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我有一个应用程序可以从列表中一个一个地播放视频。因此，为了测试此功能，我创建了一个只有一个 View Controller 的简单应用程序。我在实现 this 之前引用了此博客 View Controller 。 View Controller 命名为TNViewController，其实现如下:
#import <UIKit/UIKit.h>
#import <MediaPlayer/MediaPlayer.h>
@interface TNViewController : UIViewController {
@private
NSMutableArray *_videoArray;
int _currentVideo;
MPMoviePlayerController *_moviePlayer;
NSURL *_movieUrl;
}
@end
它的实现是:
#import "TNViewController.h"
@implementation TNViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[[UIApplication sharedApplication] setStatusBarHidden:YES animated:NO];
[self.view setFrame:CGRectMake(0, 0, 480, 320)];
[self initVideos];
[self initPlayer];
}
- (void) initVideos {
_videoArray = [[NSMutableArray alloc] init];
NSString *path = [[NSBundle mainBundle] pathForResource:@"sintel_trailer" ofType:@"mp4" inDirectory:nil];
[_videoArray addObject:path];
path = [[NSBundle mainBundle] pathForResource:@"elephants_dream_trailer" ofType:@"mp4" inDirectory:nil];
[_videoArray addObject:path];
path = [[NSBundle mainBundle] pathForResource:@"big_buck_bunny_trailer" ofType:@"mp4" inDirectory:nil];
[_videoArray addObject:path];
_currentVideo = -1;
}
- (NSString*) nextVideo {
_currentVideo++;
if (_currentVideo >= _videoArray.count) {
_currentVideo = 0;
}
return [_videoArray objectAtIndex:_currentVideo];
}
- (void) initPlayer {
_moviePlayer = [[MPMoviePlayerController alloc]init];
[self readyPlayer];
[self.view addSubview:_moviePlayer.view];
// Register to receive a notification when the movie has finished playing.
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(moviePlayBackDidFinish:)
name:MPMoviePlayerPlaybackDidFinishNotification
object:_moviePlayer];
}
- (void) readyPlayer {
_movieUrl = [NSURL fileURLWithPath:[self nextVideo]];
[_movieUrl retain];
_moviePlayer.contentURL = _movieUrl;
// For 3.2 devices and above
if ([_moviePlayer respondsToSelector:@selector(loadState)]) {
// Set movie player layout
[_moviePlayer setControlStyle:MPMovieControlStyleNone];
[_moviePlayer setFullscreen:YES];
// May help to reduce latency
[_moviePlayer prepareToPlay];
// Register that the load state changed (movie is ready)
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(moviePlayerLoadStateChanged:)
name:MPMoviePlayerLoadStateDidChangeNotification
object:nil];
} else {
// Register to receive a notification when the movie is in memory and ready to play.
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(moviePreloadDidFinish:)
name:MPMoviePlayerContentPreloadDidFinishNotification
object:nil];
}
}
/*---------------------------------------------------------------------------
* For 3.1.x devices
*--------------------------------------------------------------------------*/
- (void) moviePreloadDidFinish:(NSNotification*)notification {
// Remove observer
[[NSNotificationCenter defaultCenter] removeObserver:self
name:MPMoviePlayerContentPreloadDidFinishNotification
object:nil];
// Play the movie
[_moviePlayer play];
}
/*---------------------------------------------------------------------------
* For 3.2 and 4.x devices
*--------------------------------------------------------------------------*/
- (void) moviePlayerLoadStateChanged:(NSNotification*)notification {
NSLog(@"moviePlayerLoadStateChanged");
// Unless state is unknown, start playback
if ([_moviePlayer loadState] != MPMovieLoadStateUnknown) {
// Remove observer
[[NSNotificationCenter defaultCenter] removeObserver:self
name:MPMoviePlayerLoadStateDidChangeNotification
object:nil];
// Set frame of movie player
[[_moviePlayer view] setFrame:CGRectMake(0, 0, 480, 320)];
// Play the movie
[_moviePlayer play];
}
}
- (void) moviePlayBackDidFinish:(NSNotification*)notification {
NSLog(@"playback finished...");
NSLog(@"End Playback Time: %f", _moviePlayer.endPlaybackTime);
int reason = [[[notification userInfo] valueForKey:MPMoviePlayerPlaybackDidFinishReasonUserInfoKey] intValue];
if (reason == MPMovieFinishReasonPlaybackEnded) {
NSLog(@"Reason: movie finished playing");
}else if (reason == MPMovieFinishReasonUserExited) {
NSLog(@"Reason: user hit done button");
}else if (reason == MPMovieFinishReasonPlaybackError) {
NSLog(@"Reason: error");
}
[self playNextVideo];
}
- (void) playNextVideo {
NSString *filePath = [self nextVideo];
[_movieUrl release];
_movieUrl = [NSURL fileURLWithPath:filePath];
[_movieUrl retain];
_moviePlayer.contentURL = _movieUrl;
[_moviePlayer play];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
return (interfaceOrientation == UIInterfaceOrientationLandscapeRight);
}
- (void) dealloc {
[_moviePlayer release];
[_movieUrl release];
[_videoArray release];
[super dealloc];
}
@end
现在，我的问题是通知 MPMoviePlayerPlaybackDidFinishNotification 被调用了两次。从上面的代码可以看出，我在viewDidLoad中只注册了一次(在viewDidLoad调用的initPlayer中)。这是日志输出:
2012-07-02 12:29:17.661 DemoApp[1191:ef03] moviePlayerLoadStateChanged
2012-07-02 12:30:11.470 DemoApp[1191:ef03] playback finished...
2012-07-02 12:30:11.471 DemoApp[1191:ef03] End Playback Time: -1.000000
2012-07-02 12:30:11.472 DemoApp[1191:ef03] Reason: movie finished playing
2012-07-02 12:30:11.474 DemoApp[1191:ef03] playback finished...
2012-07-02 12:30:11.475 DemoApp[1191:ef03] End Playback Time: -1.000000
2012-07-02 12:30:11.476 DemoApp[1191:ef03] Reason: movie finished playing
2012-07-02 12:31:03.821 DemoApp[1191:ef03] playback finished...
2012-07-02 12:31:03.822 DemoApp[1191:ef03] End Playback Time: -1.000000
2012-07-02 12:31:03.824 DemoApp[1191:ef03] Reason: movie finished playing
2012-07-02 12:31:03.826 DemoApp[1191:ef03] playback finished...
2012-07-02 12:31:03.827 DemoApp[1191:ef03] End Playback Time: -1.000000
2012-07-02 12:31:03.827 DemoApp[1191:ef03] Reason: movie finished playing
如您所见，播放完成被调用了两次。这会导致从队列中跳过一个视频。 (事实上，在出现问题的原始项目中，nextVideo会预先从服务器缓存一个视频，如果缓存中存在，则返回缓存视频的路径。否则，它返回 nil。)。在这里，首先播放 sintel_trailer.mp4。播放结束后，它播放的不是 elephants_dream_trailer.mp4，而是 big_buck_bunny_trailer.mp4。也就是说，它循环播放中间跳过的视频。那么，是什么导致 MPMoviePlayerPlaybackDidFinishNotification 调用两次？我为此工作了两天，仍然没有运气。有什么想法吗？
更新 1:
目前我正在回调 moviePlayBackDidFinish: 中使用一个开关，如下所示并且正在工作:
if (!_playNextVideo) {
_playNextVideo = YES;
return;
}
_playNextVideo = NO;
// code to play video....
但我仍然想知道是什么导致回调被调用两次。我觉得当前的 switch 解决方案就像一个 hack，并希望将其删除。
更新 2:
到目前为止，我一直在使用 iPhone 4.3 模拟器进行尝试。但是，当我用 iPhone 5.0 模拟器和 iPhone 5.1 模拟器尝试相同的程序时，它没有任何问题。也就是说，电影播放完毕后只发送一个回调。这使我的小技巧(更新 1)变得毫无用处(它解决了 4.3 中的问题，但在 5.0 和 5.1 中产生了问题)。我正在使用在 MacOSX Lion - 10.7.4 上运行的 Xcode 4.3.2。你知道如何解决这个问题吗？为什么在 4.3 上有两个回调？
更新 3:
我查明了导致问题的线路。它在 playNextVideo 方法中。导致问题的行是 _moviePlayer.contentURL = _movieUrl;。在第一个回调中更改它会导致再次发送 MPMoviePlayerPlaybackDidFinishNotification。但是，它只发生在 iPhone 4.3 模拟器中。有什么想法吗？
更新 4:
不过，我对这种奇怪的行为一无所知。所以，我现在在 moviePlayBackDidFinish:
NSTimeInterval currentCallback = [NSDate timeIntervalSinceReferenceDate];
NSTimeInterval difference = currentCallback - _lastCallback;
_lastCallback = currentCallback;
if (difference < 5.0) {
return;
}
// code to play video....
最佳答案
我遇到了同样的问题。并以这种方式解决:
我创建了一种跳过视频的新方法
- (void) skipVideo {
[_moviePlayer stop];
}
在 skipVideo 中停止播放器将导致 MPMovieFinishReasonPlaybackEnded 通知(在模拟器和设备上)。现在设置播放器的contentUrl时，不会引起其他MPMovieFinishReasonPlaybackEnded通知，所以moviePlayBackDidFinish只调用一次；
在播放下一个视频之前(在playNextVideo)你必须调用
[_moviePlayer prepareToPlay];
这对我来说很好用!
关于iphone - 设置 contentURL 时在 iPhone 4.3 模拟器中再次调用 MPMoviePlayerPlaybackDidFinishNotification，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11289401/