标签栏上方出现黑条

Question

我是 iOS 编程新手，无法解决我的应用程序中的以下错误：

Xcode 5.0.2 上的故事板用于创建应用程序屏幕。一个简单的选项卡视图控制器是应用程序的主屏幕。每个选项卡栏项都通过导航控制器链接到视图控制器。其中一个视图控制器 (S1) 包含一个按钮，该按钮在录制音频几秒钟后以编程方式触发 segue。 segue 转换到另一个屏幕 (S2)，该屏幕有时在标签栏上方包含一个黑条。

编辑

有关该错误的更多详细信息：

1. 可以通过应用程序中的另一个屏幕 (S3) 访问屏幕 S2。但是，通过 S3 打开时，黑条永远不会出现在 S2 上。该栏仅在通过 S1 访问时出现在 S2 上。因此，我认为这与我在 S1 中所做的事情更相关（例如录音或sleepForTimeInterval，请参见下面的代码）。

2. 更改设备方向后黑条消失。

3. 在 S1 或 S2 中未设置布局约束。

4. 在 iPhone 4、4S 和 5 上观察到此错误。未在 5S 上尝试。

这里是S1的实现：

@interface S2ViewController () <AVAudioPlayerDelegate, AVAudioRecorderDelegate>

@property (nonatomic, strong) AVAudioRecorder *audioRecorder;
@property (nonatomic, strong) AVAudioPlayer *audioPlayer;
@property (weak, nonatomic) IBOutlet UIButton *btnRecord;
@property Parameters* parameters;
@property BOOL permissionGranted;

@end

@implementation STVIdentifyViewController

- (IBAction) recordAudio:(UIButton *)sender
{
    [self startRecordingAudio];
}

- (void) startRecordingAudio
{
    NSError* error = nil;
    NSURL* audioRecordingURL = [self audioRecordingPath];

    self.audioRecorder = [[AVAudioRecorder alloc]
                          initWithURL:audioRecordingURL
                          settings:[self audioRecordingSettings]
                          error:&error];

    if (self.audioRecorder != nil)
    {
        self.audioRecorder.delegate = self;

        if ([self.audioRecorder prepareToRecord] && [self.audioRecorder record])
        {
            [self performSelector:@selector(stopRecordingOnAudioRecorder:)
                       withObject:self.audioRecorder afterDelay:5.0];
        }
    }
}

- (void) stopRecordingOnAudioRecorder:(AVAudioRecorder *)paramRecorder
{
    [paramRecorder stop];
}

- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag
{
    if (flag)
    {
        [self doSomeProcessingOnTheAudio];
    }

    self.audioRecorder = nil;
}

- (void) doSomeProcessingOnTheAudio
{
    [NSThread sleepForTimeInterval:1.0];

    AnotherClass* ACInstance = [[AnotherClass alloc] init];
    self.parameters = [ACInstance run];

    if (self.parameters)
    {
        [self performSegueWithIdentifier: @"s1tos2" sender: self];
    }
}

- (NSDictionary *) audioRecordingSettings
{
    return @{
             AVFormatIDKey : @(kAudioFormatLinearPCM),
             AVSampleRateKey : @(11025.0f),
             AVNumberOfChannelsKey : @1,
             };
}

- (NSURL *) audioRecordingPath
{
    NSFileManager *fileManager = [[NSFileManager alloc] init];
    NSURL *docFolderUrl = [fileManager URLForDirectory:NSDocumentDirectory
                                                    inDomain:NSUserDomainMask
                                           appropriateForURL:nil
                                                      create:NO
                                                       error:nil];
    return [docFolderUrl URLByAppendingPathComponent:@"recording"];
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if([segue.identifier isEqualToString:@"s1tos2"])
    {
        S2ViewController* s2vc = (S2ViewController*) segue.destinationViewController;
        s2vc.parameters = self.parameters;
    }
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self)
    {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    AVAudioSession *session = [AVAudioSession sharedInstance];

    [session setCategory:AVAudioSessionCategoryPlayAndRecord
             withOptions:AVAudioSessionCategoryOptionDuckOthers
                   error:nil];

    [session requestRecordPermission:^(BOOL granted)
    {
        self.permissionGranted = granted;
    }];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

Answer 1

应该是自动布局问题。检查显示栏的视图底部约束。