当我的应用程序在后台并锁定时应用程序崩溃

Question

我使用下面的方法：

[filehandler writeData:[NSData dataWithBytesNoCopy:bytes length:size freeWhenDone:NO]];

filehandler是NSFileHandle，当我的手机在几秒钟后锁定值时Null和我的应用程序崩溃。

这是崩溃消息_：

 [EXCEPTION] *** Terminating app due to uncaught exception 'NSFileHandleOperationException', reason: '*** -[NSConcreteFileHandle writeData:]: Operation not permitted'
*** Fragment of the call stack:
(
    "4   libc++abi.dylib                     0x1a6c398f <redacted> + 78",
    "5   libc++abi.dylib                     0x1a6c31a3 <redacted> + 0",
    "6   libobjc.A.dylib                     0x1a6cf139 <redacted> + 0",
    "7   CoreFoundation                      0x1b447a85 <redacted> + 0",
    "8   Foundation                          0x1bd3e1af <redacted> + 144",
    "9   Foundation                          0x1bd3ea5f <redacted> + 254",
    "10  PrivateGSMEnt                       0x0014acfb -[LogFileManager level:tagLevel:mainTag:append:] + 1070",
    "11  PrivateGSMEnt                       0x00067003 log_func + 996",
    "12  PrivateGSMEnt                       0x0046c451 log_writer + 166",
    "13  PrivateGSMEnt                       0x003dfb53 pj_log + 1284",
    "14  PrivateGSMEnt                       0x003dfdf7 pj_log_4 + 64",
    "15  PrivateGSMEnt                       0x003e0e97 replace_udp_sock + 170",
    "16  PrivateGSMEnt                       0x003e13f5 ioqueue_dispatch_read_event + 590",
    "17  PrivateGSMEnt                       0x003e32ef pj_ioqueue_poll + 898",
    "18  PrivateGSMEnt                       0x003f47d5 worker_proc + 84",
    "19  PrivateGSMEnt                       0x003de4c7 thread_main + 146",
    "20  libsystem_pthread.dylib             0x1accc93b <redacted> + 216",
    "21  libsystem_pthread.dylib             0x1accc85d _pthread_start + 234",
    "22  libsystem_pthread.dylib             0x1acca468 thread_start + 8"
)
libc++abi.dylib: terminating with uncaught exception of type NSException

有什么想法吗？