问题
I have an app that uses AVAudioPlayer to play some embedded MP3 files. The volume buttons work reliably on the 3GS I mostly use for testing -- they worked under 4.1 and work now after upgrading to 4.3.1. On my boss's iPhone 4 running 4.2.1, they don't seem to work in our app at at all; and on the iPod Touch (also running 4.2.1) that's my secondary test machine, I've been able to get them to work once but can't reproduce how I did it.
I tried a hack I found, creating a dummy AVAudioPlayer at application startup but leaving it in prepareToPlay state, and found I was able to use the volume buttons on my initial screen, but once I was playing real audio they stopped working.
Anyone run into this? Any ideas why it works on some phones and not others?
Update: I updated the Touch to 4.3.1 and the problem went away. I assume therefore it's probably a bug in 4.2.1, but I'd still like to know if anyone's seen it and/or can point me to a bug report.
回答1:
I had same problem. I found that the YouTube App was setting the default volume on the AVAudioPlayer. Found this with iPhone 4.3.3 so I am not sure if you are out of the woods yet.
来源：https://stackoverflow.com/questions/5588344/avaudioplayer-volume-buttons-work-on-some-devices-and-not-others