iOS present AlertController時崩潰。 'Application tried to present modally an active controller .'

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Application tried to present modally an active controller <HKConnectViewController: 0x1050158e0>.'

 

分析：

很有可能是你的觸發事件中，觸發了多次。也就是說：不止一次調用了present。

解決辦法：

保證只執行一次

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        [self presentViewController:self.bluetoothCloseAlertC animated:YES completion:nil];
    });