iOS音频播放 (八)：NowPlayingCenter和RemoteControl

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[code]MP_EXTERN_CLASS_***AILABLE(5_0) @interface MPNowPlayingInfoCenter : NSObject

// Returns the default now playing info center.
// The default center holds now playing info about the current application.
+ (MPNowPlayingInfoCenter *)defaultCenter;

// The current now playing info for the center.
// Setting the info to nil will clear it.
@property (copy) NSDictionary *nowPlayingInfo;

@end

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[code]MPMediaItemPropertyAlbumTitle              //NSString
MPMediaItemPropertyAlbumTrackCount         //NSNumber of NSUInteger
MPMediaItemPropertyAlbumTrackNumber        //NSNumber of NSUInteger
MPMediaItemPropertyArtist                  //NSString
MPMediaItemPropertyArtwork                 //MPMediaItemArtwork
MPMediaItemPropertyComposer                //NSString
MPMediaItemPropertyDiscCount               //NSNumber of NSUInteger
MPMediaItemPropertyDiscNumber              //NSNumber of NSUInteger
MPMediaItemPropertyGenre                   //NSString
MPMediaItemPropertyPersistentID            //NSNumber of uint64_t
MPMediaItemPropertyPlaybackDuration        //NSNumber of NSTimeInterval
MPMediaItemPropertyTitle                   //NSString

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[code]MP_EXTERN_CLASS_***AILABLE(3_0) @interface MPMediaItemArtwork : NSObject

// Initializes an MPMediaItemArtwork instance with the given full-size image.
// The crop rect of the image is assumed to be equal to the bounds of the 
// image as defined by the image's size in points, i.e. tightly cropped.
- (instancetype)initWithImage:(UIImage *)image NS_DESIGNATED_INITIALIZER NS_***AILABLE_IOS(5_0);

// Returns the artwork image for an item at a given size (in points).
- (UIImage *)imageWithSize:(CGSize)size;

@property (nonatomic, readonly) CGRect bounds; // The bounds of the full size image (in points).
@property (nonatomic, readonly) CGRect imageCropRect; // The actual content area of the artwork, in the bounds of the full size image (in points).

@end

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[code]// The elapsed time of the now playing item, in seconds.
// Note the elapsed time will be automatically extrapolated from the previously 
// provided elapsed time and playback rate, so updating this property frequently
// is not required (or recommended.)
MP_EXTERN NSString *const MPNowPlayingInfoPropertyElapsedPlaybackTime NS_***AILABLE_IOS(5_0); // NSNumber (double)

// The playback rate of the now playing item, with 1.0 representing normal 
// playback. For example, 2.0 would represent playback at twice the normal rate.
// If not specified, assumed to be 1.0.
MP_EXTERN NSString *const MPNowPlayingInfoPropertyPlaybackRate NS_***AILABLE_IOS(5_0); // NSNumber (double)

// The "default" playback rate of the now playing item. You should set this
// property if your app is playing a media item at a rate other than 1.0 in a
// default playback state. e.g., if you are playing back content at a rate of
// 2.0 and your playback state is not fast-forwarding, then the default
// playback rate should also be 2.0. Conversely, if you are playing back content
// at a normal rate (1.0) but the user is fast-forwarding your content at a rate
// greater than 1.0, then the default playback rate should be set to 1.0.
MP_EXTERN NSString *const MPNowPlayingInfoPropertyDefaultPlaybackRate NS_***AILABLE_IOS(8_0); // NSNumber (double)

// The index of the now playing item in the application's playback queue.
// Note that the queue uses zero-based indexing, so the index of the first item 
// would be 0 if the item should be displayed as "item 1 of 10".
MP_EXTERN NSString *const MPNowPlayingInfoPropertyPlaybackQueueIndex NS_***AILABLE_IOS(5_0); // NSNumber (NSUInteger)

// The total number of items in the application's playback queue.
MP_EXTERN NSString *const MPNowPlayingInfoPropertyPlaybackQueueCount NS_***AILABLE_IOS(5_0); // NSNumber (NSUInteger)

// The chapter currently being played. Note that this is zero-based.
MP_EXTERN NSString *const MPNowPlayingInfoPropertyChapterNumber NS_***AILABLE_IOS(5_0); // NSNumber (NSUInteger)

// The total number of chapters in the now playing item.
MP_EXTERN NSString *const MPNowPlayingInfoPropertyChapterCount NS_***AILABLE_IOS(5_0); // NSNumber (NSUInteger)

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[code]#import <UIKit/UIKit.h>

@interface MyApplication : UIApplication

@end

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[code]int main(int argc, char * argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

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[code]// If nil is specified for principalClassName, the value for NSPrincipalClass from the Info.plist is used. If there is no
// NSPrincipalClass key specified, the UIApplication class is used. The delegate class will be instantiated using init.
UIKIT_EXTERN int UIApplicationMain(int argc, char *argv[], NSString *principalClassName, NSString *delegateClassName);

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[code]#import <UIKit/UIKit.h>
#import "AppDelegate.h"
#import "MyApplication.h"

int main(int argc, char * argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, NSStringFromClass([MyApplication class]), NSStringFromClass([AppDelegate class]));
    }
}

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[code]#import "MyApplication.h"

@implementation MyApplication

- (BOOL)canBecomeFirstResponder
{
    return YES;
}

@end

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[code]#import "MyApplication.h"

@implementation MyApplication

- (BOOL)canBecomeFirstResponder
{
    return YES;
}

- (void)remoteControlReceivedWithEvent:(UIEvent *)event
{
    switch (event.subtype)
    {
        case UIEventSubtypeRemoteControlPlay:
            //play
            break;
        case UIEventSubtypeRemoteControlPause:
            //pause
            break;
        case UIEventSubtypeRemoteControlStop:
            //stop
            break;
        default:
            break;
    }
}

@end