A problem with Media Player base on iOS4 and deploy iOS3

问题

when Run on Device 3.1.2, why it also pass if(NSClassFromString(@"MPMoviePlayerViewController") != nil) and do code of iOS4 then it will crash , how to fix this issues?

               if(NSClassFromString(@"MPMoviePlayerViewController") != nil) {
                    // iOS 4 code
                    NSLog(@"MPMoviePlayerViewController");
                    MPMoviePlayerViewController *mp = [[MPMoviePlayerViewController alloc] initWithContentURL:[NSURL URLWithString:AppDelegate.PushLink]];
                    if (mp) {
                        // save the movie player object
                        self.theMovie4 = mp;
                        [mp release];
                        //Present                       
                        [self presentMoviePlayerViewControllerAnimated:self.theMovie4];

                        // Play the movie!
                        self.theMovie4.moviePlayer.movieSourceType = MPMovieSourceTypeStreaming;
                        [self.theMovie4.moviePlayer play];
                    }
                }
                else {
                    //iOS 3 Code
                    AppDelegate = nil;
                    AppDelegate = [[UIApplication sharedApplication] delegate];
                    [AppDelegate ForceHideNavigationBar];
                    theMovie3 = nil;

                    [[NSNotificationCenter defaultCenter] addObserver:self 
                                                             selector:@selector(moviePreloadDidFinish:) 
                                                                 name:MPMoviePlayerContentPreloadDidFinishNotification 
                                                               object:theMovie3];

                    [[NSNotificationCenter defaultCenter] addObserver:self 
                                                             selector:@selector(moviePlayBackDidFinish:) 
                                                                 name:MPMoviePlayerPlaybackDidFinishNotification 
                                                               object:theMovie3];

                    // Register to receive a notification when the movie scaling mode has changed. 
                    [[NSNotificationCenter defaultCenter] addObserver:self 
                                                             selector:@selector(movieScalingModeDidChange:) 
                                                                 name:MPMoviePlayerScalingModeDidChangeNotification 
                                                               object:theMovie3];

                    theMovie3 = [[MPMoviePlayerController alloc] initWithContentURL: [NSURL URLWithString:AppDelegate.PushLink]];

                    [theMovie3 play];

                }

回答1:

I am doing a very similar thing on my app which is using 4.0 as the base SDK and yet I am targeting iOS3 devices too. I had to check the OS version to properly provide the right code for the video playback. For example:

- (void) playMovieAtURL: (NSURL*) theURL {
    NSLog(@"playMovieAtURL");

if ([[[UIDevice currentDevice] systemVersion] doubleValue] >= 3.2) {
            NSLog(@"> 3.2");
            MPMoviePlayerViewController *mp = [[MPMoviePlayerViewController alloc] initWithContentURL:theURL];

            if (mp)
            {
                // save the movie player object
                //self.moviePlayerViewController = mp;
                //[mp release];
                [self presentMoviePlayerViewControllerAnimated:mp];
                mp.moviePlayer.movieSourceType = MPMovieSourceTypeFile;
                [mp.moviePlayer play];
                [mp release];
            }

        } 
    else if ([[[UIDevice currentDevice] systemVersion] doubleValue] < 3.2) {
            NSLog(@"< 3.2");

            MPMoviePlayerController* theMovie = [[MPMoviePlayerController alloc] initWithContentURL: theURL];

            theMovie.scalingMode = MPMovieScalingModeAspectFill;

            // Register for the playback finished notification
            [[NSNotificationCenter defaultCenter]
             addObserver: self
             selector: @selector(myMovieFinishedCallback:)
             name: MPMoviePlayerPlaybackDidFinishNotification
             object: theMovie];

            // Movie playback is asynchronous, so this method returns immediately.
            [theMovie play];



        }

    }

Hope this helps!!

回答2:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(moviePlayBackDidFinish:) 
        name:MPMoviePlayerPlaybackDidFinishNotification object:nil];

  NSString *movpath = [[NSBundle mainBundle] pathForResource:@"splash" ofType:@"mp4"];
  MPMoviePlayerViewController* mpviewController = [[MPMoviePlayerViewController alloc] 
                      initWithContentURL:[NSURL fileURLWithPath:movpath]];
  [window addSubview:mpviewController.view];
        [window makeKeyAndVisible];
  MPMoviePlayerController *mp = [mpviewController moviePlayer];
  [mp prepareToPlay];
  [[mpviewController moviePlayer] play];

This code will work in iOS4

It however does quit once the movie completes because you must create the method for the notification. Also you need to release the movie there so that you can catch the memory leak.

来源：https://stackoverflow.com/questions/3092117/a-problem-with-media-player-base-on-ios4-and-deploy-ios3