iOS AVAudioSession、AudioSession Category选择和声音通道听筒、扬声器切换
原文选择一个Categorypragmamark–Valuesforthecategoryproperty–/*Usethiscategoryforbackgroundsoundssuchasrain,carenginenoise,etc.Mixeswithothermusic.*/AVF_EXPORTNSString*constAVAudioSessionCategoryAmbient;/*Us