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在我的应用程序中，我有一个音乐播放器，它实际上是来自 iTunes 的歌曲并播放预览。但是由于 AVAudio 播放器需要将文件写入本地文件才能播放。所以有时在我点击我的播放按钮后需要 2-3 秒，所以我想在我的按钮上显示一个 UIActivityIndi​​cator 视图，以便用户知道它的加载。

我知道如何为其他视图加载执行此操作，但在这里它一个接一个地发生在一个方法中，所以不知道如何执行此操作。

这是我的代码：

wait = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
        UIView * temp = (UIView *)sender;
        [temp addSubview:wait];
        [wait startAnimating];
        NSError * error;
        int tag = [sender tag]-100;
        previousTag = sender;
        active = sender;
        UIButton * button = (UIButton *)sender;
        [UIView transitionWithView:button
                          duration:0.5
                           options:UIViewAnimationOptionTransitionFlipFromLeft 
                        animations:^{ 
                            [button setBackgroundImage:pauseButtonImage.image forState:UIControlStateNormal];
                        }
                        completion:NULL];
        NSIndexPath * indexPath = [NSIndexPath indexPathForRow:tag inSection:0];
        [songsResults selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionNone];

        NSString * floatPath = [NSString stringWithFormat:@"preview%d",tag];
        NSString *uniquePath = [TMP stringByAppendingPathComponent: floatPath];
            if([[NSFileManager defaultManager] fileExistsAtPath: uniquePath])
            {
                [wait stopAnimating];
                audioPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:[NSURL fileURLWithPath:uniquePath] error:&error];
            }
            else {

            NSArray * temp = [dataToDisplay objectAtIndex:tag];
            NSString * urlString = [temp objectAtIndex:3];
            NSURL *url = [NSURL URLWithString:urlString];
            NSData *soundData = [NSData dataWithContentsOfURL:url];

            [soundData writeToFile:uniquePath atomically:YES];
                [wait stopAnimating];
            audioPlayer = [[AVAudioPlayer alloc]initWithContentsOfURL:[NSURL fileURLWithPath:uniquePath] error:&error];
            }
        float duration = [audioPlayer duration];

        timer = [NSTimer scheduledTimerWithTimeInterval:duration target:self selector:@selector(stopPreview:) userInfo:nil repeats:NO];
            [audioPlayer play];
            isPlaying = YES;
    }
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1 回答 1

2

通过调用 让阻塞任务在后台运行performSelectorInBackground。为了在任务完成时收到通知，请传递一个块或使用委托。

文件存储.h

@protocol FileStorageDelegate <NSObject>
- (void)fileStorageDidWriteToFile;
@end

@interface FileStorage

@property (nonatomic, assign) id <FileStorageDelegate> delegate;

@end

文件存储.m

@implementation FileStorage
@synthesize delegate = _delegate;

- (void)storeFile:(NSData *)data
{
   [self performSelectorInBackground:@selector(storeFileInBackground:) withObject:data];
}

- (void)storeFileInBackground:(NSData *)data
{
   // perfofm blocking task


   // Call delegate and pass some parameters if needed
   [self.delegate fileStorageDidWriteToFile];
}

@end
于 2012-04-16T00:48:41.293 回答