ios - Objective-c 没有已知的选择器类方法 'playAtTime'

Question

我正在尝试使用 AVAudioPlayer 和 playAtTime 将闹钟编程为在用户设置的时间响起，当我使用此代码时 [AVAudioPlayer playAtTime:日期时间字符串];
尝试让它在用户设置的时间播放，我收到此错误 no known class method for selector 'playAtTime'。我的其余代码如下

 #import "ViewController.h"

 @interface ViewController()
 {
      AVAudioPlayer *_myPlayer;
 }
@end

@implementation ViewController

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

NSString *path = [NSString stringWithFormat:@"%@/drum01.mp3", [[NSBundle mainBundle] resourcePath]];
NSURL *soundUrl = [NSURL fileURLWithPath:path];
_alarmPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:soundUrl error:nil];

}

-(IBAction) alarmSetButtonTapped:(id)sender {

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSString *dateTimeString = [dateFormatter stringFromDate: dateTimePicker.date ];
NSLog( @"Set button tapped : %@", dateTimeString );

[AVAudioPlayer playAtTime:dateTimeString];

[self scheduleLocalNotificationWithDate: dateTimePicker.date];

}

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

@end

还有viewcontroller.h

#import <UIKit/UIKit.h>
#import <AvFoundation/AVFoundation.h>

@interface ViewController : UIViewController <AVAudioPlayerDelegate>
  {
     IBOutlet UIDatePicker *dateTimePicker;
  }


 -(IBAction) alarmSetButtonTapped:(id)sender;

 @end

如何修复此错误并使用 playAtTime？

谢谢

Answer 1

-[AVAudioPlayer playAtTime:] 方法是实例方法，不是类方法，因此必须在实例上调用它(例如，_alarmPlayer)。此外，它的参数是一个 NSTimeInterval，而不是一个字符串。

在任何情况下，这个方法都不会做你想做的事。它用于从开始点以外的点开始播放器；该参数表示它应该从样本中开始多远。它不会安排在将来的某个时间播放音频样本。