How to addObserver for currentPlaybackTime for the system music player?

Question

Giebler OP

Created 2w

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I'm using the systemMusicPlayer to play music and want to update the playback time using addObserver forKeyPath.

[self setMusicPlayer: [MPMusicPlayerController systemMusicPlayer]];

I've tried these two methods:

[self addObserver:self forKeyPath:@"musicPlayer.currentPlaybackTime" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionInitial context:&musicPlayer]; [self.musicPlayer addObserver:self forKeyPath:@"currentPlaybackTime" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionInitial context:&musicPlayer];

I do get the initial values for currentPlaybackTime in: -(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

but I never get any calls when the player is playing the song (the whole point).

If I set the currentPlaybackTime to a specific value (locating manually using a slider), I get calls with the values I set (useless since I know what I am setting them to).

How are we supposed to track the playback time without just polling it constantly?

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Answer 1

deeje OP

2w

you can register for notifications of the player for events such as starting, stopping, pausing, etc. While the music player is playing, you'll want to set up a Timer to periodically update a progress bar. In SwiftUI you can use the TimelineView to periodically update the progress bar.

https://developer.apple.com/documentation/swiftui/timelineview

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