[英]Is currentItem of AVPlayer key value observable?
I used a AvQueuePlayer for playing audio in background. 我使用AvQueuePlayer在后台播放音频。 And to keep the playlist of AvQueuePlayer not empty, I used key-value observing to keep an eye on the currentItem of AvQueuePlayer for getting ready to load a next play item. 为了使AvQueuePlayer的播放列表不为空,我使用键值观察来密切注意AvQueuePlayer的currentItem以准备加载下一个播放项目。 Sometimes it works well, but sometimes it failes. 有时它运作良好,但有时会失败。
Here is the crash report I received: 这是我收到的崩溃报告:
Date/Time: 2011-12-16 23:43:58.963 +0800
OS Version: iPhone OS 4.3.5 (8L1)
Report Version: 104
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x4f2ecfe8
Crashed Thread: 0
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libobjc.A.dylib 0x32f0aca4 objc_msgSend + 28
1 Foundation 0x3165386c NSKVONotify + 24
2 Foundation 0x31651bb0 -[NSKeyValueObservance observeValueForKeyPath:ofObject:change:context:] + 220
3 Foundation 0x315fa7ea NSKeyValueNotifyObserver + 210
4 Foundation 0x315fa492 NSKeyValueDidChange + 230
5 Foundation 0x315e666a - [NSObject(NSKeyValueObserverNotification) didChangeValueForKey:] + 70
6 AVFoundation 0x33f190f2 -[AVPlayerItem didChangeValueForKey:] + 26
7 AVFoundation 0x33f1ceba __avplayeritem_fpItemNotificationCallback_block_invoke_1 + 2310
8 libdispatch.dylib 0x338da8e0 _dispatch_call_block_and_release + 4
9 libdispatch.dylib 0x338d61ee _dispatch_main_queue_callback_4CF$VARIANT$up + 306
10 CoreFoundation 0x34c1d934 __CFRunLoopRun + 1328
11 CoreFoundation 0x34badebc CFRunLoopRunSpecific + 224
12 CoreFoundation 0x34baddc4 CFRunLoopRunInMode + 52
13 GraphicsServices 0x33e5e418 GSEventRunModal + 108
14 GraphicsServices 0x33e5e4c4 GSEventRun + 56
15 UIKit 0x31272d62 -[UIApplication _run] + 398
16 UIKit 0x31270800 UIApplicationMain + 664
17 WeatherTunes 0x0004b31e main (main.m:17)
18 WeatherTunes 0x0004b2ac start + 32
And here is how I use key-value observing: 这就是我使用键值观察的方式:
[_queuePlayer addObserver:self forKeyPath:@"currentItem" options:NSKeyValueObservingOptionNew context:nil];
[_queuePlayer addObserver:self forKeyPath:@"currentItem.status" options:NSKeyValueObservingOptionNew context:nil];
And I looked up in the class reference of AvPlayer. 我查阅了AvPlayer的类参考。 Then I found that it was said the property "status" could be observable while it did not mention the currentItem. 然后我发现有人说,“ status”属性在未提及currentItem的情况下是可以观察到的。 But I found some people use the property currentItem as observable. 但我发现有些人将currentItem属性用作可观察的对象。 I am totally confused now. 我现在很困惑。 Please help me. 请帮我。
I had the same problem, wanted to know when a song in an AVQueuePlayer finished. 我遇到了同样的问题,想知道AVQueuePlayer中的歌曲何时播放完毕。 I ended up doing this instead, seemed safer. 我最终这样做了,似乎更安全了。
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(songFinishedWithNotification:)
name:AVPlayerItemDidPlayToEndTimeNotification
object:nil];
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