为什么我会收到进度滑块异常错误

Question

我正在制作一个将播放音频的应用程序。我使用滑块在滑块中以图形方式显示经过的时间和剩余时间。但我不知道如何以编程方式获取值。我使用了以下代码，但是它抛出异常。

 -(void) updateMyProgress
{
  float progress = [avPlayer currentTime]/[avPlayer duration];
  self.myProgressView.progress = progress;
} 

我的 viewcontoller.m 文件中的代码是

#import "ViewController.h"

@interface ViewController ()
{
    AVAudioPlayer *avPlayer;
    AVPlayer *avp;
}

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
NSString *stringPath = [[NSBundle mainBundle]pathForResource:@"naat" ofType:@"mp3"];
   NSURL *url = [NSURL fileURLWithPath:stringPath];
  NSError *error;
   avPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:url error:&error];
  [avPlayer setNumberOfLoops:2];
  [avPlayer setVolume:self.sliderVolumeOutlet.value];
  [NSTimer scheduledTimerWithTimeInterval:1 target:self      selector:@selector(updateMyProgress) userInfo:nil repeats:YES];


 }
/*-(void) updateMyProgress
{
 CGFloat progress = [avPlayer currentTime]/[avPlayer duration];
self.myProgressView.progress = progress;
}
*/
-(void) updateMyProgress

{

AVPlayerItem *currentItem = avp.currentItem ;

CMTime duration = currentItem.duration; //total time
CMTime currentTime = currentItem.currentTime; //playing time

CGFloat progress = currentTime.value/duration.value;

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

- (IBAction)sliderVolumeAction:(id)sender
{
UISlider *myslider= sender;
[avPlayer setVolume:myslider.value];
}

- (IBAction)stopButton:(id)sender
{
[avPlayer stop];
[avPlayer setCurrentTime:0];
}

- (IBAction)pauseButton:(id)sender
{
[avPlayer pause];
}

- (IBAction)playButton:(id)sender
{
[avPlayer play];
}
@end![enter image description here][1]

附图为异常截图

！ [1]：http://i.stack.imgur.com/WsxtI.png

Answer 1

• AVPlayer 没有名为“duration”的属性。
• “持续时间”是 AVPlayerItem 的属性。
• duration 和 currentTime 都是“CMTime”数据类型
• 我们必须获取 CMTime 的值，然后更新进度。

-(void) updateMyProgress

{

    AVPlayerItem *currentItem = avPlayer.currentItem;

    CMTime duration = currentItem.duration; //total time
    CMTime currentTime = currentItem.currentTime; //playing time

    CGFloat progress = currentTime.value/duration.value;

    self.myProgressView.progress = progress;
}