat:@"%@ ~= %@",currentCellularAccessTechnology,k3G]; self.cellularConnectionFast = NO; } else { self.currentCellularDataConnectionType = (NSString *)currentCellularAccessTechnology; self.cellularConnectionFast = NO; }
但是，我在Raywenderlichpost中看到评论说，当设备未连接到无线电塔时， CTTelephonyNetworkInfo.currentRadioAccessTechnology可能返回’ nil ‘。
在这种情况下我可以做什么实现？ 我使用可达性类来识别当前网络类型（无连接， WiFi或WWAN ），并仅在WWAN进行“ currentRadioAccessTechnology ”值计算。
我想你正在获得CTTelephonyNetworkInfo一个实例，然后调用currentRadioAccessTechnology （这就是我的工作）。
正如您在设备hibernate时所指出的那样，问题就出现了。 当您的应用程序在后台运行时， CTTelephoneNetworkInfo实例会继续工作，但只要您处于非活动状态; 它变得无效。
当您再次变为活动状态时，需要获取CTTelephoneNetworkInfo的新实例（响应通知UIApplicationWillBecomeActive ）。
正如您所指出的那样，当您没有连接到无线电塔时， currentRadioAccessTechnology确实返回null ，但是可达性不会返回蜂窝，因此您应该没问题。
作为免费奖励， currentRadioAccessTechnology返回的currentRadioAccessTechnology是一个字符串，因此您可以清除所有if语句。
在一次调度块中设置引用表
NSSet fastTechs = [[NSSet alloc] initWithObjects: CTRadioAccessTechnologyHSDPA, CTRadioAccessTechnologyHSDPD, CTRadioAccessTechnologyLTE, nil]; NSDictionary accessTechTypes = @{ CTRadioAccessTechnologyHSDPA :k4g, CTRadioAccessTechnologyLTE : kLTE};
然后您的常规代码如下所示：
CTRadioAcessTechnology accessTech = telephonyInfo.currentRadioAccessTechnology; self.cellularConnectionFast = [fastTechs contains:accessTech];
和
self.currentCellularDataConnectionType = accessTechTypes[accessTech]