https://developer.android.com/media/platform/mediaplayer https://developer.android.com/media/platform/mediaplayer >Note: You can play back the audio data only

https://developer.android.com/media/platform/mediaplayer https://developer.android.com/media/platform/mediaplayer >Note: You can play back the audio data only to the standard output device. That is, the mobile device speaker or a Bluetooth headset. You cannot play sound files in the conversation audio during a call. Damn google! You did this so that apps cannot do the above. You cater to spammers!