Ios AVAudioRecorder停止在iPad上工作

我有一个为IOS9发布的应用程序：一个相对次要的功能是能够录制小的声音片段。在一个新应用程序上测试一个类似的功能时，我发现同样的代码在运行iOS10的iPad上不起作用，尽管它可以在模拟器上运行。在iPad上，音频测光提供稳定的-120dB，并且永远不会调用AudioRecorderDiFinishRecording。没有记录的消息。发布的应用程序和新应用程序在iPad上都不起作用

代码如下所示：

- (void) record: (int) record_time {

record_sound = self;

AVAudioSession *audioSession = [AVAudioSession sharedInstance];
NSError *err = nil;
[audioSession setCategory :AVAudioSessionCategoryPlayAndRecord error:&err];
if(err){
    NSLog(@"audioSession: %@ %ld %@", [err domain], (long)[err code], [[err userInfo] description]);
    return;
}
[audioSession setActive:YES error:&err];
err = nil;
if(err){
    NSLog(@"audioSession: %@ %ld %@", [err domain], (long)[err code], [[err userInfo] description]);
    return;
}

NSMutableDictionary * recordSetting = [[NSMutableDictionary alloc] init];

[recordSetting setValue :[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey:AVFormatIDKey];
[recordSetting setValue:[NSNumber numberWithFloat:44100.0] forKey:AVSampleRateKey];
[recordSetting setValue:[NSNumber numberWithInt: 1] forKey:AVNumberOfChannelsKey];

[recordSetting setValue :[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];
[recordSetting setValue :[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsBigEndianKey];
[recordSetting setValue :[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsFloatKey];

// Create a new file
NSString * recorderFilePath = [Recorder getRecordFilename];

NSFileManager * fileManager = [NSFileManager defaultManager];
NSError * error = nil;
[fileManager createDirectoryAtPath:[recorderFilePath stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:&error]; //Create folder

NSURL *url = [NSURL fileURLWithPath:recorderFilePath];
err = nil;
recorder = [[ AVAudioRecorder alloc] initWithURL:url settings:recordSetting error:&err];
if(!recorder){
    NSLog(@"recorder: %@ %ld %@", [err domain], (long)[err code], [[err userInfo] description]);
    return;
}

//prepare to record
[recorder setDelegate:self];
[recorder prepareToRecord];
recorder.meteringEnabled = YES;

// start recording
[recorder recordForDuration:(NSTimeInterval) record_time];
recordEndTime = [[NSDate date] dateByAddingTimeInterval: (NSTimeInterval) (record_time + 0.5)];

---

}

我关掉iPad，重新启动，一切又开始工作了。一定有什么东西锁在AVAudioRecorder装置里了