Question

我正在创建子类AVPlayer，以便我可以在音乐队列中创建skipsBackwards的方法。我想构建一个功能齐全的音乐播放器，它使用iPod用户的音乐。这意味着AVAudioPlayer和MPMusicPlayerController一样。此外，Core Audio让我感到害怕，所以我希望暂时避开它。

我已经考虑过使用类别来扩展AVPlayer类但是我需要我的子类来创建一个类变量来存储MPMediaItemCollection所以我认为它最有意义的是子类而不是添加一个类别

这是我的例外

！[在此处输入图片说明] [1]

这是我的appDelegate代码，我在其中设置AVPlayer，其子类为SWPlayer

#import <UIKit/UIKit.h>
#import <MediaPlayer/MediaPlayer.h>
#import <AVFoundation/AVFoundation.h>
#import <AudioToolbox/AudioToolbox.h>
#import "SWPlayer.h"


@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;   
@property (nonatomic,retain)SWPlayer *bookPlayer;

@end

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

    // Setup AudioSession
    NSError *sessionError = nil;
    [[AVAudioSession sharedInstance] setDelegate:self];
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:&sessionError];

    // Allow the audio to mix with other apps (necessary for background sound)
    UInt32 doChangeDefaultRoute = 1;
    AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(doChangeDefaultRoute), &doChangeDefaultRoute);

    //Grab some Songs to Test with
    MPMediaQuery *query = [MPMediaQuery songsQuery];
    NSArray *collection = [query items];

    //Setup bookPLayer to Test
    MPMediaItem *item = [collection objectAtIndex:5];
    NSLog(@"%@",[item valueForProperty:MPMediaItemPropertyTitle]);
    NSURL *url = [item valueForProperty:MPMediaItemPropertyAssetURL];
    self.bookPlayer = [[SWPlayer alloc]initWithURL:url];
    [bookPlayer play];

    [bookPlayer skipForwards];

    return YES;
}

这是我非常基本的子类......

#import <AVFoundation/AVFoundation.h>
#import <MediaPlayer/MediaPlayer.h>

@interface SWPlayer : AVPlayer

@property(nonatomic,retain)MPMediaItemCollection *mediaItemCollection;

-(void)skipForwards;
-(void)skipBackwards;

@end

#import "SWPlayer.h"

@implementation SWPlayer

@synthesize mediaItemCollection;

-(void)skipForwards{
    NSLog(@"SWPlayer called skipForward method");
}

-(void)skipBackwards{
    NSLog(@"SWPlayer called skipBackward method");

}

@end

音乐使用我的AVPlayer子类播放。问题是，只要我调用skipForward的{{1}}方法，我就会收到无法识别的选择器错误，并且应用程序崩溃了。我在这里缺少什么？

Answer 1

问题是，您调用的playerWithURL方法由AVPlayer拥有，并且即使在子类化时也会始终返回AVPlayer，除非您覆盖它。尝试使用：

创建它

self.bookPlayer = [[SWPlayer alloc] initWithURL:url];

我如何将AVPlayer子类化？

1 个答案: